CN114134392B - Preparation method of high-purity high-hardness ZW680 plastic die steel - Google Patents

Preparation method of high-purity high-hardness ZW680 plastic die steel Download PDF

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CN114134392B
CN114134392B CN202111492289.XA CN202111492289A CN114134392B CN 114134392 B CN114134392 B CN 114134392B CN 202111492289 A CN202111492289 A CN 202111492289A CN 114134392 B CN114134392 B CN 114134392B
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furnace
steel
slag
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temperature
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CN114134392A (en
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刘道献
冯明明
曹立军
张海英
赵伟东
王朋
肖书梦
王建华
崔瑞婷
宋文建
张健
张长春
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Tangshan Zhiwei Technology Co ltd
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    • 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
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/002—Hybrid process, e.g. forging following casting
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • 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
    • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
    • C21D3/02—Extraction of non-metals
    • C21D3/06—Extraction of hydrogen
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/16—Remelting metals
    • C22B9/18—Electroslag remelting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
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    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention relates to a preparation process of high-purity high-hardness age-hardening ZW680 plastic die steel, which comprises the following steps: batching → electric furnace smelting → LF + VD refining → casting → electroslag secondary remelting → heating → forging → solid solution → aging, etc., the prepared die steel has higher purity, so that the grades of various kinds of coarse and fine inclusions of A, B, C, D can respectively reach 0.5 grade and above, and [ H ] in the steel is less than or equal to 1.5 ppm; the aging hardening hardness is more than or equal to 40HRC, the same section hardness is less than or equal to 1.5HRC, and the mirror surface polishing property is good; the aging temperature is low, the deformation is small, the aging treatment can be carried out after the processing, and the plastic mould with complexity, precision and long service life can be manufactured.

Description

Preparation method of high-purity high-hardness ZW680 plastic die steel
Technical Field
The invention relates to the technical field of die steel manufacturing, in particular to a preparation process of high-purity high-hardness age-hardening ZW680 plastic die steel.
Background
The plastic mould is an important technical device in the plastic molding processing industry, is more and more widely applied, has large consumption of steel and more varieties and specifications, and occupies a larger proportion in the mould steel. The steel grades currently used for plastic molds in China can be classified according to the characteristics of steel and the heat treatment state when in use: carbon plastic die steel, carburized plastic die steel, pre-hardened plastic die steel, age-hardened plastic die steel, corrosion-resistant plastic die steel, free-cutting plastic die steel, plastic die steel for mirror finishing, and the like.
When the plastic die steel works, the plastic die steel is subjected to the scouring and abrasion of the hot plastic melt and the corrosion of harmful gases such as chlorine, fluorine and the like. The plastic die steel is required to have good hardenability, cutting property, corrosion resistance, polishing property, pattern etching property and the like.
Disclosure of Invention
Based on the technical problems, the invention provides a preparation method of high-purity high-hardness age-hardening ZW680 plastic die steel, which is realized by the following technical means:
the preparation method comprises the following process steps:
step I: smelting in an electric furnace, wherein furnace charge consists of pig iron, carbon return steel and 38-45 wt% of scrap steel, smelting in the electric furnace by adopting an oxidation method, and oxidizing and slagging off when the C of a melt in the electric furnace is less than or equal to 0.09%, the P is less than or equal to 0.008% and the temperature is more than or equal to 1640 ℃; and adding ferrosilicon, fluorite and lime to make new slag, tapping when the temperature of the molten steel is 1640-.
Step II: and (3) LF refining, namely introducing argon into the molten steel obtained in the step I in an LF furnace for stirring, performing white slag in the whole refining process, controlling the alkalinity to be 4.0-5.5 (the high-alkalinity refining slag has higher desulfurization capacity and inclusion adsorption capacity), performing component fine adjustment after sufficient deoxidation, adjusting five element components of Cu, C, Mn, Mo and Ni, and performing VD refining after the elements are all adjusted and the melt is uniform and stable.
Step III: VD refining, namely moving the molten steel obtained in the step II from an LF furnace to a VD furnace for smelting at 1670-1700 ℃, keeping the vacuum degree in the VD furnace to be less than or equal to 60Pa and keeping the vacuum for 20-30 min, sampling and analyzing after vacuum treatment, and then performing Al alloying (reducing Al in the steel) in an Al wire feeding mode2O3Impurities) are stirred by adopting argon, and the slag surface is kept to slightly move without exposing molten steel in the argon stirring process; the components are stirred uniformly, when the temperature is 1560-1590 ℃, the electrode blank is obtained by ladle casting, and the [ H ] in the steel discharged from the station]≤1.5ppm。
Step IV: electroslag remelting (ensuring the mirror effect of the steel, improving the purity, and carrying out electroslag secondary remelting) is carried out on the surface of the electrode blank obtained in the step III, then a calcium fluoride and aluminum oxide binary slag system (generally a commercially available binary slag system with standard specification) is adopted for smelting, a deoxidizing agent is added in the smelting process, and a steel ingot is obtained after smelting.
Step V: and (3) forging, charging the steel ingot obtained in the step (IV), wherein the furnace temperature of the charging is less than or equal to 800 ℃, the steel ingot is not ignited after being charged into the furnace, the steel ingot is slowly heated to 780-810 ℃ after being subjected to material sealing for 1.5-2.5 h, the temperature is slowly raised to 780-810 ℃, the temperature is kept for 2-6 h, the temperature is raised to 1130-1160 ℃ at the speed of less than or equal to 100 ℃/h, the temperature is kept for 3-7 h, the steel ingot is discharged from the furnace and forged, upsetting is directly carried out by adopting a holding clamp (the center forging effect is improved), the open forging temperature is 1080-1100 ℃, and the final forging temperature is 800-900 ℃.
Step VI: and (3) dehydrogenation and solid solution, (the die steel is white-point sensitive steel, and a large-size forged material needs dehydrogenation treatment), the forged material obtained after the forging in the step V is put into a furnace, heat preservation is carried out for 25-40 h at the temperature of 650-680 ℃ for hydrogen diffusion, then the furnace temperature is increased to 860-900 ℃ for solid solution heating, solid solution heat preservation is carried out for 10-20 h (carbon and alloy elements such as Al, Cu, Ni and the like in the steel are fully dissolved in austenite), after the heat preservation is finished, the furnace is cooled to 400-550 ℃, and then the steel is taken out of the furnace for air cooling.
Step VII: and (3) performing surface treatment, namely performing surface milling on the forged material subjected to the solution treatment in the step VI (the forged material has low hardness, is convenient to perform surface machining treatment and has a hardness of 29-33 HRC).
Step VIII: and aging, namely heating the forged material obtained after the surface treatment in the step VI in a furnace to 510-550 ℃, and preserving heat for 20-30 h for aging treatment (in the aging process, intermetallic phases and copper-rich phases are dispersed and precipitated from the matrix to strengthen the matrix, the alloy contains Al, Cu, Ni and other alloy elements, the Al and Ni play a role in precipitating a NiAl intermetallic phase to strengthen the matrix in the aging process, and the Cu plays a role in precipitating a copper-rich phase M in the aging process2X causes strengthening effect), after the aging heat preservation is finished, the furnace is cooled to 200-300 ℃, and then the product is discharged from the furnace and cooled in air, so that the high-purity high-hardness aging hardening ZW680 plastic die steel product is obtained.
Preferably, the high-purity high-hardness age-hardening ZW680 plastic die steel comprises the following components in percentage by mass: c: 0.10-0.20%, Si is less than or equal to 0.45%, Mn: 1.35-1.95%, Mo: 0.25-0.55%, Ni: 2.80-3.20%, Cu: 0.7-1.1%, Al: 0.8-1.4%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, rare earth: 0.005-0.009%, and the balance Fe and inevitable impurities.
Preferably, in the step IV, a calcium fluoride and aluminum oxide binary slag system is adopted for smelting, and a deoxidizer is added in the smelting process, and the method specifically comprises the following steps: the electrode blank after surface cleaning and polishing is used for slagging, and the addition amount of the calcium fluoride and aluminum oxide binary slag system meets the formula (1)
GSlag＝DKnot 2×π/4×HSlag×ρSlag (1)
Wherein G isSlagThe addition amount of the binary slag system; dKnotThe diameter of the crystallizer is the electrode blank; rhoSlagIs the specific gravity of the slag; hSlagIs the thickness of the slag layer (wherein HSlag150-SlagApproximately 170-230 mm), after the slag materials are completely melted, the melting speed in a steady state stage is 8-11 kg/min, the melting speed in a feeding stage is 2.5-6.5 kg/min, an electroslag ingot is obtained, then power is cut off, and the forging process is carried out after furnace cooling is carried out for 90-110 min. Wherein the melting point of the binary slag system is 1340-1380 ℃, the binary slag system is firstly melted in the remelting process, then the electrode blank is melted, the lowest melting temperature of the electrode blank is 1490-1510 ℃, and the temperature of a slag pool in the electroslag remelting process is 1700-1900 ℃.
Preferably, the ferrosilicon, fluorite and lime added in the step I and the alloy material added in the fine adjustment process of the components in the step II are added after baking (the high-purity high-hardness age hardening plastic die steel has high Ni and Mn content and is white point sensitive steel, and the carrying amount of [ H ] in the smelting process needs to be strictly controlled).
Preferably, in step II, the five element components of Cu, C, Mn, Mo and Ni are adjusted, and the adjusted target component contents are: 0.90 to 0.11 weight percent of Cu, 0.14 to 0.15 weight percent of C, 1.55 to 1.63 weight percent of Mn, 0.24 to 0.32 weight percent of Mo and 3.1 to 3.3 weight percent of Ni.
Preferably, in the step III, when Al alloying is performed by feeding Al wire, the temperature of the molten steel is maintained at 1610-.
Preferably, a calcium fluoride and aluminum oxide binary slag system is adopted for smelting, a deoxidizing agent (Al powder needs to be added in the smelting process to avoid Al burning and Si increasing in the electroslag smelting process) is added in the smelting process, and 16-19 g (preferably 18g) of Al powder is added into a slag pool after slag materials are completely melted in the slagging stage; and in the steady state stage, 1.3-1.6 g (preferably 1.5g) of Al powder is added every minute from the beginning of electrode melting to half electrode smelting.
Preferably, the high-purity high-hardness age-hardening ZW680 plastic die steel is press-forged flat steel, the width of the die steel can reach 750mm, and the thickness of the die steel can reach 500 mm.
A high-purity high-hardness age-hardening ZW680 plastic die steel comprises the following components in percentage by mass: c: 0.10-0.20%, Si is less than or equal to 0.45%, Mn: 1.35-1.95%, Mo: 0.25-0.55%, Ni: 2.80-3.20%, Cu: 0.7-1.1%, Al: 0.8-1.4%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, rare earth: 0.005-0.009%, and the balance Fe and inevitable impurities; and the high-purity high-hardness age-hardening ZW680 plastic die steel is prepared by the preparation method.
Preferably, in the microstructure of the high-purity high-hardness age hardening ZW680 plastic die steel, the aging structure is intragranular bainite and precipitates, the precipitates are distributed on grain boundaries and in the crystal, the precipitates are uniformly distributed, and the precipitates are broken and have edges and corners, wherein the precipitates are carbides, and the aging strengthening phase intermetallic compound NiAl phase and Cu-rich phase particles are in a nanometer scale.
The invention has the beneficial effects that:
1, ZW680 provided by the invention is low-carbon low-alloy die steel, and specific amounts of Ni, Al, Mn, Mo, Cu and other alloy elements are added. Wherein, Ni in the range of the invention can improve hardenability and corrosion resistance; al can improve the phase transition temperature of bainite, easily obtain an upper bainite structure, and contribute to the particle precipitation of Ni-Al intermetallic compounds during aging treatment; mn can eliminate or weaken the hot brittleness of the steel caused by sulfur, thereby improving the hot workability of the steel; mo can improve hardenability, tempering stability, refined crystal grains and the like; cu is an effective element for precipitating and hardening fine particles of an Fe — Cu intermetallic compound during aging treatment and for improving machinability during solution treatment. After heat treatment, the hardness of the ZW680 can reach 40HRC after aging, and the invention has higher purity and better hardness uniformity and can be used for manufacturing complex, precise and long-life plastic moulds.
2, the invention adopts electric furnace steelmaking, LF external refining, VD vacuum deoxidation for impurity removal and electroslag secondary remelting with specific parameters of specific steps, especially controls the specific parameters of each step (such as H content control in slag and alloy, Al alloying molten steel temperature requirement, inclusion control in smelting process, Al powder addition requirement in electroslag remelting process and the like), so that the grades of various kinds of coarse and fine inclusions of A, B, C, D can respectively reach 0.5 grade and above, the [ H ] in steel is less than or equal to 1.5ppm, and the mirror finishing performance of steel is improved.
And 3, by setting specific parameters of the steps of heating, forging, solid solution and aging of the steel ingot and effective matching of the parameters in the steps, the uniformity of the structure and the hardness of the steel is effectively improved. The thickness of the die steel can reach 500mm, and the width of the die steel can reach 750 mm. The aging structure of the steel is mainly intragranular bainite and precipitates, the precipitates are distributed on crystal boundaries and in crystals and are relatively dispersed, the particles are relatively fine, the time-hardening hardness of the steel is more than or equal to 40HRC, and the same-section hardness of the steel is less than or equal to 1.5 HRC.
Drawings
FIG. 1 shows the metallographic structure of the die steel of the present invention.
FIG. 2 is a width-direction hardness change curve of the cross sections of the head part and the tail part of the die steel forging.
FIG. 3 is a hardness variation curve of the cross section of the head part and the tail part of the die steel forging along the thickness direction.
Detailed Description
Specific embodiments of the present invention will now be described as follows:
example 1
The ZW680 die steel comprises the following components in percentage by mass: 0.15% of C, 0.35% of Si, 1.75% of Mn, 0.45% of Mo, 3.1% of Ni, 0.92% of Cu, 0.94% of Al, 0.005% of P, 0.001% of S, 0.008% of rare earth and the balance of Fe, and carrying out batching and smelting in an electric arc furnace-LF-VD to obtain the 5.96t steel ingot. The method comprises the following specific steps:
step I: smelting in an electric furnace, wherein furnace charge consists of pig iron, carbon return steel and 40% of scrap steel, and smelting in the electric furnace by adopting an oxidation method. When the C is 0.08 percent and the P is 0.006 percent, oxidizing and slagging off are carried out at the temperature of 1640 ℃; and adding ferrosilicon, fluorite and lime to make new slag, tapping when the temperature of molten steel is 1670 ℃, and adding aluminum to deoxidize in the tapping process.
Step II: and (3) LF refining, namely introducing argon into the molten steel obtained in the step I in an LF furnace and stirring, wherein the molten steel is white slag in the whole refining process, the alkalinity is controlled to be 4.0-5.5, and the high-alkalinity refining slag has high desulfurization capacity and impurity adsorption capacity. And carrying out fine adjustment on the components after full deoxidation. The LF furnace preferentially adjusts the components of Cu and five elements of C, Mn, Mo and Ni, wherein the content of Cu is 0.92%, the content of C is 0.15%, the content of Mn is 1.75%, the content of Mo is 0.45% and the content of Ni is 3.1%, and the LF furnace is transferred to a VD furnace for smelting when the temperature is 1662 ℃ on the basis that the adjustment of the elements is finished and the uniformity is ensured.
And III, VD refining, namely moving the molten steel obtained in the step II to a VD furnace from a steel ladle, and keeping the vacuum degree less than 58Pa for 25 min. Sampling and analyzing after vacuum treatment, and carrying out Al alloying by adopting an Al wire feeding mode to reduce Al in steel2O3And (4) inclusion. Stirring by using small argon gas, and keeping the slag surface to be slightly moved without exposing molten steel; when the components are uniform and the temperature is 1575 ℃, the electrode blank is obtained by ladle pouring and is discharged from the steel]＝0.6ppm。
And IV, electroslag remelting is carried out to ensure the mirror surface effect of the steel, improve the purity and carry out electroslag secondary remelting. And (3) cleaning and polishing the surface of the electrode blank obtained in the step (III), smelting by adopting a calcium fluoride and aluminum oxide binary slag system, and adding a deoxidizer Al powder in the smelting process.
In this example, a commercially available PS-05 slag system (calcium fluoride and alumina binary slag system, slag system ratio of CaF) was used2:Al2O3＝7:3)。
And V, forging, namely conveying the steel ingot obtained in the step IV to a forging furnace for charging, wherein the temperature of the furnace for charging is less than or equal to 800 ℃. And (3) putting the steel ingot into the furnace without ignition, sealing the material for 2h, slowly heating to 800 ℃, keeping the temperature for 4h, heating to 1145 ℃ at the speed of less than or equal to 100 ℃/h, keeping the temperature for 5h, discharging and forging. The forging adopts holding tongs to directly perform upsetting and improve the center forging effect, the open forging temperature is higher than 1080 ℃, and the finish forging temperature is higher than or equal to 800 ℃. A module having a thickness of 400mm and a width of 750mm was obtained.
And VI, removing hydrogen and dissolving solid, wherein the die steel is white-spot sensitive steel, and large-size forged materials need to be subjected to hydrogen removal treatment. And after the heat preservation at 650 ℃ is finished for 25h, raising the temperature of the furnace to 900 ℃, carrying out solution heating, preserving the heat for 16h to fully dissolve carbon and alloy elements such as Al, Cu, Ni and the like in the steel into austenite, cooling the furnace to 500 ℃ after the heat preservation is finished, and taking the furnace out of the furnace for air cooling.
And step VII, performing surface treatment, wherein after the forging material is subjected to solution treatment, the hardness of the forging material is lower and is within the range of 29-33 HRC, and the forging material is convenient for surface processing treatment. It is surface milled.
And VIII, aging, namely heating the forged material obtained by the treatment in the step VII to 530 ℃, and preserving heat for 20 hours for aging treatment. Intermetallic phase and copper-rich phase are dispersed and precipitated from the matrix in the aging process to strengthen the matrix, the alloy contains alloy elements such as Al, Cu, Ni and the like, the Al and Ni are used for precipitating NiAl intermetallic phase to strengthen the matrix in the aging process, and the Cu is used for precipitating copper-rich phase M in the aging process2X causes a strengthening effect. And after the aging heat preservation is finished, cooling the furnace to 250 ℃, and discharging the furnace for air cooling.
Example 2
The ZW680 die steel comprises the following components in percentage by mass: 0.14% of C, 0.32% of Si, 1.80% of Mn, 0.42% of Mo, 3.05% of Ni, 0.96% of Cu, 1.2% of Al, 0.005% of P, 0.001% of S, 0.008% of rare earth and the balance of Fe, and carrying out batching and smelting in an electric arc furnace-LF-VD to obtain the 6.32t steel ingot. The method comprises the following specific steps:
step I: smelting in an electric furnace, wherein furnace charge consists of pig iron, carbon return steel and 40% of scrap steel, and smelting in the electric furnace by adopting an oxidation method. When the C is 0.072 percent and the P is 0.0075 percent, carrying out oxidation and slagging-off at the temperature of 1650 ℃; and adding ferrosilicon, fluorite and lime to make new slag, tapping when the temperature of molten steel is 1660 ℃, and adding aluminum to deoxidize in the tapping process.
Step II: and (3) LF refining, namely introducing argon into the molten steel obtained in the step I in an LF furnace and stirring, wherein the molten steel is white slag in the whole refining process, the alkalinity is controlled to be 4.0-5.5, and the high-alkalinity refining slag has high desulfurization capacity and impurity adsorption capacity. And carrying out fine adjustment on the components after full deoxidation. The LF furnace preferentially adjusts the components of Cu and five elements of C, Mn, Mo and Ni, wherein the content of Cu is 0.96%, the content of C is 0.14%, the content of Mn is 1.80%, the content of Mo is 0.42% and the content of Ni is 3.05%, and the LF furnace is transferred to a VD furnace for smelting when the temperature is 1670 ℃ on the basis of adjusting the elements and ensuring uniformity.
And III, VD refining, namely moving the molten steel obtained in the step II to a VD furnace from a steel ladle, and keeping the vacuum degree less than 59Pa for 25 min. Sampling and analyzing after vacuum treatment, and carrying out Al alloying by adopting an Al wire feeding mode to reduce Al in steel2O3And (4) inclusion. Stirring by using small argon gas, and keeping the slag surface to be slightly moved without exposing molten steel; when the components are uniform and the temperature is 1565 ℃, the electrode blank is obtained by ladle casting, and the electrode blank is discharged from the steel]＝0.9ppm。
And IV, electroslag remelting is carried out to ensure the mirror surface effect of the steel, improve the purity and carry out electroslag secondary remelting. And (3) cleaning and polishing the surface of the electrode blank obtained in the step (III), smelting by adopting a calcium fluoride and aluminum oxide binary slag system, and adding a deoxidizer Al powder in the smelting process.
And V, forging, namely conveying the steel ingot obtained in the step IV to a forging furnace for charging, wherein the temperature of the furnace for charging is less than or equal to 800 ℃. And (3) putting the steel ingot into the furnace without ignition, sealing the material for 2h, slowly heating to 800 ℃, keeping the temperature for 4h, heating to 1145 ℃ at the speed of less than or equal to 100 ℃/h, keeping the temperature for 5h, discharging and forging. The forging adopts holding tongs to directly perform upsetting and improve the center forging effect, the open forging temperature is higher than 1080 ℃, and the finish forging temperature is higher than or equal to 800 ℃. A module having a thickness of 340mm and a width of 750mm was obtained.
And VI, removing hydrogen and dissolving solid, wherein the die steel is white-spot sensitive steel, and large-size forged materials need to be subjected to hydrogen removal treatment. And after the heat preservation at 660 ℃ is finished for 20h, raising the temperature of the furnace to 890 ℃, carrying out solid solution heating, preserving the heat for 20h to ensure that carbon and alloy elements such as Al, Cu, Ni and the like in the steel are fully dissolved in austenite, cooling the furnace to 530 ℃ after the heat preservation is finished, and discharging and air cooling the furnace.
And step VII, surface treatment, wherein after the forging material is subjected to solution treatment, the hardness of the forging material is lower and is within the range of 29-33 HRC, and surface processing treatment is facilitated. It is surface milled.
And VIII, aging, namely heating the forged material obtained by the treatment in the step VII to 525 ℃, and preserving heat for 24 hours for aging treatment. Intermetallic phase and copper-rich phase are dispersed and precipitated from the matrix in the aging process to strengthen the matrix, the alloy contains alloy elements such as Al, Cu, Ni and the like, the Al and Ni play a role in precipitating NiAl intermetallic phase to strengthen the matrix in the aging process, and the Cu plays a role in strengthening the matrix in the aging processSeparating out copper-rich phase M2X causes a strengthening effect. And after the aging heat preservation is finished, cooling the furnace to 250 ℃, and discharging and air cooling.
Example 3
The ZW680 die steel comprises the following components in percentage by mass: 0.16% of C, 0.30% of Si, 1.70% of Mn, 0.46% of Mo, 3.0% of Ni, 0.95% of Cu, 1.15% of Al, 0.004% of P, 0.001% of S, 0.007% of rare earth and the balance of Fe, and carrying out batching and smelting in an electric arc furnace-LF-VD to obtain the 6.21t steel ingot. The method comprises the following specific steps:
step I: smelting in an electric furnace, wherein furnace charge consists of pig iron, carbon return steel and 40% of scrap steel, and smelting in the electric furnace by adopting an oxidation method. When the C is 0.07 percent and the P is 0.007 percent, oxidizing and slagging off are carried out at the temperature of 1650 ℃; and adding ferrosilicon, fluorite and lime to make new slag, tapping when the temperature of molten steel is 1666 ℃, and adding aluminum to deoxidize in the tapping process.
Step II: and (3) LF refining, namely introducing argon into the molten steel obtained in the step I in an LF furnace and stirring, wherein the molten steel is white slag in the whole refining process, the alkalinity is controlled to be 4.0-5.5, and the high-alkalinity refining slag has high desulfurization capacity and impurity adsorption capacity. And carrying out fine adjustment on the components after full deoxidation. The LF furnace preferentially adjusts the components of Cu and five elements of C, Mn, Mo and Ni, wherein the content of Cu is 0.95%, the content of C is 0.16%, the content of Mn is 1.70%, the content of Mo is 0.46% and the content of Ni is 3.00%, and the LF furnace is transferred to a VD furnace for smelting when the temperature is 1664 ℃ on the basis that the adjustment of the elements is finished and the uniformity is ensured.
And III, VD refining, namely moving the molten steel obtained in the step II to a VD furnace from a steel ladle, and keeping the vacuum degree less than 60Pa for 20 min. Sampling and analyzing after vacuum treatment, and carrying out Al alloying by adopting an Al wire feeding mode to reduce Al in steel2O3And (4) inclusion. Stirring by using small argon gas, and keeping the slag surface to be slightly moved without exposing molten steel; when the components are uniform and the temperature is 1560 ℃, the electrode blank is obtained by ladle casting, and the electrode blank is discharged from the steel]＝0.7ppm。
And IV, electroslag remelting is carried out to ensure the mirror surface effect of the steel, improve the purity and carry out electroslag secondary remelting. And (3) cleaning and polishing the surface of the electrode blank obtained in the step (III), smelting by adopting a calcium fluoride and aluminum oxide binary slag system, and adding a deoxidizer Al powder in the smelting process.
And V, forging, namely conveying the steel ingot obtained in the step IV to a forging furnace for charging, wherein the temperature of the furnace for charging is less than or equal to 800 ℃. And (3) putting the steel ingot into a furnace without ignition, sealing the material for 2h, slowly heating to 800 ℃, keeping the temperature for 4h, heating to 1150 ℃ at the speed of less than or equal to 100 ℃/h, keeping the temperature for 5h, discharging and forging. The forging adopts holding tongs to directly perform upsetting and improve the center forging effect, the open forging temperature is higher than 1080 ℃, and the finish forging temperature is higher than or equal to 800 ℃. A module having a thickness of 500mm and a width of 750mm is obtained.
And VI, removing hydrogen and dissolving solid, wherein the die steel is white-spot sensitive steel, and large-size forged materials need to be subjected to hydrogen removal treatment. And after the heat preservation at 660 ℃ is finished for 30h and hydrogen diffusion is finished, raising the temperature of the furnace to 895 ℃ for solution heating, preserving the heat for 18h to fully dissolve carbon, Al, Cu, Ni and other alloy elements in the steel into austenite, cooling the furnace to 540 ℃ after the heat preservation is finished, and discharging the furnace for air cooling.
And step VII, surface treatment, wherein after the forging material is subjected to solution treatment, the hardness of the forging material is lower and is within the range of 29-33 HRC, and surface processing treatment is facilitated. It is surface milled.
And VIII, aging, namely heating the forged material obtained by the treatment in the step VII to 530 ℃, and preserving heat for 25h for aging treatment. Intermetallic phase and copper-rich phase are dispersed and precipitated from the matrix in the aging process to strengthen the matrix, the alloy contains alloy elements such as Al, Cu, Ni and the like, the Al and Ni are used for precipitating NiAl intermetallic phase to strengthen the matrix in the aging process, and the Cu is used for precipitating copper-rich phase M in the aging process2X causes a strengthening effect. And after the aging heat preservation is finished, cooling the furnace to 250 ℃, and discharging and air cooling.
The performance test was carried out for examples 1 to 3:
A. inclusions
The grades of the forgings A, B, C, D with coarse inclusions and fine inclusions are shown in Table 1. (wherein A is a sulfide-based inclusion, B is an alumina-based inclusion, C is a silicate-based inclusion, and D is a spherical oxide-based inclusion, which are common concepts in the art).
TABLE 1
Figure BDA0003398852190000111
B. Tissue of
As shown in figure 1, the forging aging structure of the invention mainly comprises granular bainite in crystal and precipitates, wherein the precipitates are distributed on crystal boundaries and in the crystal, and the precipitates are relatively uniform and have broken edges and corners. Precipitates seen in the metallographic microstructure were carbides. The intermetallic compound NiAl phase and Cu-rich phase of the aging strengthening phase are fine and nano-sized.
C. Hardness of
The hardness values of the ZW680 die steel of the invention along the direction of the width and the thickness of the section are shown in figures 2 and 3. The section hardness of the head part of the finished product forging is 40.2-41.3HRC, the uniformity of the section hardness is less than or equal to 1.1HRC, the section hardness of the tail part is 40.3-41.6HRC, and the uniformity of the section hardness is less than or equal to 1.3 HRC; the uniformity of the hardness of the head and the tail of the finished product forging is less than or equal to 1.4 HRC.

Claims (9)

1. The preparation method of the high-purity high-hardness age hardening ZW680 plastic die steel is characterized by comprising the following steps:
step I: smelting in an electric furnace, wherein furnace materials comprise pig iron, carbon return steel and 38-45 wt% of waste steel, smelting in the electric furnace by adopting an oxidation method, and oxidizing and slagging off when the C content and the P content of a melt in the electric furnace are less than or equal to 0.09% and less than or equal to 0.008% and the temperature is more than or equal to 1640 ℃; adding ferrosilicon, fluorite and lime to make new slag, tapping when the temperature of molten steel is 1640-1680 ℃, and adding aluminum to deoxidize in the tapping process to obtain molten steel;
step II: performing LF refining, namely introducing argon into the molten steel obtained in the step I in an LF furnace, stirring, controlling the alkalinity of white slag in the whole refining process to be R = 4.0-5.5, performing component fine adjustment after full deoxidation, adjusting the components of five elements, namely Cu, C, Mn, Mo and Ni, and performing VD refining after the elements are adjusted and the melt is uniform and stable;
step III: VD refining, namely moving the molten steel obtained in the step II from an LF furnace to a VD furnace for smelting at the temperature of 1670-1700 ℃, keeping the vacuum degree in the VD furnace to be less than or equal to 60Pa, keeping the vacuum for 20-30 min, sampling and analyzing after vacuum treatment, then carrying out Al alloying by adopting an Al wire feeding mode, stirring by adopting argon, wherein the stirring strength of the argon is to keep the slag surface to be slightly moved without exposing the molten steel; uniformly stirring the components, when the temperature is 1560-1590 ℃, carrying out ladle casting to obtain an electrode blank, wherein [ H ] in the discharged steel is less than or equal to 1.5 ppm;
step IV: electroslag remelting, namely cleaning and polishing the surface of the electrode blank obtained in the step III, smelting by adopting a calcium fluoride and aluminum oxide binary slag system, adding a deoxidizing agent in the smelting process, and obtaining an electroslag ingot after smelting;
step V: forging, charging the electroslag ingot obtained in the step IV, wherein the furnace temperature of charging is less than or equal to 800 ℃, igniting the steel ingot after charging, sealing materials for 1.5-2.5 h, slowly heating to 780-810 ℃, keeping the temperature for 2-6 h, heating to 1130-1160 ℃ at the speed of less than or equal to 100 ℃/h, keeping the temperature for 3-7 h, discharging from the furnace and forging, directly upsetting by using holding tongs, wherein the forging temperature is 1080-1100 ℃, and the finish forging temperature is 800-900 ℃;
step VI: d, dehydrogenation and solid solution, namely putting the forged material obtained after forging in the step V into a furnace, preserving heat for 25-40 h at the temperature of 650-680 ℃ for hydrogen diffusion, then raising the temperature of the furnace to 860-900 ℃ for solid solution heating, preserving heat for 10-20 h, cooling the furnace to 400-550 ℃ after heat preservation, and then discharging the furnace for air cooling;
step VII: performing surface treatment, namely performing surface milling on the forged material subjected to the solution treatment in the step VI;
step VIII: aging, namely heating the forged material obtained after the surface treatment in the step VI in a furnace to 510-550 ℃, preserving heat for 20-30 h for aging treatment, cooling the forged material in the furnace to 200-300 ℃ after the aging and heat preservation, and then discharging the forged material from the furnace for air cooling to obtain a high-purity high-hardness age-hardening ZW680 plastic die steel product;
the high-purity high-hardness age-hardening ZW680 plastic die steel comprises the following components in percentage by mass: c: 0.10-0.20%, Si is less than or equal to 0.45%, Mn: 1.35-1.95%, Mo: 0.25-0.55%, Ni: 2.80-3.20%, Cu: 0.7-1.1%, Al: 0.8-1.4%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, rare earth: 0.005-0.009%, and the balance Fe and inevitable impurities.
2. The preparation method according to claim 1, wherein the calcium fluoride and alumina binary slag system is adopted for smelting in the step IV, and a deoxidizer is added in the smelting process, and the preparation method specifically comprises the following steps: the electrode blank after surface cleaning and polishing is used for slagging, and the addition amount of the calcium fluoride and aluminum oxide binary slag system meets the formula (1)
GSlag= DKnot 2×π/4×HSlag×ρSlag （1）
Wherein G isSlagThe addition amount of the binary slag system; dKnotThe diameter of the crystallizer is the electrode blank; rhoSlagIs the specific gravity of the slag; hSlagAnd (3) obtaining an electroslag ingot according to the thickness of the slag layer, wherein the melting speed in a steady state stage is 8-11 kg/min and the melting speed in a feeding stage is 2.5-6.5 kg/min after all slag is melted, then, the power is cut off, and the forging process is carried out after furnace cooling is carried out for 90-110 min.
3. The method according to claim 1, wherein the ferrosilicon, fluorite and lime added in step I and the alloy material added in the fine adjustment of the components in step II are added after baking.
4. The method according to claim 1, wherein in step II, the five element components of Cu, C, Mn, Mo and Ni are adjusted, and the target component contents are adjusted as follows: 0.90 to 1.1 weight percent of Cu, 0.14 to 0.15 weight percent of C, 1.55 to 1.63 weight percent of Mn, 0.24 to 0.32 weight percent of Mo and 3.1 to 3.3 weight percent of Ni.
5. The method as claimed in claim 1, wherein in the step III, Al alloying is performed by feeding Al wire while maintaining the temperature of molten steel at 1610-1640 ℃.
6. The preparation method according to claim 1, wherein in the step IV, a calcium fluoride and aluminum oxide binary slag system is adopted for smelting, Al powder is added as a deoxidizer in the smelting process, and in the slagging stage, 16-19 g of Al powder is added into a slag pool after slag materials are completely melted; and in the steady state stage, 1.3-1.6 g of Al powder is added every minute in the process from electrode melting to electrode smelting halving.
7. The method of claim 1, wherein the high purity high hardness age-hardened ZW680 plastic die steel is a press forged flat steel up to 750mm in width and 500mm in thickness.
8. The high-purity high-hardness age-hardening ZW680 plastic die steel is characterized by comprising the following components in percentage by mass: c: 0.10-0.20%, Si is less than or equal to 0.45%, Mn: 1.35-1.95%, Mo: 0.25-0.55%, Ni: 2.80-3.20%, Cu: 0.7-1.1%, Al: 0.8-1.4%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, rare earth: 0.005-0.009%, and the balance Fe and inevitable impurities; and the high-purity high-hardness age-hardening ZW680 plastic die steel is prepared by the preparation method of any one of claims 1 to 7.
9. The high purity, high hardness age hardened ZW680 plastic mold steel as claimed in claim 8 wherein the microstructure of the high purity, high hardness age hardened ZW680 plastic mold steel is in the form of intragranular bainite and precipitates distributed at grain boundaries and intragranular, the precipitates are uniformly distributed and are fragmented with edges and corners, wherein the precipitates are carbides and age strengthening phases, and the intermetallic NiAl phase and Cu rich phase of the age strengthening phases are on the order of nanometers.
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