A wear-resistant steel plate of HB450 grade with good Z-direction performance and a production method thereof

Abstract

The application relates to the technical field of wear-resistant steel plate production, in particular to a wear-resistant steel plate of HB450 grade with good Z-direction performance and a production method thereof, the chemical components of the steel plate include C, Si, Mn, Nb, W, Al, B, RE and the like, W is added in the steel plate and is combined with Nb micro-alloying, the quenching and tempering property is ensured, and the precipitation of harmful oxides at the grain boundary is inhibited; the rare earth element Re is added to purify the molten steel, modify the inclusions, reduce the grain boundary segregation of P, S and B, the original structure of the steel plate is refined and homogenized by controlled rolling and controlled cooling, and the residual stress is fully released by long-time tempering heat treatment, so that the risk of layered tearing and cracking is greatly reduced; finally, the low-alloy steel plate with high hardness and resistance to layered tearing of the HB450 grade and with the thickness specification of 30-60 mm is produced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wear-resistant steel plate production, in particular to a wear-resistant steel plate with a thickness of 30-60 mm, a surface hardness of HB450 level and good Z-direction performance and a production method thereof. BACKGROUND

[0002] Low-alloy wear-resistant steel plates with a surface hardness of HB450 level are widely used in the fields of engineering machinery and mining machinery for manufacturing wear-resistant components, and generally adopt a heat treatment process of quenching and tempering, and the structure is mainly low-carbon martensite.

[0003] Wear-resistant steel plates with a thickness of more than 30 mm often have a lamellar tearing phenomenon when welded or subjected to Z-direction stress, which is a phenomenon of layering cracking of the steel along the thickness direction, seriously threatening the safety of the components. In recent years, with the development of the field of engineering machinery, the requirements for the performance of high-strength steel plates are increasingly stringent. For example, key parts of engineering machinery such as coal mine scraper conveyors require not only a hardness of HB450 level but also excellent Z-direction performance.

[0004] A Chinese patent application with the publication number CN117344198A discloses a production method of high-low temperature toughness NM450 wear-resistant steel plate. The chemical composition of the steel by weight percentage is C=0.18%-0.20%, Si=0.15%-0.40%, Mn=1.10%-1.25%, P≤0.010%, S≤0.003%, Cr=0.45%-0.65%, Ni=0.40%-0.45%, Mo=0.20%-0.25%, Nb=0.020%-0.030%, Ti=0.015%-0.030%, Al=0.050%-0.090%, B=0.0014%-0.0030%, H≤0.0002%, N≤0.0060%, O≤0.0015%, and the rest is Fe and unavoidable impurities, CEV≤0.59%. The process steps include converter smelting, LF refining, vacuum degassing, continuous casting, heating, rolling, and heat treatment. The wear-resistant steel plate produced has a surface hardness of 420-480 HBW, a yield strength of ≥1100 MPa, a tensile strength of ≥1350 MPa, an elongation of ≥13%, meets 3a radius 180° cold bending, and Akv impact at -40℃ is ≥40 J. The product is a high-toughness wear-resistant steel NM450, and does not involve the Z-direction performance of the steel plate.

[0005] A Chinese patent application with publication number CN116855835A discloses a production method of a large-thickness quenched and tempered high-strength steel plate resistant to lamellar tearing. The chemical composition of the steel by weight percentage is C=0.11-0.16, Si=0.15-0.35, Mn=0.80-1.30, P≤0.010, S≤0.002, Nb=0.015-0.025, V=0.02-0.06, Ti≤0.005, Al=0.07-0.09, Cr=0.30-0.80, Mo=0.35-0.65, Ni=0.30-1.20, B=0.001-0.002, CEV≤0.70, and the balance is Fe and inevitable impurities. The process route is BOF-LF-VD-continuous casting-billet heating-rolling-pile cooling-quenching and tempering heat treatment-performance test. The billet is heated to 1180-1230℃, and the soaking time is ≥60min; the rolling is two-stage rolling, the rough rolling stage rolling temperature is ≥1120℃, and the last 3 passes are controlled according to single pass reduction ≥35mm; the finish rolling stage rolling temperature is ≤900℃, and the rolled steel plate is cooled to 250-300℃ on the cooling bed before being discharged and stacked for slow cooling, and the stacking time is ≥48h; after slow cooling, the steel plate is subjected to quenching+tempering treatment in a continuous heat treatment furnace, the quenching temperature is 900-930℃, and the tempering temperature is 620-680℃. The matrix structure of the steel plate is tempered sorbite+lower bainite, and no TiN and MnS inclusions affecting the lamellar tearing resistance of the steel plate are detected in the core. It adopts Ti-free and Al-containing composition design, optimizes the Ca treatment process, eliminates the influence of TiN and MnS inclusions on the Z-direction performance of the steel plate; light reduction combined with convex roller reduction is used during continuous casting to improve the core porosity, and a reasonable steel plate pile cooling hydrogen removal process is developed; without adjusting other alloying elements and without affecting the steelmaking and rolling production rhythm, the qualified rate of the 100-150mm Q550 and Q690 grade high-strength steel resistant to lamellar tearing is stably above 98.0%. However, the strength level of the finished steel plate is only 690MPa, which cannot reach the HB450 grade hardness, and the Al content is high, which can easily cause continuous casting nozzle blockage and more inclusions, and can affect the low temperature toughness.

[0006] A Chinese patent application with publication number CN115747657A discloses "a high-strength HY950CF steel plate for water and electricity engineering and a production method thereof", the thickness of the steel plate is 50-120 mm, and the steel plate contains the following chemical components (unit, wt%): C: 0.09-0.12, Si: 0.15-0.25, Mn: 0.30-0.60, P≤0.010, S≤0.003, Als: 0.020-0.040, Nb: 0.02-0.03, V: 0.04-0.1, Cr: 1.2-1.6, Ni: 2.4-2.8, Cu: 0.8-1.0, Mo: 0.2-0.3, Re: 0.0015-0.0025, the rest being Fe and residual elements, carbon equivalent Ceq<0.7, the microstructure is bainite tempering structure, and the longitudinal and transverse V-type impact energy at-60 ℃ is≥127 J. The production process is steel ingot casting, one-time heating, breakdown rolling, two-time heating and rolling, heat treatment, high-temperature quenching + critical quenching + tempering heat treatment, quenching and then loading into a quenching furnace at 650±20 ℃ for tempering, and air cooling to room temperature. The process adopts rolling instead of forging, and the heat treatment link is quenched multiple times to ensure the quenching penetration and refine the austenite grains, and the tempering improves the uniformity of the mechanical properties of the whole plate. The finished steel plate has high strength, high toughness, fatigue resistance, lamellar tearing resistance, and good weldability and corrosion resistance. However, it needs to be produced by using a large-thickness steel ingot, and the Cr and Ni contents in the steel are high, so that continuous casting cannot be realized.

[0007] A Chinese patent application with publication number CN108642390A discloses "a high-strength thick steel plate with thickness direction performance Z of 35-50% and a production method thereof", the components and wt% of the thick steel plate are as follows: C: 0.10-0.18%, Si: 0.10-0.40%, Mn: 1.20-1.60%, P≤0.010%, S≤0.005%, Cr: 0.10-0.50%, Mo: 0.45-0.75%, Ni: 0.05-0.20%, the sum of Nb+Ti+V is 0.040-0.06%, B: 0.0008-0.0020%, and H≤2 ppm. The production steps include: after clean steel smelting, the cast blank is continuously cast; after heating the cast blank, rough rolling is performed; finish rolling is performed; quenching is performed; tempering is performed; and natural cooling to room temperature is performed. It mainly solves the problem that high-strength steel is prone to lamellar tearing after welding or stress. 7 The stress is small under cyclic fatigue conditions, and the lamellar tearing phenomenon does not occur after welding or 10 7 cycle fatigue test. However, the hardness of the finished steel plate is lower than HB450, and high-temperature tempering heat treatment is required.

[0008] Chinese patent application CN116583610A discloses a "very thick steel plate for steam drum with excellent surface quality and resistance to lamellar tearing and a method of manufacturing the same", the steel plate composition and structure: C: 0.2% to 0.3%, Si: 0.05% to 0.5%, Mn: 1.0% to 2.0%, Al: 0.005% to 0.1%, P: 0.01% or less, S: 0.015% or less, Nb: 0.001% to 0.02%, V: 0.001% to 0.03%, Ti: 0.001% to 0.03%, Cr: 0.01% to 0.3%, Mo: 0.01% to 0.12%, Cu: 0.01% to 0.4%, Ni: 0.05% to 0.4%, Ca: 0.0005% to 0.004%, the balance being Fe and other unavoidable impurities. Ceq satisfies the range of 0.5 to 0.6; the first heating is performed on the slab at a temperature of 1100°C to 1300°C; the second heating is performed on the first intermediate material at a temperature of 1000°C to 1200°C; the third heating is performed on the second intermediate material at a temperature of 1000°C to 1200°C; normalizing heat treatment is performed after hot rolling is completed. The thickness of the steel material is 133mm to 250mm. The tensile strength of the steel material is 550MPa to 690MPa. The reduction of area (ZRA) is 35% or more. However, the steel plate needs to be heated and heat treated for multiple times in the production process, and the production process is complex.

[0009] In summary, the existing high-strength lamellar tearing resistant steel plate production has the following disadvantages: 1. The hardness of the finished steel plate is lower than HB450; 2. The production process is complex; 3. The alloy content is high, and continuous casting is not possible; 4. The Z-direction performance cannot be guaranteed. SUMMARY

[0010] The application provides a HB450 grade wear-resistant steel plate with good Z-direction performance and a production method thereof. A new chemical composition and production process design are adopted, W is added in the steel and combined with Nb micro-alloying, the hard oxide precipitation at the grain boundary is inhibited while the hardenability is ensured, rare earth element RE is added to purify the molten steel, modify the inclusions, and reduce the grain boundary segregation of P, S and B, the original structure of the steel plate is refined and homogenized by controlled rolling and controlled cooling, and the residual stress is fully released by long-time tempering heat treatment, so that the risk of lamellar tearing cracking is greatly reduced by the combination of the above technical means; finally, a low-alloy steel plate with a thickness specification of 30-60mm and a HB450 grade is produced.

[0011] In order to achieve the above purpose, the application adopts the following technical scheme:

[0012] The application discloses a wear-resistant steel plate with good Z-direction performance of HB450 level, and the chemical composition of the steel plate is as follows: C: 0.18% to 0.22%, Si: 0.60% to 0.80%, Mn: 1.1% to 1.3%, Nb: 0.015% to 0.030%, W: 0.30% to 0.40%, Al: 0.04% to 0.07%, B: 0.0005% to 0.0020%, RE: 0.0015% to 0.0035%, and 1.45% <= W+Mn <= 1.60%, and the balance is Fe and inevitable impurities; the impurity elements in the steel are controlled as follows: P <= 0.010%, S <= 0.0015%, [N] <= 0.0040%, [H] <= 0.00015%, [O] <= 0.0010%, and the residual austenite content is 3% to 5%.

[0013] The surface hardness of the finished steel plate is greater than or equal to 450 HB, the tensile strength is greater than or equal to 1250 MPa, the longitudinal impact energy Akv at -40 DEG C is greater than or equal to 30 J, the elongation A is greater than or equal to 12%, the 180 DEG cold bending D = 4a is qualified, and the thickness direction Z is greater than or equal to 25%.

[0014] The thickness of the finished steel plate is 30 to 60 mm.

[0015] The application further discloses a production method of the wear-resistant steel plate with good Z-direction performance of HB450 level, and the production process flow comprises converter smelting, refining, continuous casting, slab heating and slow cooling, slab heating, controlled rolling, controlled cooling, stacking slow cooling or high-temperature tempering, quenching and tempering heat treatment; and the following processes are controlled.

[0016] 1) refining: LF+RH refining treatment is adopted, and the RH refining vacuum circulation time is greater than or equal to 20 min; after the RH vacuum treatment, RE alloy is added through argon protection wire feeding;

[0017] 2) continuous casting: the casting speed of the slab is 0.8 to 1.0 m / min, the target superheat of the tundish is controlled to be below 20 DEG C; the whole process is protected pouring, and electromagnetic stirring is adopted; and the center segregation of the slab is controlled to be below C1.0 level;

[0018] 3) slab heating and slow cooling: the slow cooling heating starting temperature is greater than or equal to 500 DEG C, the heating speed is less than or equal to 50 DEG C / h, the temperature is heated to 600 to 630 DEG C, the temperature is kept for 24 to 36 h, then the slab is taken out from the furnace after the furnace is slowly cooled to below 300 DEG C, and the slab is air-cooled to room temperature;

[0019] 4) slab heating: the temperature of the soaking section is 1150 to 1200 DEG C, and the soaking time is 2 to 2.5 h;

[0020] 5) Controlled rolling: two-stage controlled rolling is adopted, the compression ratio, i.e. the slab thickness / finished plate thickness, is greater than or equal to 4; the speed ratio of the upper roller to the lower roller is 1.1:1 to 1.3:1; the rough rolling starting temperature is greater than or equal to 1000℃, and the rough rolling final rolling temperature is greater than or equal to 950℃; the finish rolling starting temperature is 850-880℃, the finish rolling reduction is greater than or equal to 60%, and the finish rolling final rolling temperature is 800-850℃;

[0021] 6) Controlled cooling: laminar cooling is adopted after rolling, the starting cooling temperature is greater than or equal to 760℃, and the final cooling temperature is 620-660℃;

[0022] 7) Pile-up slow cooling or high-temperature tempering: when the slab offline temperature is greater than 400℃, pile-up slow cooling is carried out, and the pile-up slow cooling time is greater than or equal to 24h; when the slab offline temperature is less than or equal to 400℃, high-temperature tempering is carried out, the tempering heating temperature is 580-630℃, and the holding time is 2.5-3.5min / mm;

[0023] 8) Quenching and tempering heat treatment: the quenching temperature is 880-900℃, and the holding time is 3.0-3.5min / mm; the low-temperature stress relief tempering temperature is 220-250℃, and the holding time is 6-8min / mm.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1) A new chemical composition and production process design are adopted, tungsten is added in the steel and combined with niobium micro-alloying, the hard oxide precipitation at the grain boundary is inhibited while the hardenability is ensured; rare earth elements RE are added to purify the molten steel, modify the inclusions, reduce the grain boundary segregation of P, S and B, refine and homogenize the original structure of the steel plate by controlled rolling and controlled cooling, and fully release the residual stress by long-time tempering heat treatment, so that the risk of lamellar tearing is greatly reduced; finally, a low-alloy steel plate with a thickness of 30-60mm and a HB450 grade high-hardness anti-lamellar tearing is produced;

[0026] 2) The surface hardness of the finished steel plate is greater than or equal to HB450, the tensile strength is greater than or equal to 1250MPa, the longitudinal impact energy Akv at-40℃ is greater than or equal to 30J, the elongation A is greater than or equal to 12%, the 180° cold bending D is qualified, and the thickness direction Z is greater than or equal to 25%;

[0027] 3) The steel plate chemical composition design is characterized by low carbon, tungsten, niobium, boron and rare earth synergistic micro-alloying, and the alloy content is relatively low, which is convenient for smelting and continuous casting, and the production process is simple. DETAILED DESCRIPTION

[0028] The application discloses a wear-resistant steel plate with good Z-direction performance of HB450 level, and the chemical components of the steel plate are as follows: C: 0.18-0.22%, Si: 0.60-0.80%, Mn: 1.1-1.3%, Nb: 0.015-0.030%, W: 0.30-0.40%, Al: 0.04-0.07%, B: 0.0005-0.0020%, RE: 0.0015-0.0035%, and 1.45%<=W+Mn<=1.60%, the rest is Fe and inevitable impurities; the impurity elements in the steel are controlled as follows: P<=0.010%, S<=0.0015%, [N]<=0.0040%, [H]<=0.00015%, [O]<=0.0010%, and the residual austenite content is 3-5%.

[0029] The chemical component design reasons of the wear-resistant steel plate are as follows:

[0030] C: carbide forming element, which can ensure that the strength of the steel plate after quenching is HB450, and can improve the hardenability of the thick-gauge steel plate, and ensure that the performance of the steel plate along the thickness direction is uniform. However, too high carbon content can reduce the plasticity and low-temperature toughness of the steel plate, and can easily cause the center segregation of the cast blank after continuous casting, and can cause the Z-direction performance of the steel plate to be reduced as a crack source after rolling. Therefore, the C content is controlled to be 0.18-0.22% in the application.

[0031] Si: non-carbide forming element, which mainly functions to inhibit the precipitation of carbides, and stabilize the residual austenite content in the steel, and the residual austenite can inhibit the formation and expansion of lamellar cracks as a soft phase during Z-direction tensile testing. However, too much Si can reduce the toughness and welding performance, therefore, the Si content is controlled to be 0.60-0.80% in the application.

[0032] Mn: functions to deoxidize and solid-solution strengthen, so as to ensure the strength of the steel plate, and can delay the austenite to ferrite and pearlite transformation, and improve the hardenability. However, Mn is easy to form center segregation in the steel, and the thickness center of the steel plate has a tendency to cause lamellar cracks; therefore, the Mn content is controlled to be 1.1-1.3% in the application.

[0033] Nb: is the most effective element for realizing controlled rolling. In the two-stage controlled rolling process, carbonitride is formed, austenite recrystallization is inhibited, austenite grains are refined, and fine martensite lath bundles can be formed after quenching, so that the occurrence of the lamellar cracks of the steel plate can be effectively prevented. Nb can also cooperate with W to delay the diffusion of B to the grain boundary, and avoid the formation of B2O3 brittle phase which can cause the lamellar cracks; however, too high Nb content can cause too much carbonitride to be precipitated, and can affect the lamellar tear resistance of the steel plate. Therefore, the Nb content is controlled to be 0.015-0.03% in the application.

[0034] Al: effective element for deoxidation and nitrogen fixation. Deoxidation can reduce oxide inclusions in steel and purify steel, and nitrogen fixation after deoxidation can ensure that B element does not combine with N to play the role of B in improving quenching. When the content of Al is less than 0.03%, the effect is small; when the content of Al is too high, a large amount of Al2O3 inclusions will be formed in the steel, which is easy to become the source of layered tearing under the action of Z stress. Therefore, the content of Al is controlled to be 0.04%-0.07% in the application.

[0035] W: can effectively inhibit the segregation of P at the grain boundary, thereby improving the Z-direction performance; W and Nb synergistically act to delay the diffusion of B to the grain boundary, avoid the formation of B2O3 brittle phase, and WC and NbC are co-grain precipitated, the carbide is finer under the same process condition, the pinning dislocation effect is doubled, the ability to inhibit the segregation of P at the grain boundary is better; W also has the effects of solid solution strengthening and grain refinement. In addition, W can significantly improve the hardenability and promote the transformation of martensite. Compared with Mo, the carbide of W is more stable, and the effect of improving the hardenability is better. Therefore, the content of W is controlled to be 0.30%-0.40% in the application. Because W and Mn have the effect of improving the hardenability at the same time, too much addition will increase the risk of layered cracking, so it is required that 1.45%≤W+Mn≤1.60%.

[0036] RE: adding 0.0015%-0.0035% of RE is mainly used for the shape control of inclusions in steel, which modifies the long strip sulfide Mns and oxide Al2O3 into spherical inclusions, avoids them from becoming Z-direction crack source, and thereby improves the Z-direction performance. At the same time, RE atoms segregate at the austenite grain boundary, can delay the proeutectoid ferrite precipitation, inhibit the grain boundary adsorption of harmful elements such as P and S, and reduce the temper brittleness. When RE is less than 0.0010%, there is no effect, and when the content is too high, coarse oxides will be formed, which reduces the Z-direction performance.

[0037] B: a small amount of boron in steel can inhibit the formation of proeutectoid ferrite, greatly improving the hardenability. When the content of B is too high (≥0.0025%), B is easy to enrich at the grain boundary, reduce the grain boundary binding energy, and then form layered cracking under the action of Z stress. Therefore, the content of B is controlled to be 0.0005%-0.0020% in the application.

[0038] Residual austenite: 3%-5% of residual austenite as hydrogen trap can prevent the formation and expansion of layered tearing cracks, but too high content of residual austenite will reduce the strength of the steel plate.

[0039] Impurity elements: P, S is easy to segregate at the grain boundary or form segregation in the heart of the steel plate, which seriously affects the low temperature toughness and Z-direction performance; H gathers at the metallurgical defects of the steel plate, which can become the crack source of lamellar tearing; in addition, the strip sulfide, oxide and sharp corner nitride in the steel can cause local stress concentration, which significantly reduces the crack arrest ability of the steel plate lamellar crack; in order to ensure good Z-direction performance, the present application controls P≤0.010%, S≤0.0015%, [N]≤0.0040%, [H]≤0.00015%, [O]≤0.0010% in the steel.

[0040] The production method of the HB450 grade wear-resistant steel plate with good Z-direction performance provided by the application has the production process flow including converter smelting, refining, continuous casting, slab heating and slow cooling, slab heating, controlled rolling, controlled cooling, stacking slow cooling or high temperature tempering, quenching and tempering heat treatment; and the following processes are controlled:

[0041] 1) Refining: LF+RH refining treatment is adopted, and the RH refining vacuum circulation time is ≥20 min; through long time vacuum treatment, [N]≤0.0040%, [O]≤0.0010%, [H]≤0.00015% in the molten steel are controlled. After RH vacuum treatment, RE alloy is added through argon protection wire feeding; the purpose is to prevent rare earth oxidation, improve the yield, and reduce the harm of sulfide and oxide inclusions by adding rare earth modification treatment.

[0042] 2) Continuous casting: the casting speed of the slab is 0.8-1.0 m / min, and the target superheat of the tundish is controlled below 20℃; the whole process is protected pouring, and the purpose is to prevent oxidation of the molten steel and hydrogen into the tundish. Electromagnetic stirring is adopted during continuous casting; the center segregation of the slab is controlled below C1.0 level; the purpose is to reduce the center segregation and prevent the center segregation from becoming the crack initiation point of the lamellar crack.

[0043] 3) Slab heating and slow cooling: the slow cooling heating starting temperature is ≥500℃, the heating speed is ≤50℃ / h, and the temperature is heated to 600-630℃, and after 24-36h of holding, the furnace is slowly cooled to below 300℃ and discharged, and air cooling is performed to room temperature; through heating, the center segregation degree of the slab is reduced, and the hydrogen content and casting internal stress in the slab are also reduced.

[0044] 4) Slab heating: the soaking section temperature is 1150-1200℃, and the soaking time is 2-2.5h; the purpose is to prevent the oxidation of rare earth elements due to long time heating in the soaking section during slab heating.

[0045] 5) Controlled rolling: two-stage controlled rolling of rough rolling and finish rolling is adopted to fully refine and homogenize the rolling structure. In order to ensure deep penetration of the core deformation, the compression ratio, i.e. the slab thickness / finished plate thickness, is controlled to be greater than or equal to 4; the speed ratio of the upper and lower rollers is controlled to be 1.1:1 to 1.3:1; the differential speed rolling of the upper and lower rollers is adopted to introduce the asymmetric deformation in the thickness direction, form the shear strain gradient, and further improve the Z-direction performance. The rough rolling starting temperature is greater than or equal to 1000℃, and the rough rolling final rolling temperature is greater than or equal to 950℃; the finish rolling starting temperature is 850-880℃, the finish rolling reduction is greater than or equal to 60%, and the finish rolling final rolling temperature is 800-850℃;

[0046] 6) Controlled cooling: laminar cooling is adopted after rolling, the cooling starting temperature is greater than or equal to 760℃, and the final cooling temperature is 620-660℃; the purpose of the controlled cooling is to prevent the grain growth and prevent the W carbide from precipitating too early.

[0047] 7) Pile-up slow cooling or high-temperature tempering: when the slab offline temperature is greater than 400℃, the pile-up slow cooling is carried out, and the pile-up slow cooling time is greater than or equal to 24h; when the slab offline temperature is less than or equal to 400℃, the high-temperature tempering is carried out, the tempering heating temperature is 580-630℃, and the holding time is 2.5-3.5min / mm; the purpose of the pile-up slow cooling or high-temperature tempering is to remove the hydrogen in the steel plate and remove the internal stress generated due to the non-uniform rolling and cooling of the steel plate.

[0048] 8) Quenching and tempering heat treatment: the quenching temperature is 880-900℃, and the holding time is 3.0-3.5min / mm; the purpose of the quenching is to obtain the martensite structure to ensure that the hardness of the steel plate reaches the HB450 level. The long quenching heating time is to diffuse the core elements under the premise that the grains do not grow too much, and to improve the core segregation. The low-temperature stress relief tempering temperature is 220-250℃, and the holding time is 6-8min / mm. The purpose of the long low-temperature tempering after quenching is to fully remove the internal stress of the steel plate formed after quenching, and to further improve the resistance to lamellar tearing performance.

[0049] The surface hardness of the finished steel plate is greater than or equal to HB450, the tensile strength is greater than or equal to 1250MPa; the longitudinal impact energy Akv at-40℃ is greater than or equal to 30J; the elongation A is greater than or equal to 12%, the 180° cold bending D=4a is qualified, and the thickness direction Z is greater than or equal to 25%.

[0050] The thickness of the finished steel plate is 30-60mm.

[0051] In order to more intuitively embody the present application, the embodiments of the present application are further described in combination with the examples. The following examples are only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can obtain the technical solutions within the technical range disclosed by the present application, including simple changes or equivalent replacements, which are all within the protection scope of the present application.

[0052] Embodiments

[0053] The chemical composition of the steel in each embodiment is shown in Table 1, the smelting process parameters are shown in Table 2, the rolling process parameters are shown in Table 3, the post-rolling slow cooling process parameters are shown in Table 4, the heat treatment process parameters are shown in Table 5, and the performance test results of the finished steel plate are shown in Table 6.

[0054] Table 1 Chemical composition of the steel, wt%

[0055]

[0056] Table 2 Smelting process parameters

[0057]

[0058] Table 3 Rolling process parameters

[0059]

[0060] Table 4 Post-rolling slow cooling process parameters

[0061]

[0062] Table 5 Heat treatment process parameters

[0063]

[0064] Table 6 Performance test results of the finished steel plate

[0065]

[0066] As can be seen, the wear-resistant steel plate produced in the embodiments has high hardness, good plasticity and toughness, and qualified cold bending performance, and the Z-direction performance is ≥25%.

[0067] The above description is only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A wear-resistant steel plate of HB450 grade with good Z-directional performance, characterized in that, The chemical composition of the steel is C: 0.18% to 0.22%, Si: 0.60% to 0.80%, Mn: 1.1% to 1.3%, Nb: 0.015% to 0.030%, W: 0.30% to 0.40%, Al: 0.04% to 0.07%, B: 0.0005% to 0.0020%, RE: 0.0015% to 0.0035%, and 1.45% ≤ W+Mn ≤ 1.60%, with the balance being Fe and inevitable impurities; the impurity elements in the steel are controlled as follows: P ≤ 0.010%, S ≤ 0.0015%, [N] ≤ 0.0040%, [H] ≤ 0.00015%, [O] ≤ 0.0010%, the content of residual austenite is 3% to 5%; the surface hardness of the finished steel plate is HB ≥ 450, the tensile strength is ≥ 1250 MPa, the longitudinal impact energy Akv at -40 ℃ is ≥ 30 J, the elongation A is ≥ 12%, the cold bending D at 180° is 4a, and the thickness direction Z is ≥ 25%; the thickness of the finished steel plate is 30 to 60 mm.

2. A method of producing a wear-resistant steel plate of the HB450 grade with good Z-directional properties according to claim 1, characterized in that, The production process flow includes converter smelting, refining, continuous casting, slab heating and slow cooling, slab heating, controlled rolling, controlled cooling, stacking and slow cooling or high temperature tempering, quenching and tempering heat treatment; the following processes are controlled: 1) Refining: LF+RH refining treatment is adopted, and the RH refining vacuum circulation time is ≥ 20 min; after the RH vacuum treatment, RE alloy is added through argon protection wire feeding; 2) Continuous casting: the casting speed of the slab is 0.8 to 1.0 m / min, and the target superheat of the tundish is controlled below 20 ℃; the whole process is protected pouring, and electromagnetic stirring is adopted; the center segregation of the slab is controlled below C1.0 level; 3) Slab heating and slow cooling: the slow cooling heating starting temperature is ≥ 500 ℃, the heating speed is ≤ 50 ℃ / h to 600 to 630 ℃, and after 24 to 36 h of holding, the furnace is slowly cooled to below 300 ℃ for discharging, and air cooling is performed to room temperature; 4) Slab heating: the soaking section temperature is 1150 to 1200 ℃, and the soaking time is 2 to 2.5 h; 5) Controlled rolling: two-stage controlled rolling is adopted, the controlled compression ratio, i.e. the thickness of the slab / the thickness of the finished plate, is ≥ 4; the control roller speed ratio of the upper and lower rollers is 1.1:1 to 1.3:1; the rough rolling opening rolling temperature is ≥ 1000 ℃, and the rough rolling final rolling temperature is ≥ 950 ℃; the fine rolling opening rolling temperature is 850 to 880 ℃, the fine rolling reduction is ≥ 60%, and the fine rolling final rolling temperature is 800 to 850 ℃; 6) Controlled cooling: after rolling, laminar flow cooling is adopted, the opening cooling temperature is ≥ 760 ℃, and the final cooling temperature is 620 to 660 ℃; 7) Stacking and slow cooling or high temperature tempering: when the slab off-line temperature is > 400 ℃, stacking and slow cooling is performed, and the stacking and slow cooling time is ≥ 24 h; when the slab off-line temperature is ≤ 400 ℃, high temperature tempering is performed, the tempering heating temperature is 580 to 630 ℃, and the holding time is 2.5 to 3.5 min / mm; 8) Quenching and tempering heat treatment: the quenching temperature is 880 to 900 ℃, the holding time is 3.0 to 3.5 min / mm; the low temperature stress relief tempering temperature is 220 to 250 ℃, and the holding time is 6 to 8 min / mm.

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