CN116652128A - Method for refining M2 high-speed steel cast structure - Google Patents

Method for refining M2 high-speed steel cast structure Download PDF

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Publication number
CN116652128A
CN116652128A CN202310552651.0A CN202310552651A CN116652128A CN 116652128 A CN116652128 A CN 116652128A CN 202310552651 A CN202310552651 A CN 202310552651A CN 116652128 A CN116652128 A CN 116652128A
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continuous casting
speed steel
refining
steel
cooling
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Inventor
赵明
李朋
朱喜达
徐乐钱
赵勇智
满廷慧
莫攸建
刘宇
陆家生
董瀚
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Shanghai University Zhejiang High End Equipment Basic Materials Research Institute
JIANGYIN HUARUN STEEL CO Ltd
University of Shanghai for Science and Technology
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Shanghai University Zhejiang High End Equipment Basic Materials Research Institute
JIANGYIN HUARUN STEEL CO Ltd
University of Shanghai for Science and Technology
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Priority to CN202310552651.0A priority Critical patent/CN116652128A/en
Publication of CN116652128A publication Critical patent/CN116652128A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/043—Curved moulds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/122—Accessories for subsequent treating or working cast stock in situ using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/166—Controlling or regulating processes or operations for mould oscillation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
    • 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
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • 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
    • C22C38/18—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
    • 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
    • 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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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  • Mechanical Engineering (AREA)
  • Materials 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 belongs to the technical field of metallurgy, and particularly relates to a method for refining an M2 high-speed steel cast structure. The invention provides a method for refining a cast structure of M2 high-speed steel, which comprises the following steps: mixing raw materials according to the element proportion of the M2 high-speed steel, and smelting to obtain a melt; mixing the molten liquid and the alloy, and sequentially carrying out alloying, LF refining and VD degassing treatment to obtain molten steel; continuously casting the molten steel to obtain a continuous casting blank; and carrying out continuous casting annealing treatment on the continuous casting blank or carrying out hot working and finished product annealing treatment on the continuous casting blank in sequence to obtain the M2 high-speed steel. The invention adopts a continuous casting mode to prepare the continuous casting blank, so that the high-content alloy elements are not too close to the segregation during solidification, the secondary dendrite spacing is reduced, and the maximum size of precipitated carbide in the M2 high-speed steel is effectively reduced, thereby refining the cast structure of the M2 high-speed steel.

Description

Method for refining M2 high-speed steel cast structure
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for refining an M2 high-speed steel cast structure.
Background
M2 high-speed steel is widely used for manufacturing high-speed cutting tools or high-load dies due to its own high hardness, high wear resistance, high toughness, and high red hardness.
At present, a die casting process is mainly adopted to produce M2 high-speed steel, but in the die casting solidification process, carbide gradually segregates due to different cooling strengths of the outer surface and the core of an ingot, so that eutectic carbide in an as-cast structure presents a coarse reticular structure; the larger the ingot size, the more severe the carbide segregation, which can affect the subsequent hot working of the material, the heat treatment process and the properties of the finished material.
Disclosure of Invention
In view of the above, the invention provides a method for refining the cast structure of M2 high-speed steel, and the preparation method provided by the invention can refine eutectic carbide in the M2 high-speed steel, so as to refine the cast structure of the M2 high-speed steel.
In order to solve the technical problems, the invention provides a method for refining an M2 high-speed steel cast structure, which comprises the following steps:
mixing raw materials according to the element proportion of the M2 high-speed steel, and smelting to obtain a melt;
carrying out alloying, LF refining and VD degassing treatment on the molten liquid in sequence to obtain molten steel;
continuously casting the molten steel to obtain a continuous casting blank;
and carrying out continuous casting annealing treatment on the continuous casting blank or carrying out hot working and finished product annealing treatment on the continuous casting blank in sequence to obtain the M2 high-speed steel.
Preferably, the continuous casting drawing speed is 0.4-1.2 m/min.
Preferably, the continuous casting is arc continuous casting, and the arc continuous casting comprises the following steps:
and conveying the molten steel to a continuous casting crystallizer for cooling through a continuous casting tundish, and then pulling out the molten steel by an arc-shaped continuous casting machine.
Preferably, the continuous casting crystallizer is non-sinusoidal, the frequency of the non-sinusoidal vibration is 80-180 times/min, and the amplitude of the non-sinusoidal vibration is 3.0-6.0 mm.
Preferably, the continuous casting crystallizer adopts strong cooling, and the specific water quantity of the strong cooling is 0.10-0.50L/kg;
the secondary cooling of continuous casting adopts weak cooling, and the specific water quantity of the weak cooling is 0.10-0.18L/kg.
Preferably, the secondary cooling is accompanied by forward and reverse rotation roller type electromagnetic stirring, the forward rotation time of the forward and reverse rotation roller type electromagnetic stirring is 14-16 s, and the reverse rotation time of the forward and reverse rotation roller type electromagnetic stirring is 4-6 s.
Preferably, the annealing treatment temperature of the continuous casting billet is 860-880 ℃, and the heat preservation time of the annealing treatment of the continuous casting billet is 4-8 hours.
Preferably, the M2 high-speed steel comprises the following element components in percentage by mass: 0.80 to 0.90wt.% of C, 0.15 to 0.40wt.% of Si, 0.20 to 0.45wt.% of Mn, 3.80 to 4.40wt.% of Cr, 5.50 to 6.75wt.% of W, 4.50 to 5.50wt.% of Mo, 1.75 to 2.20wt.% of V, 0.01 to 0.03wt.% of Nb, 0.005 to 0.05wt.% of La and Ce, and the balance of Fe and unavoidable impurities.
The invention provides a method for refining a cast structure of M2 high-speed steel, which comprises the following steps: mixing raw materials according to the element proportion of the M2 high-speed steel, and smelting to obtain a melt; mixing the molten liquid and the alloy, and sequentially carrying out alloying, LF refining and VD degassing treatment to obtain molten steel; continuously casting the molten steel to obtain a continuous casting blank; and carrying out continuous casting annealing treatment on the continuous casting blank or carrying out hot working and finished product annealing treatment on the continuous casting blank in sequence to obtain the M2 high-speed steel. According to the invention, an arc continuous casting process is adopted to refine the cast structure of the M2 high-speed steel, so that carbides in the M2 high-speed steel are tiny and uniformly distributed, the width of a carbide net is reduced, the secondary dendrite spacing is reduced, the wear resistance and fracture toughness of the M2 high-speed steel are improved, and the service life of a tool and a die is prolonged.
Drawings
FIG. 1 is a graph showing the morphology of carbides at different thicknesses of a continuous casting billet prepared in example 1;
FIG. 2 is a graph showing the morphology of carbides at different thicknesses of the die-cast slab prepared in comparative example 1.
Detailed Description
The invention provides a method for refining a cast structure of M2 high-speed steel, which comprises the following steps:
mixing raw materials according to the element proportion of the M2 high-speed steel, and smelting to obtain a melt;
mixing the molten liquid and the alloy, and sequentially carrying out alloying, LF refining and VD degassing treatment to obtain molten steel;
continuously casting the molten steel to obtain a continuous casting blank;
and carrying out continuous casting annealing treatment on the continuous casting blank or carrying out hot working and finished product annealing treatment on the continuous casting blank in sequence to obtain the M2 high-speed steel.
In the present invention, all the raw materials are conventionally commercially available products unless otherwise specified.
According to the invention, raw materials are mixed according to the element proportion of the M2 high-speed steel and smelted to obtain a molten liquid. In the invention, the M2 high-speed steel preferably comprises the following element components in percentage by mass: 0.80 to 0.90wt.% of C, 0.15 to 0.40wt.% of Si, 0.20 to 0.45wt.% of Mn, 3.80 to 4.40wt.% of Cr, 5.50 to 6.75wt.% of Mo, 4.50 to 5.50wt.% of V, 0.01 to 0.03wt.% of Nb, 0.005 to 0.05wt.% of La and Ce, the balance being Fe and unavoidable impurities, more preferably: 0.85 to 0.88wt.% of C, 0.25 to 0.30wt.% of Si, 0.30 to 0.40wt.% of Mn, 3.90 to 4.05wt.% of Cr, 5.70 to 6.50wt.% of W, 4.70 to 5.00wt.% of Mo, 1.90 to 2.10wt.% of V, 0.01 to 0.02wt.% of Nb, 0.015 to 0.03wt.% of La and Ce, and the balance of Fe and unavoidable impurities.
The invention has no special requirement on the mixing, and can be carried out in a conventional mode in the field.
In the present invention, the smelting furnace is preferably an arc furnace. The invention has no special requirement on the smelting temperature, and the raw materials can be completely melted. In the present invention, the raw material is preferably derived from scrap steel.
The invention preferably performs oxygen blowing fluxing in the smelting process, and the oxygen blowing fluxing mode preferably comprises furnace door oxygen lances and furnace wall multifunctional oxygen lances.
The invention preferably also comprises foaming slag, oxygen blowing decarburization and low-temperature dephosphorization in the smelting process. The invention has no special requirements on the foam-making slag, oxygen-blowing decarburization and low-temperature dephosphorization, and can be realized by adopting a conventional mode in the field.
After the molten liquid is obtained, the molten liquid and the alloy are mixed and sequentially subjected to alloying, LF refining and VD degassing treatment to obtain molten steel. In the present invention, the alloy is preferably one or more of ferromolybdenum, ferrovanadium and high carbon ferrochromium. The present invention preferably mixes the alloy and the melt during transfer of the melt to the ladle (tapping). In the present invention, the alloying process preferably further includes: and (3) deoxidizing the alloying system. In the invention, aluminum is preferably added into the molten steel in the tapping process for deoxidization; the aluminum is preferably an aluminum block. The invention has no special requirement on the addition amount of the aluminum, and the aluminum can be added according to the conventional mode in the field. In the present invention, lime is preferably added to the melt at the end of tapping, and the amount of lime added is preferably 400 to 600kg, more preferably 500 to 550kg. The invention preferably adds the alloy to the ladle after said tapping. The present invention preferably maintains argon blowing into the ladle during the addition of the alloy to the ladle. The invention can ensure the uniformity of components and stable temperature in the melt system by blowing argon. In the invention, 30-40 tons of steel is preferably left in the post-tapping smelting furnace to avoid oxidizing slag entering the ladle.
In the present invention, the LF refining process preferably includes deoxygenation; the deoxidation preferably comprises precipitation deoxidation and/or diffusion deoxidation. The invention preferably adopts a submerged arc mode for deoxidation. The invention preferably feeds aluminum wires in the earlier stage of LF refining, and also preferably adds refining slag formers into the ladle. Argon is preferably blown into the ladle bottom in the LF refining process; the argon is blown at the bottom of the ladle to ensure the uniformity of temperature and components in the system and promote the floating removal of gas and inclusion. In the invention, the time of the white slag in the LF refining process is preferably not less than 30min, more preferably 35-45 min.
In the present invention, the VD degassing treatment is preferably VD vacuum degassing. The vacuum degree and argon flow rate of the VD vacuum degassing are preferably dynamically controlled to avoid slag overflow. The invention has no special requirements on the vacuum degree and the argon flow, and can be realized by adopting a conventional mode in the field. In the invention, when the ultimate vacuum degree of the VD vacuum degassing is less than 67Pa, the flow rate of argon is preferably increased, and the degassing effect is ensured. In the present invention, the holding time of the VD vacuum degassing at the ultimate vacuum is preferably not less than 20 minutes, more preferably 25 to 30 minutes. In the present invention, the soft argon blowing time after vacuum is preferably not less than 20 minutes, more preferably 25 to 30 minutes. The invention can promote the floating of the inclusion by soft argon blowing. The invention preferably detects the components of the liquid in the steel ladle after soft argon blowing, and carries out subsequent continuous casting after the components of the liquid in the steel ladle are qualified. In the present invention, the temperature of the molten steel exiting the ladle is preferably 1450 to 1550 ℃, more preferably 1500 ℃.
After molten steel is obtained, the invention carries out continuous casting on the molten steel to obtain a continuous casting blank. In the present invention, the shape of the continuous casting slab is preferably a rectangular parallelepiped. In the present invention, the dimensions of the cross section of the rectangular parallelepiped are preferably 100mm×100mm to 200mm×200mm, more preferably 150mm×150mm to 180mm×180mm.
In the present invention, the drawing speed of the continuous casting is preferably 0.4 to 1.2m/min, more preferably 0.8 to 1.2m/min.
In the present invention, the continuous casting is preferably an arc continuous casting, and the arc continuous casting preferably includes the steps of: and conveying the molten steel to a continuous casting crystallizer for cooling through a continuous casting tundish, and then pulling out the molten steel by an arc-shaped continuous casting machine. In the present invention, the continuous casting mold is preferably non-sinusoidal vibration, and the frequency of the non-sinusoidal vibration is preferably 80 to 180 times/min, more preferably 100 to 150 times/min. In the present invention, the amplitude of the non-sinusoidal vibration is preferably 3.0 to 6.0mm, more preferably 4.0 to 5.0mm. The invention preferably utilizes an automatic liquid level control device to detect the vortex liquid level, and ensures that the fluctuation of the liquid level of the crystallizer is not more than +/-3 mm. The invention preferably carries out electromagnetic stirring in a crystallizer.
In the present invention, the continuous casting mold preferably employs strong cooling, and the specific water amount of the strong cooling is preferably 0.10 to 0.50L/kg, more preferably 0.23 to 0.3L/kg. The invention can increase the thickness of the blank shell by adopting forced cooling. In the present invention, the secondary cooling of the continuous casting is preferably weak cooling, and the specific water amount of the weak cooling is preferably 0.10 to 0.18L/kg, more preferably 0.13 to 0.15L/kg. In the invention, the weak cooling is adopted for the secondary cooling, so that the stress generated in the cooling process can be reduced, and the cracking is avoided. The invention preferably performs electromagnetic stirring in a secondary cooling zone, and the electromagnetic stirring is preferably roller type electromagnetic stirring. In the present invention, the secondary cooling zone roller type electromagnetic stirring mode is preferably forward and backward rotation, and the forward rotation time in the forward and backward rotation process is preferably 14-16 s, more preferably 15s, and the reverse rotation time is preferably 4-6 s, more preferably 5s.
The invention controls the withdrawal and straightening temperature of continuous casting by controlling the secondary cooling intensity, the withdrawal speed and the vibration mode of the continuous casting crystallizer, thereby refining the size of eutectic carbide in an as-cast structure and the width of a carbide net and further improving the performance of M2 high-speed steel.
In the invention, molten steel enters a continuous casting tundish through a long nozzle, and the molten steel surface is sealed by a tundish covering agent; molten steel flows into the continuous casting crystallizer through the immersed nozzle, and the liquid surface of the crystallizer is covered with special covering slag to increase the lubrication effect of the inner wall of the crystallizer; the molten steel is quickly solidified in the water-cooling crystallizer to form a blank shell. In the invention, the whole continuous casting process is protected and poured, the tundish adopts an integral nozzle, and the ladle adopts a long nozzle sealing ring and argon blowing protection. In the present invention, the superheat degree of the ladle in continuous casting is preferably 30 to 45 ℃, more preferably 35 to 40 ℃. In the invention, if the superheat degree is controlled to be too high, casting blank segregation and shrinkage cavity are aggravated; if the overheat degree is too low, the nozzle is easy to be blocked.
In the invention, the continuous casting device is preferably a four-machine four-flow vertical bending type continuous casting machine with an arc radius of 9 m.
After a continuous casting blank is obtained, the continuous casting blank is subjected to continuous casting blank annealing treatment or is subjected to hot working and finished product annealing treatment in sequence, so that the M2 high-speed steel is obtained. In the present invention, the annealing treatment of the continuous casting billet preferably further comprises: cutting the continuous casting billet. The invention has no special requirement on the size of the cut continuous casting billet, and the continuous casting billet can be cut according to the requirement. The present invention preferably performs slow cooling of the cut continuous casting slab. In the invention, the annealing treatment temperature of the continuous casting billet is preferably 860-880 ℃, more preferably 875-880 ℃; the heating rate for heating to the annealing treatment temperature of the continuous casting billet is preferably 28-32 ℃/min, more preferably 30 ℃/min; the heat preservation time of the continuous casting billet annealing treatment is preferably 4-8 hours, more preferably 6-7 hours.
In the present invention, the annealing treatment of the continuous casting billet preferably further comprises: cooling the product after annealing treatment of the continuous casting billet, wherein the temperature after cooling is preferably below 650 ℃, more preferably 500-600 ℃; the cooling is preferably furnace-wise cooling. In the present invention, the cooling rate is preferably 8 to 12 ℃ per second, more preferably 10 ℃; the cooling rate of continuous casting is 10 times higher than the cooling rate of die casting, and the width and the size of the carbide net can be effectively thinned by continuous casting under the above-defined continuous casting condition parameters.
In the present invention, the hot working preferably includes forging or rolling. The invention has no special requirements on forging and rolling, and can be carried out according to the requirements of customers on the performance of M2 high-speed steel. The invention has no special requirement on the annealing treatment of the finished product material, and the annealing treatment is limited according to the requirement of customers on the performance of the M2 high-speed steel.
According to the invention, an arc continuous casting process is adopted to refine the cast structure of the M2 high-speed steel, the obtained M2 high-speed steel has tiny carbides which are uniformly distributed, the width of a carbide net is reduced, the wear resistance and fracture toughness of the M2 high-speed steel are improved, and the service life of a tool and a die is prolonged.
The preparation method provided by the invention is used for preparing the M2 high-speed steel, so that the metal yield, the blank forming rate and the stability of the quality of the M2 high-speed steel are improved, the energy loss is saved, and the production cost is reduced.
The technical solutions provided by the present invention are described in detail below in conjunction with examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.
Example 1
The M2 high-speed steel comprises the following element components in percentage by mass: 0.85wt.% of c, 0.30wt.% of si, 0.30wt.% of mn, 4.05wt.% of cr, 5.70wt.% of w, 4.70wt.% of mo, 1.90wt.% of v, 0.02wt.% of nb, the total mass percent of La and Ce being 0.015wt.%, the balance being Fe and unavoidable impurities;
the preparation method of the M2 high-speed steel comprises the following steps:
step 1, preparing raw materials and preparing corresponding alloys according to the chemical components of the M2 high-speed steel;
step 2, adding scrap steel raw materials into an arc furnace with nominal capacity of 90 tons through a horizontal feeding system, and melting to obtain a melt; the electric arc furnace adopts an oxygen lance of a furnace door and a multifunctional oxygen lance of a furnace wall to blow oxygen to promote smelting, foam slag is produced in the whole process, oxygen is blown to decarbonize, the speed is low Wen Tuolin, steel is left for 30 tons when the electric arc furnace is tapped, oxidizing slag cannot enter a ladle, ferromolybdenum, ferrovanadium and high-carbon ferrochromium are added in the tapping process for alloying, aluminum blocks are added for deoxidization, and lime is added in the last tapping stage for 550kg; argon blowing control is performed in the whole process, so that the stability of components and temperature is ensured; feeding aluminum wires in the earlier stage of LF refining, adding a refining slag former, blowing argon gas into the ladle bottom, ensuring the uniformity of temperature and components, and promoting the floating removal of gas and inclusions; refining primary steelmaking liquid by an LF furnace, wherein aluminum powder, carbon powder and calcium carbide are adopted for diffusion deoxidation in the whole process, submerged arc operation is carried out, and the white slag time is 35min; vacuum degassing treatment by VD, dynamically controlling vacuum degree and argon flow, and avoiding slag overflow; when the vacuum degree is not more than 67Pa, the argon flow is increased, and the degassing effect is ensured; the ultimate vacuum time is 30min, and the soft argon blowing time after vacuum is 30min, so that the floating of the inclusions is promoted; after the detected components are qualified, transferring the molten steel to an arc continuous casting process, wherein the steel tapping temperature of the molten steel is 1510 ℃;
step 3, baking the continuous casting tundish (the baking time is 5h, and the tundish temperature reaches 1450+/-5 ℃); molten steel enters a continuous casting tundish through a long nozzle, and the liquidus temperature TL=1431 ℃ is calculated according to actual components; determining the superheat degree of the tundish at 30-45 ℃, and adding a tundish covering agent on the surface of molten steel; molten steel enters a continuous casting crystallizer through a submerged nozzle, and the liquid level of the crystallizer adopts special casting powder, so that the lubrication effect of a continuous casting blank and the inner wall of the crystallizer is enhanced, and the molten steel is quickly solidified in the water-cooling crystallizer to form a blank shell; the continuous caster model is a four-machine four-flow vertical bending continuous caster with an arc radius of 9M, and is used for continuously producing M2 high-speed steel continuous casting billets at a billet drawing rate of 1.20M/min; the eddy current is adopted to detect the liquid level, and the liquid level is automatically controlled, so that the fluctuation of the liquid level of the crystallizer is not more than +/-3 mm; the crystallizer is vibrated non-sinusoidally, the frequency is 150 times/min, and the amplitude is 4.0mm; the electromagnetic stirring current of the crystallizer is 300A, the frequency is 4Hz, the secondary cooling electromagnetic stirring current is 350A, and the frequency is 7Hz; the whole process of arc continuous casting is protected and poured, the tundish adopts an integral water gap, and the ladle adopts a long water gap sealing ring and argon blowing protection; in order to obtain enough shell thickness, the crystallizer is forced cooled, and the specific water quantity is 0.23L/kg; the secondary cooling of continuous casting adopts weak cooling, and the specific water quantity is 0.15L/kg; controlling the secondary cooling intensity and the withdrawal speed to ensure the withdrawal temperature and refine the size of eutectic carbide and the width of carbide net in the cast structure; the section size of the M2 high-speed steel continuous casting blank is 150mm multiplied by 150mm;
step 4, cutting the continuous casting billet according to a fixed length of 6 m; slowly cooling, delivering into an annealing furnace, wherein the annealing temperature is 880 ℃, the heating speed is 30 ℃/h, preserving heat for 6h, cooling along with the furnace, cooling to 500 ℃, and discharging.
Comparative example 1
An M2 high-speed steel was prepared according to the method of example 1, except that the continuous casting mode was replaced with die casting, and the chemical composition of the M2 high-speed steel (die casting billet cross-sectional dimension: 150mm×150 mm) was c0.86wt.%, si0.30wt.%, mn0.30wt.%, cr4.05wt.%, w5.70wt.%, mo4.70wt.%, v1.80wt.%, and the balance Fe and unavoidable impurities.
The carbide morphology of the continuous casting billet prepared in example 1 and the die casting billet prepared in comparative example 1 at the edge, 3/4, 1/2, 1/4 and center (core) was examined according to GB/T14979-1994 evaluation method for non-uniformity of eutectic carbide of steel, and the graphs shown in FIGS. 1 and 2 were obtained, wherein FIG. 1 is a graph of carbide morphology of the continuous casting billet prepared in example 1 at different thicknesses, and FIG. 2 is a graph of carbide morphology of the die casting billet prepared in comparative example 1 at different thicknesses.
As can be seen by comparing fig. 1 and fig. 2, the maximum sizes of the carbides at different positions of the M2 high-speed steel continuous casting blank are smaller than the sizes of the carbides at corresponding positions of the M2 high-speed steel die casting blank. The invention improves the cooling speed of continuous casting by limiting the condition parameters such as the drawing speed, the drawing and straightening temperature, the secondary cooling specific water quantity and the like of arc continuous casting, so that the alloy elements with high content are not too close to the segregation during solidification, the secondary dendrite spacing is reduced, and the maximum size of precipitated carbide is effectively reduced.
Although the foregoing embodiments have been described in some, but not all, embodiments of the invention, it should be understood that other embodiments may be devised in accordance with the present embodiments without departing from the spirit and scope of the invention.

Claims (8)

1. A method for refining M2 high speed steel cast structure, comprising the steps of:
mixing raw materials according to the element proportion of the M2 high-speed steel, and smelting to obtain a melt;
carrying out alloying, LF refining and VD degassing treatment on the molten liquid in sequence to obtain molten steel;
continuously casting the molten steel to obtain a continuous casting blank;
and carrying out continuous casting annealing treatment on the continuous casting blank or carrying out hot working and finished product annealing treatment on the continuous casting blank in sequence to obtain the M2 high-speed steel.
2. The method according to claim 1, wherein the continuous casting drawing speed is 0.4 to 1.2m/min.
3. The production method according to claim 1 or 2, characterized in that the continuous casting is an arc continuous casting comprising the steps of:
and conveying the molten steel to a continuous casting crystallizer for cooling through a continuous casting tundish, and then pulling out the molten steel by an arc-shaped continuous casting machine.
4. The method according to claim 3, wherein the continuous casting mold is non-sinusoidal, the frequency of the non-sinusoidal is 80-180 times/min, and the amplitude of the non-sinusoidal is 3.0-6.0 mm.
5. The method according to claim 3, wherein the continuous casting mold is cooled strongly, and the specific water content of the forced cooling is 0.10-0.50L/kg;
the secondary cooling of continuous casting adopts weak cooling, and the specific water quantity of the weak cooling is 0.10-0.18L/kg.
6. The method according to claim 5, wherein the secondary cooling is accompanied by forward and reverse rotation roller type electromagnetic stirring, the forward rotation time of the forward and reverse rotation roller type electromagnetic stirring is 14-16 s, and the reverse rotation time of the forward and reverse rotation roller type electromagnetic stirring is 4-6 s.
7. The method according to claim 1, wherein the temperature of the continuous casting billet annealing treatment is 860-880 ℃, and the heat preservation time of the continuous casting billet annealing treatment is 4-8 hours.
8. The preparation method according to claim 1, wherein the M2 high-speed steel comprises the following elemental components in percentage by mass: 0.80 to 0.90wt.% of C, 0.15 to 0.40wt.% of Si, 0.20 to 0.45wt.% of Mn, 3.80 to 4.40wt.% of Cr, 5.50 to 6.75wt.% of W, 4.50 to 5.50wt.% of Mo, 1.75 to 2.20wt.% of V, 0.01 to 0.03wt.% of Nb, 0.005 to 0.05wt.% of La and Ce, and the balance of Fe and unavoidable impurities.
CN202310552651.0A 2023-05-17 2023-05-17 Method for refining M2 high-speed steel cast structure Pending CN116652128A (en)

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