CN110656281A - High-hardness die steel and preparation method thereof - Google Patents
High-hardness die steel and preparation method thereof Download PDFInfo
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- CN110656281A CN110656281A CN201810694817.1A CN201810694817A CN110656281A CN 110656281 A CN110656281 A CN 110656281A CN 201810694817 A CN201810694817 A CN 201810694817A CN 110656281 A CN110656281 A CN 110656281A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 142
- 239000010959 steel Substances 0.000 title claims abstract description 142
- 238000002360 preparation method Methods 0.000 title abstract description 7
- 238000005242 forging Methods 0.000 claims abstract description 47
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 239000002893 slag Substances 0.000 claims description 8
- 230000001939 inductive effect Effects 0.000 claims description 4
- 229910001338 liquidmetal Inorganic materials 0.000 claims description 4
- 229910001208 Crucible steel Inorganic materials 0.000 claims description 3
- 238000003723 Smelting Methods 0.000 claims description 3
- 239000011651 chromium Substances 0.000 abstract description 24
- 229910052799 carbon Inorganic materials 0.000 abstract description 21
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 15
- 239000011159 matrix material Substances 0.000 abstract description 14
- 229910052804 chromium Inorganic materials 0.000 abstract description 12
- 229910052720 vanadium Inorganic materials 0.000 abstract description 8
- 230000000694 effects Effects 0.000 abstract description 7
- VYZAMTAEIAYCRO-UHFFFAOYSA-N chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 abstract description 6
- 229910000765 intermetallic Inorganic materials 0.000 abstract description 6
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 6
- 229910052802 copper Inorganic materials 0.000 abstract description 4
- 229910052759 nickel Inorganic materials 0.000 abstract description 4
- 238000010791 quenching Methods 0.000 abstract description 4
- 230000000171 quenching Effects 0.000 abstract description 4
- 239000000126 substance Substances 0.000 abstract description 4
- 238000005266 casting Methods 0.000 abstract description 3
- 239000000463 material Substances 0.000 description 26
- 238000005452 bending Methods 0.000 description 14
- 238000000034 method Methods 0.000 description 13
- 229910045601 alloy Inorganic materials 0.000 description 10
- 239000000956 alloy Substances 0.000 description 10
- REDXJYDRNCIFBQ-UHFFFAOYSA-N aluminium(3+) Chemical class [Al+3] REDXJYDRNCIFBQ-UHFFFAOYSA-N 0.000 description 10
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 10
- 229910000734 martensite Inorganic materials 0.000 description 8
- 150000001247 metal acetylides Chemical class 0.000 description 8
- 238000005496 tempering Methods 0.000 description 8
- 229910001566 austenite Inorganic materials 0.000 description 7
- 239000010949 copper Substances 0.000 description 7
- 230000005496 eutectics Effects 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- 238000005204 segregation Methods 0.000 description 6
- 238000005096 rolling process Methods 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 238000005275 alloying Methods 0.000 description 4
- 238000005336 cracking Methods 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 229910001349 ledeburite Inorganic materials 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium(0) Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 4
- 238000000641 cold extrusion Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 230000001131 transforming Effects 0.000 description 3
- 229910001182 Mo alloy Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000005755 formation reaction Methods 0.000 description 2
- GORXZVFEOLUTMI-UHFFFAOYSA-N methane;vanadium Chemical compound C.[V] GORXZVFEOLUTMI-UHFFFAOYSA-N 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
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- 230000000979 retarding Effects 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 238000005482 strain hardening Methods 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 210000001519 tissues Anatomy 0.000 description 2
- UFGZSIPAQKLCGR-UHFFFAOYSA-N Chromium carbide Chemical compound [Cr]#C[Cr]C#[Cr] UFGZSIPAQKLCGR-UHFFFAOYSA-N 0.000 description 1
- 229910000599 Cr alloy Inorganic materials 0.000 description 1
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 1
- 229910039444 MoC Inorganic materials 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 125000004432 carbon atoms Chemical group C* 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000010622 cold drawing Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000000875 corresponding Effects 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
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- 238000010891 electric arc Methods 0.000 description 1
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- 229910000529 magnetic ferrite Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
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- 229910052757 nitrogen Inorganic materials 0.000 description 1
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- 150000002843 nonmetals Chemical class 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
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- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N oxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 239000003638 reducing agent Substances 0.000 description 1
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- 239000000243 solution Substances 0.000 description 1
- 229910003470 tongbaite Inorganic materials 0.000 description 1
- -1 vanadium carbide Chemical class 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 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
- C22C38/02—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
- 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
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/16—Remelting metals
- C22B9/18—Electroslag remelting
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- 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
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
Abstract
The invention discloses a high-hardness die steel and a preparation method thereof, wherein the chemical component proportion is characterized in that the contents of carbon and chromium are reduced, C and Cr are controlled within a reasonable range, a certain amount of carbide forming elements such as Mo, V and the like are added, a matrix can be strengthened and toughened, the carbide form of the cold-work die steel in a casting state is improved, a better forging effect can be obtained by a smaller forging ratio during forging, and on the basis, Ni and Cu microalloy elements are added to form a Cu3.8Ni intermetallic compound which is precipitated at the grain boundary of a machine body, and the machine body is strengthened, so that the hardness of the machine body is improved. The steel has the advantages of good hardenability, lower quenching temperature, small heat treatment deformation, low price, better matching of strength and toughness, suitability for manufacturing precise complex dies and capability of replacing Cr12MoV type general cold-work die steel in a larger range.
Description
Technical Field
The invention relates to die steel, in particular to high-hardness die steel and a preparation method thereof.
Background
The high-hardness die steel is mainly used for manufacturing dies for press forming in a cold state (room temperature), such as cold drawing dies, cold heading dies, cold extrusion dies, stamping dies, rolling dies and the like. The cold-working die has working conditions somewhat similar to those of a cutting tool, but has a large deformation resistance because the material to be processed is deformed in a cold state. High hardness die steels require higher hardenability, wear resistance and toughness than cutting tool steels, while red hardness can be less, and the temperature rise of a typical die during operation does not exceed 250 ℃.
At present, the most widely applied die steel material in the domestic die material market is the high-carbon high-chromium cold-work die steel Cr12MoV which is taken as the main selection universal type cold-work die steel material. The steel material has high hardenability, wear resistance and high-temperature oxidation resistance, and can be used as a universal cold-work die steel material for manufacturing cold-work dies with various purposes, such as a punching female die, a cold extrusion die, a rolling threaded wheel, a cold shearing knife, a precision measuring tool and the like with complex shapes. However, the alloy elements in the Cr12MoV universal cold work die steel material contain high carbon and chromium elements (the material comprises, by mass, 1.45-1.70% of C, less than or equal to 0.40% of Si, less than or equal to 0.40% of Mn, 11.0-12.5% of Cr11, 0.4-0.6% of Mo0.10, less than or equal to 0.10% of Ni, less than or equal to 0.10% of Cu, less than or equal to 0.030% of P, and less than or equal to 0.030% of S), and excessive carbon and chromium elements can cause reticular ledeburite carbide in a microstructure of the material, so that the toughness of the material is not high. The mould is susceptible to chipping, breaking or collapsing in use.
The main performance indexes of the Cr12MoV steel are as follows: bending strength 2500MP, hardness 59HRC. The performance indexes are key technical indexes of cold-work die steel. The cold-working die is mainly used for cold forming of metal or nonmetal materials, and comprises cold stamping, cold extrusion, cold heading and the like. The die has large working load, high dimensional accuracy and high surface quality requirement. The cold work die steel generally selected requires sufficient strength, toughness, hardness and wear resistance. And the Cr12MoV steel has lower toughness although the hardness and the wear resistance are higher after quenching and tempering because the structure contains non-uniform ledeburite carbide. The cracking and collapse easily occur in practical use.
The Cr12MoV steel is smelted by adopting an electric arc furnace, cast into a steel ingot, forged and cogging, and the specific steps comprise steelmaking, forging and heat treatment in sequence to finally form a product. The heating temperature for forging is 1110-1130 ℃, the finish forging temperature is more than or equal to 900 ℃, and the cooling mode adopts high-temperature annealing, pit cooling or sand cooling. The Cr12MoV steel forms a large amount of coarse eutectic carbides distributed in a continuous network. The netlike eutectic carbide severely cuts the matrix and can also be used as a crack source and a crack propagation path when the die steel is broken, so that the grain boundary of the die steel is severely embrittled and the toughness is very low. In addition, because the limit of the forging ratio is applied during forging, eutectic carbide in the core part of a large-size casting blank is difficult to break up, and therefore, strip-shaped carbide segregation often exists in the structure of the die steel after forging, so that the performance of the die steel is anisotropic. And the existence of the reticular eutectic carbide is easy to cause waste products caused by cracking, overburning and the like in the forging process.
Disclosure of Invention
Aiming at the research works such as the optimization of the components of the die steel, the tissue control, the metallurgical quality control, the forging and rolling process control, the tissue control of the supply state and the use state, the micro-alloying application technology and the like, the invention develops the high-hardness die steel which has higher hardness and yield strength matching, replaces the traditional cold-work die steel material and is applied to the high-end market of the die industry.
In order to achieve the above object, the present invention adopts the following technical solutions.
On the one hand, the high-hardness die steel and the preparation method thereof comprise the following components in percentage by mass: 1.01 to 1.15% of C, 0.60 to 0.85% of Si, 0.20 to 0.40% of Mn, 0.02% of P, 0.02% of S, 7.50 to 8.20% of Cr, 2.00 to 2.20% of Mo, 0.20 to 0.40% of V, 0.20 to 0.30% of Ni, 0.15 to 0.25% of Cu, and the balance of Fe, wherein C is 1/15Cr +1/4 Mo.
In another aspect, a method of making a high hardness die steel includes:
according to the component proportion of the high-hardness die steel, after smelting in an induction furnace, placing the cast steel ingot serving as a consumable electrode in an electroslag remelting device, carrying out electroslag remelting, enabling liquid metal to fall into a lower water-cooled crystallizer through a slag layer of a slag pool, and then re-solidifying into a 2.0-3.0 t electroslag steel ingot; heating the steel ingot to the temperature of 1200-1220 ℃, preserving heat for 3-5 hours, and then forging; the initial forging temperature is 1040-1060 ℃, and the final forging temperature is more than or equal to 900 ℃.
The steel ingot is heated to 1200-1220 ℃ in a forging machine heating furnace at a heating rate of 80-120 ℃/h.
By adopting the high-hardness die steel and the preparation method thereof, the contents of carbon and chromium are reduced in the aspect of chemical component proportion, C and Cr are controlled within a reasonable range, a certain amount of carbide forming elements such as Mo, V and the like are added, the matrix can be strengthened and toughened, the carbide form of the cold-work die steel in a casting state is improved, and a better forging effect can be obtained by a smaller forging ratio during forging, namely, the carbide can be better and uniformly distributed under the condition of the same forging ratio, and the purpose of controlling the cost of alloy elements is achieved. On the basis, Ni and Cu microalloy elements are added to form a Cu3.8Ni intermetallic compound which is precipitated at the grain boundary of the organism to strengthen the organism, thereby improving the hardness of the organism. The steel has the advantages of good hardenability, lower quenching temperature, small heat treatment deformation, low price, better matching of strength and toughness, suitability for manufacturing precise complex dies and capability of replacing Cr12MoV type general cold-work die steel in a larger range. In addition, after the die steel is austenitized, a large amount of alloy elements are promoted to be dissolved into a matrix, the degree of alloying is improved, and the solid solution strengthening effect is enhanced. Meanwhile, in the process of secondary tempering, fine and uniform second-phase particles and intermetallic compounds are dispersed and precipitated and strengthened through a grain boundary, so that the hardness of the die material is improved.
Drawings
FIG. 1 is a metallographic photograph of a prior art Cr12MoV steel;
fig. 2 is a metallographic photograph of a high hardness die steel of the present invention.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
The design principle of the invention is as follows:
on the basis of Cr12MoV, C and Cr are properly reduced, Mo and V are increased to reduce and refine eutectic carbide, refine crystal grains and properly increase Si to improve the toughness. The component is dissolved in matrix with proper amount of Si, and has high toughness, high hardenability, high bending strength and high hardness, and the C content in austenite reaches about 0.6% at austenitizing temperature. The high-hardness die steel comprises the following specific components:
comprises the following components in percentage by mass: 1.01-1.15% of C, 0.60-0.85% of Si, 0.20-0.40% of Mn, 0.02% of P, 0.02% of S, 7.50-8.20% of Cr, 2.00-2.20% of Mo, 0.20-0.40% of V, 0.20-0.30% of Ni, 0.15-0.25% of Cu and the balance of Fe, and the following mathematical relation is satisfied: c1/15 Cr +1/4 Mo. Because chromium and molybdenum are strong carbide forming alloy elements, the chromium and the molybdenum can form M23C7 and M7C3 type carbides by combining with carbon and can be uniformly and dispersedly distributed on the grain boundary of a microstructure, the proper carbide type, quantity and dispersion degree distribution are the basis for obtaining high bending strength and high hardness of the material, and the material can obtain the optimal microstructure only if the content of the chromium and molybdenum alloy elements and the content of the carbon element meet the mathematical relation formula, and the optimal microstructure is characterized in that the M23C7 and the M7C3 type carbides are finely and uniformly distributed on the grain boundary of the microstructure, so that the matching of the optimal bending strength and the high hardness of the steel material is ensured.
The following are descriptions of the role and limitations of the main elements of the present invention:
C 1.01～1.15％
the C-C element is one of main chemical elements of the high-strength and high-toughness cold-work die steel, is an indispensable basic element for forming various carbides such as vanadium carbide, molybdenum carbide and chromium carbide, is an important element for influencing the composition segregation of the steel and the structural uniformity of the steel, and can ensure that the martensite has good strength and hardenability when dissolved in the martensite. The carbon content in the steel increases, the yield point and tensile strength increase, but the plasticity and impact properties decrease. In addition, carbon can increase the cold brittleness and age sensitivity of the steel. Compared with Cr12MoV steel, the carbon content of the steel is greatly reduced, and the steel aims to improve the distribution and the property of carbide in the microstructure of the steel and improve the grade of network carbide of the steel. The lower carbon content can prevent the steel from generating segregation structure in the solidification process so as to reduce the bending strength and the impact toughness of the steel. Therefore, if the carbon content is higher than the upper limit of the composition design, excessive carbide formation and segregation of the structure will occur, which will affect the net-like performance index of the steel, especially will cause the reduction of the bending strength and impact toughness of the steel; however, the design range of the carbon element lower than the composition will cause the deviation of the equivalent weight of the carbide formed by combining the carbon element and other alloy elements, and the stable fine carbide and the compound action of the carbide can not be effectively formed, thereby affecting the strength of the steel and the hardenability of the steel.
Si 0.60～0.85％
Si is dissolved in the matrix to improve the matrix strength, can block the decomposition of martensite during tempering, improves the tempering stability of steel, and can play the role of a reducing agent and a deoxidizing agent in the steelmaking process. Silicon can significantly improve the elastic limit, yield point and tensile strength of steel. Elemental silicon is effective in retarding the martensite decomposition during tempering after austenite to martensite transformation, primarily by retarding the transformation of epsilon carbides to Fe3C by simulating the growth of epsilon carbide particles and enlarging the epsilon carbide plateau. The control of the silicon content of the steel is greatly improved compared with the prior Cr12MoV steel, the aim is to further prevent the decomposition of the steel in the tempering process after the martensite transformation, and the steel has certain effect on improving the bending strength and the impact property value of the steel after quenching.
Mn 0.2～0.4％
Most of Mn is dissolved into the matrix in the austenitizing process, so that the alloy content in the matrix is increased, and the solid solution strengthening effect is enhanced, thereby improving the strength of the matrix. However, Mn has a serious positive segregation tendency, and can be enriched at eutectic cell grain boundaries to form intergranular carbides, so that the toughness of the material can be reduced. The Mn element is controlled within a certain range in order to increase the strength of the matrix and stabilize the properties of the material.
Cr 7.5～8.5％
Cr is a strong carbide forming element, can improve the hardenability of the material, and is low in price. However, Cr is also a main cause of the formation of network carbide and affects the toughness of the material, so that the content of Cr is not preferably too high. The CrMoV steel contains 11.0-13.0% of Cr, the Cr and C form net ledeburite carbide, the Cr carbide is unevenly distributed in the crystallization process of the steel and is a main alloy element for forming alloy ledeburite structure, and the microstructure not only influences the effect of improving hardenability of the Cr element in the steel, but also reduces the bending strength and impact toughness value index of the steel. The Cr content is properly reduced, so that the structure of the material is uniform, and the toughness of the material is improved.
Mo 2.00～2.20％
Mo forms dispersed second-phase precipitates in steel, and the dispersed precipitates can play a role in precipitation strengthening and can effectively inhibit the growth of austenite grains so as to improve the toughness of the material. And because Mo has strong affinity with carbon atoms, the decomposition speed of martensite is reduced in the tempering process, and the stability of the steel is improved. Compared with Cr12MoV, the content of Mo alloy element is properly increased, so that more secondary carbides are dispersed and precipitated in the structure, and the martensite has high enough strength.
V 0.20～0.40％
Vanadium is one of the strengthening ferrite and austenite phase region forming elements, has strong affinity with carbon, nitrogen and oxygen, and forms a corresponding extremely stable compound. In steel, MC carbide is mainly present. Its main role in steel is: the structure and the crystal grains of the steel are refined, and the coarsening temperature of the crystal grains is increased, so that the overheating sensitivity of the steel is reduced, and the strength and the toughness of the steel are improved; the tempering stability of the steel is increased. Vanadium is a strong carbide forming element, and a large amount of VC is dispersed and precipitated through the combination of vanadium and carbon in the aging process to strengthen the matrix. The micro-Hardness (HV) of vanadium carbide reaches 2500-. In the austenitic hot-work die steel, the vanadium can also refine austenite grains, increase the strength and toughness of the steel and improve the wear resistance of the steel.
Ni 0.20～0.30％、Cu0.15～0.25％
The nickel and copper elements are not carbide forming elements, the carbide is not formed in the organism, but the intermetallic compound of Cu3.8Ni is formed and dispersed in the organism under the action of the mutual outer layer electron attraction force of the nickel and copper elements, and the organism is strengthened on the organism grain boundary, so that the yield strength and the hardness of the material are increased.
P＜0.020％
Phosphorus is a harmful element in steel, increases the brittleness of the steel and reduces the impact toughness of the steel, so that the control of the phosphorus element is lower than that of the traditional cold-work die steel, and the phosphorus element has a certain effect on improving the performance index value.
S＜0.010％
The sulfur element easily causes deterioration of workability of the steel to a certain extent, and easily causes overheating and overburning of the steel during hot working. Therefore, the control of the sulfur content lower than that of Cr12MoV steel in the prior art can improve the processing performance and mechanical performance of the steel, and especially play a role in simulating the overheating phenomenon generated by continuous forging processing when a radial forging machine performs forging and cogging.
The preparation method of the high-hardness die steel comprises the following steps:
according to the component ratio of the steel, after the steel is smelted in an induction furnace, the cast steel ingot is placed in an electroslag remelting device as a consumable electrode to be electroslag remelted, so that liquid metal falls into a water-cooled crystallizer below through a slag layer of a slag bath and is re-solidified into 2.0-3.0 t of electroslag steel ingot; heating the steel ingot to the temperature of 1200-1220 ℃, preserving heat for 3-5 hours, and then forging; the initial forging temperature is 1040-1060 ℃, and the final forging temperature is more than or equal to 900 ℃.
The main process parameters are controlled as follows:
heating the steel ingot to 1200-1220 ℃ in a heating furnace of a forging machine at a heating rate of 80-120 ℃/h, and then preserving heat for 3-5 hours:
the steel ingot has high thermal stress sensitivity in the heating process and is easy to generate stress cracks, the temperature rise speed is controlled to be 80-120 ℃/h, the steel ingot can be prevented from generating the thermal stress cracks in the heating process, the steel ingot is heated to 1200-1220 ℃ and then is kept for 3-5 hours, so that the temperature from the whole surface to the core of the steel ingot can be kept uniform, the forgeability of the steel ingot can be improved, the cracking tendency of the steel in the forging process can be prevented, the microstructure index of the steel can be improved, and the strength and the toughness of the steel can be improved.
Forging by a forging machine at the forging temperature of 1040-1060 ℃:
because the steel is an austenite single-phase structure area of the steel at the temperature range of 1040-1060 ℃, the steel has the best high-temperature thermoplasticity, is beneficial to high-temperature deformation processing and is not easy to generate high-temperature hot processing cracking.
The forging machine stop forging temperature of the steel is more than or equal to 900 ℃:
the finish rolling temperature of the steel ingot has important influence on the rolling quality of the steel ingot, the stop forging temperature of the radial forging machine is lower than the specified control range, the steel ingot is easy to crack in the forging and cogging process of the radial forging machine, but the stop forging temperature is higher than the control range, the steel structure coarse grain phenomenon is easy to generate after the forging and cogging of the radial forging machine, serious net-shaped carbide is formed, and the performance of the steel is reduced.
The characteristics and advantages of the invention are as follows:
(1) the alloy element composition design of the die steel is to properly reduce C and Cr and increase Mo and V on the basis of Cr12MoV so as to reduce and refine eutectic carbide and refine grains. Proper amount of Si is dissolved in the matrix in a solid solution mode, so that the toughness is improved; the amount of C in austenite is about 0.6% at the austenitizing temperature, and the steel has high hardenability.
(2) Compared with Cr12MoV steel, the steel has greatly improved distribution of carbide in the microstructure and network carbide grade. Therefore, under the condition of the same forging ratio, the steel of the patent can better crush dendritic carbide in an as-cast structure than Cr12MoV, refine the microstructure of the steel and improve the performance of the steel.
(3) The reasonable chemical component proportion promotes the uniform precipitation and strengthening of carbide and the micro-alloying technology application of the intermetallic compound formed by the addition of micro-alloying elements, improves the bending strength and the body hardness of the material and obviously improves the performance index of the steel by combining with an advanced manufacturing process. Under the same wear resistance condition, the bending strength work of the traditional Cr12MoV steel is 2500MP, the hardness is 59HRC, and the performance index of the steel can reach the bending strength 3350MP, which is improved by 25 percent; the hardness can reach HRC63, and is improved by 6 percent.
Example 1
In the embodiment, the components of the high-hardness die steel are as follows by weight percent:
1.06% of C, 0.66% of Si, 0.36% of Mn, 8.18% of Cr, 2.10% of Mo, 0.35% of V, 0.28% of Ni, 0.19% of Cu, 0.016% of P, 0.013% of S and the balance of Fe.
The process of the high-hardness die steel comprises the following steps:
placing a steel ingot cast after smelting in an induction furnace as a consumable electrode in an electroslag remelting device for electroslag remelting, allowing liquid metal to fall into a lower water-cooled crystallizer through a slag layer of a slag pool, and re-solidifying into a 2.3-ton steel ingot; heating the steel ingot to 1220 ℃, and carrying out forging processing after heat preservation for 4.5 hours; initial forging temperature: 1060 ℃ and a finish forging temperature of 920 ℃.
The hardness of the high-strength and high-toughness wear-resistant cold-work die steel reaches HRC63, and is improved by 6% compared with the Cr12MoV of the general cold-work die steel; the bending strength reaches 3350MP, and the Cr12MoV of the traditional die steel is improved by 25 percent.
The specific chemical components (Wt%) of examples 2 to 6 are shown in table 2, the process parameter control is shown in table 3, and the performance index is shown in table 4.
TABLE 2
TABLE 3
TABLE 4
| Examples | Bending strength (MP) | Hardness value (HRC) |
| 2 | 3380 | 63.0 |
| 3 | 3360 | 63.5 |
| 4 | 3355 | 63.5 |
| 5 | 3355 | 63.0 |
| 6 | 3375 | 63.5 |
FIG. 1 is a metallographic photograph of Cr12MoV steel, FIG. 2 is a metallographic photograph of high hardness die steel according to example 1 of the present invention, and it is seen from FIG. 1 that segregation of ledeburitic carbides occurs to cause a decrease in the flexural strength and body hardness of the material. While it can be seen from fig. 2 that the dispersed fine alloy carbide particles and intermetallic compound particles are uniformly distributed on the sorbite matrix, such a microstructure ensures the excellent combination of bending strength and high hardness of the high hardness die steel of the present invention.
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that changes and modifications to the above described embodiments are within the scope of the claims of the present invention as long as they are within the spirit and scope of the present invention.
Claims (3)
1. A high-hardness die steel is characterized by comprising the following components in percentage by mass: 1.01 to 1.15% of C, 0.60 to 0.85% of Si, 0.20 to 0.40% of Mn, 0.02% of P, 0.02% of S, 7.50 to 8.20% of Cr, 2.00 to 2.20% of Mo, 0.20 to 0.40% of V, 0.20 to 0.30% of Ni, 0.15 to 0.25% of Cu, and the balance of Fe, wherein C is 1/15Cr +1/4 Mo.
2. The method for preparing the high hard die steel according to claim 1, comprising:
according to the component proportion of the high-hardness die steel, after smelting in an induction furnace, placing the cast steel ingot serving as a consumable electrode in an electroslag remelting device, carrying out electroslag remelting, enabling liquid metal to fall into a lower water-cooled crystallizer through a slag layer of a slag pool, and then re-solidifying into a 2.0-3.0 t electroslag steel ingot; heating the steel ingot to the temperature of 1200-1220 ℃, preserving heat for 3-5 hours, and then forging; the initial forging temperature is 1040-1060 ℃, and the final forging temperature is more than or equal to 900 ℃.
3. The method of claim 2, wherein: the steel ingot is heated to 1200-1220 ℃ in a forging machine heating furnace at a heating rate of 80-120 ℃/h.
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