CN104561802A - High-hardness high-toughness cold work die steel as well as preparation method thereof - Google Patents
High-hardness high-toughness cold work die steel as well as preparation method thereof Download PDFInfo
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- 239000010959 steel Substances 0.000 title claims description 128
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- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
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- 229910052717 sulfur Inorganic materials 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 2
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- 238000003723 Smelting Methods 0.000 claims 1
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- 230000000694 effects Effects 0.000 description 10
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- 229910001566 austenite Inorganic materials 0.000 description 8
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- 238000005204 segregation Methods 0.000 description 7
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- INZDTEICWPZYJM-UHFFFAOYSA-N 1-(chloromethyl)-4-[4-(chloromethyl)phenyl]benzene Chemical compound C1=CC(CCl)=CC=C1C1=CC=C(CCl)C=C1 INZDTEICWPZYJM-UHFFFAOYSA-N 0.000 description 2
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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- 150000001721 carbon Chemical group 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- UFGZSIPAQKLCGR-UHFFFAOYSA-N chromium carbide Chemical compound [Cr]#C[Cr]C#[Cr] UFGZSIPAQKLCGR-UHFFFAOYSA-N 0.000 description 1
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Classifications
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- 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
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Forging (AREA)
Abstract
The invention relates to high-hardness high-toughness cold work die steel as well as a preparation method thereof. The high-hardness high-toughness cold work die steel comprises the following chemical components in percentage by weight: 1.025-1.055% of C, 0.85-0.90% of Si, 0.20-0.40% of Mn, less than 0.02% of P, less than 0.02% of S, 8.30-8.50% of Cr, 1.95-2.05% of Mo, 0.20-0.40% of V and the balance of Fe and inevitable impurities, wherein the elements satisfy the following relationship: C=0.1(Cr+Mo). The preparation method comprises the following steps: smelting and pouring to obtain a steel ingot which serves as a consumable electrode and is placed in an electroslag remelting device for electroslag remelting and then re-solidifying to form the steel ingot; and heating the re-solidified steel ingot to 1200-1220 DEG C and then forging, quenching and tempering to obtain the cold work die steel. The impact energy of the steel is greater than or equal to 76J and the hardness of the steel is greater than or equal to 63HRC, and the steel has relatively good hardness and toughness match.
Description
Technical field
The present invention relates to die steel and preparation method thereof, particularly relate to a kind of high hardness high toughness cold-work die steel and preparation method thereof, the ballistic work >=76J of this cold-work die steel, hardness >=63HRC.
Background technology
Cold-work die steel mainly for the manufacture of the mould carrying out press forming under cold state (room temperature) condition, as cold drawing die, cold upsetting die of car, cold extrusion die, impressing mould, rolling die etc.The working conditions of cold-work die is a bit similar with cutlery, but is out of shape in the cold state because of machined material, therefore resistance to deformation is very large.Compared with Cutlery Steel, cold-work die steel should require higher hardening capacity, wear resistance and toughness, and the requirement of red hardness can be lower, and generally, during cold-work die work, temperature rising can not more than 200 ~ 300 DEG C.
At present, the cold working die steel material that domestic moulding stock market is most widely used is that (its chemical composition mass percent is high carbon and chromium cold-work die steel Cr12MoV: C:1.45 ~ 1.70%, Si≤0.40%, Mn≤0.40%, Cr:11.0 ~ 12.5%, Mo:0.4 ~ 0.6, Ni≤0.10, Cu≤0.10, P≤0.030%, S≤0.030%).This material is as the universal cold working die steel material of main separation, there is higher hardening capacity, hardenability, wear resistance, high-temperature oxidation resistance is good, can as universal cold working die steel material, for the manufacture of the cold-work die of various uses, such as complex-shaped punching concave die, cold extruding die, roll threading wheel, cold shears cutting knife and precision measuringtoll etc.But, containing higher carbon and chromium element in alloying element composition in the universal cold working die steel material of this Cr12MoV, too much carbon and chromium element can make to there is netted ledeburite carbide in material microstructure, cause the toughness of material not high, mould in use easily tipping, rupture or subside.
Cold-work die is mainly used in the cold-forming of metal or non-metallic material, comprises cold stamping, cold extrusion and cold-heading etc.This kind of mold work load is large, dimensional precision, surface quality requirements are high.Usually the cold-work die steel selected requires enough intensity, toughness, hardness and wear resistance.The key technical index of cold-work die steel is ballistic work, hardness, and Cr12MoV Impact Toughness of Steel is 39J, and hardness is 60HRC.Cr12MoV steel is owing to containing uneven ledeburite carbide in tissue, although have higher hardness and wear resisting property after quenching, tempering, toughness is lower, easily bursts apart and subsides in actual use.
Above-mentioned Cr12MoV steel adopts arc melting, and be cast into steel ingot hammer cogging, concrete steps are followed successively by steel-making, forging, thermal treatment, finally form product.The Heating temperature of its forging is 1110 ~ 1130 DEG C, and final forging temperature is >=900 DEG C, and the type of cooling adopts high temperature annealing, cheats cold or sand cooling.Because Cr12MoV steel forms the eutectic carbides in continuous net-shaped distribution thick in a large number, seriously isolate matrix, also can be used as formation of crack when die steel ruptures and crack propagation approach, thus make the crystal boundary serious embrittlement of die steel, toughness is very low.And when forging, owing to being subject to the restriction of forging ratio, for large size strand, the eutectic carbides in its heart portion is difficult to smash, so often there is Cold Roll segregation in die steel tissue after forging, the performance of die steel is made to occur anisotropy.And due to the existence of netted eutectic carbides, in forging process, easily there is the waste product that cracking and burning etc. cause.
Summary of the invention
The object of the present invention is to provide a kind of high hardness high toughness cold-work die steel and preparation method thereof, ballistic work >=the 76J of this cold-work die steel, hardness >=63HRC, have the cooperation of good high rigidity and high tenacity, to substitute traditional cold working die steel material, be applicable to manufacture accurate complicated die.
For achieving the above object, technical scheme of the present invention is:
A kind of high hardness high toughness cold-work die steel, its chemical component weight per-cent is: C:1.025 ~ 1.055%, Si:0.85 ~ 0.90%, Mn:0.20 ~ 0.40%, P<0.02%, S<0.02%, Cr:8.30 ~ 8.50%, Mo:1.95 ~ 2.05%, V:0.20 ~ 0.40%, all the other are Fe and inevitable impurity; And above-mentioned element needs satisfied following relation simultaneously: C=0.1 (Cr+Mo).
Further, the ballistic work >=76J of high hardness high toughness cold-work die steel of the present invention, hardness >=63HRC.
The microstructure of described high hardness high toughness cold-work die steel be sorbite+tiny carbide (alloy carbide present small and dispersed state, be evenly distributed on sorbitic matrix).
Effect and the restriction thereof of principal element of the present invention are described as follows:
C:C is the indispensable fundamental element forming the various carbide such as vanadium carbide, molybdenum carbide and chromium carbide, also be the important element affecting the component segregation of steel and the homogeneity of structure of steel, be dissolved in martensite and can ensure that martensite has good intensity and hardening capacity.In steel, carbon content increases, and yield-point and tensile strength raise, but plasticity and impact reduce.In addition, C can increase cold shortness and the aging sensitivity of steel; Lower C content can prevent steel from the process of solidifying, producing segregation tissue thus cause bending strength and the impact toughness decreased of steel.
In the present invention, if C content > 1.055%, being formed causing too much carbide and microstructure segregation generation, affecting the netted performance index of steel, particularly cause the bending strength of steel and impelling strength to reduce; But C content < 1.025% also will cause carbon C and other alloying elements to combine the equivalent generation deviation forming carbide, effectively can not form the compound action of stable, tiny carbide and carbide, affect the intensity of steel and the hardenability of steel.Therefore, the content of C controls between 1.025-1.055.
Si:Si is dissolved in matrix can improve matrix strong hardness, can hinder martensitic decomposition during tempering, improves steel belt roof bolt and stablizes, can play the effect of reductive agent and reductor in steelmaking process.Si can significantly improve the elastic limit of steel, yield-point and tensile strength.In drawing process after austenite to martensitic transformation, Si element can effectively hinder martensitic decomposition, and this mainly by suppressing growing up and expanding ε-carbide stable region of ε-carbide particle, is delayed ε-carbide to Fe
3the transformation of C.In the present invention, Si content significantly improves, and object stops the decomposition after martensitic transformation in drawing process further, to improving steel bending strength after quenching and impact property value has certain effect.Therefore, the content of Si controls between 0.85 ~ 0.9%.
Mn:Mn is in the process of austenitizing, and major part is added in the middle of matrix, improves the alloy content in matrix, strengthens solution strengthening effect, thus improves the hardness of matrix.But Mn has serious positive segregation tendency, can be enriched in eutectic cell grain boundaries, form intergranular carbide, can reduce the toughness of material.By Mn control of element in 0.2 ~ 0.4% scope, object is the hardness increasing matrix, and makes the stable performance of material.
Cr:Cr is carbide, can improve the hardening capacity of material, simultaneously cheap.But Cr is also the major cause that carbide network is formed, and affects the toughness of material.Therefore, the content of Cr is unsuitable too high, the too high webbed ledeburite carbide of Cr and C shape, carbide skewness in the crystallisation process of steel of these chromium, it is the main alloy element forming alloy ledeburite organization, this microstructure not only have impact on the effect that chromium element promotes hardening capacity in steel, and reduces bending strength and the notched bar impact strength index of steel.Suitable reduction Cr content, object makes materials microstructure even, improves the toughness of material.Therefore, the content of Cr controls between 8.3 ~ 8.5%.
Mo:Mo forms the Second Phase Precipitation thing of disperse in steel, and the precipitate of these disperses can not only play precipitation strength effect, and can effectively hinder growing up of austenite crystal, improves the obdurability of material.And because the avidity of Mo and carbon atom is strong, in drawing process, reduce martensitic decomposition rate, improve the stability of steel.The content of suitable raising Mo alloying element, makes tissue have more proeutectoid carbide disperse educt, makes martensite have sufficiently high hardness.Therefore, the content of Mo controls between 1.95 ~ 2.05%.
V:V is one of reinforced ferrite and austenite phase field forming element, and it and carbon, nitrogen, oxygen have extremely strong avidity, forms with it corresponding very stable compound.Mainly exist with the form of MC carbide in steel.Its Main Function in steel is: the tissue of refinement steel and crystal grain, improves grain coarsening temperature, thus reduces the superheated susceptivity of steel, and improves hardness and the toughness of steel, increases steel belt roof bolt stability.V is carbide, in ag(e)ing process, by the combination of V and C, and the VC that disperse educt is a large amount of, strengthening matrix.The microhardness (HV) of vanadium carbide reaches 2500 ~ 2800, after its content exceedes certain value, will harden because coherence separates out alloy carbide.V is in austenite cold-work die steel, and all right fining austenite grains, increases hardness and the toughness of steel, improve the wear resistance of steel.Therefore, the content of V controls between 0.20 ~ 0.40%.
P:P is the harmful element in steel, increases the fragility of steel, reduces the impelling strength of steel, and it is lower that P element controls more traditional cold-work die steel, has certain effect to the raising of performance index value.Therefore, the content of P controls at < 0.020%.
S:S easily causes the deterioration of the processing characteristics of steel, easily makes steel produce overheated and burn-off phenomenon in hot worked process.Therefore control sulphur content lower, can improve steel processing characteristics and mechanical property, the superheating phenomenon that the continuous forging machining particularly during diameter forging machine hammer cogging produces plays the effect of drawing up.Therefore, the content of S controls at < 0.020%.
The present invention's control C=0.1 (Cr+Mo): chromium element and molybdenum element are combined with carbon in the material and form MC23, MC7 type carbide, and this kind of carbide is the basic guarantee supporting steel high rigidity of the present invention and high tenacity, carbon element content proportioning is only had to meet this relational expression, material just can be made to obtain best microstructure, just can make tiny, uniform MC23, MC7 type distribution of carbides on whole microstructure matrix, thus obtain better hardness and best toughness, realize the object of high rigidity and high tenacity coupling.
In chemical composition design of the present invention: carbon content is lower, decrease the segregation of primary carbide, its objective is distribution and the character of the carbide improved in the microstructure of steel, improve the rank of the carbide network of steel; Mo and V forms the Second Phase Precipitation thing of disperse in steel, and the precipitate of these disperses can not only play precipitation strength effect, and can effectively hinder growing up of austenite crystal, improves hardness and the toughness of material.
The thick phenomenon that the rational proportion of alloying element of the present invention makes the carbide ledeburite eutectic under cold-work die steel as cast condition separate out improves, just can obtain with less forging ratio when forging and be uniformly distributed preferably, namely when identical forging ratio, carbide acquisition is better uniformly distributed, and makes material obtain good hardness and toughness.
Present invention also offers a kind of preparation method of high tough high abrasion height cold-work die steel, comprise the steps: to adopt induction furnace to carry out melting by above-mentioned chemical composition, be cast into steel ingot; Steel ingot is positioned in electroslag remelting device as consumable electrode, carries out esr, in the water mold of liquid metal below the slag blanket of slag bath falls to, is more again frozen into steel ingot; Above-mentioned steel ingot is heated to 1200 ~ 1220 DEG C with the heat-up rate of 80 ~ 120 DEG C/h, and carry out forging processing after insulation 2 ~ 4h, initial forging temperature is 1040 ~ 1060 DEG C, final forging temperature 850 ~ 900 DEG C; Forging is heated to 1020 ~ 1040 DEG C, insulation 2.0 ~ 2.2h carry out quench treatment, water-cooled is to room temperature; After quenching 180 ~ 230 DEG C, insulation 1.8 ~ 2.0h carry out temper, air cooling, to room temperature, namely obtains high cold-work die steel of the present invention.
Main technologic parameters of the present invention controls as follows:
The thermal stresses susceptibility of steel ingot of the present invention in heat-processed is higher, easily produces stress crack, and heat-up rate controls at 80 ~ 120 DEG C/h, can prevent steel ingot from heat-processed, producing crack due to thermal stress; 2 ~ 4 hours are incubated after being heated to 1200 ~ 1220 DEG C, make the temperature in the whole surface of steel ingot to heart portion can keep even, the malleable shape of steel ingot can be improved, prevent the tearing tendency of steel in forging process, and the microstructure index of steel can be improved, improve hardness and the toughness of steel.
The present invention is under 1200 ~ 1220 DEG C of conditions of high temperature, alloying element has the kinetic energy promoting diffusibility, and under the behavior of the diffusion that homogenizes of alloying element, microstructure more can be evenly distributed on matrix, make carbide particle very evenly tiny, improve the hardness of body material, toughness.
It is 1040 ~ 1060 DEG C that the present invention opens forging temperature through the forging of forging machine: because steel of the present invention is austenite one phase tissue regions of steel 1040 ~ 1060 DEG C of temperature ranges, there is best high temperature thermoplasticity, be conducive to high temperature deformation processing treatment, be not easy to produce high-temperature hot processing cracking.
It is 850 ~ 900 DEG C that the forging machine of steel of the present invention stops forging temperature: because steel ingot finishing temperature has important impact to steel ingot rolling quality, if footpath forging machine stops forging temperature lower than 850 DEG C, is very easy to cause steel ingot to produce ingot cracking in footpath forging machine hammer cogging process; But, stop forging temperature higher than 900 DEG C easily cause steel after footpath forging machine hammer cogging, produce steel organize coarse-grain phenomenon, and form serious carbide network, reduce the performance of steel.
The present invention, by after Quench heating to 1020 ~ 1040 DEG C of austenitizings, impels alloying element to dissolve in matrix in a large number, improves alloy degree, strengthens solid solution strengthening effect.Meanwhile, in drawing process, the second phase particles of disperse educt fine uniform, by precipitation strength, improves Fracture of Material.
Beneficial effect of the present invention:
1) chemical composition aspect: carbon and chromium content low, increase Mo content, and add the carbide forming elements such as V, to reduce and refining eutectic carbide, crystal grain thinning, can highly malleablized matrix, serves again the object reducing alloying element cost; Be solid-solution in matrix with appropriate Si, improve obdurability; Under austenitizing temperature, C in austenite is made to reach about 0.6% and have high hardenability.
2) microstructure aspect: in microstructure, carbide is evenly slightly distributed on sorbite matrix, makes the more difficult formation of carbide network.Therefore, under equal forging ratio condition, in the tissue of as cast condition of the present invention, dendroid carbide morphology obtains better fragmentation, the microstructure of refinement steel, improves hardness value and the toughness value of steel.
3) manufacturing process aspect: the control of forging process makes the temperature in the whole surface of steel ingot to heart portion can keep even, improve the malleable shape of steel ingot, prevent the tearing tendency of steel in forging process, and make large block carbide obtain effective fragmentation, carbide agglomeration difficulty, thus all even tiny being distributed on sorbite matrix can create condition with the homogenizing of microstructure for carbide.
4) the rational chemical composition proportioning of the present invention and advanced manufacturing process combine, and the performance index of steel are obviously promoted, and compared with traditional Cr12MoV steel, the ballistic work >=76J of steel of the present invention, improves more than 95%; Hardness >=63HRC, improves more than 5%.
5) hardening capacity of steel of the present invention is good, and quenching temperature is lower, and heat treatment deformation is little, and price is low, can replace Cr12MoV steel, apply to the high-end market of die industry in a big way.
Accompanying drawing explanation
Fig. 1 is the microstructure metallograph of traditional C r12MoV steel.
Fig. 2 is the microstructure metallograph of the embodiment of the present invention 1 steel.
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention will be further described.
Table 1 is the chemical composition of the embodiment of the present invention 1 ~ 6, and table 2 embodiment of the present invention 1 ~ 6 preparation technology parameter controls, and table 3 is the performance of the embodiment of the present invention 1 ~ 6 steel.
Steel ingot is cast into after carrying out melting in the chemical composition employing induction furnace in table 1, the steel ingot be cast into is positioned in electroslag remelting device as consumable electrode, carry out esr, in the water mold of liquid metal below the slag blanket of slag bath falls to, be more again frozen into 1.5 ~ 2.3 tons of steel ingots; Above-mentioned Heating Steel Ingots to 1200 ~ 1220 DEG C temperature is carried out forging processing after 2 ~ 4 hours; Initial forging temperature: 1040 ~ 1060 DEG C, final forging temperature 850 ~ 900 DEG C.Forging is heated to quenching temperature 1020 ~ 1040 DEG C, insulation was put into water and is cooled to room temperature after 2 ~ 2.2h hour, reheat to tempering temperature 180 ~ 230 DEG C, insulation after 1.8 ~ 2 hours air cooling to room temperature.
As shown in Table 3, the present invention under rational chemical composition proportioning and process regulation, the ballistic work >=76J of the cold-work die steel of manufacture, hardness >=63HRC, have the cooperation of good high rigidity and high tenacity, compared with traditional Cr12MoV steel, the performance index of steel obviously promote.
As seen from Figure 1, Figure 2, there is the segregation of ledeburite carbide in the metallographic structure of traditional C rMoV steel after Q-tempering, cause the decline of toughness of material; Sorbite matrix is uniform-distribution with the tiny carbide particle of disperse in steel microscopic structure of the present invention, guarantees that steel of the present invention has excellent hardness and toughness to coordinate.
Table 1 unit: weight percent
Table 2
Table 3
| Embodiment | Ballistic work J | Hardness value (HRC) |
| 1 | 76 | 63 |
| 2 | 77 | 63.5 |
| 3 | 81 | 63 |
| 4 | 78 | 63 |
| 5 | 82 | 63 |
| 6 | 76 | 63.5 |
Claims (6)
1. a high hardness high toughness cold-work die steel, its chemical component weight per-cent is: C:1.025 ~ 1.055%, Si:0.85 ~ 0.90%, Mn:0.20 ~ 0.40%, P<0.02%, S<0.02%, Cr:8.30 ~ 8.50%, Mo:1.95 ~ 2.05%, V:0.20 ~ 0.40%, all the other are Fe and inevitable impurity; And above-mentioned element needs satisfied following relation simultaneously: C=0.1 (Cr+Mo).
2. high hardness high toughness cold-work die steel according to claim 1, is characterized in that, the ballistic work >=76J of described high hardness high toughness cold-work die steel, hardness >=63HRC.
3. high hardness high toughness cold-work die steel according to claim 1 and 2, is characterized in that, the microstructure of described high hardness high toughness cold-work die steel is sorbite+tiny carbide.
4. the preparation method of high hardness high toughness cold-work die steel as claimed in claim 1, comprises the steps:
1) smelting, casting, remelting
Carry out melting by the chemical composition described in the claims 1, be cast into steel ingot; Steel ingot is positioned in electroslag remelting device as consumable electrode, carries out esr, is more again frozen into steel ingot;
2) Heating Steel Ingots
Again the steel ingot solidified is heated to 1200 ~ 1220 DEG C with the heat-up rate of 80 ~ 120 DEG C/h, insulation 2 ~ 4h;
3) forging processing
It is 1040 ~ 1060 DEG C that forging starts temperature, and final forging temperature is 850 ~ 900 DEG C;
4) quench treatment
Forging is heated to 1020 ~ 1040 DEG C, insulation 2 ~ 2.2h, water-cooled is to room temperature;
5) temper
Tempering temperature is 180 ~ 230 DEG C, insulation 1.8 ~ 2.0h, and air cooling, to room temperature, namely obtains described high hardness high toughness cold-work die steel.
5. preparation method according to claim 4, is characterized in that, the ballistic work >=76J of described high hardness high toughness cold-work die steel, hardness >=63HRC.
6. the preparation method according to claim 4 or 5, is characterized in that, the microstructure of described high hardness high toughness cold-work die steel is sorbite+tiny carbide.
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