CN115627419B - High-strength high-toughness Cr8 cold-work die steel and preparation method thereof - Google Patents
High-strength high-toughness Cr8 cold-work die steel and preparation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 308
- 239000010959 steel Substances 0.000 title claims abstract description 308
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 238000005242 forging Methods 0.000 claims abstract description 96
- 238000007670 refining Methods 0.000 claims abstract description 92
- 230000009467 reduction Effects 0.000 claims abstract description 40
- 238000010438 heat treatment Methods 0.000 claims abstract description 37
- 238000000137 annealing Methods 0.000 claims abstract description 27
- 238000003723 Smelting Methods 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 24
- 238000010079 rubber tapping Methods 0.000 claims abstract description 21
- 230000005540 biological transmission Effects 0.000 claims abstract description 20
- 238000005482 strain hardening Methods 0.000 claims abstract description 14
- 238000002844 melting Methods 0.000 claims abstract description 12
- 230000008018 melting Effects 0.000 claims abstract description 12
- 239000002893 slag Substances 0.000 claims description 155
- 239000002994 raw material Substances 0.000 claims description 117
- 238000007664 blowing Methods 0.000 claims description 80
- 229910052760 oxygen Inorganic materials 0.000 claims description 75
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 74
- 239000001301 oxygen Substances 0.000 claims description 74
- 239000000047 product Substances 0.000 claims description 74
- 239000000843 powder Substances 0.000 claims description 64
- 229910045601 alloy Inorganic materials 0.000 claims description 63
- 239000000956 alloy Substances 0.000 claims description 63
- 239000011261 inert gas Substances 0.000 claims description 52
- 229910052799 carbon Inorganic materials 0.000 claims description 42
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 38
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 30
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 30
- 239000004571 lime Substances 0.000 claims description 30
- 238000004458 analytical method Methods 0.000 claims description 26
- 239000000463 material Substances 0.000 claims description 26
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 26
- 150000002910 rare earth metals Chemical class 0.000 claims description 26
- 238000003756 stirring Methods 0.000 claims description 26
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 16
- 239000010436 fluorite Substances 0.000 claims description 16
- 239000007789 gas Substances 0.000 claims description 15
- 230000001502 supplementing effect Effects 0.000 claims description 15
- 230000008569 process Effects 0.000 claims description 12
- 229910004709 CaSi Inorganic materials 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 10
- 229910052748 manganese Inorganic materials 0.000 claims description 10
- 238000005266 casting Methods 0.000 claims description 9
- 239000012535 impurity Substances 0.000 claims description 9
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 9
- 229910001122 Mischmetal Inorganic materials 0.000 claims description 8
- 230000003647 oxidation Effects 0.000 claims description 8
- 238000007254 oxidation reaction Methods 0.000 claims description 8
- 238000005070 sampling Methods 0.000 claims description 8
- 238000005303 weighing Methods 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 6
- 239000013589 supplement Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 3
- 238000001514 detection method Methods 0.000 abstract description 39
- 230000005496 eutectics Effects 0.000 abstract description 17
- 230000001590 oxidative effect Effects 0.000 abstract description 5
- 238000006722 reduction reaction Methods 0.000 description 40
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 30
- 238000012360 testing method Methods 0.000 description 23
- 229910052786 argon Inorganic materials 0.000 description 15
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 238000003825 pressing Methods 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 229910052720 vanadium Inorganic materials 0.000 description 7
- 238000004321 preservation Methods 0.000 description 6
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 229910000805 Pig iron Inorganic materials 0.000 description 4
- 229910052734 helium Inorganic materials 0.000 description 4
- 239000001307 helium Substances 0.000 description 4
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 229910001021 Ferroalloy Inorganic materials 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 238000004220 aggregation Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 238000003556 assay Methods 0.000 description 3
- 238000005261 decarburization Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000011010 flushing procedure Methods 0.000 description 3
- 239000004615 ingredient Substances 0.000 description 3
- 238000002386 leaching Methods 0.000 description 3
- 238000003801 milling Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 229910004261 CaF 2 Inorganic materials 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000005262 decarbonization Methods 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- CSJDCSCTVDEHRN-UHFFFAOYSA-N methane;molecular oxygen Chemical compound C.O=O CSJDCSCTVDEHRN-UHFFFAOYSA-N 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- 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
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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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)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention provides high-strength high-toughness Cr8 cold-work die steel and a preparation method thereof. The preparation method provided by the invention comprises the steps of A) electric furnace smelting, specifically comprising a 1) melting, a 2) oxidizing, a 3) prereducing and a 4) tapping; refining in the LF furnace in the step B), wherein the method specifically comprises the steps of B1) feeding molten steel into the furnace and B2) power transmission reduction; and then carrying out vacuum refining in a VD furnace in the step C), forging in the step D) and spheroidizing annealing in the step E) to finally obtain the high-strength high-toughness Cr8 cold-working die steel. The invention is sequentially carried out according to the sequence, so that the obtained product has high heat treatment hardness and no-defect impact resistance, reduces nonmetallic inclusion, improves the uniformity of the structure and the uniformity of eutectic carbide, and is qualified in flaw detection.
Description
Technical Field
The invention relates to the field of metal materials, in particular to high-strength high-toughness Cr8 cold-work die steel and a preparation method thereof.
Background
Due to the development of light weight in the industries of automobiles and the like, the use amount of cold working dies in the automobile industry is the largest, and various novel automobiles are continuously introduced to the market in recent years, the market demand of cold stamping is in a year-by-year increasing trend, and higher requirements are put on the performance and quality of cold working die steel. The basic series of the original cold-work die steel, such as Cr12 series, cannot meet the requirement, and in order to improve the toughness of the cold-work die steel and not reduce the wear resistance of the steel, the development of the cold-work die steel with high toughness and high wear resistance is required.
Cr8 steels have been developed, such as cold-work die steels of the domestic designation Cr8Mo2SiV, for improved toughness. However, actual production shows that the steel grade still has the problems of uneven carbide and unqualified flaw detection. In order to solve the problem, CN113604744A provides a high-strength and high-toughness cold-work die steel and a preparation method thereof, wherein the cold-work die steel comprises the following components in parts by weight: 0.9 to 0.94 weight percent of C, 1.35 to 1.45 weight percent of Si, 0.4 to 0.6 weight percent of Mn, less than or equal to 0.02 weight percent of P, less than or equal to 0.003 weight percent of S, 7.4 to 7.8 weight percent of Cr, 2.1 to 2.3 weight percent of Mo, 0.3 to 0.35 weight percent of V, 0.4 to 0.5 weight percent of Nb, less than or equal to 0.2 weight percent of Cu, less than or equal to 0.2 weight percent of Ni, 0.02 to 0.03 weight percent of Al, less than or equal to 2.5ppm of H, less than or equal to 0.002 weight percent of O, 0.005 to 0.015 weight percent of rare earth Ce, and the balance of Fe. The preparation process comprises the following steps: raw material electric furnace smelting-LF furnace refining-VD vacuum refining-molten steel pouring. The non-uniformity of eutectic carbide of the finally obtained alloy reaches 0.5-1.0 level, and the tissue uniformity is improved. However, the scheme ensures that the product performance adopts high content of noble elements such as Mo, V, si and the like, and has high cost.
Disclosure of Invention
In view of the above, the invention aims to provide a high-strength high-toughness Cr8 cold-work die steel and a preparation method thereof. The high-strength high-toughness Cr8 cold-working die steel provided by the invention not only has high heat treatment hardness and impact resistance, but also can improve the uniformity of eutectic carbide and overcome the defect of failure in flaw detection, and the invention reduces the consumption of noble elements and still ensures that the product has excellent wear resistance and impact performance, and the wear resistance and impact performance still reach the Cr8Mo2SiV level while reducing the cost.
The invention provides high-strength high-toughness Cr8 cold-work die steel, which comprises the following components:
the balance being Fe and unavoidable impurities.
Preferably, the components are:
the balance being Fe and unavoidable impurities.
The invention also provides a preparation method of the high-strength high-toughness Cr8 cold-work die steel, which comprises the following steps:
a) Smelting in an electric furnace:
a1 Melting):
weighing raw materials according to the component proportion of Cr8 cold-working die steel, feeding the raw materials into an electric furnace to fully melt the raw materials, carrying out single-tube low-pressure deep oxygen blowing when the temperature of molten steel is more than or equal to 1580 ℃, and then, removing oxides of Si and Mn in slag by slag flow; stirring the molten steel by CO gas generated by the single-pipe low-pressure deep oxygen blowing, and sampling and fully analyzing after uniformly stirring;
a2 Oxidation:
carrying out power transmission and heating, and carrying out oxygen blowing and C removal when the temperature of the molten steel is more than or equal to 1600 ℃ until the C content in the molten steel reaches n percent, and stopping oxygen blowing;
wherein n% = target product carbon content-carbon content brought by the supplement; the carbon content brought by the supplementing material refers to the carbon content introduced in the alloy raw material supplemented after the step a 2); n percent is 0.04 to 0.08 percent;
a3 Pre-reduction:
adding lime, fluorite, deoxidizer and C powder into an electric furnace for pre-reduction, and blowing inert gas and stirring; taking part of slag to perform full analysis, supplementing alloy raw materials according to the content specification of each component in a target product according to an analysis result to adjust the components, and reserving part of alloy raw materials to be added during LF refining;
Wherein the mass ratio of the reserved amount of the reserved part of alloy raw materials to the total amount of the alloy raw materials which are actually required to be added is 10% -30%;
a4 Tapping:
measuring the temperature, when the temperature is more than or equal to 1650 ℃, under the condition of blowing inert gas, mixing steel with steel slag, and deslagging the steel ladle after the steel is discharged;
b) Refining in an LF furnace:
b1 Molten steel is charged into the furnace:
molten steel is sent into an LF refining furnace, and the conditions for entering the LF furnace are as follows: the temperature is more than or equal to 1550 ℃ and the slag thickness is less than or equal to 35mm;
measuring the temperature of slag thickness steel, feeding Al wires into an LF refining furnace, adding part of the alloy raw materials reserved in the step a 3), and controlling the flow of inert gas; then adding slag, smelting for 30-60 min at 1560-1620 ℃;
wherein,
the slag is as follows: lime 12.5kg// t steel, refining slag 10kg/t steel;
the slag is premelted slag, the premelting temperature is 700-800 ℃, and the premelting time is more than or equal to 6 hours;
b2 Power transmission reduction:
c powder and steel slag friends are added into an LF refining furnace for reduction, after slag is white, the content of Al in the molten steel is adjusted to be 0.03-0.04 wt%, and the white slag is kept for 15-60 min; then adding a small amount of C powder to maintain a reducing atmosphere;
wherein,
the consumption of the C powder added for the first time is 1.5-2.5 kg/t steel, and the consumption of the steel slag friends is 6.25kg/t steel;
The consumption of the C powder added with a small amount of C powder is 1.8-2.3 kg/t steel;
c) Vacuum refining in a VD furnace:
the temperature of molten steel entering a VD furnace is 1620-1660 ℃, and the thickness of slag entering the furnace is 60-100 mm; introducing inert gas into the system, vacuumizing, controlling the ultimate vacuum degree to be less than or equal to 67Pa, and keeping the ultimate vacuum for more than or equal to 15min; then, increasing the flow of inert gas until the inert gas is broken, adding rare earth raw materials into a VD furnace for refining, and then hanging and pouring;
wherein the rare earth raw material is misch metal; the consumption of the rare earth raw material is 0.1-0.125 kg/t steel;
the casting temperature of the hanging ladle is 1480-1500 ℃;
d) Forging:
preheating the anvil to 200-250 ℃ before forging, forging at 1080-1150 ℃ and 900-980 ℃ after forging, and forging by adopting a two-light-one-heavy forging mode, wherein the forging times are more than 1 time, so as to obtain a forging piece;
e) Spheroidizing annealing:
and (3) spheroidizing annealing is carried out on the forging, wherein the conditions are as follows: firstly heating to 840-870 ℃ for preserving heat for 8-10 h, then cooling to 700-740 ℃ for preserving heat for 10-20 h; and (3) after the spheroidizing annealing, obtaining the high-strength high-toughness Cr8 cold-work die steel.
Preferably, in step a 1), the single-tube low-pressure deep oxygen blowing condition is: the oxygen flow is 1000-3000 nm 3 And/h, the air pressure is 0.3-0.6 MPa.
Preferably, in step a 2), the conditions for oxygen blowing and decarbonization are as follows: the oxygen blowing flow is 3000-5000 nm 3 And/h, the air pressure is 0.1-1.0 MPa; and the oxygen blowing flow and the air pressure are both larger than those in the step a 1).
Preferably, in step a 3):
the lime consumption is 10kg/t steel, and the fluorite consumption is 2.5-3 kg/t steel;
the deoxidizer is CaSi powder and Al blocks, and the dosage is as follows: 2.5kg/t steel of CaSi powder and 3.25kg/t steel of Al block;
the consumption of the C powder is 3-5 kg/t steel;
the pre-reduction time is more than or equal to 10min.
Preferably, in step a 4), the flow rate of the inert gas is 1000 to 3000nm 3 /h。
Preferably, in step b 1):
the dosage of the Al wire is 2.5m/t steel;
the flow rate of the inert gas is 40-60 NL/min.
Preferably, in the step C), the refining time is 5-10 min.
Preferably, in step D), forging is performed using a 45MN press.
The preparation method provided by the invention comprises the steps of A) electric furnace smelting, specifically comprising a 1) melting, a 2) oxidizing, a 3) prereducing and a 4) tapping; refining in the LF furnace in the step B), wherein the method specifically comprises the steps of B1) feeding molten steel into the furnace and B2) power transmission reduction; and then carrying out vacuum refining in a VD furnace in the step C), forging in the step D) and spheroidizing annealing in the step E) to finally obtain the high-strength high-toughness Cr8 cold-working die steel. The invention is sequentially carried out according to the sequence, wherein in the smelting and pouring process, the content of C is controlled to be 0.90-1.00%, the content of Mo is controlled to be 1.45-1.60%, the content of V is controlled to be 0.20-0.60%, the feeding type, the feeding amount and the condition parameters in each step are controlled, the pouring temperature is reduced, and the steps are matched, so that the aggregation of the content of C can be reduced, the hardenability of steel is improved, the structure and the crystal grains are refined, the segregation is reduced, the gas content in steel ingots is reduced, the obtained product has high heat treatment hardness and no-defect impact resistance, nonmetallic inclusion is reduced, the uniformity of the structure and the uniformity of eutectic carbide are improved, and the flaw detection is qualified.
The test result shows that the Cr8 cold-work die steel prepared by the invention has the advantages of reduced nonmetallic inclusion content, qualified low-power structure, lower decarburized layer depth, higher uniformity of eutectic carbide, higher heat treatment hardness of more than 58HRC, no notch impact energy of more than 70J, and higher heat treatment hardness and no notch impact energy; the microstructure is uniform; and qualified ultrasonic flaw detection.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a microstructure test chart of the product obtained in example 1;
FIG. 2 is a chart showing the microstructure of the product obtained in example 1.
Detailed Description
The invention provides high-strength high-toughness Cr8 cold-work die steel, which comprises the following components:
the balance being Fe and unavoidable impurities.
In the invention, the high-strength high-toughness Cr8 cold-work die steel is Cr8Mo2SiV cold-work die steel, and the components are as described above.
Wherein,
the Cr (i.e., cr element) content is 5wt% to 10.5wt%, specifically 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 8.6wt%, 8.7wt%, 8.8wt%, 8.9wt%, 9.0wt%, 9.1wt%, 9.2wt%, 9.3wt%, 9.4wt%, 9.5wt%, 9.6wt%, 9.7wt%, 9.8wt%, 9.9wt%, 10.0wt%, 10.1wt%, 10.2wt%, 10.3wt%, 10.4wt%, 10.5wt%.
The Mo (i.e., molybdenum element) content is 1.45wt% to 1.60wt%, specifically 1.45wt%, 1.46wt%, 1.47wt%, 1.48wt%, 1.49wt%, 1.50wt%, 1.51wt%, 1.52wt%, 1.53wt%, 1.54wt%, 1.55wt%, 1.56wt%, 1.57wt%, 1.58wt%, 1.59wt%, 1.60wt%.
The Si (i.e., si element) content is 0.40wt% to 0.65wt%, specifically 0.40wt%, 0.41wt%, 0.42wt%, 0.43wt%, 0.44wt%, 0.45wt%, 0.46wt%, 0.47wt%, 0.48wt%, 0.49wt%, 0.50wt%, 0.51wt%, 0.52wt%, 0.53wt%, 0.54wt%, 0.55wt%, 0.56wt%, 0.57wt%, 0.58wt%, 0.59wt%, 0.60wt%, 0.61wt%, 0.62wt%, 0.63wt%, 0.64wt%, 0.65wt%.
The content of V (i.e. vanadium element) is 0.20wt% to 0.60wt%, and specifically may be 0.20wt%, 0.25wt%, 0.30wt%, 0.35wt%, 0.40wt%, 0.45wt%, 0.50wt%, 0.55wt%, 0.60wt%.
The content of C (i.e., carbon element) is 0.90wt% to 1.00wt%, specifically 0.90wt%, 0.91wt%, 0.92wt%, 0.93wt%, 0.94wt%, 0.95wt%, 0.96wt%, 0.97wt%, 0.98wt%, 0.99wt%, 1.00wt%.
The Al (i.e., aluminum element) content is 0.020wt% to 0.030wt%, specifically 0.020wt%, 0.021wt%, 0.022wt%, 0.023wt%, 0.024wt%, 0.025wt%, 0.026wt%, 0.027wt%, 0.028wt%, 0.029wt%, 0.030wt%.
The Ce (namely, cerium element) content is 0.005wt% to 0.015wt%, specifically, 0.005wt%, 0.006wt%, 0.007wt%, 0.008wt%, 0.009wt%, 0.010wt%, 0.011wt%, 0.012wt%, 0.013wt%, 0.014wt%, 0.015wt%.
The content of P (i.e., phosphorus element) is less than or equal to 0.015wt%, and specifically may be 0.001wt%, 0.005wt%, 0.010wt%, 0.011wt%, 0.012wt%, 0.013wt%, 0.014wt%, 0.015wt%.
The S (namely sulfur element) content is less than or equal to 0.003wt%, and can be specifically 0.001wt%, 0.002wt% and 0.003wt%.
The content of N (namely nitrogen element) is less than or equal to 0.012wt%, and can be specifically 0.001wt%, 0.005wt%, 0.010wt%, 0.011wt% and 0.012wt%.
The content of O (i.e. oxygen element) is less than or equal to 0.0019wt%, and specifically can be 0.0010wt%, 0.0011wt%, 0.0012wt%, 0.0013wt%, 0.0014wt%, 0.0015wt%, 0.0016wt%, 0.0017wt%, 0.0018wt% and 0.0019wt%.
The balance being Fe and unavoidable impurities.
In one embodiment of the invention, the high-strength high-toughness Cr8 cold work die steel comprises the following components:
the balance being Fe and unavoidable impurities.
The invention also provides a preparation method of the high-strength high-toughness Cr8 cold-work die steel, which comprises the following steps:
a) Smelting in an electric furnace:
a1 Melting):
weighing raw materials according to the component proportion of Cr8 cold-working die steel, feeding the raw materials into an electric furnace to fully melt the raw materials, carrying out single-tube low-pressure deep oxygen blowing when the temperature of molten steel is more than or equal to 1580 ℃, and then, removing oxides of Si and Mn in slag by slag flow; stirring the molten steel by CO gas generated by the single-pipe low-pressure deep oxygen blowing, and sampling and fully analyzing after uniformly stirring;
a2 Oxidation:
carrying out power transmission and heating, and carrying out oxygen blowing and C removal when the temperature of the molten steel is more than or equal to 1600 ℃ until the C content in the molten steel reaches n percent, and stopping oxygen blowing;
wherein n% = target product carbon content-carbon content brought by the supplement; the carbon content brought by the supplementing material refers to the carbon content introduced in the alloy raw material supplemented after the step a 2);
a3 Pre-reduction:
adding lime, fluorite, deoxidizer and C powder into an electric furnace for pre-reduction, and blowing inert gas and stirring; taking part of slag to perform full analysis, supplementing alloy raw materials according to the content specification of each component in a target product according to an analysis result to adjust the components, and reserving part of alloy raw materials to be added during LF refining;
Wherein the mass ratio of the reserved amount of the reserved part of alloy raw materials to the total amount of the alloy raw materials which are actually required to be added is 10% -30%;
a4 Tapping:
measuring the temperature, when the temperature is more than or equal to 1650 ℃, under the condition of blowing inert gas, mixing steel with steel slag, and deslagging the steel ladle after the steel is discharged;
b) Refining in an LF furnace:
b1 Molten steel is charged into the furnace:
molten steel is sent into an LF refining furnace, and the conditions for entering the LF furnace are as follows: the temperature is more than or equal to 1550 ℃ and the slag thickness is less than or equal to 35mm;
measuring the temperature of slag thickness steel, feeding Al wires into an LF refining furnace, adding part of the alloy raw materials reserved in the step a 3), and controlling the flow of inert gas; then adding slag, smelting for 30-60 min at 1560-1620 ℃;
wherein,
the slag is as follows: lime 12.5kg// t steel, refining slag 10kg/t steel;
the slag is premelted slag, the premelting temperature is 700-800 ℃, and the premelting time is more than or equal to 6 hours;
b2 Power transmission reduction:
c powder and steel slag friends are added into an LF refining furnace for reduction, after slag is white, the content of Al in the molten steel is adjusted to be 0.03-0.04 wt%, and the white slag is kept for 15-60 min; then adding a small amount of C powder to maintain a reducing atmosphere;
wherein,
the consumption of the C powder added for the first time is 1.5-2.5 kg/t steel, and the consumption of the steel slag friends is 6.25kg/t steel;
The consumption of the C powder added with a small amount of C powder is 1.8-2.3 kg/t steel;
c) Vacuum refining in a VD furnace:
the temperature of molten steel entering a VD furnace is 1620-1660 ℃, and the thickness of slag entering the furnace is 60-100 mm; introducing inert gas into the system, vacuumizing, controlling the ultimate vacuum degree to be less than or equal to 67Pa, and keeping the ultimate vacuum for more than or equal to 15min; then, increasing the flow of inert gas until the inert gas is broken, adding rare earth raw materials into a VD furnace for refining, and then hanging and pouring;
wherein the rare earth raw material is misch metal; the consumption of the rare earth raw material is 0.1-0.125 kg/t steel;
the casting temperature of the hanging ladle is 1480-1500 ℃;
d) Forging:
preheating the anvil to 200-250 ℃ before forging, forging at 1080-1150 ℃ and 900-980 ℃ after forging, and forging by adopting a two-light-one-heavy forging mode, wherein the forging times are more than 1 time, so as to obtain a forging piece;
e) Spheroidizing annealing:
and (3) spheroidizing annealing is carried out on the forging, wherein the conditions are as follows: firstly heating to 840-870 ℃ for preserving heat for 8-10 h, then cooling to 700-740 ℃ for preserving heat for 10-20 h; and (3) after the spheroidizing annealing, obtaining the high-strength high-toughness Cr8 cold-work die steel.
Regarding step A) electric furnace smelting：
The step A) comprises the following steps: a1 Melting- & gt a 2) oxidizing- & gt a 3) pre-reducing- & gt a 4) tapping.
[ concerning step a1]: and (5) melting.
a1 Melting): weighing raw materials according to the component proportion of Cr8 cold-working die steel, feeding the raw materials into an electric furnace to fully melt the raw materials, carrying out single-tube low-pressure deep oxygen blowing when the temperature of molten steel is more than or equal to 1580 ℃, and then, removing oxides of Si and Mn in slag by slag flow; and stirring the molten steel by CO gas generated by the single-pipe low-pressure deep oxygen blowing, and sampling and fully analyzing after uniformly stirring.
In the invention, raw materials are firstly weighed according to the component proportion of a Cr8 cold-work die steel target product, the types of the raw materials are not particularly limited, and the raw materials are conventional raw materials for preparing cold-work die steel in the field, and the cold-work die steel comprises a carbon crop, a steel return material, an iron alloy, low-P low-S pig iron (the P content is less than or equal to 0.030 wt%) and structural members. The above steel raw materials are all clean and dry raw materials. The steel material size specification meets the steel material size specification of qualified charging, namely: the maximum size is less than or equal to 800mm, the single weight is less than or equal to 1500kg, and the proportion of large materials is less than or equal to 40% during the material mixing; the steel materials which do not meet the requirements are processed to be qualified and then put into the furnace.
After the raw materials are weighed, the raw materials are sent into an electric furnace to be fully melted, and when the temperature of molten steel is more than or equal to 1580 ℃, single pipe low pressure deep oxygen blowing is performed. Wherein, the molten steel temperature can reach 1580-1620 ℃ for single tube low pressure deep oxygen blowing, and can be 1580 ℃, 1590 ℃, 1600 ℃, 1610 ℃ and 1620 ℃. Wherein the oxygen flow of the oxygen blowing is 1000-3000 nm 3 /h, in particular 1000nm 3 /h、1500nm 3 /h、2000nm 3 /h、2500nm 3 /h、3000nm 3 /h; the air pressure of oxygen blowing is 0.3-0.6 MPa, and can be specifically 0.3MPa, 0.4MPa, 0.5MPa and 0.6MPa; the oxygen blowing time is preferably 10 to 20 minutes, and specifically may be 10 minutes, 15 minutes, or 20 minutes. And after the oxygen blowing is finished, slag flows (namely slag charge is removed), so that oxides of Si and Mn in the slag are removed.
After slag flow, the molten steel is stirred by CO gas generated by single-tube low-pressure deep oxygen blowing (CO gas is generated by carbon-oxygen reaction generated by oxygen blowing), and the mixture is sampled and fully analyzed after uniform stirring. The purpose of the component analysis is to monitor whether the component meets the target requirements.
[ concerning step a2]: and (5) oxidizing.
a2 Oxidation: and (3) power transmission and temperature rise, when the temperature of the molten steel is more than or equal to 1600 ℃, oxygen blowing and C removal are carried out, and oxygen blowing is stopped until the content of C in the molten steel reaches n percent.
After the step a 1) is finished, power is transmitted to heat, and when the temperature of the molten steel is more than or equal to 1600 ℃, oxygen blowing, C removal, degassing and impurity removal are carried out. Wherein, when the temperature of the molten steel specifically reaches 1600-1650 ℃, oxygen blowing and C removal are carried out; the temperature can be 1600 ℃, 1610 ℃, 1620 ℃, 1630 ℃ and 1650 ℃. Wherein the oxygen flow of the oxygen blowing and the oxygen removal C is 3000-5000 nm 3 Per h, may be in particular 3000nm 3 /h、3500nm 3 /h、4000nm 3 /h、4500nm 3 /h、5000nm 3 /h; the oxygen blowing pressure is 0.1-1.0 MPa, and can be specifically 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa and 1.0MPa; the oxygen blowing flow and the air pressure are both larger than those in the step a 1); in step a 2), oxygen is concentrated and blown by increasing the flow rate of the blown oxygen to perform oxidative desorption C.
In the invention, the C content of the molten steel in the step a 2) is determined according to the Cr content in the molten steel in the step a 2), and oxygen blowing is stopped when the C content in the molten steel in the step a 2) reaches n%. Wherein n% = target product carbon content-carbon content brought by the supplement; the target carbon content is the carbon content in the target product, and is specifically 0.90-1.00 wt%. The carbon content brought by the supplement refers to the carbon content introduced in the alloy raw material added after the step a 2). Namely controlling the sum of the C content n% + of the molten steel in the step a 2) and the carbon content brought by the additive to be 0.90-1.00 wt% of the carbon content of the target product. Wherein, n% is specifically 0.04% -0.08%, specifically 0.04%, 0.05%, 0.06%, 0.07%, 0.08%.
[ concerning step a3]: pre-reduction.
a3 Pre-reduction: lime, fluorite, deoxidizer and C powder are added into an electric furnace for pre-reduction, and inert gas is blown for stirring; and taking part of slag to perform full analysis, supplementing alloy raw materials according to the content specification of each component in the target product according to the analysis result to adjust the components, and reserving part of alloy raw materials to be added during LF refining.
In the invention, after the step a 2) is finished, lime, fluorite, deoxidizer and C powder are added into an electric furnace for pre-reduction. Wherein the dosage of the lime is 10kg/t steel; the lime is preferably selected lime just coming out of the kiln, has the granularity of 30-80 mm, does not allow the powdered lime to be naturally pulverized, and does not have carbon residues. The fluorite consumption is 2.5-3.0 kg/t steel, and can be specifically 2.5kg/t steel, 2.6kg/t steel, 2.7kg/t steel, 2.8kg/t steel, 2.9kg/t steel and 3.0kg/t steel; the water content of the fluorite is less than or equal to 0.5wt%. The deoxidizer is preferably CaSi powder and Al blocks, and the dosage is preferably: caSi powder 2.5kg/t steel, al block 3.25kg/t steel. The dosage of the C powder (namely carbon powder) is 3-5 kg/t of steel, and can be 3kg/t, 3.5kg/t, 4kg/t, 4.5kg/t and 5kg/t.
In the present invention, the pre-reduction temperature is preferably 1580 to 1630 ℃, and more specifically 1580 ℃, 1585 ℃, 1590 ℃, 1600 ℃, 1610 ℃, 1620 ℃ and 1630 ℃. In the invention, the pre-reduction time is more than or equal to 10min, preferably 15-30 min, and particularly 15min, 20min, 25min and 30min.
In the invention, inert gas blowing stirring is assisted in the pre-reduction process. The kind of the inert gas is not particularly limited in the present invention, and may be a conventional inert gas such as nitrogen, helium or argon, etc., which are well known to those skilled in the art.
After the pre-reduction reaction is finished, under the condition of good molten steel deoxidization and fluidity, the slag flowing part is sampled and fully analyzed, according to the analysis result, alloy raw materials are added according to the content specification of each component in the target product to adjust the components, and the reserved part of alloy raw materials are added during LF refining, so that the exceeding of the alloy addition caused by uneven components of the molten steel in the electric furnace is avoided. The above process specifically includes taking part of slag to perform full analysis after the pre-reduction reaction is finished, adding alloy raw materials according to the analysis result and the content specification of each component in the target product to adjust the components, for example, the analyzed Mo content is 0.90wt%, the Mo content in the target product is 1.45wt% -1.60 wt%, i.e., the Mo content does not reach the target product specification yet, and adding corresponding alloy raw materials (such as FeMo alloy) to adjust the Mo content. In the invention, when the component content is adjusted, alloy raw materials (namely the difference amount) are not added completely according to actual requirements, but are divided into two parts, wherein one part is added in the step, the other part is added in the subsequent LF furnace refining, namely, the reserved part of alloy raw materials are added in the LF refining when the component content compensation is adjusted; for example, in the above example, the Mo content of the target product is 1.54wt% and the Mo content is still 0.64wt% worse than the target content, but the 0.64wt% is not completely supplemented when the alloy raw material is supplemented, but is supplemented in two steps, a part is reserved and added in the subsequent LF refining, and the rest is added in this step. In the invention, the mass ratio of the reserved part of alloy raw materials to the total amount of the alloy raw materials which are actually required to be added is 10% -30%, and the mass ratio can be specifically 10%, 15%, 20%, 25% and 30%. In the invention, the alloy raw materials of the easily oxidized elements such as V, si are not fed and adjusted in the step, and are all fed and adjusted in the refining process of the LF furnace.
[ concerning step a4]: tapping.
a4 Tapping:
and measuring the temperature, when the temperature is more than or equal to 1650 ℃, under the condition of blowing inert gas, mixing and punching steel from the steel slag, and deslagging the steel ladle after the steel is discharged.
In the invention, after the step a 3) is finished, the temperature is measured, and when the temperature is more than or equal to 1650 ℃, the steel slag is mixed and punched to obtain the steel under the condition of blowing inert gas. The temperature may be 1650 to 1680 ℃, specifically 1650 ℃, 1660 ℃, 1670 ℃, 1680 ℃. In the present invention, the kind of the inert gas is not particularly limited, and may be a conventional inert gas known to those skilled in the art, such as nitrogen, helium, argon, or the like. The flow rate of the inert gas is preferably 1000-3000 nm 3 /h, in particular 1000nm 3 /h、1500nm 3 /h、2000nm 3 /h、2500nm 3 /h、3000nm 3 And/h. Under the condition of inert gas purging, steel slag is mixed and punched to be tapped, and slag is removed from the steel ladle in time after the tapping is finished.
Regarding step B): LF furnace refining
The step B) comprises the following steps: b1 Molten steel is charged into a furnace, and b 2) power transmission reduction is performed.
[ concerning step b1]: molten steel is put into a furnace.
In the invention, after tapping in the step a 4), molten steel is sent into an LF refining furnace, and the charging conditions are as follows: the temperature is more than or equal to 1550 ℃ and the slag thickness is less than or equal to 35mm. Wherein the temperature can be 1550-1590 ℃, and can be 1550 ℃ and 1560 DEG C1570 ℃, 1580 ℃, 1590 ℃. After molten steel is sent into an LF refining furnace, slag thickness and steel temperature are measured, and the slag material consumption and the proportion are adjusted according to the slag thickness, so that the purpose that the slag components meet the control requirements is achieved. In the invention, the control standard of slag components is as follows: caO 45% -55%, al 2 O 3 25％-35％，SiO 2 ≤8％；。
In the invention, after slag thickness and steel temperature are measured, al wires are fed into an LF refining furnace, and part of alloy raw materials reserved in the step a 3) are added. Wherein the Al wire is preferably used in an amount of 2.5m/t steel; the amount of the reserved part of the alloy raw material is as described in the previous step a 3), and will not be described herein.
In the invention, after the materials are added, the flow of inert gas is adjusted and controlled. The kind of the inert gas is not particularly limited in the present invention, and may be a conventional inert gas well known to those skilled in the art, such as nitrogen, helium, argon, etc., and more preferably argon. The flow rate of the inert gas is preferably 40 to 60NL/min, and specifically 40NL/min, 45NL/min, 50NL/min, 55NL/min, and 60NL/min.
In the invention, slag is added after the treatment. The slag is preferably lime and refining slag; the dosage is preferably as follows: lime 12.5kg// t steel, refining slag 10kg/t steel. Wherein the refining slag is preferably Al 2 O 3 Refining slag, more preferably high Al 2 O 3 Refining slag, most preferably 80Al 2 O 3 Refining slag (i.e. Al) 2 O 3 80%, the rest is CaO, mgO, siO 2 And CaF 2 Wherein the CaO content is about 7% ± 0.8%, the MgO content is about 7% ± 0.8%, and the SiO content is about 7% ± 0.8% 2 About 2% + -0.8% CaF content 2 Content about 2% ± 0.8%). The lime is preferably selected lime just coming out of the kiln, has the granularity of 30-80 mm, does not allow the powdered lime to be naturally pulverized, and does not have carbon residues. The water content of the refining slag is less than or equal to 0.5wt%. In the invention, the slag is premelted slag, and the premelted baking temperature is preferably 700-800 ℃, specifically 700 ℃, 710 ℃, 720 ℃, 730 ℃, 740 ℃, 750 ℃, 760 ℃, 770 ℃, 780 ℃, 790 ℃ and 800 ℃; the baking time of the premelting is preferably more than or equal to 6 hours, can be 6 to 12 hours, and can be specifically6h、7h、8h、9h、10h、11h、12h。
In the invention, after slag is added, smelting is performed. In the invention, the smelting temperature is 1560-1620 ℃, specifically 1560 ℃, 1570 ℃, 1580 ℃, 1590 ℃, 1600 ℃, 1610 ℃, 1620 ℃. The smelting time is preferably 30-60 min, and can be specifically 30min, 35min, 40min, 45min, 50min, 55min and 60min.
[ concerning step b2]: and (5) power transmission reduction.
In the invention, after the smelting in the step b 1) is finished, C powder and steel slag friends are added into an LF refining furnace for reduction. Wherein the addition amount of the C powder is 1.5-2.5 kg/t steel, and can be specifically 1.5kg/t steel, 2.0kg/t steel and 2.5kg/t steel. The consumption of the steel slag friends is 6.25kg/t steel. The water content of the steel slag friends is less than or equal to 0.5wt%; the source of the steel slag friends is not particularly limited, and the steel slag friends are commercial products. In the present invention, the temperature conditions for the reduction are preferably 1580 to 1630 ℃, and more specifically 1580 ℃, 1590 ℃, 1600 ℃, 1610 ℃, 1620 ℃ and 1630 ℃. After thorough reduction and white slag, adjusting the content of Al in the whole Al to be 0.03-0.04 wt% of the molten steel, and specifically 0.03-0.04 wt%; the white slag holding time is controlled to be 15-60 min, and can be 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min and 60min. Then, a small amount of carbon powder was added to maintain the reducing atmosphere. The specific dosage of the added small amount of carbon powder is 1.8-2.3 kg/t steel, and can be 1.8kg/t steel, 1.9kg/t steel, 2.0kg/t steel, 2.1kg/t steel, 2.2kg/t steel and 2.3kg/t steel.
Regarding step C): vacuum refining in VD furnace：
In the present invention, after the end of step b 2), the molten steel is fed into a VD furnace for vacuum refining. In the invention, the temperature of molten steel entering the VD furnace is 1620-1660 ℃, specifically 1620 ℃, 1630 ℃, 1640 ℃, 1650 ℃ and 1660 ℃. The thickness of the slag is 60-100 mm, and can be 60mm, 70mm, 80mm, 90mm and 100mm.
And after molten steel enters a furnace, introducing inert gas into the system and vacuumizing. The inert gas is not particularly limited in kind, and may be a conventional inert gas well known to those skilled in the art, such as nitrogen, helium, argon, or the like, and more preferably argon. The vacuumizing is specifically controlling the ultimate vacuum degree to be less than or equal to 67Pa, and the holding time under the ultimate vacuum is more than or equal to 15min, preferably 15-45 min, and specifically 15min, 20min, 25min, 30min, 35min, 40min and 45min. Then, after increasing the flow of inert gas to break the blank, adding rare earth raw materials into the VD furnace for refining. Among them, the rare earth material is preferably misch metal. The rare earth raw material is preferably used in an amount of 0.1 to 0.125kg/t steel, specifically 0.100kg/t steel, 0.110kg/t steel, 0.120kg/t steel, 0.125kg/t steel. The refining time after adding the rare earth raw material is preferably 5-10 min, and can be specifically 5min, 6min, 7min, 8min, 9min and 10min.
And (5) pouring the refined ladle. The temperature of the casting of the hanging bag is preferably 1480-1500 ℃, and can be 1480 ℃, 1481 ℃, 1482 ℃, 1483 ℃, 1484 ℃, 1485 ℃, 1486 ℃, 1487 ℃, 1488 ℃, 1489 ℃, 1490 ℃, 1491 ℃, 1492 ℃, 1493 ℃, 1494 ℃, 1495 ℃, 1496 ℃, 1497 ℃, 1499 ℃ 1500 ℃.
Regarding step D): forging
In the invention, the forging is preferably performed by using a 45MN press. In the invention, the anvil is preheated before forging (or a hot anvil after forging is used), so long as the anvil is hot, the cold anvil is forbidden. In the present invention, the preheating is preferably performed to 200 to 250 ℃, and specifically 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃ and 250 ℃.
In the present invention, the forging temperature is 1080-1150 ℃, specifically 1080 ℃, 1090 ℃, 1100 ℃, 1110 ℃, 1120 ℃, 1130 ℃, 1140 ℃ 1150 ℃. The final forging temperature is 900-980 ℃, specifically 900 ℃, 910 ℃, 920 ℃, 930 ℃, 940 ℃, 950 ℃, 960 ℃, 970 ℃ and 980 ℃. In the invention, a forging mode of two light weight and one heavy weight is adopted for forging, the initial forging and the final forging are performed by light pressing and heavy pressing in the middle, the deformation of each part is required to be uniform in the forging process, and the temperature of each part is required to be kept uniform; the upsetting times are more than 1 time to ensure that the deformation is sufficient. In the invention, the total forging ratio of the forging is preferably not less than 8. When the edges and corners are dark, the forging should be stopped, and the furnace should be returned in time. In the invention, the head and the tail are thermally cut in the forging process, and the head and the tail are cut to clean the rotten materials and burrs, so that the surface quality is ensured.
Regarding step E): spheroidizing annealing
In the invention, spheroidizing annealing is performed in time after the forging in the step D) is finished. In the invention, the spheroidizing annealing conditions are as follows: heating to 840-870 ℃ for 8-10 h, cooling to 700-740 ℃ for 10-20 h. Wherein the temperature can be raised to 840 ℃, 850 ℃, 860 ℃ and 870 ℃; the heat preservation time after temperature rise can be specifically 8 hours, 9 hours or 10 hours. The temperature reduction can be specifically reduced to 700 ℃, 710 ℃, 720 ℃, 730 ℃ and 740 ℃; the heat preservation time after cooling can be specifically 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h and 20h. After the treatment, the high-strength high-toughness Cr8 cold-work die steel is obtained.
The preparation method provided by the invention comprises the steps of A) electric furnace smelting, specifically comprising a 1) melting, a 2) oxidizing, a 3) prereducing and a 4) tapping; refining in the LF furnace in the step B), wherein the method specifically comprises the steps of B1) feeding molten steel into the furnace and B2) power transmission reduction; and then carrying out vacuum refining in a VD furnace in the step C), forging in the step D) and spheroidizing annealing in the step E) to finally obtain the high-strength high-toughness Cr8 cold-working die steel. The invention sequentially carries out the smelting and the casting according to the sequence, wherein in the smelting and the casting process, the content of C is controlled to be 0.90-1.00%, the content of Mo is controlled to be 1.45-1.60%, the content of V is controlled to be 0.20-0.60%, the feeding type, the feeding amount and the condition parameters in each step are controlled, the casting temperature is reduced, the aggregation of the content of C can be reduced, the hardenability of steel is improved, the structure and the crystal grains are refined, the segregation is reduced, the gas content in the steel ingot is reduced, the obtained product has high hardness and no-defect impact resistance, nonmetallic inclusion is reduced, the uniformity of the structure and the uniformity of eutectic carbide are improved, and the flaw detection is qualified.
The test result shows that the Cr8 cold-work die steel prepared by the invention has the advantages of reduced nonmetallic inclusion content, qualified low-power structure, lower decarburized layer depth, higher uniformity of eutectic carbide, higher heat treatment hardness of more than 58HRC, no notch impact energy of more than 70J, and higher heat treatment hardness and no notch impact energy; the microstructure is uniform; and qualified ultrasonic flaw detection.
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention, and are not limiting of the claims of the invention.
Example 1
1. Preparation
Target product Cr8Mo2SiV cold work die steel: 0.93% of C, 0.55% of Si, 0.29% of Mn, less than or equal to 0.015% of P, less than or equal to 0.003% of S, 8.60% of Cr, 1.54% of Mo, 0.30% of V, 0.020% of Al, 0.010% of Ce, less than or equal to 0.012% of N, less than or equal to 0.0019% of O, and the balance of Fe and unavoidable impurities.
A) Smelting in an electric furnace:
a1 Melting):
adopting carbon crop, return materials, ferroalloy, low-P low-S pig iron (P content is less than or equal to 0.030 wt%) and structural component ingredients, weighing raw materials according to the component proportion of Cr8 cold-working die steel, feeding the raw materials into an electric furnace to fully melt the raw materials, when the temperature of molten steel reaches 1580 ℃, carrying out single-tube low-pressure deep oxygen blowing, and then removing oxides of Si and Mn in slag by slag flowing; stirring the molten steel by CO gas generated by the single-pipe low-pressure deep oxygen blowing, and sampling and fully analyzing after uniformly stirring;
Wherein, the single-tube low-pressure deep oxygen blowing condition is: oxygen flow 2000nm 3 And/h, the air pressure is 0.5MPa.
a2 Oxidation:
carrying out power transmission and heating, and carrying out oxygen blowing and C removal when the temperature of the molten steel reaches 1600 ℃ until the C content in the molten steel reaches n percent, and stopping oxygen blowing;
wherein,
the conditions for oxygen blowing and C removal are as follows: oxygen blowing flow rate of 3000nm 3 And/h, the air pressure is 0.7MPa;
n% = target product carbon content (0.93%) -carbon content by make-up (0.05%); the carbon content brought by the supplementing material refers to the carbon content introduced in the alloy raw material supplemented after the step a 2);
a3 Pre-reduction:
adding lime, fluorite, deoxidizer and C powder into an electric furnace for pre-reduction, and blowing inert gas and stirring; taking part of slag to perform full analysis, supplementing alloy raw materials according to the content specification of each component in a target product according to an analysis result to adjust the components, and reserving part of alloy raw materials to be added during LF refining; the alloy raw material of the easily oxidizable element V, si was not adjusted in this step, but was adjusted in addition to the LF furnace refining.
Wherein,
lime is used for 10kg/t of steel, and fluorite is used for 2.5kg/t of steel;
the deoxidizer is CaSi powder and Al blocks, and the dosage is as follows: 2.5kg/t steel of CaSi powder and 3.25kg/t steel of Al block;
The consumption of the C powder is 4kg/t steel;
the pre-reduction time is 10min;
the mass ratio of the reserved amount of the reserved part of alloy raw materials to the total amount of the alloy raw materials which are actually required to be added is 10%;
a4 Tapping:
measuring temperature, when the temperature reaches 1650deg.C, blowing argon (flow 2000 nm) 3 And/h) under the condition of steel slag mixed flushing tapping, and deslagging a ladle after tapping;
b) Refining in an LF furnace:
b1 Molten steel is charged into the furnace:
molten steel is sent into an LF refining furnace, and the conditions for entering the LF furnace are as follows: the temperature is 1550 ℃ and the slag thickness is 35mm;
measuring the temperature of slag thickness steel, feeding an Al wire into an LF refining furnace, adding part of the alloy raw material reserved in the step a 3), and controlling the flow rate of argon gas (50 NL/min); then adding slag, and smelting at 1600 ℃ for 40min;
wherein,
the dosage of the Al wire is 2.5m/t steel;
the slag is as follows: lime 12.5kg// t steel, refining slag (80 Al 2 O 3 Refining slag) 10kg/t steel;
the slag is premelted slag, the premelting temperature is 750 ℃, and the premelting time is 6 hours;
b2 Power transmission reduction:
c powder and steel slag friends are added into an LF refining furnace for reduction, after slag is white, the content of Al in the whole Al is adjusted to be 0.03 weight percent in molten steel, and the white slag is kept for 60 minutes; then adding a small amount of C powder to maintain a reducing atmosphere;
Wherein,
the consumption of the C powder added for the first time is 2.0kg/t steel, and the consumption of the steel slag friends is 6.25kg/t steel;
the consumption of C powder added with a small amount of C powder is 2.0kg/t steel;
c) Vacuum refining in a VD furnace:
the temperature of molten steel entering a VD furnace is 1640 ℃, and the thickness of slag entering the furnace is 80mm; argon is introduced into the system and vacuumized, the ultimate vacuum degree is controlled to be less than or equal to 67Pa, and the holding time under the ultimate vacuum is 15min; then, after increasing the flow of inert gas to break the blank, adding rare earth raw materials into a VD furnace for refining for 10min, and then hanging and pouring.
Wherein the rare earth raw material is misch metal; the consumption of the rare earth raw material is 0.100kg/t steel;
the pouring temperature of the hanging bag is 1490 ℃;
d) Forging:
adopting a 45MN press for quick forging, preheating the anvil to 230 ℃ before forging, wherein the forging temperature is 1100 ℃, the final forging temperature is 950 ℃, forging by adopting a two-light-one-heavy forging mode, and carrying out initial forging, final forging light pressing and middle heavy pressing, wherein in the forging process, the deformation of each part needs to be uniform, and the temperature of each part needs to be kept uniform; the upsetting times are 2 times, the total forging ratio is 8, the head and the tail are hot cut in the forging process, and the head and the tail are cut to remove rotten materials and burrs, so that the forging is obtained.
E) Spheroidizing annealing:
spheroidizing annealing is carried out on the forge piece, and the conditions are as follows: firstly heating to 850 ℃ for heat preservation for 9 hours, and then cooling to 720 ℃ for heat preservation for 15 hours; and (3) after the spheroidizing annealing, obtaining the high-strength high-toughness Cr8 cold-work die steel. The product size specification is as follows: 2000mm long by 410mm wide by 125mm thick.
2. Detection of
(1) Component analysis
Chemical component assay analysis was performed on samples of the product, see table 1 for results:
table 1: chemical composition (wt%) of the product obtained in example 1
| Element(s) | C | Si | Mn | P | S | Cr | Mo | V | Al | Ce | N | O |
| Content of | 0.93 | 0.55 | 0.29 | 0.010 | 0.002 | 8.60 | 1.54 | 0.30 | 0.020 | 0.010 | 0.011 | 0.0019 |
(2) Nonmetallic inclusion detection
Detection is carried out according to the standard of GB/T10561-2005 'microscopic detection method of standard rating diagram for determination of nonmetallic inclusion content in Steel', and the detection results are shown in Table 2:
table 2: nonmetallic inclusion of the product obtained in example 1
As can be seen from the test results in Table 2, the product obtained in example 1 has a low nonmetallic inclusion content.
(3) Low power tissue detection
Product samples were subjected to low-power tissue testing, see table 3 for results:
table 3: low power tissue of the product obtained in example 1
| Transverse acid leaching | Ingot segregation | Center porosity |
| Without any means for | 0.5 | 0.5 |
From the test results in Table 3, it can be seen that the product obtained in example 1 was of low-power quality.
(4) Detecting the depth of a decarburized layer:
the depth of the decarburized layer of the product was detected with reference to standard GB/T1299-2014, and the result is shown as follows: 0,0. It has been shown that this steel eliminates surface decarburization by milling.
(5) Eutectic carbide non-uniformity detection:
the eutectic carbide non-uniformity of the product was examined with reference to standard GB/T14979, with higher grade numbers representing more severe carbide aggregation. The test results were shown as follows: 3.0 level. The eutectic carbide of the obtained product has been proved to show better uniformity.
(6) Heat treatment hardness and impact work detection:
the heat treatment system is as follows: air cooling is performed at 1030 ℃ for 30min, at 200 ℃ for 2h and at 200 ℃ for 2 h. After the above heat treatment, the samples were tested for hardness and unnotched impact energy, and the test results are shown in table 4:
table 4: heat-treated hardness and unnotched impact Power of the product obtained in example 1
| Hardness (HRC) | No-notch impact 10X 10mm (J) |
| 60.5 | 72.5 |
As can be seen from the test results in Table 4, the heat treatment hardness of the obtained product reaches 60.5HRC, the unnotched impact energy reaches 72.5J, the obtained product shows higher heat treatment hardness and unnotched impact resistance, and the material has better toughness.
(7) Microstructure of microstructure
The product was subjected to microscopic observation, and the results are shown in fig. 1 and fig. 2, wherein fig. 1 and fig. 2 are microscopic observation charts of the product obtained in example 1, and the two charts are different observation magnification. As can be seen from fig. 1-2, the tissue is uniform and the carbides are finely dispersed.
(8) Ultrasonic flaw detection
And carrying out ultrasonic flaw detection on the product, wherein the flaw detection of a module with the specification of 225 multiplied by 430mm meets the CB/T4162B-level requirement.
Example 2
1. Preparation
Target product Cr8Mo2SiV cold work die steel: as in example 1.
A) Smelting in an electric furnace:
a1 Melting):
adopting carbon crop, return materials, ferroalloy, low-P low-S pig iron (P content is less than or equal to 0.030 wt%) and structural component ingredients, weighing raw materials according to the component proportion of Cr8 cold-working die steel, feeding the raw materials into an electric furnace to fully melt the raw materials, when the temperature of molten steel reaches 1580 ℃, carrying out single-tube low-pressure deep oxygen blowing, and then removing oxides of Si and Mn in slag by slag flowing; stirring the molten steel by CO gas generated by the single-pipe low-pressure deep oxygen blowing, and sampling and fully analyzing after uniformly stirring;
Wherein, the single-tube low-pressure deep oxygen blowing condition is: oxygen flow 2000nm 3 And/h, the air pressure is 0.3MPa.
a2 Oxidation:
carrying out power transmission and heating, and carrying out oxygen blowing and C removal when the temperature of the molten steel reaches 1600 ℃ until the C content in the molten steel reaches n percent, and stopping oxygen blowing;
wherein,
the conditions for oxygen blowing and C removal are as follows: oxygen blowing flow rate of 3000nm 3 And/h, the air pressure is 0.7MPa;
n% = target product carbon content (0.93%) -carbon content by make-up (0.05%); the carbon content brought by the supplementing material refers to the carbon content introduced in the alloy raw material supplemented after the step a 2);
a3 Pre-reduction:
adding lime, fluorite, deoxidizer and C powder into an electric furnace for pre-reduction, and blowing inert gas and stirring; taking part of slag to perform full analysis, supplementing alloy raw materials according to the content specification of each component in a target product according to an analysis result to adjust the components, and reserving part of alloy raw materials to be added during LF refining; the alloy raw material of the easily oxidizable element V, si was not adjusted in this step, but was adjusted in addition to the LF furnace refining.
Wherein,
lime is used for 10kg/t of steel, and fluorite is used for 2.5kg/t of steel;
the deoxidizer is CaSi powder and Al blocks, and the dosage is as follows: 2.5kg/t steel of CaSi powder and 3.25kg/t steel of Al block;
The consumption of the C powder is 4kg/t steel;
the pre-reduction time is 10min;
the mass ratio of the reserved amount of the reserved part of alloy raw materials to the total amount of the alloy raw materials which are actually required to be added is 10%;
a4 Tapping:
measuring temperature, when the temperature reaches 1650deg.C, blowing argon (flow 2000 nm) 3 And/h) under the condition of steel slag mixed flushing tapping, and deslagging a ladle after tapping;
b) Refining in an LF furnace:
b1 Molten steel is charged into the furnace:
molten steel is sent into an LF refining furnace, and the conditions for entering the LF furnace are as follows: the temperature is 1550 ℃ and the slag thickness is 35mm;
measuring the temperature of slag thickness steel, feeding an Al wire into an LF refining furnace, adding part of the alloy raw material reserved in the step a 3), and controlling the flow rate of argon gas (50 NL/min); then adding slag, and smelting at 1600 ℃ for 40min;
wherein,
the use amount of the Al wire is 100m/t steel;
the slag is as follows: lime 500kg// t steel, refining slag (80 Al 2 O 3 Refining slag) 400kg/t steel;
the slag is premelted slag, the premelting temperature is 700 ℃, and the premelting time is 8 hours;
b2 Power transmission reduction:
c powder and steel slag friends are added into an LF refining furnace for reduction, after slag is white, the content of Al in the molten steel is adjusted to be 0.04 weight percent, and the white slag is kept for 40min; then adding a small amount of C powder to maintain a reducing atmosphere;
Wherein,
the consumption of the C powder added for the first time is 2.5kg/t steel, and the consumption of the steel slag friends is 250kg/t steel;
the consumption of the C powder added with a small amount of C powder is 1.8kg/t of steel;
c) Vacuum refining in a VD furnace:
the temperature of molten steel entering a VD furnace is 1640 ℃, and the thickness of slag entering the furnace is 80mm; argon is introduced into the system and vacuumized, the ultimate vacuum degree is controlled to be less than or equal to 67Pa, and the holding time under the ultimate vacuum is 15min; then, after increasing the flow of inert gas to break the blank, adding rare earth raw materials into a VD furnace for refining for 10min, and then hanging and pouring.
Wherein the rare earth raw material is misch metal; the consumption of the rare earth raw material is 0.120kg/t steel;
the pouring temperature of the hanging bag is 1480 ℃;
d) Forging:
adopting a 45MN press for quick forging, preheating the anvil to 200 ℃ before forging, wherein the forging temperature is 1080 ℃, the final forging temperature is 900 ℃, forging by adopting a two-light-one-heavy forging mode, and carrying out initial forging, final forging light pressing and middle heavy pressing, wherein in the forging process, the deformation of each part needs to be uniform, and the temperature of each part needs to be kept uniform; the upsetting times are 2 times, the total forging ratio is 8, the head and the tail are hot cut in the forging process, and the head and the tail are cut to remove rotten materials and burrs, so that the forging is obtained.
E) Spheroidizing annealing:
spheroidizing annealing is carried out on the forge piece, and the conditions are as follows: firstly heating to 840 ℃ for 10 hours, then cooling to 700 ℃ for 20 hours; and (3) after the spheroidizing annealing, obtaining the high-strength high-toughness Cr8 cold-work die steel. The product size specification is as follows: 2500mm long by 430mm wide by 225mm thick.
2. Detection of
The product obtained in example 2 was subjected to various tests according to the test method of example 1, with the following results:
(1) Component analysis
Chemical component assay analysis was performed on samples of the product, and the results were the same as in example 1.
(2) Nonmetallic inclusion detection
The detection results of nonmetallic inclusion are shown in table 5:
table 5: nonmetallic inclusion of the product obtained in example 2
As can be seen from the test results in Table 5, the product obtained in example 2 has a low nonmetallic inclusion content.
(3) Low power tissue detection
Product samples were subjected to low-power tissue testing, see table 6 for results:
table 6: low power tissue of the product obtained in example 2
| Transverse acid leaching | Ingot segregation | Center porosity |
| Without any means for | 0.5 | 0.5 |
As can be seen from the test results in Table 7, the product obtained in example 2 was of low-power quality.
(4) Detecting the depth of a decarburized layer:
the detection result of the decarburized layer depth is shown as follows: 0,0. It has been shown that this steel eliminates surface decarburization by milling.
(5) Eutectic carbide non-uniformity detection:
the results of the eutectic carbide non-uniformity test were shown to be: 2.0 level. The eutectic carbide of the obtained product has been proved to show better uniformity.
(6) Heat treatment hardness and impact work detection:
test results for heat treatment hardness and notched impact energy detection are shown in table 7:
Table 7: heat-treated hardness and unnotched impact Power of the product obtained in example 2
| Hardness (HRC) | No-notch impact 10X 10mm (J) |
| 61 | 75 |
As can be seen from the test results in Table 7, the heat treatment hardness of the obtained product reaches 61HRC, the impact energy without defects reaches 75J, the heat treatment hardness and the impact resistance without defects are higher, and the material has better toughness.
(7) Microstructure of microstructure
Microscopic structural observation results show that the structure is uniform and the carbide is finely dispersed.
(8) Ultrasonic flaw detection
The module flaw detection with the specification of 225 multiplied by 430mm meets the CB/T4162B-level requirement.
Example 3
1. Preparation
Target product Cr8Mo2SiV cold work die steel: as in example 1.
A) Smelting in an electric furnace:
a1 Melting):
adopting carbon crop, return materials, ferroalloy, low-P low-S pig iron (P content is less than or equal to 0.030 wt%) and structural component ingredients, weighing raw materials according to the component proportion of Cr8 cold-working die steel, feeding the raw materials into an electric furnace to fully melt the raw materials, when the temperature of molten steel reaches 1580 ℃, carrying out single-tube low-pressure deep oxygen blowing, and then removing oxides of Si and Mn in slag by slag flowing; stirring the molten steel by CO gas generated by the single-pipe low-pressure deep oxygen blowing, and sampling and fully analyzing after uniformly stirring;
wherein, the single-tube low-pressure deep oxygen blowing condition is: oxygen flow 3000nm 3 And/h, the air pressure is 0.6MPa.
a2 Oxidation:
carrying out power transmission and heating, and carrying out oxygen blowing and C removal when the temperature of the molten steel reaches 1600 ℃ until the C content in the molten steel reaches n percent, and stopping oxygen blowing;
wherein,
the conditions for oxygen blowing and C removal are as follows: oxygen blowing flow rate of 3000nm 3 And/h, the air pressure is 0.7MPa;
n% = target product carbon content (0.93%) -carbon content by make-up (0.05%); the carbon content brought by the supplementing material refers to the carbon content introduced in the alloy raw material supplemented after the step a 2);
a3 Pre-reduction:
adding lime, fluorite, deoxidizer and C powder into an electric furnace for pre-reduction, and blowing inert gas and stirring; taking part of slag to perform full analysis, supplementing alloy raw materials according to the content specification of each component in a target product according to an analysis result to adjust the components, and reserving part of alloy raw materials to be added during LF refining; the alloy raw material of the easily oxidizable element V, si was not adjusted in this step, but was adjusted in addition to the LF furnace refining.
Wherein,
lime is used for 10kg/t of steel, and fluorite is used for 2.5kg/t of steel;
the deoxidizer is CaSi powder and Al blocks, and the dosage is as follows: 2.5kg/t steel of CaSi powder and 3.25kg/t steel of Al block;
the consumption of the C powder is 4kg/t steel;
the pre-reduction time is 10min;
The mass ratio of the reserved amount of the reserved part of alloy raw materials to the total amount of the alloy raw materials which are actually required to be added is 10%;
a4 Tapping:
measuring temperature, when the temperature reaches 1650deg.C, blowing argon (flow 2000 nm) 3 And/h) under the condition of steel slag mixed flushing tapping, and deslagging a ladle after tapping;
b) Refining in an LF furnace:
b1 Molten steel is charged into the furnace:
molten steel is sent into an LF refining furnace, and the conditions for entering the LF furnace are as follows: the temperature is 1550 ℃ and the slag thickness is 35mm;
measuring the temperature of slag thickness steel, feeding an Al wire into an LF refining furnace, adding part of the alloy raw material reserved in the step a 3), and controlling the flow rate of argon gas (50 NL/min); then adding slag, and smelting at 1600 ℃ for 40min;
wherein,
the use amount of the Al wire is 100m/t steel;
the slag is as follows: lime 500kg// t steel, refining slag (80 Al 2 O 3 Refining slag) 400kg/t steel;
the slag is premelted slag, the premelting temperature is 800 ℃, and the premelting time is 6 hours;
b2 Power transmission reduction:
c powder and steel slag friends are added into an LF refining furnace for reduction, after slag is white, the content of Al in the whole Al is adjusted to be 0.04 weight percent, and the white slag is kept for 15min; then adding a small amount of C powder to maintain a reducing atmosphere;
wherein,
the consumption of the C powder added for the first time is 1.5kg/t steel, and the consumption of the steel slag friends is 250kg/t steel;
The consumption of the C powder added with a small amount of C powder is 2.3kg/t steel;
c) Vacuum refining in a VD furnace:
the temperature of molten steel entering a VD furnace is 1640 ℃, and the thickness of slag entering the furnace is 80mm; argon is introduced into the system and vacuumized, the ultimate vacuum degree is controlled to be less than or equal to 67Pa, and the holding time under the ultimate vacuum is 15min; then, after increasing the flow of inert gas to break the blank, adding rare earth raw materials into a VD furnace for refining for 10min, and then hanging and pouring.
Wherein the rare earth raw material is misch metal; the consumption of the rare earth raw material is 0.125kg/t steel;
the casting temperature of the hanging ladle is 1500 ℃;
d) Forging:
adopting a 45MN press for quick forging, preheating the anvil to 250 ℃ before forging, wherein the forging temperature is 1150 ℃, the final forging temperature is 980 ℃, forging by adopting a two-light-one-heavy forging mode, and carrying out initial forging, final forging light pressing and middle heavy pressing, wherein in the forging process, the deformation of each part needs to be uniform, and the temperature of each part needs to be kept uniform; the upsetting times are 2 times, the total forging ratio is 8, the head and the tail are hot cut in the forging process, and the head and the tail are cut to remove rotten materials and burrs, so that the forging is obtained.
E) Spheroidizing annealing:
spheroidizing annealing is carried out on the forge piece, and the conditions are as follows: firstly heating to 870 ℃ for heat preservation for 9 hours, and then cooling to 740 ℃ for heat preservation for 15 hours; and (3) after the spheroidizing annealing, obtaining the high-strength high-toughness Cr8 cold-work die steel. The product size specification is as follows: 2500mm long by 410mm wide by 85mm thick.
2. Detection of
The product obtained in example 3 was subjected to various tests according to the test method of example 1, with the following results:
(1) Component analysis
Chemical component assay analysis was performed on samples of the product, and the results were the same as in example 1.
(2) Nonmetallic inclusion detection
The detection results of nonmetallic inclusion are shown in table 8:
table 8: nonmetallic inclusion of the product obtained in example 3
As can be seen from the test results in Table 8, the product of example 3 has a low nonmetallic inclusion content.
(3) Low power tissue detection
Product samples were subjected to low-power tissue testing and the results are shown in table 9:
table 9: low power tissue of the product obtained in example 3
| Transverse acid leaching | Ingot segregation | Center porosity |
| Without any means for | 0.5 | 0.5 |
As can be seen from the test results in Table 11, the product obtained in example 3 was of low-power quality.
(4) Detecting the depth of a decarburized layer:
the detection result of the decarburized layer depth is shown as follows: 0,0. It has been shown that this steel eliminates surface decarburization by milling.
(5) Eutectic carbide non-uniformity detection:
the results of the eutectic carbide non-uniformity test were shown to be: 1.0 grade. The eutectic carbide of the obtained product has been proved to show better uniformity.
(6) Heat treatment hardness and impact work detection:
test results for heat treatment hardness and notched impact energy detection are shown in table 10:
Table 10: heat-treated hardness and unnotched impact energy of the product obtained in example 3
| Hardness (HRC) | No-notch impact 10X 10mm (J) |
| 59.5 | 86 |
As can be seen from the test results in Table 10, the heat treatment hardness of the obtained product reaches 59.5HRC, the unnotched impact energy reaches 86J, the obtained product shows higher heat treatment hardness and unnotched impact resistance, and the material has better toughness.
(7) Microstructure of microstructure
Microscopic structural observation results show that the structure is uniform and the carbide is finely dispersed.
(8) Ultrasonic flaw detection
The module flaw detection with the specification of 225 multiplied by 430mm meets the CB/T4162B-level requirement.
As can be seen from examples 1-3, the Cr8 cold-work die steel prepared by the invention has the advantages of reduced nonmetallic inclusion content, qualified microstructure, lower decarburized layer depth, higher uniformity of eutectic carbide, higher heat treatment hardness of 58HRC or more, and no notch impact energy of 70J or more, and higher heat treatment hardness and no notch impact energy; the microstructure is uniform; and qualified ultrasonic flaw detection.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to aid in understanding the method of the invention and its core concept, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims. The scope of the patent protection is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
Claims (10)
1. A high-strength high-toughness Cr8 cold-work die steel is characterized by comprising the following components:
the balance of Fe and unavoidable impurities;
the high-strength high-toughness Cr8 cold-work die steel is prepared by the following preparation method:
a) Smelting in an electric furnace:
a1 Melting):
weighing raw materials according to the component proportion of Cr8 cold-working die steel, feeding the raw materials into an electric furnace to fully melt the raw materials, carrying out single-tube low-pressure deep oxygen blowing when the temperature of molten steel is more than or equal to 1580 ℃, and then, removing oxides of Si and Mn in slag by slag flow; stirring the molten steel by CO gas generated by the single-pipe low-pressure deep oxygen blowing, and sampling and fully analyzing after uniformly stirring;
a2 Oxidation:
carrying out power transmission and heating, and carrying out oxygen blowing and C removal when the temperature of the molten steel is more than or equal to 1600 ℃ until the C content in the molten steel reaches n percent, and stopping oxygen blowing;
wherein n% = target product carbon content-carbon content brought by the supplement; the carbon content brought by the supplementing material refers to the carbon content introduced in the alloy raw material supplemented after the step a 2); n percent is 0.04 to 0.08 percent;
a3 Pre-reduction:
adding lime, fluorite, deoxidizer and C powder into an electric furnace for pre-reduction, and blowing inert gas and stirring; taking part of slag to perform full analysis, supplementing alloy raw materials according to the content specification of each component in a target product according to an analysis result to adjust the components, and reserving part of alloy raw materials to be added during LF refining;
Wherein the mass ratio of the reserved amount of the reserved part of alloy raw materials to the total amount of the alloy raw materials which are actually required to be added is 10% -30%;
a4 Tapping:
measuring the temperature, when the temperature is more than or equal to 1650 ℃, under the condition of blowing inert gas, mixing steel with steel slag, and deslagging the steel ladle after the steel is discharged;
b) Refining in an LF furnace:
b1 Molten steel is charged into the furnace:
molten steel is sent into an LF refining furnace, and the conditions for entering the LF furnace are as follows: the temperature is more than or equal to 1550 ℃ and the slag thickness is less than or equal to 35mm;
measuring the temperature of slag thickness steel, feeding Al wires into an LF refining furnace, adding part of the alloy raw materials reserved in the step a 3), and controlling the flow of inert gas; then adding slag, smelting for 30-60 min at 1560-1620 ℃;
wherein,
the slag is as follows: lime 12.5kg/t steel, refining slag 10kg/t steel;
the slag is premelted slag, the premelting temperature is 700-800 ℃, and the premelting time is more than or equal to 6 hours;
b2 Power transmission reduction:
c powder and steel slag friends are added into an LF refining furnace for reduction, after slag is white, the content of Al in the molten steel is adjusted to be 0.03-0.04 wt%, and the white slag is kept for 15-60 min; then adding a small amount of C powder to maintain a reducing atmosphere;
wherein,
the consumption of the C powder added for the first time is 1.5-2.5 kg/t steel, and the consumption of the steel slag friends is 6.25kg/t steel;
The consumption of the C powder added with a small amount of C powder is 1.8-2.3 kg/t steel;
c) Vacuum refining in a VD furnace:
the temperature of molten steel entering a VD furnace is 1620-1660 ℃, and the thickness of slag entering the furnace is 60-100 mm; introducing inert gas into the system, vacuumizing, controlling the ultimate vacuum degree to be less than or equal to 67Pa, and keeping the ultimate vacuum for more than or equal to 15min; then, increasing the flow of inert gas until the inert gas is broken, adding rare earth raw materials into a VD furnace for refining, and then hanging and pouring;
wherein the rare earth raw material is misch metal; the consumption of the rare earth raw material is 0.1-0.125 kg/t steel;
the casting temperature of the hanging ladle is 1480-1500 ℃;
d) Forging:
preheating the anvil to 200-250 ℃ before forging, forging at 1080-1150 ℃ and 900-980 ℃ after forging, and forging by adopting a two-light-one-heavy forging mode, wherein the forging times are more than 1 time, so as to obtain a forging piece;
e) Spheroidizing annealing:
and (3) spheroidizing annealing is carried out on the forging, wherein the conditions are as follows: firstly heating to 840-870 ℃ for preserving heat for 8-10 h, then cooling to 700-740 ℃ for preserving heat for 10-20 h; and (3) after the spheroidizing annealing, obtaining the high-strength high-toughness Cr8 cold-work die steel.
2. The high strength and high toughness Cr8 cold work die steel according to claim 1, wherein the composition is:
The balance being Fe and unavoidable impurities.
3. A method for preparing the high-strength high-toughness Cr8 cold-work die steel according to any one of claims 1 to 2, comprising the steps of:
a) Smelting in an electric furnace:
a1 Melting):
weighing raw materials according to the component proportion of Cr8 cold-working die steel, feeding the raw materials into an electric furnace to fully melt the raw materials, carrying out single-tube low-pressure deep oxygen blowing when the temperature of molten steel is more than or equal to 1580 ℃, and then, removing oxides of Si and Mn in slag by slag flow; stirring the molten steel by CO gas generated by the single-pipe low-pressure deep oxygen blowing, and sampling and fully analyzing after uniformly stirring;
a2 Oxidation:
carrying out power transmission and heating, and carrying out oxygen blowing and C removal when the temperature of the molten steel is more than or equal to 1600 ℃ until the C content in the molten steel reaches n percent, and stopping oxygen blowing;
wherein n% = target product carbon content-carbon content brought by the supplement; the carbon content brought by the supplementing material refers to the carbon content introduced in the alloy raw material supplemented after the step a 2); n percent is 0.04 to 0.08 percent;
a3 Pre-reduction:
adding lime, fluorite, deoxidizer and C powder into an electric furnace for pre-reduction, and blowing inert gas and stirring; taking part of slag to perform full analysis, supplementing alloy raw materials according to the content specification of each component in a target product according to an analysis result to adjust the components, and reserving part of alloy raw materials to be added during LF refining;
Wherein the mass ratio of the reserved amount of the reserved part of alloy raw materials to the total amount of the alloy raw materials which are actually required to be added is 10% -30%;
a4 Tapping:
measuring the temperature, when the temperature is more than or equal to 1650 ℃, under the condition of blowing inert gas, mixing steel with steel slag, and deslagging the steel ladle after the steel is discharged;
b) Refining in an LF furnace:
b1 Molten steel is charged into the furnace:
molten steel is sent into an LF refining furnace, and the conditions for entering the LF furnace are as follows: the temperature is more than or equal to 1550 ℃ and the slag thickness is less than or equal to 35mm;
measuring the temperature of slag thickness steel, feeding Al wires into an LF refining furnace, adding part of the alloy raw materials reserved in the step a 3), and controlling the flow of inert gas; then adding slag, smelting for 30-60 min at 1560-1620 ℃;
wherein,
the slag is as follows: lime 12.5kg/t steel, refining slag 10kg/t steel;
the slag is premelted slag, the premelting temperature is 700-800 ℃, and the premelting time is more than or equal to 6 hours;
b2 Power transmission reduction:
c powder and steel slag friends are added into an LF refining furnace for reduction, after slag is white, the content of Al in the molten steel is adjusted to be 0.03-0.04 wt%, and the white slag is kept for 15-60 min; then adding a small amount of C powder to maintain a reducing atmosphere;
wherein,
the consumption of the C powder added for the first time is 1.5-2.5 kg/t steel, and the consumption of the steel slag friends is 6.25kg/t steel;
The consumption of the C powder added with a small amount of C powder is 1.8-2.3 kg/t steel;
c) Vacuum refining in a VD furnace:
the temperature of molten steel entering a VD furnace is 1620-1660 ℃, and the thickness of slag entering the furnace is 60-100 mm; introducing inert gas into the system, vacuumizing, controlling the ultimate vacuum degree to be less than or equal to 67Pa, and keeping the ultimate vacuum for more than or equal to 15min; then, increasing the flow of inert gas until the inert gas is broken, adding rare earth raw materials into a VD furnace for refining, and then hanging and pouring;
wherein the rare earth raw material is misch metal; the consumption of the rare earth raw material is 0.1-0.125 kg/t steel;
the casting temperature of the hanging ladle is 1480-1500 ℃;
d) Forging:
preheating the anvil to 200-250 ℃ before forging, forging at 1080-1150 ℃ and 900-980 ℃ after forging, and forging by adopting a two-light-one-heavy forging mode, wherein the forging times are more than 1 time, so as to obtain a forging piece;
e) Spheroidizing annealing:
and (3) spheroidizing annealing is carried out on the forging, wherein the conditions are as follows: firstly heating to 840-870 ℃ for preserving heat for 8-10 h, then cooling to 700-740 ℃ for preserving heat for 10-20 h; and (3) after the spheroidizing annealing, obtaining the high-strength high-toughness Cr8 cold-work die steel.
4. The method according to claim 3, wherein in the step a 1), the single-tube low-pressure deep oxygen blowing condition is: the oxygen flow is 1000-3000 nm 3 And/h, the air pressure is 0.3-0.6 MPa.
5. The method according to claim 3, wherein in the step a 2), the conditions for oxygen blowing and dec-ating are: the oxygen blowing flow is 3000-5000 nm 3 And/h, the air pressure is 0.1-1.0 MPa; and the oxygen blowing flow and the air pressure are both larger than those in the step a 1).
6. A method according to claim 3, wherein in step a 3):
the lime consumption is 10kg/t steel, and the fluorite consumption is 2.5-3 kg/t steel;
the deoxidizer is CaSi powder and Al blocks, and the dosage is as follows: 2.5kg/t steel of CaSi powder and 3.25kg/t steel of Al block;
the consumption of the C powder is 3-5 kg/t steel;
the pre-reduction time is more than or equal to 10min.
7. The process according to claim 3, wherein in step a 4), the flow rate of the inert gas is 1000 to 3000nm 3 /h。
8. A method according to claim 3, wherein in step b 1):
the dosage of the Al wire is 2.5m/t steel;
the flow rate of the inert gas is 40-60 NL/min.
9. A method according to claim 3, wherein in step C), the refining time is from 5 to 10 minutes.
10. A method according to claim 3, wherein in step D), forging is performed using a 45MN press.
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