CN116287992A - NM 400-level quenching martensitic wear-resistant steel plate and preparation method thereof - Google Patents

NM 400-level quenching martensitic wear-resistant steel plate and preparation method thereof Download PDF

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CN116287992A
CN116287992A CN202310190848.4A CN202310190848A CN116287992A CN 116287992 A CN116287992 A CN 116287992A CN 202310190848 A CN202310190848 A CN 202310190848A CN 116287992 A CN116287992 A CN 116287992A
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steel plate
resistant steel
temperature
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李忠波
吴志方
吴润
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Wuhan University of Science and Engineering WUSE
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • B22D11/18—Controlling or regulating processes or operations for pouring
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/84—Controlled slow 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • 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
    • C22C38/04—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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • 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
    • C21D2211/001—Austenite
    • 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
    • C21D2211/008—Martensite
    • 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
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Abstract

The invention relates to an NM 400-level quenched martensitic wear-resistant steel plate and a preparation method thereof. The martensitic wear-resistant steel plate comprises the following chemical components in percentage by mass: 0.19 to 0.21 percent of C, 0.22 to 0.26 percent of Si, 1.20 to 1.30 percent of Mn, 0.85 to 0.90 percent of Cr, 0.35 to 0.38 percent of Mo, 0.75 to 0.77 percent of Ni, 0.035 to 0.055 percent of Als, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, and the balance of Fe and unavoidable impurities. The preparation steps of the invention are as follows: smelting by a top-bottom combined blown converter; refining in an LF furnace; performing VD vacuum treatment; molding a water-cooling copper plate crystallizer; heating; rolling; cooling control is performed; cooling in a stacking way; offline quenching; and (5) stacking. The thickness of the product is 140-150 mm, and the metallographic structure is martensite and residual austenite; the tensile strength is 1250-1449 MPa, the elongation after breaking is 10-13%, the impact energy at 0 ℃ is 40-79J, and the surface hardness is 400-430 HB. The invention has simple process, low cost and excellent mechanical property.

Description

NM 400-level quenching martensitic wear-resistant steel plate and preparation method thereof
Technical Field
The invention belongs to the technical field of martensite wear-resistant steel plates. In particular to an NM 400-level quenching martensitic wear-resistant steel plate and a preparation method thereof.
Background
Wear, corrosion and fracture are the primary failure modes in the service of metallic materials. Although wear does not directly cause metal work-pieces to fail as corrosion and breakage to cause catastrophic damage, it causes equipment parts to fail, resulting in frequent repair and replacement of parts, resulting in reduced equipment operating efficiency, consuming a large amount of energy and materials, and also causing significant economic losses.
The wear-resistant steel is widely applied to industries such as metallurgy, mines, buildings, electric power, railways and the like, is the wear-resistant material with the largest dosage at present, and has various types, mainly including manganese steel, medium and low alloy wear-resistant steel and the like. The martensite wear-resistant steel is typical low-alloy wear-resistant steel, the production process is simple, and the lath martensite with high hardness and high dislocation density can well resist the expansion of cracks during wear resistance, so that the martensite wear-resistant steel has the most wide application under the working condition of medium and low stress and has remarkable economic benefit. However, it is disadvantageous in that it is abrasion resistant mainly by the hardness of the martensitic matrix, and thus, it has high requirements for chemical composition control and heat treatment process.
The patent technology of HB400 grade abrasion-resistant steel with low cost and a production method thereof (CN 104451409A) comprises the following chemical components in percentage by mass: 0.08 to 0.19 percent of Si:0.20 to 0.50 percent of Mn:1.30 to 1.60 percent, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, and Cr:0.30 to 0.65 percent of Nb:0.02 to 0.05 percent of Ti: 0.005-0.025%, B:0.001 to 0.005 percent, als: 0.010-0.040%, and the balance of Fe and trace impurity elements, the wear-resistant steel produced by adopting the components and continuous casting, controlled rolling and sub-temperature quenching processes of the technology meets the requirements, but the thickness range of the produced steel plate is smaller and is only 10-50 mm.
The patent technology of a method for producing thin-specification high-Ti abrasion-resistant steel NM400 by on-line quenching (CN 106987760A) comprises the following chemical components in percentage by mass: 0.12 to 0.20 percent, si:0.20 to 0.40 percent, mn:1.20 to 1.80 percent, mo:0.15 to 0.30 percent, cr:0.20 to 0.50 percent, nb:0.030 to 0.060 percent, ti:0.10 to 0.15 percent, B: 0.0006-0.0015%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, and the balance is Fe and unavoidable impurities.
"rare earth abrasion-resistant steel NM400 coiled plate with excellent low temperature resistance toughness and production method thereof" (CN 112322976A) patent technology, the mass percentage content of the chemical components is C:0.18 to 0.20 percent of Si:0.30 to 0.50 percent of Mn:1.30 to 1.45 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.003 percent, and Nb: 0.015-0.025%, ti:0.010 to 0.025 percent, cr:0.25 to 0.40 percent of Ce:0.0005 to 0.0015 percent, ca:0.0010 to 0.0030 percent of Al: the wear-resistant steel produced by adopting the components and continuous casting, two-stage controlled rolling and two-stage cooling processes of the technology meets the requirements, but the thickness of the produced steel plate is only 7mm, rare earth elements are compositely added in the components, and meanwhile, the content of H, O, N gas is strictly controlled, so that the cost in the smelting process is increased.
The patent technology of 'low alloy wear-resistant steel NM400 thick plate and manufacturing method' (CN 108754317A) comprises the following chemical components in percentage by mass: 0.20 to 0.33 percent of Si:0.20 to 0.60 percent of Mn:0.50 to 1.10 percent, less than or equal to 0.012 percent of P, less than or equal to 0.003 percent of S, and Cr:0.30 to 1.00 percent of Mo:0.20 to 0.60 percent of Ni:0.30 to 0.80 percent of Ti: 0.008-0.030%, nb:0.015 to 0.050 percent, B: 0.0008-0.0025%, N is less than or equal to 0.0040%, O is less than or equal to 0.0025%, and the balance is Fe and unavoidable impurities, the wear-resistant steel produced by adopting the components and continuous casting, controlled rolling, off-line quenching and tempering processes of the technology meets the requirements, the thickness of the steel plate is 90mm, but the added alloy elements are more, meanwhile, the off-line quenching and tempering processes are adopted, the process flow is long, the requirements on off-line heat treatment equipment are high, and the production cost is increased.
Disclosure of Invention
The invention aims to overcome the defects existing in the prior art, and aims to provide a preparation method of NM 400-grade quenched martensitic wear-resistant steel plate which has the advantages of simple chemical components, simple preparation method, low production cost and thickness specification of 140-150 mm, wherein the metallographic structure of the NM 400-grade quenched martensitic wear-resistant steel plate prepared by the method is martensite and retained austenite, and the mechanical property is excellent.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the NM 400-level quenching martensitic wear-resistant steel plate comprises the following chemical components in percentage by weight: 0.19 to 0.21 weight percent of C, 0.22 to 0.26 weight percent of Si, 1.20 to 1.30 weight percent of Mn, 0.85 to 0.90 weight percent of Cr, 0.35 to 0.38 weight percent of Mo, 0.75 to 0.77 weight percent of Ni, 0.035 to 0.055 weight percent of Als, less than or equal to 0.010 weight percent of P, less than or equal to 0.002 weight percent of S, and the balance of Fe and unavoidable impurities.
The preparation method of the NM 400-level quenching martensitic wear-resistant steel plate comprises the following steps:
and 1, smelting molten iron with the temperature of 1300-1500 ℃ and the weight percent of P being less than or equal to 0.035 and the weight percent of S being less than or equal to 0.004 in a converter, and tapping when the set carbon end point is reached, adopting a slag blocking cone to block slag.
Step 2, refining molten steel in an LF furnace: lime addition amount is 11-12 kg/t, alkalinity is 4.0-6.0, and white slag retention time is 35-40 min during slag making; and in the refining process, ferrochrome, nickel plates, ferromanganese and ferromolybdenum are sequentially added according to the chemical components and the content of the NM 400-grade quenched martensitic wear-resistant steel plate.
Step 3, the refined molten steel is fed into a VD furnace for vacuum treatment: vacuum degree is 30-67 Pa, and vacuum is maintained for 18-25 min; soft argon blowing is carried out for 3-5 min after the air breaking, the molten steel is covered with the covering slag in the soft argon blowing process, and then the VD furnace is vacuumized to ensure that the H content in the molten steel is less than or equal to 1.2ppm, and the soft argon blowing is carried out for 8-10 min.
Step 4, casting by adopting a water-cooling copper plate crystallizer ingot mould: the temperature difference between the water inlet and the water outlet of the ingot mould of the copper plate crystallizer is 6-10 ℃, and the cooling water flow rate from the initial stage of pouring to the time of 1h after pouring is 400-450 m 3 And/h, the flow rate of cooling water after casting is 300-400 m for 1-2 h 3 And/h, the flow rate of cooling water after casting is 260-350 m for 2-3 h 3 And/h, the cooling water flow rate after casting is 230-280 m for 3-4 h 3 And/h, cooling water flow rate from 4h after pouring to demoulding is 200-250 m 3 And/h, the thickness of the steel ingot after casting is 740mm.
Step 5, placing the steel ingot into a heating furnace, and preserving heat for 2-5 hours at the temperature of 250-400 ℃; then heating to 880-920 ℃ at the speed of 60-80 ℃/h, and preserving heat for 5-6 h; then heating to 1230-1250 ℃ at the speed of 80-120 ℃/h, and preserving heat for 13-13.5 h.
Step 6, adopting a recrystallization type controlled rolling RCR process: the initial rolling temperature is 1000-1100 ℃, the final rolling temperature is 900-980 ℃, 13 passes of rolling are performed, the reduction of each pass is 35-60 mm, and the thickness of the rolled steel plate is 158-170 mm.
Step 7, cooling the rolled steel plate by adopting a high-density laminar cooling ACC process: the ACC header pipe and the side spraying are fully opened, the water ratio is 1.8-2.2, the roller speed is 0.6-1.0 m/s, the steel plate is cooled for 1 or 2 times after rolling, and the reddening temperature is 600-650 ℃.
And 8, placing the steel plate subjected to controlled cooling into a hot-rolled material slow cooling pit, wherein the temperature of the hot-rolled material slow cooling pit is 350-450 ℃, and the slow cooling time is 48-60 hours.
Step 9, carrying out off-line quenching on the slowly cooled steel plate, wherein the austenitizing temperature is 920-930 ℃, and quenching the steel plate into water with the temperature of 12-25 ℃ after austenitizing; the running speed of the quenched steel plate in a quenching water tank is 0.5-0.7 m/min, the water pressure in the water tank is 0.8-1.1 MPa, and the flow is 4500-5000 m 3 And/h, the temperature of the quenched steel plate is 30-40 ℃.
And step 10, the quenched steel plate enters a heat treatment slow cooling pit for stacking and slow cooling within 12h, the temperature of the heat treatment slow cooling pit is 200-300 ℃, and the slow cooling stacking time is 80-96 h, so that the NM 400-level quenched martensitic wear-resistant steel plate is prepared.
The room temperature thickness of the NM 400-level quenching type martensitic wear-resistant steel plate is 140-150 mm.
The metallurgical structure of the NM 400-level quenched martensitic wear-resistant steel plate is martensite and retained austenite; the sum of sulfide, oxide, silicate and spherical oxide is less than 1.5 level, and the band structure is less than 1.0 level.
The chemical composition and mass percent design thought of the invention are as follows:
1) In the invention, C is an important element affecting the strength, hardness, toughness, wear resistance and hardenability of the steel plate, and the C content is too high, and the high-carbon sheet-shaped martensite formed after quenching has high hardness but low toughness and is easy to generate cracks during quenching; the content of C is too low, the hardness is low, and the wear resistance is poor. The C content in the present invention is thus from 0.19 to 0.21% by weight.
2) Si in the invention is an element for stabilizing austenite, the transformation temperature of steel can be improved, when the content of Si in the steel is below 1.3wt%, the strength, toughness and plasticity of the steel are increased along with the increase of the content of Si, but Si is also an overheat sensitive element, and especially when the Si and Mn are used as alloy elements at the same time. The Si content in the present invention is thus 0.22 to 0.26wt%.
3) Mn is an element which improves the hardenability of steel strongly, is also a proper deoxidizer and desulfurizer, is a weak carbide forming element, can strengthen ferrite by solid solution, can strengthen cementite, has great influence on the hardness and impact toughness of steel by solid solution strengthening of Mn, increases the hardness of steel along with the increase of Mn content, and decreases the impact toughness along with the increase of Mn content. Thus, the Mn content in the present invention is 1.20 to 1.30wt%.
4) Cr is a weak carbide forming element, and when the Cr content is not more than 5wt%, cementite (Cr, fe) is formed 7 C 3 The wear resistance of the steel can be improved, cr can be dissolved in ferrite in a solid solution mode, the ferrite is strengthened, the structure is thinned, the strength and the hardness of the steel are improved, the hardenability of the Cr can be increased, and the tempering stability of the steel is improved. Thus, the Cr content in the present invention is 0.85 to 0.90wt%.
5) In the invention, mo is a medium-strength carbide forming element, and is dispersed and distributed in a matrix mainly in a carbide form in steel to strengthen the matrix, so that the hardness of the steel is improved; however, as the Mo content increases, the number of Mo carbides increases, and the splitting effect of the carbides distributed at the grain boundary on the matrix is enhanced, resulting in a decrease in toughness of the steel; mo can also effectively refine the as-cast structure of the steel, improve the hardenability and tempering stability of the steel, inhibit tempering brittleness, and slow down precipitation of lath martensite matrix grain boundary carbide in the phase transformation process, thereby improving the impact toughness of the steel and the comprehensive performance. Thus, the Mo content in the present invention is 0.35 to 0.38wt%.
6) In the invention, ni is an element for stabilizing austenite, ni and Fe exist in an alpha phase and a gamma phase in steel in a mutually soluble form to strengthen the steel, and the low-temperature performance of the steel is improved by refining grains, so that the austenite is stabilized, the hardenability of the steel is improved without reducing the toughness of the steel, but the cost is high. Thus, the Ni content in the present invention is 0.75 to 0.77wt%.
7) Al is a deoxidizer and is combined with N to generate AlN, and an austenite grain boundary is pinned in the reheating austenitizing process of off-line quenching to prevent austenite grains from growing. Thus, the Als content in the invention is 0.035-0.055 wt%.
8) In the invention, P is a harmful element, and seriously damages the plasticity and toughness of the steel plate; the P element is easy to combine with Mn element and the like in steel to form sulfide inclusions, and is especially unfavorable for the transverse plasticity and toughness of the steel; p and S are both unavoidable impurity elements, and the lower the content is, the better, and in consideration of the actual steelmaking level, 0.010wt% or less of P and 0.002wt% or less of S are required.
The invention adopts converter smelting, refining and vacuum treatment to remove H, O and other harmful gases in the steel, ensure the cleanliness of the molten steel, and adds ferrochrome, nickel plates, ferromanganese, ferromolybdenum and other necessary alloy elements to adjust the alloy elements so as to ensure the basic component requirements of the molten steel.
The invention adopts the water-cooling copper plate crystallizer ingot mould to pour, the cooling capacity of the copper mould is strong, the precipitation of Cr and Mo carbide in steel is restrained, the carbide can be fully dissolved in the steel, the effect of solid solution strengthening is exerted as much as possible, the quality of the pouring process is ensured by controlling reasonable superheat degree, the looseness and segregation in the steel ingot are reduced, and finally the produced steel ingot has the characteristics of fine crystal grains, high equiaxial crystal proportion and compact structure.
According to the invention, recrystallization type controlled rolling is adopted, as the equiaxed crystal structure can adopt large pass reduction in rolling, each pass reduction is 35-60 mm, deformation induces carbide precipitation of Mo, the carbide prevents crystal grains from growing in the cooling process after rolling, and in the reheating austenitizing process of off-line quenching, the carbide can pin austenite crystal boundaries to prevent the austenite crystal grains from growing, so that the austenite crystal grains are ensured to be tiny, and the fine martensite lath is obtained after quenching.
The invention controls the cooling process after rolling and the off-line quenching process to obtain fine lath martensitic structure, and controls the form and distribution of the residual austenite, so that the performance of the produced thick plate is uniform. By adopting the off-line quenching process, the production process of the wear-resistant steel which can replace the traditional off-line quenching and tempering is obtained, the production period is shortened, and the process cost and the process energy consumption are reduced.
Therefore, the NM 400-grade quenched martensitic wear-resistant steel plate prepared by the invention has the following remarkable progress and characteristics:
1. according to the invention, mn, cr, ni, mo and other elements are added, so that the hardenability of the steel is improved, and lath martensitic transformation is facilitated; the strength, hardness and wear resistance of the steel are improved by solid solution strengthening of Mn and Ni and precipitation strengthening of carbide of Mo and Cr.
2. The invention adopts die casting, recrystallization control rolling, high-density laminar cooling and off-line quenching technology to replace the traditional wear-resistant steel production technology, shortens the production period, saves the process cost, reduces the process energy consumption and improves the process operability. The die casting technology is adopted to inhibit carbide precipitation of Cr and Mo, the solid solution strengthening effect is fully exerted, an equiaxial crystal structure with a large proportion is obtained, the deformation under a large pressure can be adopted during rolling, the carbide precipitation of Mo is induced, the precipitated carbide inhibits the growth of crystal grains in the subsequent technology, the effects of fine grain strengthening and precipitation strengthening are increased, and finally, a fine lath martensite+retained austenite structure is obtained.
3. The NM 400-level quenched martensitic wear-resistant steel plate with the thickness of 140-150 mm prepared by the invention is detected: the tensile strength is 1250-1449 MPa, the elongation after breaking is 10-13%, the impact energy at 0 ℃ is 40-79J, the surface hardness is 400-430 HB, and the mechanical properties are uniform.
Therefore, the chemical components and the production method are simple, the production cost is low, and the thickness specification of the prepared product is 140-150 mm and the mechanical property is good.
Drawings
FIG. 1 is a metallographic structure diagram of a NM 400-grade quenched martensitic wear-resistant steel plate surface layer prepared by the invention;
FIG. 2 is a metallographic structure diagram of the NM 400-level quenched martensitic wear-resistant steel plate shown in FIG. 1 at a position 1/4 away from the surface layer;
FIG. 3 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 1 at a position 1/2 away from the surface layer;
FIG. 4 is a metallographic structure diagram of the surface layer of another NM 400-grade quenched martensitic wear-resistant steel plate prepared by the invention;
FIG. 5 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 4 at a position 1/4 away from the surface layer;
FIG. 6 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 4 at a position 1/2 away from the surface layer;
FIG. 7 is a metallographic structure diagram of a surface layer of a NM 400-grade quenched martensitic wear-resistant steel plate prepared by the invention;
FIG. 8 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 7 at a position 1/4 distance from the surface layer;
FIG. 9 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 7 at a position 1/2 away from the surface layer.
As can be seen from figures 1-9, the surface-to-core structure of the NM 400-grade quenched martensitic wear-resistant steel plate obtained by the invention is martensitic and residual austenitic, and the wear-resistant steel plate has uniform structure.
Detailed Description
The invention is further described below in connection with the drawings and the detailed description, without limiting the scope thereof.
NM 400-level quenched martensitic wear-resistant steel plate and a preparation method thereof.
The NM 400-level quenching martensitic wear-resistant steel plate comprises the following chemical components in percentage by weight: 0.19 to 0.21 weight percent of C, 0.22 to 0.26 weight percent of Si, 1.20 to 1.30 weight percent of Mn, 0.85 to 0.90 weight percent of Cr, 0.35 to 0.38 weight percent of Mo, 0.75 to 0.77 weight percent of Ni, 0.035 to 0.055 weight percent of Als, less than or equal to 0.010 weight percent of P, less than or equal to 0.002 weight percent of S, and the balance of Fe and unavoidable impurities.
The preparation method of the NM 400-level quenching martensitic wear-resistant steel plate comprises the following steps:
and 1, smelting molten iron with the temperature of 1300-1500 ℃ and the weight percent of P being less than or equal to 0.035 and the weight percent of S being less than or equal to 0.004 in a converter, and tapping when the set carbon end point is reached, adopting a slag blocking cone to block slag.
Step 2, refining molten steel in an LF furnace: lime addition amount is 11-12 kg/t, alkalinity is 4.0-6.0, and white slag retention time is 35-40 min during slag making; and in the refining process, ferrochrome, nickel plates, ferromanganese and ferromolybdenum are sequentially added according to the chemical components and the content of the NM 400-grade quenched martensitic wear-resistant steel plate.
Step 3, the refined molten steel is fed into a VD furnace for vacuum treatment, the vacuum degree is 30-67 Pa, and the vacuum is maintained for 18-25 min; soft argon blowing is carried out for 3-5 min after the air breaking, the molten steel is covered with the covering slag in the soft argon blowing process, and then the VD furnace is vacuumized to ensure that the H content in the molten steel is less than or equal to 1.2ppm, and the soft argon blowing is carried out for 8-10 min.
Step 4, casting by adopting a water-cooling copper plate crystallizer ingot mould: the temperature difference between the water inlet and the water outlet of the ingot mould of the copper plate crystallizer is 6-10 ℃, and the cooling water flow rate from the initial stage of pouring to the time of 1h after pouring is 400-450 m 3 And/h, the flow rate of cooling water after casting is 300-400 m for 1-2 h 3 And/h, the flow rate of cooling water after casting is 260-350 m for 2-3 h 3 And/h, the cooling water flow rate after casting is 230-280 m for 3-4 h 3 And/h, cooling water flow rate from 4h after pouring to demoulding is 200-250 m 3 And/h, the thickness of the steel ingot after casting is 740mm.
Step 5, placing the steel ingot into a heating furnace, and preserving heat for 2-5 hours at the temperature of 250-400 ℃; then heating to 880-920 ℃ at the speed of 60-80 ℃/h, and preserving heat for 5-6 h; then heating to 1230-1250 ℃ at the speed of 80-120 ℃/h, and preserving heat for 13-13.5 h.
Step 6, adopting a recrystallization type controlled rolling RCR process: the initial rolling temperature is 1000-1100 ℃, the final rolling temperature is 900-980 ℃, 13 passes of rolling are performed, the reduction of each pass is 35-60 mm, and the thickness of the rolled steel plate is 158-170 mm.
Step 7, cooling the rolled steel plate by adopting a high-density laminar cooling ACC process: the ACC header pipe and the side spraying are fully opened, the water ratio is 1.8-2.2, the roller speed is 0.6-1.0 m/s, the steel plate is cooled for 1 or 2 times after rolling, and the reddening temperature is 600-650 ℃.
And 8, placing the steel plate subjected to controlled cooling into a hot-rolled material slow cooling pit, wherein the temperature of the hot-rolled material slow cooling pit is 350-450 ℃, and the slow cooling time is 48-60 hours.
Step 9, carrying out off-line quenching on the slowly cooled steel plate, wherein the austenitizing temperature is 920-930 ℃, and quenching the steel plate into water with the temperature of 12-25 ℃ after austenitizing; the running speed of the quenched steel plate in a quenching water tank is 0.5-0.7 m/min, the water pressure in the water tank is 0.8-1.1 MPa, and the flow is 4500-5000 m 3 And/h, the temperature of the quenched steel plate is 30-40 ℃.
And step 10, the quenched steel plate enters a heat treatment slow cooling pit for stacking and slow cooling within 12h, the temperature of the heat treatment slow cooling pit is 200-300 ℃, and the slow cooling stacking time is 80-96 h, so that the NM 400-level quenched martensitic wear-resistant steel plate is prepared.
The room temperature thickness of the NM 400-level quenching type martensitic wear-resistant steel plate is 140-150 mm.
In this embodiment:
the NM 400-grade quenched martensitic wear-resistant steel plate comprises: the metallographic structure is martensite and residual austenite; the sum of sulfide, oxide, silicate and spherical oxide is less than 1.5 level, and the band structure is less than 1.0 level.
The embodiments are not described in detail.
Example 1
NM 400-level quenched martensitic wear-resistant steel plate and a preparation method thereof. The NM 400-level quenching martensitic wear-resistant steel plate comprises the following chemical components in percentage by weight: 0.192wt% of C, 0.22wt% of Si, 1.20wt% of Mn, 0.862wt% of Cr, 0.356wt% of Mo, 0.750wt% of Ni, 0.035wt% of Als, 0.009wt% of P, 0.001wt% of S, and the balance of Fe and unavoidable impurities.
The preparation method of the NM 400-level quenching martensitic wear-resistant steel plate comprises the following steps:
and 1, smelting molten iron with the temperature of 1300 ℃ and the P of 0.035wt% and the S of 0.004wt% in a converter, and tapping when the molten iron reaches the set endpoint carbon, wherein a slag blocking cone is adopted for slag blocking during tapping.
Step 2, refining molten steel in an LF furnace: lime addition amount is 11kg/t, alkalinity is 4.0, and white slag holding time is 35min during slag making; and in the refining process, ferrochrome, nickel plates, ferromanganese and ferromolybdenum are sequentially added according to the chemical components and the content of the NM 400-grade quenched martensitic wear-resistant steel plate.
Step 3, the refined molten steel is fed into a VD furnace for vacuum treatment, the vacuum degree is 67Pa, and the vacuum is maintained for 18min; soft argon blowing is carried out for 3min after the air breaking, the molten steel is covered with the covering slag in the soft argon blowing process, and then the VD furnace is vacuumized to ensure that the H content in the molten steel is 1.2ppm, and the soft argon blowing is carried out for 8min.
Step 4, casting by adopting a water-cooling copper plate crystallizer ingot mould: the temperature difference between water inlet and water outlet of the ingot mould of the copper plate crystallizer is 6 ℃, and the flow of cooling water from the initial stage of pouring to the time of 1h after the completion of pouring is 400m 3 And/h, wherein the cooling water flow rate after casting for 1h is 400m 3 And/h, wherein the cooling water flow rate after casting is 350m for 2h 3 And/h, wherein the cooling water flow rate after casting is 280m for 3h 3 And/h, cooling water flow rate from 4h after pouring to 200m during demolding 3 And/h, the thickness of the steel ingot after casting is 740mm.
Step 5, placing the steel ingot into a heating furnace, and preserving heat for 5 hours at the temperature of 250 ℃; heating to 880 ℃ at a speed of 60 ℃/h, and preserving heat for 6h; then the temperature is raised to 1230 ℃ at a rate of 80 ℃/h, and the temperature is kept for 13.5h.
Step 6, adopting a recrystallization type controlled rolling RCR process: the rolling process control parameters of the initial rolling temperature, the final rolling temperature, the rolling pass, the rolling reduction of each pass and the thickness of the rolled steel plate are shown in Table 1 in detail.
TABLE 1 Rolling Process control parameters
Figure BDA0004105371670000101
Step 7, cooling the rolled steel plate by adopting a high-density laminar cooling ACC process: the ACC header and the side spray are fully opened, the water ratio is 1.8, the roller speed is 0.6m/s, the steel plate is cooled for 2 times after rolling, and the reddening temperature is 600 ℃.
And 8, placing the steel plate subjected to controlled cooling into a hot-rolled material slow cooling pit, wherein the temperature of the hot-rolled material slow cooling pit is 350 ℃, and the slow cooling time is 60 hours.
Step 9, carrying out off-line quenching on the slowly cooled steel plate, wherein the austenitizing temperature is 920 ℃, and quenching the steel plate into water with the temperature of 12 ℃ after austenitizing; the speed of the quenched steel plate running in a quenching water tank is 0.7m/min, the water pressure in the water tank is 0.8MPa and the flow is 4500m 3 And/h, the temperature of the steel plate after quenching is 40 ℃.
And step 10, the quenched steel plate enters a heat treatment slow cooling pit for stacking and slow cooling within 12h, the temperature of the heat treatment slow cooling pit is 200 ℃, the slow cooling stacking time is 96h, and the NM 400-level quenched martensitic wear-resistant steel plate is prepared.
The room temperature thickness of the NM 400-grade quenched martensitic wear-resistant steel plate is 140mm.
The NM 400-level quenched wear-resistant steel plate prepared by the invention is detected by the following steps: the tensile strength is 1449MPa, the elongation after break is 13%, the impact energy at 0 ℃ is 79J, the surface hardness is 430HB, and the mechanical properties are uniform.
Example 2
NM 400-level quenched martensitic wear-resistant steel plate and a preparation method thereof. The NM 400-level quenching martensitic wear-resistant steel plate comprises the following chemical components in percentage by weight: 0.208wt% of C, 0.247wt% of Si, 1.25wt% of Mn, 0.891wt% of Cr, 0.351wt% of Mo, 0.768wt% of Ni, 0.046wt% of Als, 0.010wt% of P, 0.002wt% of S, and the balance of Fe and unavoidable impurities.
The preparation method of the NM 400-level quenching martensitic wear-resistant steel plate comprises the following steps:
and 1, smelting molten iron with the temperature of 1500 ℃ and the P of 0.032wt% and the S of 0.003wt% in a converter, and tapping when the molten iron reaches the set endpoint carbon, wherein a slag blocking cone is adopted to block slag during tapping.
Step 2, refining molten steel in an LF furnace: lime addition amount is 12kg/t, alkalinity is 5.2, white slag holding time is 40min, S is 0.002wt%; and in the refining process, ferrochrome, nickel plates, ferromanganese and ferromolybdenum are sequentially added according to the chemical components and the content of the NM 400-grade quenched martensitic wear-resistant steel plate.
Step 3, the refined molten steel is fed into a VD furnace for vacuum treatment, the vacuum degree is 30Pa, and the vacuum is maintained for 25min; soft argon blowing is carried out for 4min after the air breaking, the molten steel is covered with the covering slag in the soft blowing process, and then the VD furnace is vacuumized to ensure that the H content in the molten steel is 1.1ppm, and the soft argon blowing is carried out for 9.1min.
Step 4, casting by adopting a water-cooling copper plate crystallizer ingot mould: the temperature difference between water inlet and water outlet of the ingot mould of the copper plate crystallizer is 10 ℃, and the flow rate of cooling water from the initial stage of pouring to the time of 1h after pouring is 450m 3 And/h, wherein the cooling water flow rate after casting is 350m for 1.5h 3 And/h, wherein the cooling water flow rate after casting is 300m for 2.4h 3 And/h, the cooling water flow rate after casting is 260m for 3.5h 3 And/h, cooling water flow rate after pouring is finished for 4h to demoulding is 230m 3 And/h, the thickness of the steel ingot after casting is 740mm.
Step 5, placing the steel ingot into a heating furnace, and preserving heat for 2 hours at 400 ℃; heating to 920 ℃ at the speed of 80 ℃/h, and preserving heat for 5h; then the temperature is raised to 1250 ℃ at the speed of 120 ℃/h, and the temperature is kept for 13h.
Step 6, adopting a recrystallization type controlled rolling RCR process: the rolling process control parameters of the start rolling temperature, the finish rolling temperature, the rolling pass, the reduction of each pass and the thickness of the rolled steel plate are shown in table 1 in detail.
TABLE 1 Rolling Process control parameters
Figure BDA0004105371670000111
Step 7, cooling the rolled steel plate by adopting a high-density laminar cooling ACC process: the ACC header and the side spray are fully opened, the water ratio is 2.2, the roller speed is 1.0m/s, the steel plate is cooled for 2 times after rolling, and the reddening temperature is 630 ℃.
And 8, placing the steel plate subjected to controlled cooling into a hot-rolled material slow cooling pit, wherein the temperature of the hot-rolled material slow cooling pit is 400 ℃, and the slow cooling time is 54 hours.
Step 9, carrying out off-line quenching on the slowly cooled steel plate, wherein the austenitizing temperature is 930 ℃, and quenching the steel plate into water with the temperature of 25 ℃ after austenitizing; the running speed of the quenched steel plate in a quenching water tank is 0.5m/min, the water pressure in the water tank is 1.1MPa and the flow is 5000m 3 And/h, the temperature of the steel plate after quenching is 30 ℃.
And 10, entering a heat treatment slow cooling pit for stacking and slow cooling within 12h after quenching, wherein the temperature of the heat treatment slow cooling pit is 300 ℃, and the slow cooling stacking time is 80h, so that the NM 400-level quenched martensitic wear-resistant steel plate is prepared.
The room temperature thickness of the NM 400-grade quenched martensitic wear-resistant steel plate is 145mm.
The NM 400-level quenched martensitic wear-resistant steel plate prepared by the invention is detected by the following steps: the tensile strength is 1430MPa, the elongation after breaking is 11%, the impact energy at 0 ℃ is 43J, the surface hardness is 410HB, and the mechanical properties are uniform.
Example 3
NM 400-level quenched martensitic wear-resistant steel plate and a preparation method thereof. The NM 400-level quenching martensitic wear-resistant steel plate comprises the following chemical components in percentage by weight: 0.201wt% of C, 0.259wt% of Si, 1.29wt% of Mn, 0.851wt% of Cr, 0.378wt% of Mo, 0.759wt% of Ni, 0.055wt% of Als, 0.009wt% of P, 0.001wt% of S, and the balance of Fe and unavoidable impurities.
The preparation method of the NM 400-level quenching martensitic wear-resistant steel plate comprises the following steps:
and 1, smelting molten iron with the temperature of 1450 ℃ and the weight percent of P of 0.030 and the weight percent of S of 0.0035 by the converter, and tapping when the molten iron reaches the set endpoint carbon, wherein a slag blocking cone is adopted to block slag during tapping.
Step 2, refining molten steel in an LF furnace: lime addition amount is 11.3kg/t, alkalinity is 6.0, white slag holding time is 39min, S is 0.0019wt% during slag making; and in the refining process, ferrochrome, nickel plates, ferromanganese and ferromolybdenum are sequentially added according to the chemical components and the content of the NM 400-grade quenched martensitic wear-resistant steel plate.
Step 3, the refined molten steel is fed into a VD furnace for vacuum treatment, the vacuum degree is 47Pa, and the vacuum is maintained for 21min; soft argon blowing is carried out for 5min after the air breaking, the molten steel is covered with the covering slag in the soft argon blowing process, and then the VD furnace is vacuumized to ensure that the H content in the molten steel is 1.0ppm, and the soft argon blowing is carried out for 10min.
Step 4, casting by adopting a water-cooling copper plate crystallizer ingot mould: the temperature difference between water inlet and water outlet of the ingot mould of the copper plate crystallizer is 8.2 ℃, and the flow of cooling water from the initial stage of pouring to the time of 1h after pouring is 420m 3 And/h, wherein the cooling water flow rate after casting is 300m for 2h 3 And/h, wherein the cooling water flow rate after casting is 260m for 3h 3 And/h, wherein the cooling water flow rate after 4h of pouring is 230m 3 And/h, cooling water flow rate after pouring is finished for 4h to demoulding is 250m 3 And/h, the thickness of the steel ingot after casting is 740mm.
Step 5, placing the steel ingot into a heating furnace, and preserving heat for 4 hours at 300 ℃; heating to 900 ℃ at the speed of 70 ℃/h, and preserving heat for 5.5h; then the temperature is raised to 1240 ℃ at a rate of 100 ℃/h, and the temperature is kept for 13.3h.
Step 6, adopting a recrystallization type controlled rolling RCR process: the rolling process control parameters of the initial rolling temperature, the final rolling temperature, the rolling pass, the rolling reduction of each pass and the thickness of the rolled steel plate are shown in Table 1 in detail.
TABLE 1 Rolling Process control parameters
Figure BDA0004105371670000131
Step 7, cooling the rolled steel plate by adopting a high-density laminar cooling ACC process: the ACC header and the side spray are fully opened, the water ratio is 1.8, the roller speed is 1.0m/s, the steel plate is cooled for 1 time after rolling, and the reddening temperature is 650 ℃.
And 8, placing the steel plate subjected to controlled cooling into a hot-rolled material slow cooling pit, wherein the temperature of the hot-rolled material slow cooling pit is 450 ℃, and the slow cooling time is 48 hours.
Step 9, carrying out off-line quenching on the slowly cooled steel plate, wherein the austenitizing temperature is924 ℃, austenitizing and then quenching into water with the temperature of 18 ℃; the speed of the quenched steel plate running in a quenching water tank is 0.6m/min, the water pressure in the water tank is 1.0MPa and the flow is 4800m 3 And/h, the temperature of the steel plate after quenching is 35 ℃.
And step 10, the quenched steel plate enters a heat treatment slow cooling pit for stacking and slow cooling within 12h, the temperature of the heat treatment slow cooling pit is 260 ℃, the slow cooling stacking time is 89h, and the NM 400-level quenched martensitic wear-resistant steel plate is prepared.
The room temperature thickness of the NM 400-grade quenched martensitic wear-resistant steel plate is 150mm.
The NM 400-grade quenched martensitic wear-resistant steel plate prepared in the embodiment is detected: the tensile strength is 1250MPa, the elongation after breaking is 10%, the impact energy at 0 ℃ is 40J, the surface hardness is 400HB, and the mechanical properties are uniform.
The NM 400-level quenched martensitic wear-resistant steel plate adopted in the specific embodiment has simple chemical components and content, and the harmful gases such as H, O in the steel are removed by converter smelting, refining and vacuum treatment, so that the cleanliness of the molten steel is ensured; adding necessary alloying elements such as ferrochrome, nickel plates, ferromanganese, ferromolybdenum and the like, and adjusting the alloying elements to ensure the basic component requirements of molten steel.
The concrete implementation mode adopts the water-cooling copper plate crystallizer ingot mould to carry out pouring, the cooling capacity of the copper mould is strong, the precipitation of Cr and Mo carbide in steel is restrained, the carbide can be fully dissolved in the steel, the effect of solid solution strengthening is exerted as much as possible, the quality of the pouring process is ensured by controlling reasonable superheat degree, the looseness and segregation in the steel ingot are reduced, and finally the produced steel ingot has the characteristics of fine crystal grains, high equiaxial crystal proportion and compact structure.
In the specific embodiment, recrystallization type controlled rolling is adopted, as the equiaxed crystal structure can adopt large pass reduction in rolling, each pass reduction is 35-60 mm, deformation induces carbide precipitation of Mo, the carbide prevents crystal grains from growing in the cooling process after rolling, and in the reheating austenitizing process of off-line quenching, the carbide can pin austenite crystal boundaries to prevent the growth of austenite crystal grains, the tiny austenite crystal grains are ensured, and the fine martensite lath is obtained after quenching.
The specific embodiment controls the cooling process after rolling and the off-line quenching process to obtain a fine lath martensitic structure, and controls the form and distribution of the residual austenite, so that the produced thick plate has uniform performance. By adopting the off-line quenching process, the production process of the wear-resistant steel which can replace the traditional off-line quenching and tempering is obtained, the production period is shortened, and the process cost and the process energy consumption are reduced.
Therefore, the NM 400-grade quenched martensitic wear-resistant steel plate prepared by the specific embodiment has the following remarkable progress and characteristics:
1. in the specific embodiment, mn, cr, ni, mo and other elements are added, so that the hardenability of the steel is improved, and the lath martensitic structure transformation is facilitated; the strength, hardness and wear resistance of the steel are improved by solid solution strengthening of Mn and Ni and precipitation strengthening of carbide of Mo and Cr.
2. The specific embodiment adopts die casting, recrystallization control rolling, high-density laminar cooling and off-line quenching technology to replace the traditional wear-resistant steel production technology, shortens the production period, saves the process cost, reduces the process energy consumption and improves the process operability. The die casting technology is adopted to inhibit carbide precipitation of Cr and Mo, the solid solution strengthening effect is fully exerted, an equiaxial crystal structure with a large proportion is obtained, the deformation under a large pressure can be adopted during rolling, the carbide precipitation of Mo is induced, the precipitated carbide inhibits the growth of crystal grains in the subsequent technology, the effects of fine grain strengthening and precipitation strengthening are increased, and finally, a fine lath martensite+retained austenite structure is obtained.
3. The NM 400-level quenched martensitic wear-resistant steel plate prepared by the specific embodiment is shown in the accompanying drawings: FIG. 1 is a metallographic structure diagram of a surface layer of a NM 400-grade quenched martensitic wear-resistant steel plate prepared in example 1; FIG. 2 is a metallographic structure diagram of the NM 400-level quenched martensitic wear-resistant steel plate shown in FIG. 1 at a position 1/4 away from the surface layer; FIG. 3 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 1 at a position 1/2 away from the surface layer; FIG. 4 is a metallographic structure diagram of the surface layer of the NM 400-grade quenched martensitic wear-resistant steel plate prepared in example 2; FIG. 5 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 4 at a position 1/4 away from the surface layer; FIG. 6 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 4 at a position 1/2 away from the surface layer; FIG. 7 is a metallographic structure diagram of the surface layer of the NM 400-grade quenched martensitic wear-resistant steel plate prepared in example 3; FIG. 8 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 7 at a position 1/4 distance from the surface layer; FIG. 9 is a metallographic structure diagram of the NM 400-grade quenched martensitic wear-resistant steel plate shown in FIG. 7 at a position 1/2 away from the surface layer. As can be seen from fig. 1 to 9, the surface-to-core structure of the NM 400-grade quenched martensitic wear-resistant steel plate obtained by the invention is martensitic and residual austenitic, and the wear-resistant steel plate has uniform structure.
The NM 400-grade quenched martensitic wear-resistant steel plate with the thickness of 140-150 mm prepared by the specific embodiment is detected: the tensile strength is 1250-1449 MPa, the elongation after breaking is 10-13%, the impact energy at 0 ℃ is 40-79J, the surface hardness is 400-430 HB, and the mechanical properties are uniform.
Therefore, the chemical components and the production method in the specific embodiment are simple, the production cost is low, and the thickness specification of the prepared NM 400-grade quenched martensitic wear-resistant steel plate is 140-150 mm, and the mechanical property is good.

Claims (2)

1. The preparation method of the NM 400-level quenching type martensitic wear-resistant steel plate is characterized by comprising the following chemical components in percentage by weight: 0.19 to 0.21 weight percent of C, 0.22 to 0.26 weight percent of Si, 1.20 to 1.30 weight percent of Mn, 0.85 to 0.90 weight percent of Cr, 0.35 to 0.38 weight percent of Mo, 0.75 to 0.77 weight percent of Ni, 0.035 to 0.055 weight percent of Als, less than or equal to 0.010 weight percent of P, less than or equal to 0.002 weight percent of S, and the balance of Fe and unavoidable impurities;
the preparation method of the NM 400-level quenching martensitic wear-resistant steel plate comprises the following steps:
step 1, smelting molten iron with the temperature of 1300-1500 ℃ and the weight percent of P being less than or equal to 0.035 and the weight percent of S being less than or equal to 0.004 in a converter, and tapping when the set carbon end point is reached, adopting a slag blocking cone to block slag;
step 2, refining molten steel in an LF furnace: lime addition amount is 11-12 kg/t, alkalinity is 4.0-6.0, and white slag retention time is 35-40 min during slag making; in the refining process, ferrochrome, nickel plates, ferromanganese and ferromolybdenum are sequentially added according to the chemical components and the content of the NM 400-level quenching martensitic wear-resistant steel plate;
step 3, the refined molten steel is fed into a VD furnace for vacuum treatment: vacuum degree is 30-67 Pa, and vacuum is maintained for 18-25 min; soft argon blowing is carried out for 3-5 min after the air breaking, the molten steel is covered with the covering slag in the soft argon blowing process, then the VD furnace is vacuumized to ensure that the H content in the molten steel is less than or equal to 1.2ppm, and the soft argon blowing is carried out for 8-10 min;
step 4, casting by adopting a water-cooling copper plate crystallizer ingot mould: the temperature difference between the water inlet and the water outlet of the ingot mould of the copper plate crystallizer is 6-10 ℃, and the cooling water flow rate from the initial stage of pouring to the time of 1h after pouring is 400-450 m 3 And/h, the flow rate of cooling water after casting is 300-400 m for 1-2 h 3 And/h, the flow rate of cooling water after casting is 260-350 m for 2-3 h 3 And/h, the cooling water flow rate after casting is 230-280 m for 3-4 h 3 And/h, cooling water flow rate from 4h after pouring to demoulding is 200-250 m 3 And/h, the thickness of the steel ingot after casting is 740mm;
step 5, placing the steel ingot into a heating furnace, and preserving heat for 2-5 hours at the temperature of 250-400 ℃; then heating to 880-920 ℃ at the speed of 60-80 ℃/h, and preserving heat for 5-6 h; then heating to 1230-1250 ℃ at the speed of 80-120 ℃/h, and preserving heat for 13-13.5 h;
step 6, adopting a recrystallization type controlled rolling RCR process: the initial rolling temperature is 1000-1100 ℃, the final rolling temperature is 900-980 ℃, 13 passes of rolling are performed, the rolling reduction of each pass is 35-60 mm, and the thickness of the rolled steel plate is 158-170 mm;
step 7, cooling the rolled steel plate by adopting a high-density laminar cooling ACC process: the ACC header pipe and the side spraying are fully opened, the water ratio is 1.8-2.2, the roller speed is 0.6-1.0 m/s, the steel plate is cooled for 1 or 2 times after rolling, and the reddening temperature is 600-650 ℃;
step 8, placing the steel plate subjected to controlled cooling into a hot-rolled material slow cooling pit, wherein the temperature of the hot-rolled material slow cooling pit is 350-450 ℃, and the slow cooling time is 48-60 hours;
step 9, carrying out off-line quenching on the slowly cooled steel plate, wherein the austenitizing temperature is 920-930 ℃, and quenching the steel plate into water with the temperature of 12-25 ℃ after austenitizing; the running speed of the quenched steel plate in the quenching water tank is 0.5-0.7 m/min, the water pressure in the water tank is 0.8-1.1 MPa, and the flow is 4500-5000 m 3 And/h, wherein the temperature of the quenched steel plate is 30-40 ℃;
step 10, the quenched steel plate enters a heat treatment slow cooling pit for stacking and slow cooling within 12 hours, the temperature of the heat treatment slow cooling pit is 200-300 ℃, and the slow cooling stacking time is 80-96 hours, so that the NM 400-level quenched martensitic wear-resistant steel plate is prepared;
the room temperature thickness of the NM 400-level quenching type martensitic wear-resistant steel plate is 140-150 mm.
2. A NM 400-grade quenched martensitic wear-resistant steel sheet, characterized in that the NM 400-grade quenched martensitic wear-resistant steel sheet is a NM 400-grade quenched martensitic wear-resistant steel sheet produced by the production method of a NM 400-grade quenched martensitic wear-resistant steel sheet according to claim 1;
the metallurgical structure of the NM 400-level quenched martensitic wear-resistant steel plate is martensite and retained austenite; the sum of sulfide, oxide, silicate and spherical oxide is less than 1.5 level, and the band structure is less than 1.0 level.
CN202310190848.4A 2023-03-02 2023-03-02 NM 400-level quenching martensitic wear-resistant steel plate and preparation method thereof Pending CN116287992A (en)

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