CN113322409B

CN113322409B - High-strength and high-toughness mining chain steel and manufacturing method thereof

Info

Publication number: CN113322409B
Application number: CN202010129796.6A
Authority: CN
Inventors: 高加强; 赵四新; 王维; 章军
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2020-02-28
Filing date: 2020-02-28
Publication date: 2022-06-28
Anticipated expiration: 2040-02-28
Also published as: JP2023515115A; US20230235435A1; WO2021169941A1; JP7497447B2; ES3001523T3; BR112022016824A2; EP4089197A1; EP4089197B1; MX2022010591A; KR20220129609A; EP4089197A4; CN113322409A

Abstract

A high-strength and high-toughness mining chain steel and a manufacturing method thereof are disclosed, which comprises the following components by weight percent: c: 0.20 to 0.28%, Si: 0.01 to 0.40%, Mn: 0.50-1.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Cr: 0.30 to 2.00%, Ni: 0.50 to 2.00%, Mo: 0.10 to 0.80%, Cu: 0.01-0.30%, Al: 0.01 to 0.05%, Nb: 0.001-0.10%, V: 0.001-0.10% of Fe, less than or equal to 0.00018% of H, less than or equal to 0.0150% of N, less than or equal to 0.0020% of O, and the balance of Fe and inevitable impurities. The manufacturing process comprises the working procedures of smelting, refining, vacuum treatment, casting, heating, forging or rolling, quenching, tempering, heat treatment and the like. The chain steel has higher strength, good impact toughness, elongation and reduction of area, can resist stress corrosion cracking, has good weather resistance, wear resistance and fatigue resistance, and can be used for occasions requiring high-strength and high-toughness steel products, such as engineering machinery, ocean engineering and the like.

Description

High-strength and high-toughness mining chain steel and manufacturing method thereof

Technical Field

The invention relates to high-strength steel, in particular to high-strength and high-toughness mining chain steel and a manufacturing method thereof.

Background

The high-strength and high-toughness steel bar is generally applied to high-safety machinery and structural parts, for example, a mining round-link chain is a key wearing part of coal mine machinery, and has high strength, high toughness, wear resistance, corrosion resistance, high fatigue performance and the like.

The high-strength and high-toughness steel is researched at home and abroad, and the high-strength and high-toughness steel is produced by selecting proper chemical components and adopting a controlled rolling, controlled cooling or quenching and tempering process. The controlled rolling and cooling method is adopted to produce high-strength steel, and the overall uniformity of the mechanical property of the steel is influenced due to the large control difficulty in the rolling and cooling processes. The quenching and tempering process is adopted to produce high-strength steel, and the hardenability of the steel is improved by optimizing the contents of alloy elements and carbon elements, so that the steel forms a martensite structure in the cooling process. High strength steel materials, mainly martensite, have a high dislocation density, resulting in poor impact toughness, and also rapidly fail by fracture when minute defects such as microcracks occur during the drawing process, resulting in low fracture toughness.

The Mn-Cr-Ni-Mo alloy steel has good obdurability, so that the Mn-Cr-Ni-Mo alloy steel is widely applied to the fields of engineering machinery, automobiles, bridges, marine equipment and the like, the safe use strength level of the Mn-Cr-Ni-Mo alloy steel is generally 900-1000 MPa, and the application of steel with higher strength level can not only lighten the equipment, but also save resources, so that the high strength of the alloy steel is a necessary trend for future development. However, as the strength grade of steel is increased, the difficulty of processing and manufacturing is increased, and the hydrogen embrittlement sensitivity thereof is bound to increase. The hydrogen-induced delayed fracture sensitivity of the high-strength steel can be greatly reduced by structure refinement, microalloying, grain boundary strengthening and addition of alloy elements.

In a Mn-Cr-Ni-Mo component system with low silicon content in the latest national standard GB/T10560-2017 (steel for a mining welding round-link chain), the highest strength grade of the steel for the mining round-link chain is 1180MPa, and the mechanical property indexes after quenching and tempering (880 ℃ quenching and 430 ℃ tempering) are as follows: yield strength R_eLGreater than or equal to 1060MPa, tensile strength R_mMore than or equal to 1180MPa, elongation A more than or equal to 10 percent, reduction of area Z more than or equal to 50 percent, Charpy impact energy A_kvMore than or equal to 60J. The quenched and tempered state (880 ℃ quenching +400 ℃ tempering) mechanical property indexes of the steel for the mining chain with the highest strength grade used by the Chinese coal mine machinery are as follows: yield strength R_eLNot less than 980MPa, tensile strength R_m1180MPa or more, elongation A of 10% or more, reduction of area Z of 50% or more, Charpy impact energy A_kU≥40J。

Aiming at humid mine environmental conditions, the Mn-Cr-Ni-Mo alloy steel chain bears large load and dynamic impact, is easy to generate stress corrosion, can generate brittle fracture seriously, and causes huge economic loss and even safety accidents.

Disclosure of Invention

The invention aims to provide high-strength and high-toughness mining chain steel and a manufacturing method thereof, wherein the high-strength steel has good impact toughness, elongation and surface shrinkage, can resist stress corrosion cracking, has good weather resistance, wear resistance and fatigue resistance, and can be used in occasions requiring high-strength and high-toughness steel, such as engineering machinery, ocean engineering and the like.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a high-strength and high-toughness mining chain steel comprises the following components in percentage by weight: c: 0.20 to 0.28%, Si: 0.01-0.40%, Mn: 0.50-1.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Cr: 0.30 to 2.00%, Ni: 0.50 to 2.00%, Mo: 0.10 to 0.80%, Cu: 0.01-0.30%, Al: 0.01 to 0.05%, Nb: 0.001-0.10%, V: 0.001-0.10% of Fe, less than or equal to 0.00018% of H, less than or equal to 0.0150% of N, less than or equal to 0.0020% of O, and the balance of Fe and inevitable impurities; among the inevitable impurities, B is less than or equal to 0.0010 percent, Ti is less than or equal to 0.003 percent, and Ca is less than or equal to 0.005 percent; and the number of the first and second electrodes,

the atomic ratio of the total amount of the microalloy elements to the nitrogen element exceeds 1, and the microalloy element coefficient r is defined_M/NThe range of (A) is as follows: 1.0 to 9.9;

r_M/N＝([Al]/2+[Nb]/7+[V]/4)/[N]；

trace elements As: less than or equal to 0.05, Pb: 0.05 or less, Sn: less than or equal to 0.02, Sb: less than or equal to 0.01, Bi: less than or equal to 0.01, coefficient of harmful element J_H≤500，

J_H＝([P]+[Sn]+[As]+[Pb]+[Sb]+[Bi])*([Si]+[Mn])*10000；

Controlling the carbon equivalent Ceq to be less than or equal to 0.80,

Ceq＝[C]+[Mn]/6+([Cr]+[Mo]+[V])/5+([Ni]+[Cu])/15；

the atmospheric corrosion resistance index I is more than or equal to 7.0,

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。

preferably, among the inevitable impurities, B is not more than 0.0010%, Ti is not more than 0.003%, and Ca is not more than 0.005%.

The microstructure of the high-strength and high-toughness mining chain steel is tempered martensite, a small amount of bainite and retained austenite.

The yield strength R of the high-strength and high-toughness mining chain steel_p0.2Greater than or equal to 1000MPa, tensile strength R_mMore than or equal to 1200MPa, the elongation A more than or equal to 12 percent, the reduction of area Z more than or equal to 50 percent, the Charpy impact energy A_kvMore than or equal to 60J, and the hydrogen brittleness coefficient eta (Z) is less than or equal to 15 percent.

In the composition design of the chain steel, the following components are adopted:

c can improve the hardenability of steel, so that the steel forms a phase change structure with higher hardness in the quenching and cooling process. An increase in the content of C increases the proportion of hard phases and increases the hardness of the steel, but decreases the toughness. Too low C content results in low contents of phase transformation structures such as martensite and bainite, and a high tensile strength cannot be obtained. In the present invention, the C content is set to 0.20 to 0.28%.

Si is beneficial for strength enhancement in steel. An appropriate amount of Si avoids the formation of coarse carbides during tempering, but a higher Si content reduces the impact toughness of the steel. The invention adopts a low Si component system, and the Si content is set as follows: 0.01 to 0.40 percent.

Mn exists mainly in solid solution form in steel. Can improve the hardenability of steel, form a high-strength low-temperature phase transformation structure during quenching, and obtain steel with good wear resistance. An excessively high Mn content results in the formation of more retained austenite, decreases the yield strength of the steel, and easily causes center segregation. In the invention, the Mn content is set as follows: 0.50 to 1.50 percent.

P is segregated in the steel at grain boundaries, and the grain boundary bonding energy is lowered, thereby deteriorating the impact toughness of the steel. In the invention, the content of P is set as follows: less than or equal to 0.015 percent. S can be segregated in steel, and form more sulfide inclusions, thereby reducing the shock resistance. In the invention, the S content is set as follows: less than or equal to 0.005 percent.

Cr can improve the hardenability of steel, form a hardened martensite structure, and improve the strength of steel. Too high Cr content results in coarse carbide formation and reduced impact properties. In the invention, the Cr content is set as follows: 0.30 to 2.00 percent. Ni exists in solid solution in the steel, and can improve the low-temperature impact property of the steel. However, too high Ni content causes too high residual austenite content in the steel material to lower the strength of the steel, and in the present invention, Ni content is set as follows: 0.50 to 2.00 percent. Mo can be dissolved in steel in a solid mode, and is beneficial to improving the hardenability of the steel and improving the strength of steel. At higher temperatures tempering will form fine carbides further increasing the strength of the steel. Considering the cost of the Mo element of the noble alloy, the Mo content is set as follows: 0.10 to 0.80 percent.

Cu can improve the strength of the steel and is beneficial to improving the corrosion resistance of the steel. If the Cu content is too high, it may concentrate at grain boundaries during heating, resulting in weakening of grain boundaries to cause cracking. In the present invention, the Cu content is set as: 0.01 to 0.30 percent. The Ca element is added into the steel, so that the size and the appearance of sulfide inclusion can be improved, and the deterioration of impact toughness can be avoided, therefore, the Ca content is set as follows: less than or equal to 0.005 percent.

Al forms fine AlN precipitates in steel and suppresses the growth of austenite grains. Too high an Al content results in the formation of larger Al oxides and coarse AlN hard inclusions reduce the impact toughness and fatigue properties of the steel. In the present invention, the Al content is set as: 0.01 to 0.05 percent.

Nb is added into the steel to form a fine precipitated phase, which plays a role in inhibiting steel recrystallization and can refine grains. Too high Nb content will form coarse NbC particles during the smelting process, which in turn will reduce the impact toughness. The grain refinement plays an important role in improving the mechanical properties of the steel, particularly the strength and the toughness, and meanwhile, the grain refinement is also beneficial to reducing the hydrogen embrittlement sensitivity of the steel. In the present invention, the Nb content is set as: 0.001 to 0.10%.

V forms precipitates with C or N in the steel, and increases the strength of the steel. If the C and V contents are too high, coarse VC particles are formed. In the invention, the content of V is set as follows: 0.001 to 0.10%.

Ti is added into steel to form a fine precipitated phase, but if the content of Ti is too high, coarse TiN particles with edges and corners are formed in the smelting process, and the impact toughness is reduced. In the present invention, the Ti content is set as: less than or equal to 0.003 percent.

Because the B element is easy to be partially polymerized, the content of the B element is controlled as follows: less than or equal to 0.0010 percent.

Ca element is easy to form inclusion to influence the fatigue performance of the final product, and the content of Ca is controlled as follows: less than or equal to 0.005 percent.

N is a gap atom and is also an MX type precipitate forming element, and in order to avoid the enrichment of the N element in steel, the content of N is required to be set as follows in the component design of the invention: less than or equal to 0.015 percent. Controlling the proportional relation between the contents of Al, Nb and V and the content of N, requiring the atomic ratio of the total content of the microalloy elements to the nitrogen element to exceed 1, and defining the microalloy element coefficient r_M/N：1.0～9.9；

r_M/N＝([Al]/2+[Nb]/7+[V]/4)/[N]。

The trace elements such As Sn, Sb, As, Bi, Pb, etc. segregate to the grain boundary at the tempering temperature, so that the bonding force between the grains is weakened, and Mn and Si can promote the segregation of harmful elements, so that the embrittlement is intensified. And elements such As Sn, Sb, As, Bi, Pb, etc. are harmful to the environment, in the present invention, As: less than or equal to 0.05, Pb: 0.05 or less, Sn: less than or equal to 0.02, Sb: less than or equal to 0.01, Bi: less than or equal to 0.01. Considering the influence of P, defining the harmful element coefficient J_H≤500；

J_H＝([P]+[Sn]+[As]+[Pb]+[Sb]+[Bi])*([Si]+[Mn])*10000。

H will accumulate at the defects in the steel and hydrogen delayed fracture will occur in steels with tensile strength levels above 1000 MPa. In the invention, the tensile strength exceeds 1200MPa, and the content of H is controlled as follows: less than or equal to 0.00018 percent. N forms nitrides or carbonitrides in steel and plays a role in refining austenite grains, but too high N content forms coarse grains and does not play a role in refining grains, and the grains are enriched as interstitial atoms at grain boundaries and defects, so that the impact toughness is reduced. In the invention, the content of N is controlled as follows: less than or equal to 0.0150 percent. O and Al in the steel form oxides, composite oxides and the like, and in order to ensure the uniformity of steel structures and the low-temperature impact power-level fatigue performance, the content of O is controlled as follows: less than or equal to 0.0020 percent.

In order to meet the requirements of welding occasions of mining chain steel, the carbon equivalent (Ceq) of steel is required to be controlled, and the Ceq is as follows: less than or equal to 0.80;

Ceq＝[C]+[Mn]/6+([Cr]+[Mo]+[V])/5+([Ni]+[Cu])/15。

in order to ensure the weather resistance of the mining chain steel and improve the stress corrosion cracking resistance, the atmospheric corrosion resistance index I value is as follows: not less than 7.0.

The order of the susceptibility of the different structures to hydrogen embrittlement is generally considered to be, from large to small, that original martensite > low-temperature tempered martensite > tempered troostite with original martensite orientation > bainite > tempered sorbite (high-temperature tempering). The chain steel in the past is a low-temperature tempered martensite structure, and by adopting the chemical components designed by the invention, the influence of various alloy elements and microalloy elements on phase change and microstructure is fully utilized, and after quenching and tempering heat treatment, a complex-phase microstructure of tempered martensite, a small amount of bainite and retained austenite is formed. Meanwhile, the contents of C, P, S, N, O and H are controlled, the strength, impact toughness, elongation, plasticity and the like of the steel are ensured, the high-toughness mining chain steel with ultrahigh toughness and strong plasticity matching is produced, and the high-toughness mining chain steel has good weather resistance, wear resistance, stress corrosion resistance, fatigue resistance and the like.

The manufacturing method of the high-strength and high-toughness mining chain steel comprises the working procedures of smelting, casting, heating, forging or rolling, quenching and tempering heat treatment; in the heating process, the heating temperature is 1050-1250 ℃, and the heat preservation time is 3-24 h; in the forging or rolling process, the finish rolling temperature or the finish forging temperature is more than or equal to 800 ℃; the austenitizing temperature of quenching heat treatment is 850-1000 ℃, the heat preservation time is 60-240 min, and water quenching treatment is adopted after austenitizing; the tempering temperature of the tempering heat treatment is 350-550 ℃, the heat preservation time is 60-240 min, and air cooling or water cooling is carried out after tempering.

Preferably, the smelting can adopt electric furnace smelting or converter smelting, and is refined and subjected to vacuum treatment.

Preferably, the casting is die casting or continuous casting.

Preferably, in the forging process, the forging is directly carried out until the size of a final finished product is obtained; in the rolling process, directly rolling the billet to the size of a final finished product; or rolling the steel billet to the specified size of an intermediate billet, heating and rolling to the size of a final finished product, wherein the heating temperature of the intermediate billet is 1050-1250 ℃, and the heat preservation time is 3-24 h.

Preferably, in the rolling process, the billet is taken out of the heating furnace and is descaled by high-pressure water, then the billet starts to be rolled, and air cooling or slow cooling is adopted after rolling.

The yield strength R of the high-strength and high-toughness mining chain steel_p0.2Greater than or equal to 1000MPa, tensile strength R_mMore than or equal to 1200MPa, the elongation A more than or equal to 12 percent, the reduction of area Z more than or equal to 50 percent, the Charpy impact energy A_kvMore than or equal to 60J, and the hydrogen brittleness coefficient eta (Z) is less than or equal to 15 percent. The high-strength and high-toughness steel has good strength, plasticity and toughness, and good weather resistance and stress corrosion resistance.

The high-strength and high-toughness mining chain steel can be used in mining and other occasions requiring high-strength bars, and the size specification range of the bars is phi 50-170 mm.

The high-strength and high-toughness mining chain steel is heated at 1000-1250 ℃ to be completely austenitized. During heating, carbides and nitrides of Al, Nb, V and carbonitrides, carbides of Cr and Mo are partially or totally dissolved in austenite, and during subsequent rolling/forging and cooling, Al, Nb, V form fine precipitates. Mn, Cr, and Mo solid-dissolved in austenite can improve hardenability of steel and improve hardness and strength of martensite. Under the condition that the finish rolling or finish forging temperature is more than or equal to 800 ℃, a complex phase matrix structure with refined martensite, a small amount of bainite and residual austenite is formed, and fine and dispersed precipitates are formed.

After rolling or forging, the steel is heated to 850-1000 ℃ and quenched after heat preservation. During the heating, precipitates of carbide-forming elements Al, Nb, V, Cr and Mo are partially dissolved, undissolved precipitates pin the grain boundary, and the coarsening of austenite grains (austenite grain size is not less than 6 grades) is suppressed. During the quenching and cooling process, the alloy elements dissolved in the austenite provide the steel with high strength and good toughness. The quenched steel is subjected to tempering heat treatment at 350-550 ℃, Al, Nb, V, Cr and Mo can form fine precipitates with C, N, and the matching of the strength and the ductility and toughness of the steel is improved. Within the range of the quenching and tempering temperature, the steel has good strong plasticity and toughness, and is beneficial to processing and using bars, such as producing high-performance mining chains by forging or welding.

Compared with the prior patent, the invention comprises the following steps:

the U.S. Pat. No. 5,420,583 discloses an Alloy steel composition and chain products prepared in a sub Alloy, which comprises the following components: c: 0.15-0.28%, Cr: 0.2 to 1.0%, Mo: 0.1 to 1.0%, Ni: 0.3-1.5%, V: 0.05-0.2 percent, the balance of Fe and inevitable impurities, the strength of the chain can reach 800MPa, the chain has stress corrosion resistance, and a high-strength and high-toughness chain is formed through forging, welding and heat treatment.

Compared with the patent, the invention comprises the following steps: the Cu content in the components is different, and the content of C, N and the content of alloying elements such as Mn, Cr, Ni, Mo and the like and the content of microalloy elements such as Al, V, Nb and the like are optimized. The invention utilizes the design of C, Ni and Cu elements and combines the optimization of Mn, Cr, Mo and other elements to form a complex phase microstructure of tempered martensite and a small amount of bainite and retained austenite. And the mechanical property is obviously superior to that of the patent.

Chinese patent publication No. CN103276303A discloses 'a high-strength mining chain steel and a preparation method thereof', which comprises the following components: c: 0.21 to 0.25%, Mn: 0.20 to 0.25%, Si: 0.15-0.35%, Cr: 0.40-0.65%, Ni: 0.60-0.70%, Cu: 0.07-0.15%, Alt: 0.02-0.05%, N is less than or equal to 0.012%, S is less than or equal to 0.015%, P is less than or equal to 0.015%, and the balance is Fe. The preparation method comprises the following steps; the method comprises the following steps of smelting in an electric furnace or a converter, refining outside the furnace, continuously casting billets and heating and rolling, so that straight bars with the specification phi of 20-50 mm are obtained, and the high-strength mining chain steel is obtained after annealing.

Compared with the patent, the invention comprises the following steps: the components of Cr, Mn, Ni and Mo containThe amounts are completely different, and the invention optimizes the composition ranges of C, Cu, Al, Nb, V and the like and limits the N, Ca content. By adopting the alloy element range, the microstructure of tempered martensite and retained austenite is formed, and the alloy has high-strength and high-toughness mechanical properties. For high-strength steel with tensile strength of more than 1000MPa, H in the environment is adsorbed to cause delayed cracking, and the high-strength steel bar is more sensitive to hydrogen in large-size high-strength steel bars, so that the element H in the steel is limited in the invention, but the requirement is not met in the patent, so the stress corrosion resistance and the delayed cracking resistance of the invention are better than those of the steel grade disclosed in the patent. The manufacturing method is used for manufacturing straight bars with phi of 20-50 mm, and the manufacturing method can be used for manufacturing bars with phi of 50-170 mm, and is larger in applicable specification and wider in applicable range. Therefore, the invention is completely different from the technical route of the patent in the aspects of components, organization, process design and the like. Tensile Strength R of the invention _mGreater than or equal to 1200MPa and yield strength R_p0.2More than or equal to 1000MPa and impact energy A_kvThe strength grade of the invention is higher than that of the patent and the invention has excellent impact toughness and stress corrosion cracking resistance.

The invention has the beneficial effects that:

1. according to the invention, high-strength and high-toughness steel is developed by reasonably designing chemical components and combining an optimization process, and the rolled or forged bar is quenched and then is tempered and heat treated to form tempered martensite, a small amount of bainite and residual austenite, and fine and dispersed precipitates.

2. The components and the process design of the steel are reasonable, the process window is loose, and the batch commercial production can be realized on a bar or high-speed wire production line.

3. Yield strength R of steel produced by the invention_p0.2Not less than 1000MPa, tensile strength R_mMore than or equal to 1200MPa, the elongation A more than or equal to 12 percent, the reduction of area Z more than or equal to 50 percent, the Charpy impact energy A_kv≥60J。

The invention relates to a method for evaluating the stress corrosion resistance of steel by using the elongation change under the environmental condition in the engineering field, which refers to the requirement of Norwegian classification society on hydrogen embrittlement sensitivity, and adopts the tensile test reduction of area with the strain rate less than or equal to 0.0003/s and defines the hydrogen embrittlement coefficient eta (Z) to evaluate the stress corrosion resistance of the steel:

η(Z)＝(Z₁-Z₂)/Z₁×100％

wherein: z₁Baking at 250 ℃ for 2h to remove the hydrogen, and then testing the reduction of area of the round steel tensile test;

Z₂And the reduction of area of the round steel in the tensile test.

When the hydrogen embrittlement coefficient η (Z) is smaller, the stress corrosion tendency is smaller. The hydrogen embrittlement coefficient eta (Z) of the steel produced by the invention is less than or equal to 15 percent, and the steel has good stress corrosion resistance.

Drawings

FIG. 1 is a metallographic photograph (magnification 500X) of the microstructure of a round steel according to example 2 of the present invention;

FIG. 2 is a metallographic photograph (magnification 500X) of the microstructure of a chain prepared in example 2 of the present invention.

Detailed Description

The present invention will be described in more detail with reference to the following examples, which are given in conjunction with the accompanying drawings. These examples are merely illustrative of the best mode of carrying out the invention and do not limit the scope of the invention in any way.

The compositions of the round steel examples according to the invention are shown in table 1. In the high-strength and high-toughness steels of embodiments 1 to 6 of the invention, the component coefficients are shown in Table 2, and it can be seen that the ratio coefficient r of the contents of the microalloy elements Al, Nb and V to the content of N_M/NThe range of (1) to (6.0); the atmospheric corrosion resistance coefficient I is more than or equal to 7.0; the carbon equivalent Ceq is less than or equal to 0.80; coefficient of harmful element J_H≤500。

The manufacturing method of the embodiment of the invention is shown in the table 3, the mechanical property of the prepared sample is tested, and the test result is shown in the table 4.

Example 1

Smelting in an electric furnace according to chemical components shown in the table 1, casting into a continuous casting billet after refining and vacuum treatment, heating the continuous casting billet to 1050 ℃, and keeping the temperature for 4 hours; the billet is taken out of the heating furnace and starts to be rolled after being descaled by high-pressure water, the finishing temperature is 800 ℃, and the size of the intermediate billet is 200 x 200 mm. Heating the intermediate billet to 1050 ℃, preserving heat for 24h, discharging from the furnace, descaling by high-pressure water, and then starting rolling, wherein the finish rolling temperature is 850 ℃, and the specification of the finished bar is phi 50 mm. And air cooling after rolling. The quenching heating temperature is 850 ℃, the heating time is 60min, the tempering temperature is 390 ℃, the tempering time is 90min, and air cooling is carried out after tempering.

Example 2

The implementation mode is the same as that of example 1, wherein the heating temperature is 1080 ℃, the heat preservation time is 3 hours, the finish rolling temperature is 880 ℃, and the size of the intermediate billet is 220 multiplied by 220 mm. Heating the intermediate billet to 1120 ℃, keeping the temperature for more than or equal to 3h, and keeping the finish rolling temperature at 850 ℃, wherein the specification of the finished bar is phi 75 mm. And air cooling after rolling. The quenching heating temperature is 870 ℃, the heating time is 100min, the tempering temperature is 550 ℃, the tempering time is 60min, and water cooling is carried out after tempering.

Example 3

The implementation mode is the same as that of the embodiment 1, wherein the heating temperature is 1120 ℃, the heat preservation time is 8h, the finish rolling temperature is 940 ℃, and the size of the intermediate billet is 260 multiplied by 260 mm. Heating the intermediate billet to 1200 ℃, keeping the temperature for 5h, keeping the finish rolling temperature at 880 ℃, and ensuring the specification of the finished bar to be phi 100 mm. And air cooling after rolling. The quenching heating temperature is 890 ℃, the heating time is 150min, the tempering temperature is 430 ℃, the tempering time is 100min, and air cooling is carried out after tempering.

Example 4

The implementation mode is the same as that of the embodiment 1, wherein the heating temperature is 1250 ℃, the heat preservation time is 14h, the hot continuous rolling forming is carried out, the finish rolling temperature is 900 ℃, and the specification of a finished bar is phi 150 mm. And slowly cooling after rolling. The quenching heating temperature is 990 ℃, the heating time is 210min, the tempering temperature is 350 ℃, the tempering time is 180min, and water cooling is carried out after tempering.

Example 5

Smelting in a converter according to the chemical components shown in the table 1, refining, performing vacuum treatment, and then casting into steel ingots, wherein the heating temperature is 1180 ℃, the heat preservation time is 3.5 hours, the finish rolling temperature is 980 ℃, and the size of the intermediate billet is 280 x 280 mm. The intermediate billet is heated to 1250 ℃, the heat preservation time is 12h, the finish rolling temperature is 950 ℃, and the specification of the finished bar is phi 160 mm. And slowly cooling after rolling. The quenching heating temperature is 900 ℃, the heating time is 210min, the tempering temperature is 450 ℃, the tempering time is 180min, and water cooling is carried out after tempering.

Example 6

The implementation mode is the same as that of example 5, wherein the heating temperature is 1200 ℃, the heat preservation time is 24 hours, the forging forming is carried out, the finish forging temperature is 920 ℃, and the specification of the finished bar is phi 170 mm. And (5) forging and then slowly cooling. The quenching heating temperature is 920 ℃, the heating time is 240min, the tempering temperature is 450 ℃, the tempering time is 240min, and air cooling is carried out after tempering.

As can be seen from Table 2, the high-toughness steels of the present invention have the yield strengths R_p0.2Not less than 1000MPa, tensile strength R_mMore than or equal to 1200MPa, the elongation A more than or equal to 12 percent, the reduction of area Z more than or equal to 50 percent, the Charpy impact energy A_kvNot less than 60J, and the hydrogen embrittlement coefficient eta (Z) is not more than 15%.

The round steel prepared in example 2 and the mining chain prepared from example 2 as a raw material were subjected to microstructure study, and optical micrographs are shown in fig. 1 and fig. 2. It can be seen from the figure that the microstructure of the steel bar is tempered martensite and a small amount of bainite and retained austenite, while the microstructure of the chain is refined tempered martensite and a small amount of bainite.

Claims

1. A high-strength and high-toughness mining chain steel comprises the following components in percentage by weight: c: 0.20 to 0.28%, Si: 0.01-0.40%, Mn: 0.50-1.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Cr: 0.30 to 2.00%, Ni: 0.50 to 2.00%, Mo: 0.10 to 0.80%, Cu: 0.01-0.30%, Al: 0.01 to 0.05%, Nb: 0.001-0.10%, V: 0.001 to 0.10 percent of the total weight of the alloy, less than or equal to 0.00018 percent of H, less than or equal to 0.0150 percent of N and less than or equal to 0.0020 percent of OThe balance being Fe and inevitable impurities; and the atomic ratio of the total amount of the microalloy elements to the nitrogen element exceeds 1, and the microalloy element coefficient r_M/NThe range of (A) is as follows: 1.0 to 9.9 percent of a metal oxide,

r_M/N＝([Al]/2+[Nb]/7+[V]/4)/[N]；

J_H＝([P]+[Sn]+[As]+[Pb]+[Sb]+[Bi])*([Si]+[Mn])*10000；

Controlling Ceq to be less than or equal to 0.80,

Ceq＝[C]+[Mn]/6+([Cr]+[Mo]+[V])/5+([Ni]+[Cu])/15；

the atmospheric corrosion resistance index I is more than or equal to 7.0,

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 yield strength R of the high-strength and high-toughness mining chain steel_p0.2Not less than 1000MPa, tensile strength R_mMore than or equal to 1200MPa, the elongation A more than or equal to 12 percent, the reduction of area Z more than or equal to 50 percent, the Charpy impact energy A_kvNot less than 60J, and the hydrogen embrittlement coefficient eta (Z) is not more than 15%.

2. The high-toughness chain steel for mining according to claim 1, wherein B is not more than 0.0010%, Ti is not more than 0.003%, and Ca is not more than 0.005% of the inevitable impurities.

3. The high strength and toughness chain steel for mining according to claim 1 or 2, wherein the microstructure of the high strength and toughness chain steel for mining is tempered martensite, a small amount of bainite, and retained austenite.

4. The manufacturing method of the high-strength and high-toughness mining chain steel as claimed in claim 1 or 2, which is characterized by comprising the steps of smelting, casting, heating, forging or rolling, quenching and tempering heat treatment; in the heating process, the heating temperature is 1050-1250 ℃, and the heat preservation time is 3-24 h; in the forging or rolling process, the finish rolling temperature or the finish forging temperature is more than or equal to 800 ℃; the austenitizing temperature of quenching heat treatment is 850-1000 ℃, the heat preservation time is 60-240 min, and water quenching treatment is adopted after austenitizing; the tempering temperature of the tempering heat treatment is 350-450 ℃, the heat preservation time is 60-240 min, and air cooling or water cooling is carried out after tempering.

5. The method for manufacturing the high-strength and high-toughness chain steel for the mine according to claim 4, wherein the smelting comprises electric furnace smelting or converter smelting, and refining and vacuum treatment are performed; the casting adopts die casting or continuous casting.

6. The manufacturing method of the high-strength and high-toughness mining chain steel as claimed in claim 4, wherein in the forging process, the steel is directly forged to the size of a final finished product; in the rolling process, directly rolling the billet to the size of a final finished product; or rolling the steel billet to the specified size of an intermediate billet, heating and rolling to the size of a final finished product, wherein the heating temperature of the intermediate billet is 1050-1250 ℃, and the heat preservation time is 3-24 h.

7. The method for manufacturing the high strength and toughness chain steel for the mine according to claim 4 or 6, wherein in the rolling process, the billet is taken out of the heating furnace, descaling is carried out by high pressure water, and then rolling is started, and air cooling or slow cooling is adopted after rolling.