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WO2024193566A1 - Stress-corrosion-resistant high-strength and high-toughness medium carbon steel and manufacturing method therefor - Google Patents

Stress-corrosion-resistant high-strength and high-toughness medium carbon steel and manufacturing method therefor Download PDF

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Publication number
WO2024193566A1
WO2024193566A1 PCT/CN2024/082622 CN2024082622W WO2024193566A1 WO 2024193566 A1 WO2024193566 A1 WO 2024193566A1 CN 2024082622 W CN2024082622 W CN 2024082622W WO 2024193566 A1 WO2024193566 A1 WO 2024193566A1
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strength
carbon steel
medium carbon
stress corrosion
steel
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PCT/CN2024/082622
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French (fr)
Chinese (zh)
Inventor
赵四新
高加强
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宝山钢铁股份有限公司
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Publication of WO2024193566A1 publication Critical patent/WO2024193566A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D11/00—Process control or regulation for heat treatments
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Definitions

  • the present invention relates to a steel material and a manufacturing method thereof, and in particular to a medium carbon steel and a manufacturing method thereof.
  • High-strength and toughness steel bars are usually used in high-safety machinery and structural components, such as wind power fasteners and other key vulnerable parts. They should have high strength, high toughness, stress corrosion resistance and high fatigue performance.
  • controlled rolling, controlled cooling or quenching + tempering processes are used to produce high-strength and tough steel.
  • the controlled rolling and controlled cooling method is used to produce high-strength steel. Since it is difficult to control during the rolling and cooling processes, it affects the overall uniformity of the mechanical properties of the steel.
  • the quenching + tempering process is used to produce high-strength steel. By optimizing the content of alloy elements and carbon elements, the hardenability of the steel is improved, and a martensitic structure is formed during the cooling process.
  • High-strength steels mainly composed of martensite have a large dislocation density, resulting in poor impact toughness, and will quickly break and fail if tiny defects such as microcracks appear during the tensile process, and the fracture toughness is low.
  • Cr-Ni-Mo medium carbon low alloy steel is widely used in engineering machinery, automobiles, bridges, marine equipment and other fields due to its good strength and toughness. Its safe use strength level does not exceed 1000MPa, and the application of higher strength steel can not only make the equipment lighter, but also save resources. However, as the strength level of steel increases, the difficulty of processing and manufacturing increases, and its hydrogen embrittlement sensitivity is bound to increase.
  • a Chinese patent document with publication number CN102242322A and publication date of November 16, 2011, entitled “An improved 40CrNiMo steel and its preparation method” discloses a medium carbon steel, wherein the chemical elements by weight are: 0.37-0.45% C, 1.65-1.85% Cr, 0.45-0.65% Ni, 0.15-0.25% Mo, 0.90-1.20% Mn, 0. .40 ⁇ 0.55% Si, 0.0025 ⁇ 0.0045% B, 0.22 ⁇ 0.28% N, 0.007 ⁇ 0.012% Ca, 0.002 ⁇ 0.005% Mg, 0.03 ⁇ 0.06% Nb, 0.04 ⁇ 0.08% Ti, 0.02 ⁇ 0.06% RE, ⁇ 0.015% S and ⁇ 0.025% P and ⁇ 0.0008% Al, Fe is the balance.
  • the tensile strength of the steel is ⁇ 1195MPa, and the impact energy is better than 85J, but it does not involve stress corrosion resistance.
  • a Chinese patent document with publication number CN104726783A and publication date June 24, 2015, entitled “A steel for wind power yaw and pitch bearing ring and preparation method thereof” discloses a steel material whose chemical composition by mass percentage is: C: 0.37-0.42, Mn: 0.50-0.80, Mo: 0.20-0.30, Ni: 1.30-1.70, Cr: 0.70-1.00, Si: 0.20-0.50, Al acid solution: 0.035-0.055, V: 0.07-0.12, N: ⁇ 0.004, O: ⁇ 0.0008, H: ⁇ 0.00015, S: ⁇ 0.010, P: ⁇ 0.015, and the rest is Fe and a small amount of impurities.
  • the preparation method of the above-mentioned wind turbine yaw and pitch bearing ring is to heat treat the processed wind turbine yaw and pitch bearing ring, first heat it to 860-890°C and keep it for 3-5h to austenitize and then oil quench it, then heat it to 580-630°C and keep it for 3-5h and oil cool it to room temperature.
  • the steel has excellent hardenability, and all mechanical properties fully meet the standards and use requirements of steel for high-power wind turbine yaw and pitch bearing. However, this steel type does not involve stress corrosion resistance.
  • One of the purposes of the present invention is to provide a high-strength and tough medium carbon steel resistant to stress corrosion.
  • the steel has good impact toughness, elongation and area reduction, can resist stress corrosion cracking and has good weather resistance and fatigue resistance. It can be used in occasions such as engineering machinery and marine engineering that require high-strength and tough steel.
  • the present invention provides a high-strength and tough medium carbon steel resistant to stress corrosion, which contains Fe and inevitable impurities, and further contains the following chemical elements in the following mass percentages:
  • the present invention also provides a high-strength and tough medium carbon steel resistant to stress corrosion, wherein each chemical element The mass percentage is:
  • C can improve the hardenability of steel, so that the steel forms a phase transformation structure with higher hardness during the quenching and cooling process. If the C content is increased, the hard phase ratio will be increased, and the hardness of the steel will be increased, but the toughness will be reduced. If the C content is too low, it is difficult to obtain a higher strength. Based on this, the present invention controls the C content to 0.37-0.43%.
  • Si It is beneficial to improve the strength of steel. A proper amount of Si can avoid the formation of coarse carbides during tempering, but a higher Si content will reduce the impact toughness of the steel. Based on this, the present invention adopts a low Si component system and limits the Si content to 0.10-0.40%.
  • Mn It exists in steel mainly in the form of solid solution, which can improve the hardenability of steel and form a high-strength low-temperature phase transformation structure during quenching. The resulting steel has good wear resistance. However, too high a Mn content will lead to the formation of more retained austenite, reduce the yield strength of the steel, and easily cause center segregation. Based on this, the present invention controls the Mn content to be: 0.50-0.90%.
  • the present invention controls the Cr content to: 0.60-1.25%.
  • Ni exists in the steel in the form of solid solution, which can improve the low-temperature impact performance of the steel. However, too high a Ni content will lead to too high a content of retained austenite in the steel, thereby reducing the strength of the steel. Based on this, the present invention controls the Ni content to be: 1.30-2.00%.
  • Mo can be dissolved in steel and is beneficial to improving the hardenability and strength of steel. When tempered at a higher temperature, fine carbides will be formed to further improve the strength of steel. Considering the cost of precious alloy Mo element, the present invention controls the Mo content to be: 0.15-0.30%.
  • Al forms fine AlN precipitates in steel, which can inhibit the growth of austenite grains.
  • too high Al content will lead to the formation of larger Al oxides, and coarse AlN hard inclusions will reduce the impact toughness and fatigue properties of the steel.
  • the present invention controls the Al content to 0.02-0.05%.
  • Nb is added to steel to form fine precipitates, which inhibits the recrystallization of steel.
  • the Nb content is too high, coarse NbC particles will be formed during the smelting process, which will reduce the impact toughness.
  • Grain refinement plays an important role in improving the mechanical properties of steel, especially strength and toughness. More importantly, in the present invention, grain refinement also helps to reduce the hydrogen embrittlement sensitivity of steel. Based on this, the present invention controls the Nb content to be: 0.001-0.030%.
  • the high-strength and tough medium carbon steel resistant to stress corrosion described in the present invention also contains at least one of the following chemical elements: 0 ⁇ Cu ⁇ 0.3%, 0 ⁇ V ⁇ 0.06%, 0 ⁇ Ti ⁇ 0.03%, 0 ⁇ Ca ⁇ 0.003%.
  • Cu Further optional addition of Cu can improve the strength of the steel and help improve the corrosion resistance of the steel. However, if the Cu content is too high, it will be enriched in the grain boundaries during the heating process, resulting in weakening of the grain boundaries and cracking. Based on this, the present invention can choose to add Cu, and control its upper limit to 0.30%.
  • Ca element is added to steel to improve the size and morphology of sulfide inclusions and avoid deterioration of impact toughness. Based on this, the present invention can choose to add Ca and control its upper limit to 0.003%.
  • V can form precipitates with C or N in steel to improve the strength of the steel. If the C and V content is too high, coarse VC particles will be formed. Based on this, the present invention can choose to add V, and control its upper limit to 0.06%.
  • Ti can form fine precipitates when added to steel, but if the Ti content is too high, coarse and angular TiN particles will be formed during the smelting process, reducing the impact toughness. Based on this, the present invention can choose to add Ti, and control its upper limit to ⁇ 0.03%.
  • the inevitable impurities in the present invention are mainly P, S, N, O and H. Under the condition that technical conditions permit, it is expected that the content of these impurities is as low as possible. Among them:
  • P is concentrated at the grain boundaries in steel, which reduces the grain boundary bonding energy and deteriorates the impact toughness of the steel.
  • the upper limit of P is preferably controlled to 0.020%.
  • the upper limit is preferably controlled to 0.015%.
  • the present invention preferably controls the total mass percentage of P+S to ⁇ 0.030%.
  • N is an interstitial atom and also an element that forms MX-type precipitates.
  • the upper limit of the present invention is controlled to be 0.012%.
  • H will accumulate at defects in steel.
  • the upper limit of H content is controlled to 0.0002%.
  • the present invention preferably controls the upper limit of O content to 0.0020%.
  • each element also satisfies: Mn+Cr+Ni+Mo+Cu ⁇ 4.0, where each chemical element is substituted into the value before the percentage sign of the mass percentage content of the chemical element.
  • the present invention requires that the atomic ratio of the total amount of microalloying elements to nitrogen element exceeds 1, and the microalloying elements are Al, Nb and Ti.
  • each chemical element is substituted into the value before the percentage sign of the mass percentage content of the chemical element.
  • the rolled microstructure of the stress corrosion resistant high-strength medium carbon steel of the present invention is bainite + martensite and/or residual austenite, and contains nano-scale precipitates, wherein the volume phase ratio of bainite is ⁇ 60%.
  • the rolled state refers to the state of the steel after forging or rolling and before heat treatment (such as quenching + tempering).
  • microstructure of the high-strength and tough medium-carbon low-alloy steel after quenching and tempering heat treatment is mainly fine-grained tempered troostite and contains nano-scale precipitates.
  • the austenite grain size is ⁇ grade 6.
  • the high-strength and tough medium carbon steel resistant to stress corrosion described in the present invention has a yield strength R p0.2 ⁇ 1000MPa, a tensile strength R m ⁇ 1150MPa, an elongation A ⁇ 12%, a cross-sectional shrinkage Z ⁇ 50%, a room temperature Charpy impact energy A kv ⁇ 60J, a -40°C Charpy impact energy A kv ⁇ 30J, and an anti-hydrogen embrittlement coefficient ⁇ (Z) ⁇ O.85.
  • the high-strength and tough medium-carbon steel resistant to stress corrosion described in the present invention has a yield strength R p0.2 ⁇ 1020MPa, a tensile strength R m ⁇ 1150MPa, an elongation A ⁇ 12%, a cross-sectional shrinkage Z ⁇ 55%, a room temperature Charpy impact energy A kv ⁇ 65J, a -40°C Charpy impact energy A kv ⁇ 35J, and an anti-hydrogen embrittlement coefficient ⁇ (Z) ⁇ 0.89.
  • the high-strength and tough medium carbon steel resistant to stress corrosion described in the present invention has a yield strength R p0.2 of 1020 to 1100 MPa, a tensile strength R m of 1150 to 1200 MPa, an elongation A of 12 to 18%, a cross-sectional shrinkage Z of 50 to 65%, such as 58 to 65%, a room temperature Charpy impact energy A kv of 65 to 100 J, a -40°C Charpy impact energy A kv of 35 to 80 J, and an anti-hydrogen embrittlement coefficient ⁇ (Z) of 0.89 to 0.98.
  • Another object of the present invention is to provide a method for manufacturing high-strength and tough medium-carbon steel resistant to stress corrosion.
  • the present invention provides a method for manufacturing the above-mentioned stress corrosion resistant high-strength and tough medium carbon steel, which comprises the steps of:
  • Heating Control the heating temperature to 1050-1250°C and the insulation time to 3-24h;
  • Quenching + tempering where the quenching temperature ranges from 830 to 910 °C, the holding time is 30 to 200 min, and then water quenching is used; the tempering temperature is 530 to 640 °C, the holding time is 30 to 200 min, and air or water cooling is used after tempering.
  • step (4) rolling or forging may be performed directly to the finished size.
  • step (4) the steel is first rolled to an intermediate billet size, then intermediately heated, and then rolled to a final finished product size; wherein the intermediate heating temperature is 1050-1250° C., and the holding time is 3-24 hours.
  • the steel billet is descaled by high-pressure water after leaving the heating furnace and then begins rolling. After rolling, air cooling or slow cooling is used.
  • the high-strength and tough medium carbon steel obtained by the above manufacturing method can be used for wind power fasteners and other
  • the size specification range of the bars can be ⁇ 20 ⁇ 130mm.
  • the high-strength and tough medium carbon steel of the present invention is completely austenitized at a heating temperature of 1050°C to 1250°C.
  • carbides and nitrides of Al, Nb, V, Ti, and carbonitrides, and carbides of Cr and Mo are partially or completely dissolved in austenite, and in the subsequent rolling/forging and cooling processes, Al, Nb, V, and Ti form fine precipitates.
  • Mn, Cr, and Mo dissolved in austenite can improve the hardenability of steel and improve the hardness and strength of martensite.
  • the steel is heated to 830-910°C and then quenched in water.
  • the precipitates of carbide-forming elements Al, Nb, V, Ti, Cr and Mo are partially dissolved, and the undissolved precipitates pin the grain boundaries, inhibiting the coarsening of austenite grains, so that the austenite grain size is ⁇ 6.
  • the alloying elements dissolved in austenite give the steel high strength and good toughness.
  • the steel After quenching, the steel is tempered at 530-640°C. Al, Nb, V, Cr, Ti and Mo will form fine precipitates with C and N, which improves the strength and plasticity of the steel.
  • tempered troostite tempered martensite
  • the high-strength and tough medium-carbon steel resistant to stress corrosion described in the present invention is developed into a high-strength and tough steel by rationally designing the chemical composition and combining the optimized process.
  • the rolled or forged bars are subjected to a tempering heat treatment process after quenching to form a structure of tempered martensite and a small amount of bainite and residual austenite, as well as fine dispersed precipitates.
  • This structure enables the steel to have good impact toughness, elongation and area reduction, can resist stress corrosion cracking, and has good weather resistance and fatigue resistance.
  • the high-strength and tough medium carbon steel resistant to stress corrosion described in the present invention has a yield strength ⁇ 1000MPa, a tensile strength R m ⁇ 1150MPa, an elongation A ⁇ 12%, a cross-sectional shrinkage Z ⁇ 50%, a room temperature Charpy impact energy A kv ⁇ 60J, a -40°C low-temperature Charpy impact energy A kv ⁇ 30J, and a hydrogen embrittlement resistance coefficient ⁇ (Z) ⁇ 0.85.
  • the manufacturing method of the stress corrosion resistant high-strength and tough medium carbon steel of the present invention has a reasonable process design and a wide process window, and can realize batch commercial production on a bar or high-speed wire production line.
  • the stress corrosion resistant high-strength and tough medium carbon steels of Examples 1-8 were all prepared by the following steps:
  • Smelting is carried out according to the chemical composition shown in the following Table 1-1 and Table 1-2: In actual operation, vacuum induction furnace smelting, electric furnace smelting or converter smelting can be adopted, and then refined and vacuum treated.
  • Casting Casting is carried out by mold casting or continuous casting to obtain ingots.
  • Heating The ingot is placed in a heating furnace for heating, and the heating temperature is controlled to be 1050-1250°C, and the insulation time is 3-24 hours; during heating, the temperature can be directly raised to the heating temperature, or the temperature can be raised to the heating temperature in a step-by-step manner.
  • Forging or rolling Control the final rolling temperature or final forging temperature to be ⁇ 850°C, and cool after rolling or forging.
  • the cooling method can be air cooling or wind cooling.
  • the intermediate heating temperature of the intermediate billet can be controlled between 1050 and 1250°C, and the insulation time can be controlled between 3 and 24 hours.
  • Quenching + tempering where the quenching temperature ranges from 830 to 910 °C, the holding time is 30 to 200 min, and then water quenching is used; the tempering temperature is 530 to 640 °C, the holding time is 30 to 200 min, and air or water cooling is used after tempering.
  • Comparative Examples 1-3 are basically the same as those of the present invention, except that their chemical compositions or specific process parameters do not meet the design requirements of the present invention.
  • Comparative Example 4 uses commercially available round steel.
  • Table 1-1 lists the mass percentages of the chemical elements of the stress corrosion resistant high-strength and tough medium carbon steels of Examples 1-8 and the comparative steels of Comparative Examples 1-4.
  • Table 1-2 lists the synergistic relationship between the components of the stress corrosion resistant high strength and toughness medium carbon steels of Examples 1-8 and the comparative steels of Comparative Examples 1-4.
  • each chemical element is substituted with the numerical value before the percentage sign of the mass percentage content of the chemical element.
  • the smelting was carried out in a 50kg vacuum induction furnace, the molten steel obtained by smelting was mold-cast into an ingot, and the ingot was heated, and then forged into a blank.
  • the heating temperature was controlled to be 1050°C, and forging was carried out after holding for 5h.
  • the final forging temperature was controlled to be 850°C, and the final forging was forged into a bar with a diameter of ⁇ 50mm, and air-cooled after forging.
  • the quenching heating temperature was 860°C, the holding time was 30min, the tempering temperature was 550°C, the tempering time was 60min, and water-cooled after tempering.
  • the smelting was carried out in a 150kg vacuum induction furnace.
  • the molten steel obtained by smelting was mold-cast into ingots, and the ingots were heated and then forged.
  • the heating temperature was controlled at 1180°C, and forging was carried out after holding for 12 hours.
  • the final forging temperature was controlled at 960°C, and finally forged into ⁇ 70mm bars, and then air-cooled.
  • the quenching heating temperature was 910°C
  • the holding time was 100min
  • the tempering temperature was 600°C
  • the tempering time was 90min
  • water-cooled after tempering was 910°C
  • the smelting was carried out in a 500kg vacuum induction furnace.
  • the molten steel obtained by smelting was mold-cast into ingots, and the ingots were heated and then forged.
  • the heating temperature was controlled to be 1080°C
  • the subsequent forging was carried out after holding for 24 hours.
  • the final forging temperature was controlled to be 980°C, and the final forging was forged into ⁇ 90mm bars, which were piled up and slowly cooled after forging.
  • the quenching heating temperature was 870°C
  • the holding time was 135min
  • the tempering temperature was 560°C
  • the tempering time was 120min
  • air cooling was performed after tempering.
  • the ingot is obtained by die casting.
  • the ingot is heated in a step-by-step manner. First, it is heated to 620°C in the preheating section, and then continued to be heated to 950°C in the first heating section. After insulation, it is continued to be heated to 1200°C in the second heating section. After insulation for 9 hours, it enters the soaking section and then undergoes subsequent rolling.
  • the billet is removed from the heating furnace and descaled by high-pressure water before rolling begins.
  • the final rolling temperature is controlled to be 970°C, and finally rolled into a ⁇ 120mm bar. Air cooling after rolling.
  • the quenching heating temperature is 850°C
  • the insulation time is 200min
  • the tempering temperature is 530°C
  • the tempering time is 200min
  • air cooling is performed after tempering.
  • the steel is smelted in a converter, refined and vacuum treated, and then cast into a mold casting billet.
  • the billet is heated to 1180°C and kept warm for 12 hours before subsequent rolling.
  • the billet is rolled after being descaled by high-pressure water after leaving the heating furnace, and rolled into an intermediate billet.
  • the final rolling temperature is controlled to be 1010°C, and the size of the intermediate billet is 220mm ⁇ 220mm.
  • the intermediate billet is heated to 1080°C, kept warm for 24 hours, and then removed from the furnace and descaled by high-pressure water before rolling.
  • the final rolling temperature of the intermediate billet is controlled to be 900°C, and the specification of the finished bar is ⁇ 80mm.
  • the quenching heating temperature is 870°C
  • the holding time is 120min
  • the tempering temperature is 550°C
  • the tempering time is 100min
  • air cooling is performed after tempering.
  • the quenching heating temperature is 890°C
  • the holding time is 150min
  • the tempering temperature is 640°C
  • the tempering time is 135min
  • air cooling is carried out after tempering.
  • the final rolling temperature is controlled to be 1050°C, and the intermediate billet size is obtained to be 260mm ⁇ 260mm, and air cooling is performed after rolling. Then the intermediate billet is heated to 680°C in the preheating section, 1050°C in the first heating section, and 1250°C in the second heating section. After insulation for 6h, it enters the soaking section, and starts rolling after being descaled by high-pressure water after leaving the furnace.
  • the final rolling temperature of the intermediate billet is controlled to be 950°C, and the finished bar specification is ⁇ 80mm. After rolling, it is air-cooled, and then ultrasonic and magnetic particle inspections are performed.
  • the quenching heating temperature is 880°C, the holding time is 120 minutes, the tempering temperature is 560°C, the tempering time is 100 minutes, and air-cooling is performed after tempering.
  • the final rolling temperature of the intermediate billet is controlled to be 850°C, and the specification of the finished bar is ⁇ 30mm. After rolling, it is air-cooled, and then normalized at 870°C, and non-destructive inspection is carried out by ultrasonic flaw detection and magnetic particle flaw detection.
  • the quenching heating temperature is 830°C
  • the holding time is 50min
  • the tempering temperature is 540°C
  • the tempering time is 30min
  • smelting was carried out in a 50kg vacuum induction furnace.
  • the molten steel was mold-cast into ingots, heated and forged to form blanks.
  • the heating temperature was 1050°C, and forging was carried out after holding for 5 hours.
  • the final forging temperature was controlled at 860°C, and finally forged into bars with a diameter of ⁇ 50mm.
  • air cooling was carried out.
  • the quenching heating temperature was 860°C
  • the holding time was 75min
  • the tempering temperature was 550°C
  • the tempering time was 60min
  • water cooling was carried out after tempering.
  • smelting was carried out in a 150kg vacuum induction furnace.
  • the molten steel was molded into an ingot, heated and forged to form a blank.
  • the heating temperature was 1180°C, and the forging was carried out after holding for 12 hours.
  • the final forging temperature was controlled at 960°C, and the final forging was forged into a ⁇ 70mm bar, which was then air-cooled.
  • the quenching heating temperature was 900°C, the holding time was 100min, the tempering temperature was 600°C, the tempering time was 90min, and the tempering was water-cooled after tempering.
  • the steel was smelted in a 500kg vacuum induction furnace.
  • the molten steel was mold-cast into an ingot, heated and forged to form a blank.
  • the heating temperature was 1080°C, and the forging was carried out after holding for 20 hours.
  • the final forging temperature was controlled at 980°C, and the final forging was forged into a ⁇ 90mm bar, and then pile-cooled.
  • Annealing at 640°C.
  • the quenching heating temperature was 870°C
  • the holding time was 135min
  • the tempering temperature was 560°C
  • the tempering time was 120min
  • air cooling was performed after tempering.
  • the commercially available round steel is selected and heat-treated, wherein the quenching heating temperature is 900°C, the holding time is 100 minutes, the tempering temperature is 600°C, the tempering time is 90 minutes, and the tempering is followed by water cooling.
  • Table 2-1 and Table 2-2 list the specific process parameters of Examples 1-8 and Comparative Examples 1-4 in the above manufacturing method.
  • the rolled round steels of Examples 1-8 and Comparative Examples 1-4 (the rolled round steel in Comparative Example 4 refers to commercially available round steel that has not been heat treated) were sampled respectively, and metallographic specimens were prepared in accordance with GB/T 13298-2015, and the microstructure was analyzed with reference to GB/T 13299-1991.
  • the sample steels of each embodiment and comparative example were further water quenched after being kept at 910°C for 4 hours, and the austenite grain size was evaluated in accordance with standard ASTM E112-10 after sample preparation.
  • the relevant test and analysis results are listed in Table 3 below.
  • Table 3 lists the metallographic structure analysis results of the round steels of Examples 1-8 and Comparative Examples 1-4.
  • the rolled microstructure of the steels of Examples 1-8 is bainite + martensite and/or retained austenite, and contains nano-scale precipitates, the volume phase ratio of bainite is ⁇ 60%, and the austenite grain size is ⁇ 6.
  • the finished round steels of Examples 1-8 were sampled respectively, and metallographic specimens were prepared in accordance with GB/T 13298-2015.
  • the microstructure was analyzed with reference to GB/T 13299-1991. It was found that after quenching + tempering heat treatment, a microstructure mainly composed of tempered troostite containing nano-scale precipitates was formed.
  • the inventors further sampled the prepared finished steels of Examples 1-8 and Comparative Examples 1-4, prepared the samples according to GB/T 2975-2018 "Sampling location and specimen preparation for mechanical properties test of steel and steel products", and conducted tensile tests according to GB/T 228.1-2010 "Tensile test of metallic materials Part 1: Room temperature test method", and measured the tensile strength R m , yield strength R p0.2 and elongation A.
  • GB/T 229-2007 Chargepy pendulum impact test method for metallic materials was used to test the Charpy impact energy A kv of each embodiment and comparative example at room temperature and -40°C. The test results are shown in Table 4.
  • the engineering field usually uses the change in tensile test surface shrinkage under environmental conditions to reflect the tendency of stress corrosion.
  • the requirements for hydrogen embrittlement sensitivity in this invention are in accordance with GB/T 2975-2018 "Steel and Steel Products Mechanical Properties Test Sampling Location and Sample Preparation" to prepare circular cross-section specimens with a diameter of 10 mm.
  • the tensile test is carried out in accordance with the national standard GB/T 228.1-2010, with a strain rate of ⁇ 0.0003/s to obtain the cross-sectional shrinkage Z, and the hydrogen embrittlement resistance coefficient ⁇ (Z) is defined to evaluate the hydrogen-induced cracking resistance of steel:
  • Z1 represents the cross-sectional shrinkage rate obtained after the round steel is subjected to a tensile test after dehydrogenation treatment at 250°C for 2h
  • Z2 represents the cross-sectional shrinkage rate obtained after the tensile test of the round steel.
  • Table 4 Based on the hydrogen embrittlement resistance coefficient ⁇ (Z) designed by the present invention, the larger the hydrogen embrittlement resistance coefficient ⁇ (Z), the smaller the stress corrosion tendency of the steel, and the better its hydrogen embrittlement resistance and stress corrosion resistance.
  • Table 4 lists the performance test results of Examples 1-8 and Comparative Examples 1-4.
  • the yield strength R p0.2 of the high-strength and toughness steel materials of the present invention is higher than 1000MPa
  • tensile strength R m is higher than 1150MPa
  • section shrinkage Z is greater than 50%
  • room temperature Charpy impact energy A kv ⁇ 60J, -40°C low temperature Charpy impact energy A kv is greater than 30J
  • hydrogen embrittlement resistance coefficient ⁇ (Z) is greater than 0.85.
  • the chemical element composition design of Comparative Examples 1-4 does not meet the design requirements of the present invention.
  • the carbon content of Comparative Example 1 is low, and its tensile strength is also low;
  • the hydrogen embrittlement resistance coefficient of Comparative Example 2 is low, because more Mn elements are added, although the strength is improved, the stress corrosion resistance is insufficient;
  • the low-temperature impact energy of the steel materials of Comparative Examples 3 and Comparative Example 4 is low, and the microalloy coefficient of Comparative Example 3 is low, and its austenite grain size is not ideal, where 6 (1) means that the average grain size is 6, but double grain size appears, and there are coarse grains of level 1, which has an adverse effect on low-temperature toughness;
  • the carbon content of Comparative Example 4 is high, and although the tensile strength of the steel material is improved, the toughness is insufficient, the stress corrosion cracking effect is not good, and the fatigue performance cannot meet the use requirements.

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Abstract

Disclosed in the present invention is stress-corrosion-resistant high-strength and high-toughness medium carbon steel. The medium carbon steel contains Fe and inevitable impurities, and further contains the following chemical elements in percentages by mass: C: 0.37-0.43%, Si: 0.10-0.40%, Mn: 0.50-0.90%, Cr: 0.60-1.25%, Ni: 1.30-2.00%, Mo: 0.15-0.30%, Al: 0.02-0.05% and Nb: 0.001-0.030%. Correspondingly, further provided in the present invention is a manufacturing method for the stress-corrosion-resistant high-strength and high-toughness medium carbon steel. The steel of the present invention has good impact toughness, elongation and surface shrinkage, also has stress corrosion cracking resistance, and has good weather resistance and fatigue resistance.

Description

一种耐应力腐蚀的高强韧中碳钢及其制造方法A kind of high-strength and tough medium carbon steel resistant to stress corrosion and its manufacturing method 技术领域Technical Field

本发明涉及一种钢材及其制造方法，尤其涉及一种中碳钢及其制造方法。The present invention relates to a steel material and a manufacturing method thereof, and in particular to a medium carbon steel and a manufacturing method thereof.

背景技术Background Art

高强韧钢棒材通常应用于高安全性机械及结构类部件，如风电紧固件等关键易损件，应具有高强度、高韧型、耐应力腐蚀及高疲劳性能等。High-strength and toughness steel bars are usually used in high-safety machinery and structural components, such as wind power fasteners and other key vulnerable parts. They should have high strength, high toughness, stress corrosion resistance and high fatigue performance.

在现有技术中，通常选取适当的化学成分，采用控制轧制控制冷却或淬火+回火工艺，生产高强韧钢材。其中，采用控轧控冷方式生产高强度钢材，由于在轧制和冷却过程中控制难度较大，影响钢力学性能的整体均匀性。采用淬火+回火工艺生产高强度钢材，通过优化合金元素和碳元素的含量，提高钢的淬透性，使钢在冷却过程中形成马氏体组织。以马氏体为主的高强度钢材位错密度大，导致冲击韧性较差，而且在拉伸过程中出现微小缺陷如微裂纹的情况下会迅速断裂失效，断裂韧性较低。In the prior art, appropriate chemical compositions are usually selected, and controlled rolling, controlled cooling or quenching + tempering processes are used to produce high-strength and tough steel. Among them, the controlled rolling and controlled cooling method is used to produce high-strength steel. Since it is difficult to control during the rolling and cooling processes, it affects the overall uniformity of the mechanical properties of the steel. The quenching + tempering process is used to produce high-strength steel. By optimizing the content of alloy elements and carbon elements, the hardenability of the steel is improved, and a martensitic structure is formed during the cooling process. High-strength steels mainly composed of martensite have a large dislocation density, resulting in poor impact toughness, and will quickly break and fail if tiny defects such as microcracks appear during the tensile process, and the fracture toughness is low.

此外，Cr-Ni-Mo系中碳低合金钢因具有良好的强韧性而广泛应用于工程机械、汽车、桥梁、海洋装备等领域，其安全使用强度级别不超过1000MPa，而更高强度级别钢的应用，不仅可以使得装备轻量化，而且还可以节约资源。然而，随着钢强度级别的提高，加工制造难度增大，其氢脆敏感性势必会增加。In addition, Cr-Ni-Mo medium carbon low alloy steel is widely used in engineering machinery, automobiles, bridges, marine equipment and other fields due to its good strength and toughness. Its safe use strength level does not exceed 1000MPa, and the application of higher strength steel can not only make the equipment lighter, but also save resources. However, as the strength level of steel increases, the difficulty of processing and manufacturing increases, and its hydrogen embrittlement sensitivity is bound to increase.

公开号为CN102242322A，公开日为2011年11月16日，名称为“一种改进型40CrNiMo钢及其制备方法”的中国专利文献公开了一种中碳钢，其化学元素重量％为：0.37～0.45％的C，1.65～1.85％的Cr，0.45～0.65％的Ni，0.15～0.25％的Mo，0.90～1.20％的Mn，0.40～0.55％的Si，0.0025～0.0045％的B，0.22～0.28％的N，0.007～0.012％的Ca，0.002～0.005％的Mg，0.03～0.06％的Nb，0.04～0.08％的Ti，0.02～0.06％的RE，≤0.015％的S和≤0.025％的P和≤0.0008％的Al，Fe为余量。该钢材的抗拉强度≥1195MPa，冲击功优于85J，但是其不涉及耐应力腐蚀性能。 A Chinese patent document with publication number CN102242322A and publication date of November 16, 2011, entitled “An improved 40CrNiMo steel and its preparation method” discloses a medium carbon steel, wherein the chemical elements by weight are: 0.37-0.45% C, 1.65-1.85% Cr, 0.45-0.65% Ni, 0.15-0.25% Mo, 0.90-1.20% Mn, 0. .40～0.55% Si, 0.0025～0.0045% B, 0.22～0.28% N, 0.007～0.012% Ca, 0.002～0.005% Mg, 0.03～0.06% Nb, 0.04～0.08% Ti, 0.02～0.06% RE, ≤0.015% S and ≤0.025% P and ≤0.0008% Al, Fe is the balance. The tensile strength of the steel is ≥1195MPa, and the impact energy is better than 85J, but it does not involve stress corrosion resistance.

公开号为CN104726783A，公开日为2015年6月24日，名称为“一种风电偏航、变桨轴承套圈用钢及其制备方法”的中国专利文献公开了一种钢材，其化学成分质量百分比为：C：0.37～0.42、Mn：0.50～0.80、Mo：0.20～0.30、Ni：1.30～1.70、Cr：：0.70～1.00、Si：0.20～0.50、Al酸溶：0.035～0.055、V：0.07～0.12、N：≤0.004、O：≤0.0008、H：≤0.00015、S：≤0.010、P：≤0.015，其余部分为Fe和少量杂质。上述风电偏航、变桨轴承套圈的制备方法是对加工成的风电偏航、变桨轴承套圈进行热处理，首先加热到860～890℃温度保温3-5h进行奥氏体化后油淬处理，然后再加热到580～630℃温度保温3-5h油冷至室温。该钢具有优异的淬透性，各项力学性能完全达到大功率风电偏航和变桨轴承用钢的标准和使用要求。但是，该钢种也不涉及耐应力腐蚀性能。A Chinese patent document with publication number CN104726783A and publication date June 24, 2015, entitled “A steel for wind power yaw and pitch bearing ring and preparation method thereof” discloses a steel material whose chemical composition by mass percentage is: C: 0.37-0.42, Mn: 0.50-0.80, Mo: 0.20-0.30, Ni: 1.30-1.70, Cr: 0.70-1.00, Si: 0.20-0.50, Al acid solution: 0.035-0.055, V: 0.07-0.12, N: ≤0.004, O: ≤0.0008, H: ≤0.00015, S: ≤0.010, P: ≤0.015, and the rest is Fe and a small amount of impurities. The preparation method of the above-mentioned wind turbine yaw and pitch bearing ring is to heat treat the processed wind turbine yaw and pitch bearing ring, first heat it to 860-890℃ and keep it for 3-5h to austenitize and then oil quench it, then heat it to 580-630℃ and keep it for 3-5h and oil cool it to room temperature. The steel has excellent hardenability, and all mechanical properties fully meet the standards and use requirements of steel for high-power wind turbine yaw and pitch bearing. However, this steel type does not involve stress corrosion resistance.

此外，从上述现有技术可以看出，在当前现有技术中，为了获得高性能的中碳合金钢，本领域技术人员采用增加大量合金元素或添加B、Nb、Mg、稀土等微合金元素提升强度，改善性能，并以此来获得高性能的中碳合金钢。但是这种添加较大含量合金元素的设计方案，很容易增加制造成本，并且钢中合金元素含量过高时，会形成粗大的碳化物颗粒，如Cr、Mo、V、Ti的碳化物等，降低钢材的冲击韧性。In addition, it can be seen from the above-mentioned prior art that in the current prior art, in order to obtain high-performance medium-carbon alloy steel, those skilled in the art adopt the method of adding a large amount of alloying elements or adding micro-alloying elements such as B, Nb, Mg, rare earth, etc. to improve strength and performance, and thereby obtain high-performance medium-carbon alloy steel. However, this design scheme of adding a large content of alloying elements is likely to increase the manufacturing cost, and when the content of alloying elements in the steel is too high, coarse carbide particles such as carbides of Cr, Mo, V, and Ti will be formed, which will reduce the impact toughness of the steel.

此外，针对潮湿的服役环境条件，Cr-Ni-Mo系中碳低合金钢零部件承受大载荷以及动态冲击，容易出现应力腐蚀，严重地可发生脆性断裂，造成巨大的经济损失甚至出现安全事故。In addition, in humid service environment conditions, Cr-Ni-Mo medium-carbon low-alloy steel parts are subjected to large loads and dynamic impacts, and are prone to stress corrosion. In severe cases, brittle fracture may occur, causing huge economic losses and even safety accidents.

基于此，希望获得一种具有耐应力腐蚀性能的高强韧中碳钢。Based on this, it is hoped to obtain a high-strength and tough medium-carbon steel with stress corrosion resistance.

发明内容Summary of the invention

本发明的目的之一在于提供一种耐应力腐蚀的高强韧中碳钢，该钢材具有良好的冲击韧性和延伸率及面缩率，可抗应力腐蚀开裂并有良好的耐候性和抗疲劳性能，可用于工程机械及海洋工程等需要高强韧钢材的场合。One of the purposes of the present invention is to provide a high-strength and tough medium carbon steel resistant to stress corrosion. The steel has good impact toughness, elongation and area reduction, can resist stress corrosion cracking and has good weather resistance and fatigue resistance. It can be used in occasions such as engineering machinery and marine engineering that require high-strength and tough steel.

为了实现上述目的，本发明提出了一种耐应力腐蚀的高强韧中碳钢，其含有Fe和不可避免的杂质，此外其还含有质量百分含量如下的下述各化学元素：In order to achieve the above object, the present invention provides a high-strength and tough medium carbon steel resistant to stress corrosion, which contains Fe and inevitable impurities, and further contains the following chemical elements in the following mass percentages:

C：0.37～0.43％、Si：0.10～0.40％、Mn：0.50～0.90％、Cr：：0.60～1.25％、Ni：1.30～2.00％、Mo：0.15～0.30％、Al：0.02～0.05％、Nb：0.001～0.030％。C: 0.37～0.43%, Si: 0.10～0.40%, Mn: 0.50～0.90%, Cr: 0.60～1.25%, Ni: 1.30～2.00%, Mo: 0.15～0.30%, Al: 0.02～0.05%, Nb: 0.001～0.030%.

相应地，本发明还提供了一种耐应力腐蚀的高强韧中碳钢，其各化学元素 质量百分含量为：Accordingly, the present invention also provides a high-strength and tough medium carbon steel resistant to stress corrosion, wherein each chemical element The mass percentage is:

C：0.37～0.43％、Si：O.10～0.40％、Mn：0.50～0.90％、Cr：0.60～1.25％、Ni：1.30～2.00％、Mo：0.15～0.30％、A1：0.02～0.05％、Nb：0.001～0.030％；余量为Fe和不可避免的杂质。C: 0.37～0.43%, Si: 0.10～0.40%, Mn: 0.50～0.90%, Cr: 0.60～1.25%, Ni: 1.30～2.00%, Mo: 0.15～0.30%, A1: 0.02～0.05%, Nb: 0.001～0.030%; the balance is Fe and unavoidable impurities.

在本发明所述的耐应力腐蚀的高强韧中碳钢中的各化学元素成分设计原理如下：The design principles of the chemical elements in the stress corrosion resistant high-strength and tough medium carbon steel of the present invention are as follows:

C：可以提高钢材的淬透性，使钢在淬火冷却过程中形成硬度较高的相变组织。C含量提高，则会提高硬质相比例，提高钢材的硬度，但会导致韧性下降。C含量太低，难以获得较高的强度。基于此，本发明控制C含量为0.37～0.43％。C: can improve the hardenability of steel, so that the steel forms a phase transformation structure with higher hardness during the quenching and cooling process. If the C content is increased, the hard phase ratio will be increased, and the hardness of the steel will be increased, but the toughness will be reduced. If the C content is too low, it is difficult to obtain a higher strength. Based on this, the present invention controls the C content to 0.37-0.43%.

Si：在钢中有益于强度提升，适量的Si在回火时可避免形成粗大的碳化物，但较高的Si含量会降低钢材的冲击韧性。基于此，本发明采用低Si成分体系，限定Si含量为：0.10～0.40％。Si: It is beneficial to improve the strength of steel. A proper amount of Si can avoid the formation of coarse carbides during tempering, but a higher Si content will reduce the impact toughness of the steel. Based on this, the present invention adopts a low Si component system and limits the Si content to 0.10-0.40%.

Mn：在钢中主要以固溶形式存在，可提高钢的淬透性，淬火时形成高强度的低温相变组织，所得钢材具有良好的耐磨性。然而Mn含量过高会导致形成较多的残留奥氏体，降低钢的屈服强度，并容易导致中心偏析。基于此，本发明控制Mn含量为：0.50～0.90％。Mn: It exists in steel mainly in the form of solid solution, which can improve the hardenability of steel and form a high-strength low-temperature phase transformation structure during quenching. The resulting steel has good wear resistance. However, too high a Mn content will lead to the formation of more retained austenite, reduce the yield strength of the steel, and easily cause center segregation. Based on this, the present invention controls the Mn content to be: 0.50-0.90%.

Cr：可以提高钢的淬透性，形成硬化的马氏体组织，提高钢材强度。然而Cr含量过高，会形成粗大的碳化物，降低冲击性能。基于此，本发明控制Cr含量为：0.60～1.25％。Cr: can improve the hardenability of steel, form hardened martensite structure, and improve the strength of steel. However, if the Cr content is too high, coarse carbides will be formed, which will reduce the impact performance. Based on this, the present invention controls the Cr content to: 0.60-1.25%.

Ni：在钢中以固溶形式存在，可提高钢的低温冲击性能。但过高的Ni含量会导致钢材中的残留奥氏体含量过高，而降低钢的强度。基于此，本发明控制Ni含量为：1.30～2.00％。Ni: exists in the steel in the form of solid solution, which can improve the low-temperature impact performance of the steel. However, too high a Ni content will lead to too high a content of retained austenite in the steel, thereby reducing the strength of the steel. Based on this, the present invention controls the Ni content to be: 1.30-2.00%.

Mo：可在钢中固溶，并有利于提高钢的淬透性，提高钢材强度。在较高的温度回火，会形成细小的碳化物进一步提高钢的强度。考虑贵重合金Mo元素的成本，本发明控制Mo含量为：0.15～0.30％。Mo: can be dissolved in steel and is beneficial to improving the hardenability and strength of steel. When tempered at a higher temperature, fine carbides will be formed to further improve the strength of steel. Considering the cost of precious alloy Mo element, the present invention controls the Mo content to be: 0.15-0.30%.

Al：在钢中形成细小的AlN析出物，可抑制奥氏体晶粒长大。然而Al含量过高会导致较大的Al的氧化物形成，粗大的AlN硬质夹杂会降低钢的冲击韧性和疲劳性能。基于此，本发明控制Al含量为：0.02～0.05％。Al: forms fine AlN precipitates in steel, which can inhibit the growth of austenite grains. However, too high Al content will lead to the formation of larger Al oxides, and coarse AlN hard inclusions will reduce the impact toughness and fatigue properties of the steel. Based on this, the present invention controls the Al content to 0.02-0.05%.

Nb：Nb加入钢中形成细小析出相，起到对钢再结晶的抑制作用，可以细 化晶粒。然而Nb含量过高则在冶炼过程中会形成粗大的NbC颗粒，反而降低冲击韧性。晶粒细化在提高钢的力学性能尤其是强度和韧性方面有重要的作用，更重要的是，在本发明中，晶粒细化还有助于降低钢的氢脆敏感性。基于此，本发明控制Nb含量为：0.001～0.030％。Nb: Nb is added to steel to form fine precipitates, which inhibits the recrystallization of steel. However, if the Nb content is too high, coarse NbC particles will be formed during the smelting process, which will reduce the impact toughness. Grain refinement plays an important role in improving the mechanical properties of steel, especially strength and toughness. More importantly, in the present invention, grain refinement also helps to reduce the hydrogen embrittlement sensitivity of steel. Based on this, the present invention controls the Nb content to be: 0.001-0.030%.

进一步地，在本发明所述的耐应力腐蚀的高强韧中碳钢中，其还含有下述各化学元素的至少其中之一：0＜Cu≤0.3％、0＜V≤0.06％、0＜Ti≤0.03％、0＜Ca≤0.003％。Furthermore, the high-strength and tough medium carbon steel resistant to stress corrosion described in the present invention also contains at least one of the following chemical elements: 0＜Cu≤0.3%, 0＜V≤0.06%, 0＜Ti≤0.03%, 0＜Ca≤0.003%.

Cu：进一步可选地添加Cu可以提高钢材的强度，并有利于提高钢材的耐腐蚀能力。然而如果Cu含量过高，在加热过程中会富集在晶界，导致晶界弱化以致开裂。基于此，本发明可以选择添加Cu，并控制其上限为0.30％。Cu: Further optional addition of Cu can improve the strength of the steel and help improve the corrosion resistance of the steel. However, if the Cu content is too high, it will be enriched in the grain boundaries during the heating process, resulting in weakening of the grain boundaries and cracking. Based on this, the present invention can choose to add Cu, and control its upper limit to 0.30%.

Ca：Ca元素添加到钢中，可以改善硫化物夹杂的尺寸和形貌，避免冲击韧性恶化。基于此，本发明可以选择添加Ca，并控制其上限为0.003％。Ca: Ca element is added to steel to improve the size and morphology of sulfide inclusions and avoid deterioration of impact toughness. Based on this, the present invention can choose to add Ca and control its upper limit to 0.003%.

V：V在钢中可与C或N形成析出物，提高钢的强度。如果C和V含量过高，则会形成粗大的VC颗粒。基于此，本发明可以选择添加V，并控制其上限为0.06％。V: V can form precipitates with C or N in steel to improve the strength of the steel. If the C and V content is too high, coarse VC particles will be formed. Based on this, the present invention can choose to add V, and control its upper limit to 0.06%.

Ti：Ti加入钢中，可以形成细小析出相，但Ti含量过高则在冶炼过程中会形成粗大的带棱角的TiN颗粒，降低冲击韧性。基于此，本发明可以选择添加Ti，并控制其上限为≤0.03％。Ti: Ti can form fine precipitates when added to steel, but if the Ti content is too high, coarse and angular TiN particles will be formed during the smelting process, reducing the impact toughness. Based on this, the present invention can choose to add Ti, and control its upper limit to ≤0.03%.

进一步地，在本发明所述的耐应力腐蚀的高强韧中碳钢的不可避免的杂质中，N≤0.012％、O≤0.002％、H≤0.0002％、P≤0.02％、S≤0.015％，并且P+S≤0.03％。Furthermore, among the inevitable impurities of the stress corrosion resistant high-strength and tough medium carbon steel of the present invention, N≤0.012%, O≤0.002%, H≤0.0002%, P≤0.02%, S≤0.015%, and P+S≤0.03%.

本发明中不可避免的杂质主要是P、S、N、O和H，在技术条件允许的情况下，期望其含量越低越好。其中：The inevitable impurities in the present invention are mainly P, S, N, O and H. Under the condition that technical conditions permit, it is expected that the content of these impurities is as low as possible. Among them:

P在钢中晶界处偏聚，会降低晶界结合能，恶化钢的冲击韧性。优选地控制其上限为0.020％。P is concentrated at the grain boundaries in steel, which reduces the grain boundary bonding energy and deteriorates the impact toughness of the steel. The upper limit of P is preferably controlled to 0.020%.

S在钢中会发生偏聚，且形成较多的硫化物夹杂，降低抗冲击性能。优选地控制其上限为0.015％。S will segregate in the steel and form more sulfide inclusions, which will reduce the impact resistance. The upper limit is preferably controlled to 0.015%.

此外，为了进一步提升耐应力腐蚀性能，本发明优选地控制P+S的质量百分含量总量≤0.030％。In addition, in order to further improve the stress corrosion resistance, the present invention preferably controls the total mass percentage of P+S to ≤0.030%.

N为间隙原子，同时也是MX型析出物形成元素，为了避免N元素在钢中 富集，优选地本发明控制其上限为0.012％。N is an interstitial atom and also an element that forms MX-type precipitates. In order to avoid N in steel The enrichment, preferably, the upper limit of the present invention is controlled to be 0.012%.

H会在钢中缺陷处聚集，为了防止发生氢致延迟断裂，若抗拉强度超过1150MPa，控制H含量上限为0.0002％。H will accumulate at defects in steel. In order to prevent hydrogen-induced delayed fracture, if the tensile strength exceeds 1150 MPa, the upper limit of H content is controlled to 0.0002%.

O会与钢中的Al形成氧化物以及复合氧化物，为了保证钢组织均匀性和低温冲击功级疲劳性能，本发明优选地控制O含量上限为0.0020％。O will form oxides and composite oxides with Al in the steel. In order to ensure uniformity of steel structure and low-temperature impact energy level fatigue performance, the present invention preferably controls the upper limit of O content to 0.0020%.

进一步地，在本发明所述的耐应力腐蚀的高强韧中碳钢中，其中各元素还满足：Mn+Cr+Ni+Mo+Cu≤4.0，式中各化学元素均代入该化学元素质量百分含量的百分号前面的数值。Furthermore, in the stress corrosion resistant high-strength and tough medium carbon steel described in the present invention, each element also satisfies: Mn+Cr+Ni+Mo+Cu≤4.0, where each chemical element is substituted into the value before the percentage sign of the mass percentage content of the chemical element.

进一步地，在本发明所述的耐应力腐蚀的高强韧中碳钢中，其微合金元素系数rM/N的范围为：1.0～5.9，其中，rM/N＝([Al]/2+[Nb]/6+[Ti]/4)/[N]，式中各化学元素均代入该化学元素质量百分含量的百分号前面的数值。此外，本发明要求微合金元素总量与氮元素的原子比超过1，所述微合金元素为Al、Nb和Ti。Further, in the stress corrosion resistant high-strength medium carbon steel of the present invention, the microalloying element coefficient r M/N ranges from 1.0 to 5.9, wherein r M/N =([Al]/2+[Nb]/6+[Ti]/4)/[N], wherein each chemical element is substituted into the numerical value before the percentage sign of the mass percentage of the chemical element. In addition, the present invention requires that the atomic ratio of the total amount of microalloying elements to nitrogen element exceeds 1, and the microalloying elements are Al, Nb and Ti.

进一步地，在本发明所述的耐应力腐蚀的高强韧中碳钢中，其耐大气腐蚀指数I≥7.0，其中：Furthermore, in the stress corrosion resistant high-strength and tough medium carbon steel of the present invention, its atmospheric corrosion resistance index I≥7.0, wherein:

I＝26.0[Cu]+3.9[Ni]+1.2[Cr]+1.5[Si]+17.3[P]-7.3[Cu][Ni]-9.1[Ni][P]-33.4[Cu]2 I＝26.0[Cu]+3.9[Ni]+1.2[Cr]+1.5[Si]+17.3[P]-7.3[Cu][Ni]-9.1[Ni][P]-33.4[Cu] 2

式中各化学元素均代入该化学元素质量百分含量的百分号前面的数值。In the formula, each chemical element is substituted into the value before the percentage sign of the mass percentage content of the chemical element.

进一步地，本发明所述的耐应力腐蚀的高强韧中碳钢的轧态微观组织为贝氏体+马氏体和/或残余奥氏体，并且含有纳米级析出物，其中贝氏体的体积相比例≥60％。本发明中，轧态是指钢处于锻造或轧制之后、热处理(例如淬火+回火)之前的状态。Furthermore, the rolled microstructure of the stress corrosion resistant high-strength medium carbon steel of the present invention is bainite + martensite and/or residual austenite, and contains nano-scale precipitates, wherein the volume phase ratio of bainite is ≥ 60%. In the present invention, the rolled state refers to the state of the steel after forging or rolling and before heat treatment (such as quenching + tempering).

进一步地，本发明所述高强韧中碳低合金钢经过淬火+回火热处理后的显微组织主体为细晶粒回火索氏体，并且含有纳米级析出物。Furthermore, the microstructure of the high-strength and tough medium-carbon low-alloy steel after quenching and tempering heat treatment is mainly fine-grained tempered troostite and contains nano-scale precipitates.

通常认为不同组织对氢脆敏感性从大到小的排序为：原始马氏体＞低温回火的马氏体＞带有原始马氏体位向的回火屈氏体＞贝氏体＞回火索氏体(高温回火)。本发明采用特定的化学成分设计，充分利用各种合金元素及微合金元素对相变和微观组织的影响，经淬火+回火热处理后，形成主体为回火索氏体的微观组织，含有纳米级析出物，同时控制杂质含量，以保证钢的强度、冲击韧性、延伸率和塑性，并具有良好的耐候性、耐磨性和抗应力腐蚀性能及抗疲劳性能。 It is generally believed that the sensitivity of different structures to hydrogen embrittlement is ranked from large to small as follows: original martensite> low temperature tempered martensite> tempered troostite with original martensite orientation>bainite> tempered troostite (high temperature tempering). The present invention adopts a specific chemical composition design, fully utilizing the influence of various alloy elements and microalloy elements on phase transformation and microstructure, and after quenching + tempering heat treatment, a microstructure with tempered troostite as the main body is formed, containing nano-scale precipitates, and at the same time controlling the impurity content to ensure the strength, impact toughness, elongation and plasticity of the steel, and has good weather resistance, wear resistance, stress corrosion resistance and fatigue resistance.

进一步地，在本发明所述的耐应力腐蚀的高强韧中碳钢中，其奥氏体晶粒度≥6级。Furthermore, in the stress corrosion resistant high-strength and tough medium carbon steel described in the present invention, the austenite grain size is ≥ grade 6.

进一步地，本发明所述的耐应力腐蚀的高强韧中碳钢，其屈服强度Rp0.2≥1000MPa，抗拉强度Rm≥1150MPa，延伸率A≥12％，断面收缩率Z≥50％，室温夏比冲击功Akv≥60J，-40℃夏比冲击功Akv≥30J，抗氢脆系数η(Z)≥O.85。Furthermore, the high-strength and tough medium carbon steel resistant to stress corrosion described in the present invention has a yield strength R p0.2 ≥1000MPa, a tensile strength R m ≥1150MPa, an elongation A ≥12%, a cross-sectional shrinkage Z ≥50%, a room temperature Charpy impact energy A kv ≥60J, a -40°C Charpy impact energy A kv ≥30J, and an anti-hydrogen embrittlement coefficient η(Z) ≥O.85.

在一些实施方案中，本发明所述的耐应力腐蚀的高强韧中碳钢，其屈服强度Rp0.2≥1020MPa，抗拉强度Rm≥1150MPa，延伸率A≥12％，断面收缩率Z≥55％，室温夏比冲击功Akv≥65J，-40℃夏比冲击功Akv≥35J，抗氢脆系数η(Z)≥0.89。In some embodiments, the high-strength and tough medium-carbon steel resistant to stress corrosion described in the present invention has a yield strength R p0.2 ≥1020MPa, a tensile strength R m ≥1150MPa, an elongation A ≥12%, a cross-sectional shrinkage Z ≥55%, a room temperature Charpy impact energy A kv ≥65J, a -40°C Charpy impact energy A kv ≥35J, and an anti-hydrogen embrittlement coefficient η(Z) ≥0.89.

在一些实施方案中，本发明所述的耐应力腐蚀的高强韧中碳钢，其屈服强度Rp0.2为1020～1100MPa，抗拉强度Rm为1150～1200MPa，延伸率A为12～18％，断面收缩率Z为50～65％、如58～65％，室温夏比冲击功Akv为65～100J，-40℃夏比冲击功Akv为35～80J，抗氢脆系数η(Z)为0.89～0.98。In some embodiments, the high-strength and tough medium carbon steel resistant to stress corrosion described in the present invention has a yield strength R p0.2 of 1020 to 1100 MPa, a tensile strength R m of 1150 to 1200 MPa, an elongation A of 12 to 18%, a cross-sectional shrinkage Z of 50 to 65%, such as 58 to 65%, a room temperature Charpy impact energy A kv of 65 to 100 J, a -40°C Charpy impact energy A kv of 35 to 80 J, and an anti-hydrogen embrittlement coefficient η(Z) of 0.89 to 0.98.

本发明的另一目的在于提供一种耐应力腐蚀的高强韧中碳钢的制造方法。Another object of the present invention is to provide a method for manufacturing high-strength and tough medium-carbon steel resistant to stress corrosion.

基于上述发明目的，本发明提供了上文所述的耐应力腐蚀的高强韧中碳钢的制造方法，其包括步骤：Based on the above invention objectives, the present invention provides a method for manufacturing the above-mentioned stress corrosion resistant high-strength and tough medium carbon steel, which comprises the steps of:

(1)冶炼；(1) Smelting;

(2)铸造；(2) Casting;

(3)加热：控制加热温度为1050～1250℃，保温时间为3～24h；(3) Heating: Control the heating temperature to 1050-1250°C and the insulation time to 3-24h;

(4)锻造或轧制：控制终轧温度或终锻温度≥850℃；(4) Forging or rolling: control the final rolling temperature or final forging temperature ≥ 850°C;

(5)淬火+回火，其中淬火温度范围为830～910℃，保温时间为30～200min，然后采用水淬处理；回火温度为530～640℃，保温时间为30～200min，回火后空冷或水冷。(5) Quenching + tempering, where the quenching temperature ranges from 830 to 910 °C, the holding time is 30 to 200 min, and then water quenching is used; the tempering temperature is 530 to 640 °C, the holding time is 30 to 200 min, and air or water cooling is used after tempering.

在一些实施方式中，在步骤(4)中，可以直接轧制或锻造至成品尺寸。In some embodiments, in step (4), rolling or forging may be performed directly to the finished size.

在另外一些实施方式中，在步骤(4)中，先轧制到中间坯尺寸，再进行中间加热，然后轧制到最终成品尺寸；其中，中间加热温度为1050～1250℃，保温时间为3～24h。In some other embodiments, in step (4), the steel is first rolled to an intermediate billet size, then intermediately heated, and then rolled to a final finished product size; wherein the intermediate heating temperature is 1050-1250° C., and the holding time is 3-24 hours.

此外在轧制过程中，钢坯出加热炉经高压水除鳞后开始轧制，轧制后采用空冷或缓冷。In addition, during the rolling process, the steel billet is descaled by high-pressure water after leaving the heating furnace and then begins rolling. After rolling, air cooling or slow cooling is used.

采用上述制造方法获得的高强韧中碳钢可以用于风电紧固件等需要高强 度棒材的场合，棒材的尺寸规格范围可以为Φ20～130mm。The high-strength and tough medium carbon steel obtained by the above manufacturing method can be used for wind power fasteners and other In the case of high-strength bars, the size specification range of the bars can be Φ20～130mm.

在本发明所述的制造方法中，本发明所述的高强韧中碳钢在1050℃～1250℃的加热温度下完全奥氏体化。在加热过程中，Al、Nb、V、Ti的碳化物和氮化物及碳氮化物、Cr和Mo的碳化物部分或全部溶解于奥氏体中，在随后的轧制/锻造和冷却过程中，Al、Nb、V、Ti形成细小的析出物。固溶在奥氏体中的Mn、Cr和Mo可以提高钢的淬透性，并提高马氏体的硬度和强度。In the manufacturing method of the present invention, the high-strength and tough medium carbon steel of the present invention is completely austenitized at a heating temperature of 1050°C to 1250°C. During the heating process, carbides and nitrides of Al, Nb, V, Ti, and carbonitrides, and carbides of Cr and Mo are partially or completely dissolved in austenite, and in the subsequent rolling/forging and cooling processes, Al, Nb, V, and Ti form fine precipitates. Mn, Cr, and Mo dissolved in austenite can improve the hardenability of steel and improve the hardness and strength of martensite.

然后，在终轧或终锻温度≥850℃的条件下，形成具有细化的贝氏体+少量马氏体和/或残留奥氏体的基体组织，且有细小弥散的纳米级析出物。Then, under the condition of final rolling or final forging temperature ≥ 850°C, a matrix structure having refined bainite + a small amount of martensite and/or retained austenite and fine dispersed nano-scale precipitates is formed.

此外，钢材轧制或锻造后加热到830～910℃保温后水淬。加热过程中，碳化物形成元素Al、Nb、V、Ti、Cr和Mo的析出物部分溶解，未溶解的析出物钉扎晶界，抑制奥氏体晶粒粗大，使得奥氏体晶粒度≥6级。在淬火冷却过程中，固溶在奥氏体中的合金元素使得钢材具有高强度和良好的韧性。In addition, after rolling or forging, the steel is heated to 830-910℃ and then quenched in water. During the heating process, the precipitates of carbide-forming elements Al, Nb, V, Ti, Cr and Mo are partially dissolved, and the undissolved precipitates pin the grain boundaries, inhibiting the coarsening of austenite grains, so that the austenite grain size is ≥ 6. During the quenching cooling process, the alloying elements dissolved in austenite give the steel high strength and good toughness.

淬火后的钢在530～640℃做回火热处理，Al、Nb、V、Cr、Ti和Mo会和C、N形成细小的析出物，提高了钢的强度和塑韧性匹配。经淬火+回火热处理后，形成主体为回火索氏体(即回火马氏体)的微观组织，含有纳米级析出物。After quenching, the steel is tempered at 530-640℃. Al, Nb, V, Cr, Ti and Mo will form fine precipitates with C and N, which improves the strength and plasticity of the steel. After quenching + tempering, a microstructure with tempered troostite (tempered martensite) as the main body is formed, containing nano-scale precipitates.

本发明所述的耐应力腐蚀的高强韧中碳钢具有以下有益效果：The stress corrosion resistant high-strength and tough medium carbon steel of the present invention has the following beneficial effects:

本发明所述的耐应力腐蚀的高强韧中碳钢通过合理设计的化学成分并结合优化工艺，开发出高强韧钢材，轧制或锻造好的棒材在淬火后采用回火热处理工艺，形成回火马氏体和少量贝氏体及残留奥氏体的组织，以及细小弥散的析出物，该组织使得钢材具有良好的冲击韧性和延伸率及面缩率，可抗应力腐蚀开裂并有良好的耐候性和抗疲劳性能。The high-strength and tough medium-carbon steel resistant to stress corrosion described in the present invention is developed into a high-strength and tough steel by rationally designing the chemical composition and combining the optimized process. The rolled or forged bars are subjected to a tempering heat treatment process after quenching to form a structure of tempered martensite and a small amount of bainite and residual austenite, as well as fine dispersed precipitates. This structure enables the steel to have good impact toughness, elongation and area reduction, can resist stress corrosion cracking, and has good weather resistance and fatigue resistance.

其中，本发明所述的耐应力腐蚀的高强韧中碳钢，其屈服强度≥1000MPa，抗拉强度Rm≥1150MPa，延伸率A≥12％，断面收缩率Z≥50％，室温夏比冲击功Akv≥60J，-40℃低温夏比冲击功Akv≥30J，抗氢脆系数η(Z)≥0.85。Among them, the high-strength and tough medium carbon steel resistant to stress corrosion described in the present invention has a yield strength ≥1000MPa, a tensile strength R m ≥1150MPa, an elongation A ≥12%, a cross-sectional shrinkage Z ≥50%, a room temperature Charpy impact energy A kv ≥60J, a -40°C low-temperature Charpy impact energy A kv ≥30J, and a hydrogen embrittlement resistance coefficient η(Z) ≥0.85.

本发明所述的耐应力腐蚀的高强韧中碳钢的制造方法的工艺设计合理，工艺窗口宽松，可以在棒材或高速线材产线上实现批量商业化生产。The manufacturing method of the stress corrosion resistant high-strength and tough medium carbon steel of the present invention has a reasonable process design and a wide process window, and can realize batch commercial production on a bar or high-speed wire production line.

具体实施方式DETAILED DESCRIPTION

下面将结合具体的实施例对本发明所述的耐应力腐蚀的高强韧中碳钢及其制造方法做进一步的解释和说明，然而该解释和说明并不对本发明的技术方 案构成不当限定。The following will further explain and illustrate the stress corrosion resistant high-strength medium carbon steel and its manufacturing method in conjunction with specific embodiments of the present invention. However, this explanation and description does not constitute an indirect explanation of the technical aspects of the present invention. The case constitutes improper limitation.

实施例1-8和对比例1-4Examples 1-8 and Comparative Examples 1-4

实施例1-8的耐应力腐蚀的高强韧中碳钢均采用以下步骤制得：The stress corrosion resistant high-strength and tough medium carbon steels of Examples 1-8 were all prepared by the following steps:

(1)按照下述表1-1和表1-2所示的化学成分进行冶炼：在实际操作时，可以采用真空感应炉冶炼、电炉冶炼或转炉冶炼，并经过精炼及真空处理。(1) Smelting is carried out according to the chemical composition shown in the following Table 1-1 and Table 1-2: In actual operation, vacuum induction furnace smelting, electric furnace smelting or converter smelting can be adopted, and then refined and vacuum treated.

(2)铸造：采用模铸或连铸进行铸造，以获得铸锭。(2) Casting: Casting is carried out by mold casting or continuous casting to obtain ingots.

(3)加热：将铸锭放到加热炉内加热，并控制加热温度为1050～1250℃，保温时间为3～24h；其中，在加热时，可以直接升温至加热温度，也可以采用阶梯式升温至加热温度。(3) Heating: The ingot is placed in a heating furnace for heating, and the heating temperature is controlled to be 1050-1250°C, and the insulation time is 3-24 hours; during heating, the temperature can be directly raised to the heating temperature, or the temperature can be raised to the heating temperature in a step-by-step manner.

(4)锻造或轧制：控制终轧温度或终锻温度≥850℃，并在轧后或锻后进行冷却，冷却方式可以为空冷、风冷。(4) Forging or rolling: Control the final rolling temperature or final forging temperature to be ≥850℃, and cool after rolling or forging. The cooling method can be air cooling or wind cooling.

当进行锻造或锻造时，可以直接轧制或锻造至成品尺寸，也可以先轧制到中间坯尺寸，再进行中间加热，然后轧制到最终成品尺寸；当采用上述分段式轧制时，中间坯的中间加热温度可以控制在1050～1250℃之间，保温时间可以控制在为3～24h之间。When forging or forging is performed, it can be directly rolled or forged to the finished product size, or it can be first rolled to the intermediate billet size, then intermediate heated, and then rolled to the final finished product size; when the above-mentioned segmented rolling is adopted, the intermediate heating temperature of the intermediate billet can be controlled between 1050 and 1250°C, and the insulation time can be controlled between 3 and 24 hours.

(5)淬火+回火，其中淬火温度范围为830～910℃，保温时间为30～200min，然后采用水淬处理；回火温度为530～640℃，保温时间为30～200min，回火后空冷或水冷。(5) Quenching + tempering, where the quenching temperature ranges from 830 to 910 °C, the holding time is 30 to 200 min, and then water quenching is used; the tempering temperature is 530 to 640 °C, the holding time is 30 to 200 min, and air or water cooling is used after tempering.

需要说明的是，对比例1-3的制造流程基本与本发明相同，只是其化学成分或具体工艺参数不满足本发明设计要求。对比例4采用的是市售的圆钢。It should be noted that the manufacturing processes of Comparative Examples 1-3 are basically the same as those of the present invention, except that their chemical compositions or specific process parameters do not meet the design requirements of the present invention. Comparative Example 4 uses commercially available round steel.

表1-1列出了实施例1-8的耐应力腐蚀的高强韧中碳钢和对比例1-4的对比钢材的各化学元素的质量百分配比。Table 1-1 lists the mass percentages of the chemical elements of the stress corrosion resistant high-strength and tough medium carbon steels of Examples 1-8 and the comparative steels of Comparative Examples 1-4.

表1-1.(wt.％，余量为Fe和除P、S、O、H和N以外的其他不可避免的杂质)

Table 1-1. (wt.%, the balance is Fe and other inevitable impurities except P, S, O, H and N)

表1-2列出了实施例1-8的耐应力腐蚀的高强韧中碳钢和对比例1-4的对比钢材的成分协同关系。Table 1-2 lists the synergistic relationship between the components of the stress corrosion resistant high strength and toughness medium carbon steels of Examples 1-8 and the comparative steels of Comparative Examples 1-4.

表1-2.
Table 1-2.

注：表1-2中，rM/N＝([Al]/2+[Nb]/6+[Ti]/4)/[N]；Note: In Table 1-2, r M/N = ([Al]/2+[Nb]/6+[Ti]/4)/[N];

I＝26.0[Cu]+3.9[Ni]+1.2[Cr]+1.5[Si]+17.3[P]-7.3[Cu][Ni]-9.1[Ni][P]-33.4[Cu]2 I＝26.0[Cu]+3.9[Ni]+1.2[Cr]+1.5[Si]+17.3[P]-7.3[Cu][Ni]-9.1[Ni][P]-33.4[Cu] 2

；两式中各化学元素均代入该化学元素质量百分含量的百分号前面的数值。 ; In both formulas, each chemical element is substituted with the numerical value before the percentage sign of the mass percentage content of the chemical element.

在本发明中，实施例1-8的耐应力腐蚀的高强韧中碳钢和对比例1-4的对比钢材的具体生产工艺操作如下所述：In the present invention, the specific production process operations of the stress corrosion resistant high-strength and tough medium carbon steels of Examples 1-8 and the comparative steels of Comparative Examples 1-4 are as follows:

实施例1Example 1

按表1-1和1-2所示的化学成分在50kg真空感应炉上进行冶炼，冶炼获得的钢水模铸成钢锭，并对铸锭进行加热，而后锻造开坯。其中，控制加热为温度1050℃，保温5h后进行锻造，控制终锻温度为850℃，最终锻造成直径为Φ50mm的棒料，锻后空冷。淬火加热温度为860℃，保温时间为30min，回火温度为550℃，回火时间为60min，回火后水冷。According to the chemical composition shown in Tables 1-1 and 1-2, the smelting was carried out in a 50kg vacuum induction furnace, the molten steel obtained by smelting was mold-cast into an ingot, and the ingot was heated, and then forged into a blank. Among them, the heating temperature was controlled to be 1050℃, and forging was carried out after holding for 5h. The final forging temperature was controlled to be 850℃, and the final forging was forged into a bar with a diameter of Φ50mm, and air-cooled after forging. The quenching heating temperature was 860℃, the holding time was 30min, the tempering temperature was 550℃, the tempering time was 60min, and water-cooled after tempering.

实施例2Example 2

按表1-1和1-2所示的化学成分在150kg真空感应炉上进行冶炼，冶炼获得的钢水经模铸制成钢锭，并对钢锭进行加热，而后锻造开坯。其中，控制加热温度1180℃，保温12h后进行锻造，控制终锻温度为960℃，最终锻造成Φ70mm的棒料，而后进行风冷。淬火加热温度为910℃，保温时间为100min，回火温度为600℃，回火时间为90min，回火后水冷。According to the chemical composition shown in Tables 1-1 and 1-2, the smelting was carried out in a 150kg vacuum induction furnace. The molten steel obtained by smelting was mold-cast into ingots, and the ingots were heated and then forged. Among them, the heating temperature was controlled at 1180℃, and forging was carried out after holding for 12 hours. The final forging temperature was controlled at 960℃, and finally forged into Φ70mm bars, and then air-cooled. The quenching heating temperature was 910℃, the holding time was 100min, the tempering temperature was 600℃, the tempering time was 90min, and water-cooled after tempering.

实施例3Example 3

按表1-1和1-2所示的化学成分在500kg真空感应炉上进行冶炼，冶炼获得的钢水经模铸制成钢锭，并对钢锭进行加热，而后锻造开坯。其中，控制加热温度为1080℃，保温24h后进行后续锻造，控制终锻温度为980℃，最终锻造成Φ90mm棒料，锻后堆积缓冷。淬火加热温度为870℃，保温时间为135min，回火温度为560℃，回火时间为120min，回火后空冷。According to the chemical composition shown in Tables 1-1 and 1-2, the smelting was carried out in a 500kg vacuum induction furnace. The molten steel obtained by smelting was mold-cast into ingots, and the ingots were heated and then forged. Among them, the heating temperature was controlled to be 1080℃, and the subsequent forging was carried out after holding for 24 hours. The final forging temperature was controlled to be 980℃, and the final forging was forged into Φ90mm bars, which were piled up and slowly cooled after forging. The quenching heating temperature was 870℃, the holding time was 135min, the tempering temperature was 560℃, the tempering time was 120min, and air cooling was performed after tempering.

实施例4Example 4

按表1-1和1-2所示的化学成分进行转炉冶炼，并进行精炼和真空处理，而后模铸获得铸坯，控制铸坯阶梯式加热，首先在预热段加热至620℃，然后在第一加热段继续加热至950℃，保温后继续在第二加热段加热至1200℃，保温9h后进入均热段，然后进行后续轧制。钢坯出加热炉经高压水除鳞后开始轧制，控制终轧温度为970℃，最终轧制成Φ120mm棒料。轧制后空冷。淬火加热温度为850℃，保温时间为200min，回火温度为530℃，回火时间为200min，回火后空冷。According to the chemical composition shown in Tables 1-1 and 1-2, converter smelting is carried out, and refining and vacuum treatment are carried out. Then, the ingot is obtained by die casting. The ingot is heated in a step-by-step manner. First, it is heated to 620℃ in the preheating section, and then continued to be heated to 950℃ in the first heating section. After insulation, it is continued to be heated to 1200℃ in the second heating section. After insulation for 9 hours, it enters the soaking section and then undergoes subsequent rolling. The billet is removed from the heating furnace and descaled by high-pressure water before rolling begins. The final rolling temperature is controlled to be 970℃, and finally rolled into a Φ120mm bar. Air cooling after rolling. The quenching heating temperature is 850℃, the insulation time is 200min, the tempering temperature is 530℃, the tempering time is 200min, and air cooling is performed after tempering.

实施例5 Example 5

按表1-1和1-2所示的化学成分进行转炉冶炼，并进行精炼和真空处理，而后浇铸成模铸坯。控制铸坯加热至1180℃，保温12h后进行后续轧制。钢坯出加热炉经高压水除鳞后开始轧制，轧制成中间坯，控制终轧温度为1010℃，中间坯尺寸220mm×220mm。而后再将中间坯加热至1080℃，保温24h后，出炉经高压水除鳞后开始轧制，控制中间坯终轧温度为900℃，成品棒材规格为Φ80mm，轧后空冷。砂轮剥皮后，采用超声波探伤和涡流探伤。淬火加热温度为870℃，保温时间为120min，回火温度为550℃，回火时间为100min，回火后空冷。According to the chemical composition shown in Tables 1-1 and 1-2, the steel is smelted in a converter, refined and vacuum treated, and then cast into a mold casting billet. The billet is heated to 1180℃ and kept warm for 12 hours before subsequent rolling. The billet is rolled after being descaled by high-pressure water after leaving the heating furnace, and rolled into an intermediate billet. The final rolling temperature is controlled to be 1010℃, and the size of the intermediate billet is 220mm×220mm. Then the intermediate billet is heated to 1080℃, kept warm for 24 hours, and then removed from the furnace and descaled by high-pressure water before rolling. The final rolling temperature of the intermediate billet is controlled to be 900℃, and the specification of the finished bar is Φ80mm. It is air-cooled after rolling. After grinding wheel peeling, ultrasonic flaw detection and eddy current flaw detection are used. The quenching heating temperature is 870℃, the holding time is 120min, the tempering temperature is 550℃, the tempering time is 100min, and air cooling is performed after tempering.

实施例6Example 6

按表1-1和1-2所示的化学成分进行电炉冶炼，并进行精炼和真空处理，而后连铸成280mm×280mm连铸坯。控制连铸坯缓慢加热至1200℃，保温10h后轧制。钢坯出加热炉经高压水除鳞后开始轧制，控制终轧温度为970℃，成品棒材规格为Φ100mm。轧制后空冷。而后进一步进行精整，精整具体包括热处理、表面处理和无损探伤，其在910℃正火处理(热处理)后车削剥皮(表面处理)，并经过超声波探伤和磁粉探伤(无损探伤)。淬火加热温度为890℃，保温时间为150min，回火温度为640℃，回火时间为135min，回火后空冷。According to the chemical composition shown in Tables 1-1 and 1-2, electric furnace smelting is carried out, and refining and vacuum treatment are carried out, and then continuous casting is carried out into 280mm×280mm continuous casting billets. The continuous casting billets are controlled to be slowly heated to 1200℃, and rolled after being kept warm for 10h. The billets are rolled after being descaled by high-pressure water after leaving the heating furnace, and the final rolling temperature is controlled to be 970℃, and the finished bar specification is Φ100mm. Air cooling after rolling. Then further finishing is carried out, and finishing specifically includes heat treatment, surface treatment and non-destructive testing. After normalizing treatment (heat treatment) at 910℃, it is turned and peeled (surface treatment), and ultrasonic testing and magnetic particle testing (non-destructive testing) are carried out. The quenching heating temperature is 890℃, the holding time is 150min, the tempering temperature is 640℃, the tempering time is 135min, and air cooling is carried out after tempering.

实施例7Example 7

按表1-1和1-2所示的化学成分进行电炉冶炼，并进行LF精炼和VD真空处理，而后浇铸成320mm×425mm连铸坯。控制连铸坯首先在预热段加热至600℃，然后在第一加热段继续加热至950℃，保温后继续在第二加热段加热至1230℃，保温8h后进入均热段，保温后进行后续轧制。钢坯出加热炉经高压水除鳞后开始轧制，轧制成中间坯，控制终轧温度为1050℃，获得中间坯尺寸为260mm×260mm，轧后空冷。而后再将中间坯预热段加热至680℃，第一加热段加热至1050℃，第二加热段加热至1250℃，保温6h后进入均热段，出炉经高压水除鳞后开始轧制，控制中间坯终轧温度为950℃，成品棒材规格为Φ80mm。轧制后空冷，而后经过超声波探伤和磁粉探伤。淬火加热温度为880℃，保温时间为120min，回火温度为560℃，回火时间为100min，回火后空冷。According to the chemical composition shown in Tables 1-1 and 1-2, electric furnace smelting is carried out, and LF refining and VD vacuum treatment are carried out, and then cast into 320mm×425mm continuous casting billets. The continuous casting billet is first heated to 600℃ in the preheating section, and then continued to be heated to 950℃ in the first heating section, and then heated to 1230℃ in the second heating section after insulation. After insulation for 8h, it enters the soaking section, and then subsequent rolling is carried out after insulation. The billet is rolled after being descaled by high-pressure water after leaving the heating furnace, and rolled into an intermediate billet. The final rolling temperature is controlled to be 1050℃, and the intermediate billet size is obtained to be 260mm×260mm, and air cooling is performed after rolling. Then the intermediate billet is heated to 680℃ in the preheating section, 1050℃ in the first heating section, and 1250℃ in the second heating section. After insulation for 6h, it enters the soaking section, and starts rolling after being descaled by high-pressure water after leaving the furnace. The final rolling temperature of the intermediate billet is controlled to be 950℃, and the finished bar specification is Φ80mm. After rolling, it is air-cooled, and then ultrasonic and magnetic particle inspections are performed. The quenching heating temperature is 880°C, the holding time is 120 minutes, the tempering temperature is 560°C, the tempering time is 100 minutes, and air-cooling is performed after tempering.

实施例8Example 8

按表1-1和1-2所示的化学成分进行电炉冶炼，并进行LF精炼和VD真空处理，而后连铸成320mm×425mm连铸坯。控制连铸坯经预热后缓慢加热至 1250℃，保温3h后进行轧制。钢坯出加热炉经高压水除鳞后开始轧制，轧制成中间坯，控制终轧温度为1000℃，获得中间坯尺寸为140mm×140mm，轧后空冷。而后再将中间坯缓慢加热至1130℃，保温3h后出炉经高压水除鳞后开始轧制，控制中间坯终轧温度为850℃，成品棒材规格为Φ30mm。轧制后空冷，之后在870℃正火，通过超声波探伤和磁粉探伤进行无损检验。淬火加热温度为830℃，保温时间为50min，回火温度为540℃，回火时间为30min，回火后空冷。According to the chemical composition shown in Tables 1-1 and 1-2, electric furnace smelting is carried out, and LF refining and VD vacuum treatment are carried out, and then continuous casting is carried out into 320mm×425mm continuous casting billets. The continuous casting billets are controlled to be slowly heated to 1250℃, keep warm for 3h before rolling. The billet is rolled after being descaled by high-pressure water after leaving the heating furnace, and rolled into an intermediate billet. The final rolling temperature is controlled to be 1000℃, and the size of the intermediate billet is 140mm×140mm, and air-cooled after rolling. Then the intermediate billet is slowly heated to 1130℃, kept warm for 3h, and then taken out of the furnace and descaled by high-pressure water before rolling. The final rolling temperature of the intermediate billet is controlled to be 850℃, and the specification of the finished bar is Φ30mm. After rolling, it is air-cooled, and then normalized at 870℃, and non-destructive inspection is carried out by ultrasonic flaw detection and magnetic particle flaw detection. The quenching heating temperature is 830℃, the holding time is 50min, the tempering temperature is 540℃, the tempering time is 30min, and air-cooled after tempering.

对比例1Comparative Example 1

按表1-1和1-2所示的化学成分在50kg真空感应炉上进行冶炼。钢水经模铸制成钢锭，加热并经锻造开坯，加热温度1050℃，保温5h后进行锻造，并控制终锻温度为860℃，最终锻造成直径为Φ50mm的棒料，锻后空冷。淬火加热温度为860℃，保温时间为75min，回火温度为550℃，回火时间为60min，回火后水冷。According to the chemical composition shown in Tables 1-1 and 1-2, smelting was carried out in a 50kg vacuum induction furnace. The molten steel was mold-cast into ingots, heated and forged to form blanks. The heating temperature was 1050℃, and forging was carried out after holding for 5 hours. The final forging temperature was controlled at 860℃, and finally forged into bars with a diameter of Φ50mm. After forging, air cooling was carried out. The quenching heating temperature was 860℃, the holding time was 75min, the tempering temperature was 550℃, the tempering time was 60min, and water cooling was carried out after tempering.

对比例2Comparative Example 2

按照表1-1和1-2所示的化学成分在150kg真空感应炉上进行冶炼。钢水模铸成钢锭，加热并经锻造开坯，加热温度1180℃，保温12h后进行锻造，控制终锻温度为960℃，最终锻造成Φ70mm棒料，而后进行风冷。淬火加热温度为900℃，保温时间为100min，回火温度为600℃，回火时间为90min，回火后水冷。According to the chemical composition shown in Tables 1-1 and 1-2, smelting was carried out in a 150kg vacuum induction furnace. The molten steel was molded into an ingot, heated and forged to form a blank. The heating temperature was 1180℃, and the forging was carried out after holding for 12 hours. The final forging temperature was controlled at 960℃, and the final forging was forged into a Φ70mm bar, which was then air-cooled. The quenching heating temperature was 900℃, the holding time was 100min, the tempering temperature was 600℃, the tempering time was 90min, and the tempering was water-cooled after tempering.

对比例3Comparative Example 3

按照表1-1和1-2所示的化学成分在500kg真空感应炉上进行冶炼。钢水模铸成钢锭，加热并经锻造开坯，加热温度为1080℃，保温20h后进行锻造，控制终锻温度为980℃，最终锻造成Φ90mm棒料，而后进行堆冷。640℃退火。淬火加热温度为870℃，保温时间为135min，回火温度为560℃，回火时间为120min，回火后空冷。According to the chemical composition shown in Tables 1-1 and 1-2, the steel was smelted in a 500kg vacuum induction furnace. The molten steel was mold-cast into an ingot, heated and forged to form a blank. The heating temperature was 1080℃, and the forging was carried out after holding for 20 hours. The final forging temperature was controlled at 980℃, and the final forging was forged into a Φ90mm bar, and then pile-cooled. Annealing at 640℃. The quenching heating temperature was 870℃, the holding time was 135min, the tempering temperature was 560℃, the tempering time was 120min, and air cooling was performed after tempering.

对比例4Comparative Example 4

选自市售商品圆钢。对该市售商品圆钢进行热处理，其中淬火加热温度为900℃，保温时间为100min，回火温度为600℃，回火时间为90min，回火后水冷。The commercially available round steel is selected and heat-treated, wherein the quenching heating temperature is 900°C, the holding time is 100 minutes, the tempering temperature is 600°C, the tempering time is 90 minutes, and the tempering is followed by water cooling.

表2-1和表2-2列出了实施例1-8和对比例1-4在上述制造方法中的具体工艺参数。 Table 2-1 and Table 2-2 list the specific process parameters of Examples 1-8 and Comparative Examples 1-4 in the above manufacturing method.

表2-1.
Table 2-1.

表2-2.
Table 2-2.

将实施例1-8的轧态圆钢和对比例1-4的轧态圆钢(对比例4中轧态圆钢是指未经热处理的市售商品圆钢)分别取样，并按照GB/T 13298-2015制备金相试样，参考GB/T 13299-1991分析微观组织。对各实施例和对比例的试样钢材进一步在910℃保温4小时后进行水淬，制样后按照标准ASTM E112-10评定其奥氏体晶粒度。相关检测分析结果列于下述表3之中。The rolled round steels of Examples 1-8 and Comparative Examples 1-4 (the rolled round steel in Comparative Example 4 refers to commercially available round steel that has not been heat treated) were sampled respectively, and metallographic specimens were prepared in accordance with GB/T 13298-2015, and the microstructure was analyzed with reference to GB/T 13299-1991. The sample steels of each embodiment and comparative example were further water quenched after being kept at 910°C for 4 hours, and the austenite grain size was evaluated in accordance with standard ASTM E112-10 after sample preparation. The relevant test and analysis results are listed in Table 3 below.

表3列出了实施例1-8和对比例1-4的圆钢的金相组织分析结果。Table 3 lists the metallographic structure analysis results of the round steels of Examples 1-8 and Comparative Examples 1-4.

表3.
Table 3.

由上述表3可以看出，在本发明中，实施例1-8的钢的轧态微观组织为贝氏体+马氏体和/或残余奥氏体，并且含有纳米级析出物，贝氏体的体积相比例均≥60％，且奥氏体晶粒度均≥6级。It can be seen from Table 3 above that in the present invention, the rolled microstructure of the steels of Examples 1-8 is bainite + martensite and/or retained austenite, and contains nano-scale precipitates, the volume phase ratio of bainite is ≥60%, and the austenite grain size is ≥6.

另外，将实施例1-8的成品圆钢分别取样，并按照GB/T 13298-2015制备金相试样，参考GB/T 13299-1991分析微观组织，发现其淬火+回火热处理后，形成主体为回火索氏体的微观组织，含有纳米级析出物。In addition, the finished round steels of Examples 1-8 were sampled respectively, and metallographic specimens were prepared in accordance with GB/T 13298-2015. The microstructure was analyzed with reference to GB/T 13299-1991. It was found that after quenching + tempering heat treatment, a microstructure mainly composed of tempered troostite containing nano-scale precipitates was formed.

发明人进一步将制备的成品实施例1-8和对比例1-4的对比钢材分别取样，按照GB/T 2975-2018《钢及钢产品力学性能试验取样位置及试样制备》制备样品，并按照GB/T 228.1-2010《金属材料拉伸试验第1部分：室温试验方法》进行拉伸试验，测得抗拉强度Rm、屈服强度Rp0.2和延伸率A，同时采用GB/T 229-2007《金属材料夏比摆锤冲击试验方法》测试各实施例和对比例在室温和-40℃夏比冲击功Akv，测试结果见表4。 The inventors further sampled the prepared finished steels of Examples 1-8 and Comparative Examples 1-4, prepared the samples according to GB/T 2975-2018 "Sampling location and specimen preparation for mechanical properties test of steel and steel products", and conducted tensile tests according to GB/T 228.1-2010 "Tensile test of metallic materials Part 1: Room temperature test method", and measured the tensile strength R m , yield strength R p0.2 and elongation A. At the same time, GB/T 229-2007 "Charpy pendulum impact test method for metallic materials" was used to test the Charpy impact energy A kv of each embodiment and comparative example at room temperature and -40°C. The test results are shown in Table 4.

需要说明的是，工程领域通常采用环境条件下拉伸试验面缩率变化来反映应力腐蚀倾向，本发明对氢脆敏感性的要求按照GB/T 2975-2018《钢及钢产品力学性能试验取样位置及试样制备》制备圆形截面试样，试样直径为10mm。并按国标GB/T 228.1-2010进行拉伸试验，应变速率≤0.0003/s，以获得断面收缩率Z，并定义抗氢脆系数η(Z)来评价钢材的抗氢致开裂性能：It should be noted that the engineering field usually uses the change in tensile test surface shrinkage under environmental conditions to reflect the tendency of stress corrosion. The requirements for hydrogen embrittlement sensitivity in this invention are in accordance with GB/T 2975-2018 "Steel and Steel Products Mechanical Properties Test Sampling Location and Sample Preparation" to prepare circular cross-section specimens with a diameter of 10 mm. The tensile test is carried out in accordance with the national standard GB/T 228.1-2010, with a strain rate of ≤0.0003/s to obtain the cross-sectional shrinkage Z, and the hydrogen embrittlement resistance coefficient η(Z) is defined to evaluate the hydrogen-induced cracking resistance of steel:

η(Z)＝Z2/Z1 η(Z)＝Z 2 /Z 1

其中，Z1表示经过250℃烘烤2h去氢处理后的圆钢经拉伸试验后获得的断面收缩率；Z2表示圆钢经拉伸试验后获得的断面收缩率。测试结果见表4。基于本发明所设计的这种抗氢脆系数η(Z)，当抗氢脆系数η(Z)越大，则表示钢材的应力腐蚀倾向则越小，其抗氢脆能力和抗应力腐蚀性能越优异。Wherein, Z1 represents the cross-sectional shrinkage rate obtained after the round steel is subjected to a tensile test after dehydrogenation treatment at 250°C for 2h; Z2 represents the cross-sectional shrinkage rate obtained after the tensile test of the round steel. The test results are shown in Table 4. Based on the hydrogen embrittlement resistance coefficient η(Z) designed by the present invention, the larger the hydrogen embrittlement resistance coefficient η(Z), the smaller the stress corrosion tendency of the steel, and the better its hydrogen embrittlement resistance and stress corrosion resistance.

表4列出了实施例1-8和对比例1-4的性能检测结果。Table 4 lists the performance test results of Examples 1-8 and Comparative Examples 1-4.

表4.
Table 4.

从表4可以看出，本发明涉及的高强韧钢材的屈服强度Rp0.2均高于 1000MPa，抗拉强度Rm均高于1150MPa，延伸率A≥12％，断面收缩率Z均大于50％，室温夏比冲击功Akv≥60J，-40℃低温夏比冲击功Akv均大于30J，抗氢脆系数η(Z)均大于0.85。It can be seen from Table 4 that the yield strength R p0.2 of the high-strength and toughness steel materials of the present invention is higher than 1000MPa, tensile strength R m is higher than 1150MPa, elongation A ≥ 12%, section shrinkage Z is greater than 50%, room temperature Charpy impact energy A kv ≥ 60J, -40℃ low temperature Charpy impact energy A kv is greater than 30J, and hydrogen embrittlement resistance coefficient η (Z) is greater than 0.85.

反观对比例1-4，其化学元素成分设计均存在不符合本发明设计要求之处。其中，对比例1的碳含量偏低，其抗拉强度也较低；对比例2抗氢脆系数较低，因为添加了较多的Mn元素，虽然强度有所提升，但耐应力腐蚀性能不足；对比例3和对比例4钢材的低温冲击功偏低，对比例3的微合金系数偏低，其奥氏体晶粒度不理想，其中6(1)表示平均晶粒度为6，但出现了双重晶粒度，存有级别为1的粗大晶粒，这对低温韧性有不利影响；而对比例4的碳含量较高，其钢材抗拉强度虽有提升，但韧性不足，抗应力腐蚀开裂效果不佳，疲劳性能不能满足使用要求。On the other hand, the chemical element composition design of Comparative Examples 1-4 does not meet the design requirements of the present invention. Among them, the carbon content of Comparative Example 1 is low, and its tensile strength is also low; the hydrogen embrittlement resistance coefficient of Comparative Example 2 is low, because more Mn elements are added, although the strength is improved, the stress corrosion resistance is insufficient; the low-temperature impact energy of the steel materials of Comparative Examples 3 and Comparative Example 4 is low, and the microalloy coefficient of Comparative Example 3 is low, and its austenite grain size is not ideal, where 6 (1) means that the average grain size is 6, but double grain size appears, and there are coarse grains of level 1, which has an adverse effect on low-temperature toughness; and the carbon content of Comparative Example 4 is high, and although the tensile strength of the steel material is improved, the toughness is insufficient, the stress corrosion cracking effect is not good, and the fatigue performance cannot meet the use requirements.

需要说明的是，本案中各技术特征的组合方式并不限本案权利要求中所记载的组合方式或是具体实施例所记载的组合方式，本案记载的所有技术特征可以以任何方式进行自由组合或结合，除非相互之间产生矛盾。It should be noted that the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

还需要注意的是，以上所列举的实施例仅为本发明的具体实施例。显然本发明不局限于以上实施例，随之做出的类似变化或变形是本领域技术人员能从本发明公开的内容直接得出或者很容易便联想到的，均应属于本发明的保护范围。 It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with by those skilled in the art from the contents disclosed in the present invention, and all should belong to the protection scope of the present invention.

Claims (15)

一种耐应力腐蚀的高强韧中碳钢，其含有Fe和不可避免的杂质，其特征在于，还含有质量百分含量如下的下述各化学元素：A high-strength and tough medium carbon steel resistant to stress corrosion, containing Fe and inevitable impurities, characterized in that it also contains the following chemical elements in the following mass percentages: C：0.37～0.43％、Si：0.10～0.40％、Mn：0.50～0.90％、Cr：0.60～1.25％、Ni：1.30～2.00％、Mo：0.15～0.30％、Al：0.02～0.05％、Nb：0.001～0.030％。C: 0.37～0.43%, Si: 0.10～0.40%, Mn: 0.50～0.90%, Cr: 0.60～1.25%, Ni: 1.30～2.00%, Mo: 0.15～0.30%, Al: 0.02～0.05%, Nb :0.001～0.030%. 如权利要求1所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其各化学元素质量百分含量为：The stress corrosion resistant high-strength and tough medium carbon steel according to claim 1 is characterized in that the mass percentage of each chemical element is: C：0.37～0.43％、Si：0.10～0.40％、Mn：0.50～0.90％、Cr：0.60～1.25％、Ni：1.30～2.00％、Mo：0.15～0.30％、Al：0.02～0.05％、Nb：0.001～0.030％；余量为Fe和不可避免的杂质。C: 0.37～0.43%, Si: 0.10～0.40%, Mn: 0.50～0.90%, Cr: 0.60～1.25%, Ni: 1.30～2.00%, Mo: 0.15～0.30%, Al: 0.02～0.05%, Nb: 0.001～0.030%; the balance is Fe and unavoidable impurities. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其还含有下述各化学元素的至少其中之一：0＜Cu≤0.30％、0＜V≤0.06％、0＜Ti≤0.03％、0＜Ca≤0.003％。The stress corrosion resistant high strength and toughness medium carbon steel as described in claim 1 or 2 is characterized in that it also contains at least one of the following chemical elements: 0＜Cu≤0.30%, 0＜V≤0.06%, 0＜Ti≤0.03%, 0＜Ca≤0.003%. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，在不可避免的杂质中，N≤0.012％、O≤0.002％、H≤0.0002％、P≤0.02％、S≤0.015％，并且P+S≤0.03％。The stress corrosion resistant high strength and toughness medium carbon steel as described in claim 1 or 2 is characterized in that, among the inevitable impurities, N≤0.012%, O≤0.002%, H≤0.0002%, P≤0.02%, S≤0.015%, and P+S≤0.03%. 如权利要求1-3中任意一项所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其中各元素还满足：Mn+Cr+Ni+Mo+Cu≤4.0，式中各化学元素均代入该化学元素质量百分含量的百分号前面的数值。The stress corrosion resistant high-strength and tough medium carbon steel as described in any one of claims 1 to 3 is characterized in that each element further satisfies: Mn+Cr+Ni+Mo+Cu≤4.0, wherein each chemical element is substituted into the numerical value before the percentage sign of the mass percentage content of the chemical element. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其微合金元素系数rM/N的范围为：1.0～5.9，其中，rM/N＝([Al]/2+[Nb]/6+[Ti]/4)/[N]，式中各化学元素均代入该化学元素质量百分含量的百分号前面的数值。The stress corrosion resistant high strength and toughness medium carbon steel according to claim 1 or 2, characterized in that the microalloying element coefficient r M / N is in the range of 1.0 to 5.9, wherein r M / N = ([Al] / 2 + [Nb] / 6 + [Ti] / 4) / [N], wherein each chemical element is substituted into the value before the percentage sign of the mass percentage of the chemical element. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其耐大气腐蚀指数I≥7.0，其中：
I＝26.0[Cu]+3.9[Ni]+1.2[Cr]+1.5[Si]+17.3[P]-7.3[Cu][Ni]-9.1[Ni][P]-33.4[Cu]2 The stress corrosion resistant high-strength and tough medium carbon steel according to claim 1 or 2, characterized in that its atmospheric corrosion resistance index I is ≥ 7.0, wherein:
I＝26.0[Cu]+3.9[Ni]+1.2[Cr]+1.5[Si]+17.3[P]-7.3[Cu][Ni]-9.1[Ni][P]-33.4[Cu] 2 式中各化学元素均代入该化学元素质量百分含量的百分号前面的数值。In the formula, each chemical element is substituted into the value before the percentage sign of the mass percentage content of the chemical element. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其轧 态微观组织为贝氏体+马氏体和/或残余奥氏体，其中贝氏体的体积相比例≥60％。The stress corrosion resistant high-strength medium carbon steel according to claim 1 or 2, characterized in that its rolling The microstructure of the alloy is bainite + martensite and/or retained austenite, wherein the volume phase proportion of bainite is ≥60%. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其淬火+回火后的微观组织的主体为回火索氏体，并且含有纳米级析出物。The stress corrosion resistant high-strength and tough medium carbon steel as described in claim 1 or 2 is characterized in that the main body of its microstructure after quenching and tempering is tempered troostite and contains nano-scale precipitates. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其奥氏体晶粒度≥6级。The stress corrosion resistant high-strength and tough medium carbon steel as described in claim 1 or 2 is characterized in that its austenite grain size is ≥ grade 6. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其屈服强度Rp0.2≥1000MPa，抗拉强度Rm≥1150MPa，延伸率A≥12％，断面收缩率Z≥50％，室温夏比冲击功Akv≥60J，-40℃夏比冲击功Akv≥30J，抗氢脆系数η(Z)≥0.85。The high-strength and tough medium carbon steel resistant to stress corrosion as described in claim 1 or 2 is characterized in that its yield strength R p0.2 ≥1000MPa, tensile strength R m ≥1150MPa, elongation A ≥12%, cross-sectional shrinkage Z ≥50%, room temperature Charpy impact energy A kv ≥60J, -40°C Charpy impact energy A kv ≥30J, and hydrogen embrittlement resistance coefficient η(Z) ≥0.85. 如权利要求1或2所述的耐应力腐蚀的高强韧中碳钢，其特征在于，其屈服强度Rp0.2≥1020MPa，抗拉强度Rm≥1150MPa，延伸率A≥12％，断面收缩率Z≥55％，室温夏比冲击功Akv≥65J，-40℃夏比冲击功Akv≥35J，抗氢脆系数η(Z)≥0.89。The high-strength and tough medium carbon steel resistant to stress corrosion as described in claim 1 or 2 is characterized in that its yield strength R p0.2 ≥1020MPa, tensile strength R m ≥1150MPa, elongation A ≥12%, cross-sectional shrinkage Z ≥55%, room temperature Charpy impact energy A kv ≥65J, -40°C Charpy impact energy A kv ≥35J, and hydrogen embrittlement resistance coefficient η(Z) ≥0.89. 如权利要求1-12中任意一项所述的耐应力腐蚀的高强韧中碳钢的制造方法，其特征在于，其包括步骤：The method for manufacturing a stress corrosion resistant high-strength and tough medium carbon steel according to any one of claims 1 to 12, characterized in that it comprises the steps of: (1)冶炼；(1) Smelting; (2)铸造；(2) Casting; (3)加热：控制加热温度为1050～1250℃，保温时间为3～24h；(3) Heating: Control the heating temperature to 1050-1250°C and the insulation time to 3-24h; (4)锻造或轧制：控制终轧温度或终锻温度≥850℃；(4) Forging or rolling: control the final rolling temperature or final forging temperature ≥ 850°C; (5)淬火+回火，其中淬火温度范围为830～910℃，保温时间为30～200min；回火温度为530～640℃，保温时间为30～200min。(5) Quenching + tempering, where the quenching temperature ranges from 830 to 910°C and the holding time is 30 to 200 min; the tempering temperature is 530 to 640°C and the holding time is 30 to 200 min. 如权利要求13所述的制造方法，其特征在于，在步骤(4)中，直接轧制或锻造至成品尺寸。The manufacturing method according to claim 13 is characterized in that in step (4), it is directly rolled or forged to the finished product size. 如权利要求14所述的制造方法，其特征在于，在步骤(4)中，先轧制到中间坯尺寸，再进行中间加热，然后轧制到最终成品尺寸；其中，中间加热温度为1050～1250℃，保温时间为3～24h。 The manufacturing method as described in claim 14 is characterized in that in step (4), the steel is first rolled to the intermediate billet size, then intermediate heating is performed, and then rolled to the final finished product size; wherein the intermediate heating temperature is 1050-1250°C and the holding time is 3-24h.
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