An isotropic high-toughness wear-resistant steel plate and a production method thereof

Abstract

The application belongs to the technical field of steel material, and discloses an isotropic high-strength and high-toughness wear-resistant steel plate, main chemical components and mass percentages thereof include: C 0.31-0.44%, Mn 0.2-1.5%, Si 0.01-0.15%, Cr+Mo 0.65-1.25%, V 0.15-0.43%, Ti 0.012-0.043%, Zr 0.011-0.023%, Ca 0.012-0.031%, Mg 0.011-0.025%, B 0.005-0.011%, RE 0.005-0.009%, P≤0.015%, S≤0.005%, Al≤0.0015%, and the rest is Fe and inevitable impurity elements.The wear-resistant steel plate has good strength and toughness and isotropy, has excellent comprehensive performance, and can effectively reduce production cost, improve production efficiency and has wide applicability.

Description

Technical Field

[0001] This invention belongs to the field of steel materials technology, specifically relating to an isotropic high-strength, high-toughness, and wear-resistant steel plate and its production method. Background Technology

[0002] Due to limitations in processing technology, traditional steel plates exhibit significant differences in properties in all directions. Anisotropic steel plates will show different characteristics depending on the loading direction during loading. Although they have been applied because they show particularly excellent performance in some directions, isotropic materials can improve safety, performance and efficiency. In most application fields, it is still necessary to avoid anisotropy.

[0003] The core application scenarios of wear-resistant steel generally involve multi-directional stress and complex wear patterns, and have extremely high requirements for "long-term wear resistance reliability" and "failure resistance". Isotropic properties help to solve the pain points of traditional wear-resistant steel from three core dimensions: "wear uniformity, mechanical matching, and life stability". The specific advantages are as follows: (1) Improve wear uniformity and avoid local excessive wear failure; (2) Optimize mechanical property matching and enhance impact resistance and fatigue resistance. In addition, wear-resistant steel is not necessarily better the higher the hardness. It is necessary to balance hardness (wear resistance basis) and toughness (impact resistance and crack resistance) and adapt to multi-directional stress. The core of isotropic properties is uniform structure (fine equiaxed crystals + uniformly distributed carbides), which can avoid the contradiction of traditional wear-resistant steel being "hard and brittle in the longitudinal direction and tough and soft in the transverse direction", and achieve a balance of high hardness (HB400~600) + high toughness, which can resist abrasive cutting and withstand impact loads.

[0004] Wear-resistant steel requires processing steps such as cutting, welding, bending, and assembly before use. Anisotropy can lead to processing defects. Isotropic wear-resistant steel has consistent processing properties in all directions, making it particularly suitable for wear-resistant parts with complex shapes (such as irregularly shaped liners and wear-resistant bends). Furthermore, some extreme working conditions place extremely high demands on the isotropy of wear-resistant steel. For example, in low-temperature wear-resistant scenarios (such as cold-region mines and polar engineering machinery), anisotropy exacerbates low-temperature brittleness, while isotropy ensures stable toughness in all directions at low temperatures, preventing low-temperature impact fracture. In high-stress wear-resistant scenarios (such as high-pressure wear-resistant pipelines and crusher hammers), under multi-directional high stress, isotropy can prevent early failure caused by localized stress concentration. In corrosion-wear composite scenarios (such as marine wear-resistant parts and chemical wear-resistant equipment), isotropy can prevent corrosive media from penetrating along the weak points of the structure (such as banded structures), reducing the synergistic failure of "corrosion + wear". Therefore, isotropic high-strength and high-toughness wear-resistant steel is particularly important for achieving the core values ​​of "more uniform wear resistance, more reliable use, longer service life, and lower cost," especially for medium- and high-strength wear-resistant steels (such as NM450, NM500, NM500, etc.) and wear-resistant steels for extreme working conditions.

[0005] Currently, the main approaches to improving the isotropy of steel plates are as follows: (1) Composition design, using low carbon and multi-element microalloying (Nb, V, Ti, B, etc.) to control S and P < 0.02%; (2) Process innovation, using cross / asynchronous rolling to destroy texture + short-time high-temperature heat treatment to homogenize the structure + precise controlled cooling to suppress banded structure; (3) Structure control, obtaining a uniform and fine ferrite + bainite + retained austenite composite structure to eliminate banded and textured structures. However, no isotropy control schemes for wear-resistant steel have been found yet, and due to the special characteristics of the composition, process, structure, and properties of wear-resistant steel, the above-mentioned existing improved processes are not applicable to improving the isotropy of wear-resistant steel.

[0006] Therefore, designing and developing an isotropic high-strength / hardness, high-toughness wear-resistant steel can achieve more uniform wear resistance, more reliable use, longer service life, lower cost, and better suitability for extreme working conditions, resulting in very high economic benefits. Summary of the Invention

[0007] The main objective of this invention is to address the series of failure problems caused by anisotropy in existing wear-resistant steels under multi-directional stress and complex wear conditions, such as localized excessive wear-through, low-temperature brittle cracking, localized stress concentration, accelerated fatigue crack propagation, and poor processing adaptability. It also addresses the shortcomings of existing isotropic improvement processes that cannot be directly applied to the production of wear-resistant steel. The invention provides an isotropic high-strength and high-toughness wear-resistant steel plate and its production method, which can balance excellent strength, toughness, and impact resistance, and has wide applicability.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An isotropic high-strength and high-toughness wear-resistant steel plate, the main chemical composition and their mass percentages include: C 0.31-0.44%, Mn 0.2-1.5%, Si 0.01-0.15%, Cr+Mo 0.65-1.25%, V 0.15-0.43%, Ti 0.012-0.043%, Zr 0.011-0.023%, Ca 0.012-0.031%, Mg 0.011-0.025%, B 0.005-0.011%, RE 0.005-0.009%, P≤0.015%, S≤0.005%, Al≤0.0015%, with the remainder being Fe and unavoidable impurity elements.

[0009] In the above scheme, the RE can be one or more of La, Ce, Pr, Nd, Y, etc.

[0010] Furthermore, the Cr content is 0.25-0.72%.

[0011] In the above scheme, the main metallographic structure of the isotropic high-strength and high-toughness wear-resistant steel plate is lath martensite, containing a small amount of retained austenite, with no obvious orientation, and the proportion of original austenite grains with an aspect ratio ≤1.11 ≥92%; the average diameter of the inclusions is 0.13-0.55µm, and the number of inclusions per unit area is 8500-11000 / mm. 2 .

[0012] Furthermore, the inclusions include one or more of the following oxides: Mn, Si, Ti, Zr, Ca, Mg, RE, etc., which are dispersedly distributed, as well as composite particulate inclusions with oxides as the core and sulfur / nitrogen compounds (sulfur compounds and / or nitrogen compounds) as the outer layer.

[0013] In the above scheme, the isotropic high strength and toughness wear-resistant steel plate has a thickness of 30-50mm, hardness ≥HB450, tensile strength ≥1450MPa, elongation A ≥9%, impact energy at -20℃ ≥85J, and performance differences in the longitudinal, transverse, and 45° directions ≤8%.

[0014] This invention also provides a method for producing the above-mentioned isotropic high-strength and high-toughness wear-resistant steel plate, the core innovative and improved processes of which include the following: (1) Smelting process: control of inclusion size and modification treatment, change the morphology of inclusions in wear-resistant steel, transform the B-type long strip MnS inclusions into dispersed granular composite inclusions with oxides as the core and sulfur / nitrides as the strata, and control the type and quantity of oxides. (2) Continuous casting process: further control the size of inclusions and improve the casting grains; The specific implementation steps include the following: 1) Converter smelting; Before tapping from the converter, the oxygen content is controlled at 0.020-0.025%. When the tapping yield reaches 65-71%, ferrosilicon and ferromanganese are added at a ratio of Mn:Si = 0.2-0.9 for pre-deoxidation, so that the MnO:SiO2 (mass ratio) reaches the target range of 0.015-0.045 and the oxygen content reaches the target range of 0.0075-0.0085%. Appropriate amounts of other alloys (except Ti, Ca, Mg, RE, and B) are added according to the steel composition requirements. 2) Perform Ar-LF-RH treatment sequentially; key control requirements include the following: Purge with argon for 8-20 minutes to allow the inclusions to float to the surface and the composition to become uniform. LF treatment; LF fine-tuning of composition and regulation of molten steel temperature to 1580-1610℃; RH vacuum treatment; In the early stage of RH vacuum treatment (vacuuming to 100-200Pa), add the alloy according to Ti:Zr=2-2.5 and fine-tune the alloy composition until Ti reaches the target range; In the later stage of RH vacuum treatment (when the vacuum level rises to 200-500Pa), a pre-made Ca-Mg-RE-B composite wire is fed in, and the feeding amount is controlled according to the requirement of Ca:S=5-10. Then, argon blowing and stirring are performed (3-6 minutes). 3) During the continuous casting stage, the cooling rate of the billet is controlled at 300-450℃ / min until it is completely solidified, and then it is cut into blocks and stacked to cool slowly to room temperature; 4) Control rolling and control cooling; heat the cooled billet, use cross rolling in the austenite recrystallization zone, adjust the initial rolling temperature, deformation rate, pass reduction rate and rolling thickness, cool to the non-recrystallization zone of austenite and roll to the finished thickness, the final rolling temperature is ≥860℃, and then quickly cool to room temperature; 5) Quenching and tempering heat treatment; The steel plate cooled in step 4) is heated, water-quenched to room temperature, and then tempered at low temperature to obtain the isotropic high strength and toughness wear-resistant steel plate.

[0015] Furthermore, in the RH vacuum treatment process, the intermediate stage between the early and late stages is a high vacuum; the vacuum condition is ≤67Pa.

[0016] In the above scheme, the mass ratio of the effective components Ca, Mg, B and RE in the Ca-Mg-RE-B composite line is (2.8-3.2): (1.8-2.2): (0.8-1.2):1.

[0017] Furthermore, in the Ca-Mg-RE-B composite line, RE is one or more of La, Ce, Pr, Nd, and Y.

[0018] In the above scheme, the Ca-Mg-RE-B composite line is fed in at a speed of 2-4 m / s.

[0019] Furthermore, the diameter of the Ca-Mg-RE-B composite wire is 9-14 mm.

[0020] In the above scheme, the thickness of the billet obtained in step 3) is 220-300mm.

[0021] In the above scheme, in step 4), the billet heating temperature is 1200-1230℃, and the holding time is 30-55min.

[0022] In the above scheme, in step 4), the initial rolling temperature is controlled at 1080-1120℃, and the deformation rate is 2-4 s. -1 The pass reduction rate is 20-25%; the rapid cooling rate is 12-18℃ / s.

[0023] In the above scheme, in step 4), the thickness after rolling is 100-120mm.

[0024] In the above scheme, during the cross rolling process, the horizontal widening rolling is performed first, and then the longitudinal rolling is performed after the width is appropriate.

[0025] In the above scheme, in step 5), the steel plate is heated to 860-880℃ and held for 10-30 minutes.

[0026] In the above scheme, the temperature used in the low-temperature tempering step is 180-220℃, and the tempering time is 180-220min.

[0027] The technical principles of this invention include the following: In the steel composition designed in this invention, C is the most effective interstitial solid solution strengthening element, which helps to significantly improve the hardness and wear resistance of the martensitic matrix; Mn improves strength and hardenability; the combined addition of Cr and Mo improves the hardenability of the steel, which is beneficial for obtaining lath martensite structure and can refine grains, thereby improving strength and toughness; V and Ti are strong carbide forming elements, which have the effects of grain refinement strengthening, precipitation strengthening and solid solution strengthening; S and P in the steel are harmful impurity elements, and the lower the content of P and S, the better; elements such as Si, Zr, Ca, Mg, B, and RE are elements remaining in the inclusion treatment process, which have certain beneficial effects on the properties of wear-resistant steel (such as B improving hardenability, and Zr and RE refining grains), but their main role is in the modification of inclusions; further, the improvement principle of the process includes the following: 1) Improvement of smelting process; 1-1) Converter smelting ensures that the P content meets the target requirements. Before tapping from the converter, the O content is controlled at 0.020-0.025%. This high-oxidizing atmosphere reduces the residual Al element in the molten steel to below 0.0015%. Although the steel system described in this invention requires high-melting-point ultrafine oxide inclusions to become the core of composite inclusions and the heterogeneous nucleation core of intracrystalline ferrite, Al oxides are generally pure corundum, and sulfur / nitrogen compounds are difficult to deposit on them, which is not conducive to changing the morphology of MnS inclusions, and thus not conducive to the formation of intracrystalline ferrite. At the same time, the increase in aluminum concentration can cause unfavorable structures to form in the steel, such as promoting the formation of WF phases in the steel, which reduces the toughness of the steel. When the Al content is less than 0.0015%, the activity of Al2O3 is much lower than that of Ti2O3 when Ti alloy is added later, thus avoiding the formation of brittle oxide Al2O3. 1-2) In the later stage of steel tapping (if the steel tapping volume reaches 2 / 3), ferrosilicon and ferromanganese are added at Mn:Si = 0.2-0.9 for early deoxidation, so that MnO:SiO2 reaches the target range of 0.015-0.045. This process can effectively prevent the precipitation of MnS. The composite oxide of silicon and manganese, MnO-SiO2, has a high sulfur capacity, which is conducive to the precipitation of MnS on the surface of the composite oxide, promoting the formation of manganese-poor zone, and thus conducive to the formation of intracrystalline ferrite. After Si-Mn composite deoxidation, the O content reaches the target range of 0.0075-0.0085%. At this time, an appropriate amount of other alloys are added according to the steel composition requirements, which ensures the alloy yield and prepares the conditions for the subsequent process to continue to form oxide cores.

[0028] 2) Improvement of continuous casting process; Based on the above-mentioned smelting control methods, Ar-LF-RH treatment is further performed sequentially, with the specific steps including: 2-1) In the early stage of RH vacuum treatment, add the alloy according to Ti:Zr=2-2.5 and fine-tune the alloy composition until Ti reaches the target range (0.012-0.043%), forming the main oxide core Ti2O3 (Ti oxide can serve as the nucleation core of intracrystalline ferrite, with cation vacancies, which can not only further precipitate MnS on the surface of Ti2O3 particles, but also allow nitride particles to preferentially nucleate on its surface (N is an unavoidable gaseous element in smelting). After the precipitation of MnS particles, a Mn-depleted layer is formed around Ti2O3, and the Ti2O3 adsorbed with nitrides can promote the formation of intracrystalline ferrite); the composite deoxidation process based on Zr and Ti is more conducive to the fine and uniform distribution of oxide particles in steel, enhancing the role of single Ti2O3, but the Zr content cannot exceed the limited Ti / Zr ratio (too much Zr will generate oxides with too high a specific gravity, which will sink during the refining process, which is not conducive to the uniform dispersion of oxides in steel).

[0029] 2-1) In the later stage of RH vacuum treatment, a prefabricated Ca-Mg-RE-B composite wire is fed into the ladle. The feeding amount is controlled according to the requirement of Ca:S=5-10, followed by argon blowing and stirring for 3-6 minutes. Feeding the prefabricated Ca-Mg-RE-B composite wire can promote the further formation of fine oxides and further modify the inclusions. The preferred feeding speed of the Ca-Mg-RE-B wire is 2-4 m / s to promote the full dissolution of the Ca-Mg-RE-B wire into the molten steel for modification and to achieve a higher yield. The feeding amount is adjusted to ensure that the Ca:S ratio in the molten steel is 5-10 after feeding to obtain the best effect on inclusion modification, transforming long strip-shaped and chain-shaped MnS inclusions into spherical composite inclusions, which can effectively prevent the inclusions from oriented along the rolling direction.

[0030] Furthermore, the components in the Ca-Mg-RE-B line and their mechanisms of action include: Mg+Ca: Adding Mg for deoxidation allows for more stable control of oxygen content, resulting in more stable addition amounts and inclusion quantities. The Mg and Ca composites form finer particulate inclusions. These finer inclusions effectively pinnate grain boundary movement, inhibiting grain growth during solidification and significantly suppressing austenite grain growth in the heat-affected zone of welded steel plates.

[0031] RE (Rare Earth Elements): RE is mainly used to further control the morphology of MnS inclusions, reduce phosphorus segregation, and reduce carbide precipitation. RE can also form high-melting-point intermetallic compounds with low-melting-point elements such as tin, lead, phosphorus, arsenic, and antimony in steel, thereby eliminating the harmful effects of these impurity elements in the steel and purifying the steel quality. RE reacts with oxygen and sulfur to generate high-melting-point rare earth oxides or rare earth sulfur oxides, which can act as heterogeneous nuclei, promote the formation of intracrystalline ferrite, improve the columnar crystal structure during crystallization, and have a good grain-refining effect on the billet. The metamorphic effect of rare earth elements on oxides transforms Al2O3 into RE1O3 and RE2O2S, which have lower hardness and higher coefficients of thermal expansion, reducing the harmful effects of Al2O3 on performance (although the Al content is strictly controlled, a small amount is inevitably present). However, RE oxides have a relatively high specific gravity, which is not conducive to the uniform dispersion of oxides in steel; therefore, the amount added should be much less than that of Ca. B: Element B plays a decisive role in the average diameter and distribution of inclusions. The addition of B in the Ca-Mg-RE-B line of this invention can reduce the average diameter of inclusions in steel and increase the number of inclusions per unit area. Element B has a small atomic radius and a fast diffusion rate in molten steel. When Ca, Mg, RE react with O and S in molten steel to generate rare earth oxides, calcium and magnesium oxides, and other inclusions, B atoms adsorb onto the critical nucleus surface of these inclusions, providing a large number of additional nucleation sites, thus reducing the average diameter of inclusions and significantly increasing the number of inclusions per unit area. Inclusions grow in molten steel through diffusion aggregation or collision aggregation, and the introduced B element can improve the chemical stability of inclusions, blocking their aggregation and growth through interfacial adsorption and other effects. For spherical inclusions generated by Ca-Mg-RE modification, the adsorption of B element can further stabilize their spherical morphology, preventing the inclusions from being stretched into strips or chains during rolling. In addition, element B has an interfacial segregation effect, which will spontaneously accumulate at the interface between inclusions and the steel matrix, thereby enhancing the bonding force between inclusions and the matrix.

[0032] After the wire feeding is completed, argon is blown and stirred for a certain period of time, such as 3-6 minutes, depending on the temperature of the molten steel. Argon blowing and stirring can cause some oxide inclusions to aggregate, grow and float to the surface, which is beneficial to further improve the comprehensive mechanical properties of the steel.

[0033] During the continuous casting stage, the billet cooling rate is controlled at 300-450℃ / min until complete solidification. It is then cut into blocks, stacked, and slowly cooled to room temperature, with a billet thickness of 220-300mm. The primary purpose of rapid cooling at 300-450℃ / min is to maintain the high-energy and metastable state of inclusions, making them less prone to dissolution or coarsening in subsequent high-temperature processes. Instead, they continue to serve as heterogeneous nucleation sites for austenite grain refinement. Secondly, it promotes uniform dispersion and anchoring of inclusions at grain boundaries during solidification, preventing significant agglomeration areas and hindering their growth. This allows them to continue inhibiting grain growth and serving as nucleation sites in subsequent processes. Furthermore, it prevents the formation of columnar crystals in the billet (columnar crystals grow along the solidification direction, easily leading to directional mechanical properties), promotes the formation of equiaxed crystals (equiaxed crystals have no obvious orientation, resulting in more uniform properties), and effectively suppresses central segregation and carbide precipitation, reducing compositional inhomogeneity. Cooling rates exceeding 450°C / min pose a risk of cracking or even breakage.

[0034] By combining the above-mentioned improved smelting-continuous casting process, columnar crystals are effectively controlled, and the as-cast grains are mainly fine, uniform, and equiaxed. With the as-cast grains effectively controlled, the target performance requirements can be achieved without subsequent complex rolling and heat treatment processes.

[0035] 4) Controlled rolling and controlled cooling; Preferably, the billet is heated to 1200-1230℃ and held at that temperature for an appropriate period. Cross-rolling is used in the austenite recrystallization zone, with the initial rolling temperature controlled at 1080-1120℃ and the deformation rate at 2-4 s. -1 The reduction rate per pass is 20-25%, and the rolling thickness is 100-120 mm. Appropriate billet heating temperature and cross-rolling, along with controlled rolling temperature and deformation rate, prevent abnormal growth and orientation of the equiaxed grains obtained from the initial smelting-continuous casting process during heating and rolling. After cooling to the non-recrystallized austenite region, roll to the finished thickness. The final rolling temperature should be ≥860℃, followed by rapid cooling to room temperature. Controlling the final rolling temperature and cooling rate during this stage is crucial to prevent two-phase rolling from causing microstructural abnormalities.

[0036] During the quenching stage, the steel plate is heated to 860-880℃ and held for 10-30 minutes, then water-quenched to room temperature. Appropriate heating temperature and holding time result in uniform, equiaxed austenite grains, and after quenching, a martensite structure without obvious orientation is obtained. Low-temperature tempering is then performed, with the tempering temperature controlled at 180-220℃ and the tempering time controlled at 180-220 minutes. This eliminates the stress generated during quenching and adjusts the martensite hardness to achieve the optimal balance of strength and toughness.

[0037] Through the above rolling-heat treatment process, the average diameter and number of inclusions per unit area of ​​the finished steel plate can be controlled. The original austenite grains are fine, uniform, and equiaxed, and the martensite structure has no obvious orientation, ensuring the strength, toughness, and isotropy of the wear-resistant steel. The oxides also include oxides such as Ti, Zr, Ca, Mg, and RE, and form a diffusely distributed composite granular inclusion with sulfur / nitrogen compounds on the outer layer, with the oxide inclusions as the core.

[0038] Compared with the prior art, the beneficial effects of the present invention include: (1) The smelting process controls the type, quantity, size and distribution of inclusions, giving full play to the beneficial role of inclusion nucleation and thus refining the as-cast grains; further, the cooling rate of the continuous casting process is combined to effectively control the growth of inclusions, and inhibit columnar crystals to promote the formation of equiaxed crystals (equiaxed, fine and uniform as-cast grains), ensuring the strength, toughness and homogeneity of wear-resistant steel, avoiding the need to improve performance through complex rolling and heat treatment processes, and effectively reducing costs and improving production efficiency while improving the performance of steel; (2) The S content in the steel system described in this invention does not need to be treated to an excessively low level, which can greatly reduce the production cost of wear-resistant steel, while shortening the difficulty of secondary desulfurization of LF and further improving the steel production efficiency. (3) It has both good strength and toughness and anisotropy, and obtains wear-resistant steel with excellent comprehensive performance; the inclusions in the steel plate are fine granular composite inclusions. These inclusions can act as nucleation cores, promote intragranular nucleation, and make the grains fine, uniform and equiaxed, which lays the foundation for the strength, toughness and isotropy of the steel plate. The strength and toughness (especially the impact toughness) are greatly improved. The difference in longitudinal and transverse mechanical properties of the steel plate can be controlled within 8%, which greatly improves the wear resistance of the wear-resistant steel and greatly reduces the defect rate during the processing. Attached Figure Description

[0039] Figure 1 Comparison of the morphology of wear-resistant steel inclusions before and after implementing the process described in this invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0041] The specific production steps of the high-strength, high-toughness, and wear-resistant steel plates described in Examples 1-6 include the following steps: 1) Before tapping steel from the converter, control the O content to 0.020-0.025%; when the steel reaches 2 / 3 (67%), add ferrosilicon and ferromanganese (meeting national standards) at a ratio of Mn:Si=0.2-0.9 for pre-deoxidation, so that the MnO:SiO2 (mass ratio) reaches the target range of 0.015-0.045 and the O content reaches the target range of 0.0075-0.0085%, and add appropriate amounts of other alloys according to the steel composition requirements (see Table 2); 2) Perform Ar-LF-RH (RH vacuum treatment) treatment sequentially. The key control steps are as follows: Purge with argon for 8-20 minutes to allow the inclusions to float to the surface and the composition to become uniform. LF treatment; LF fine-tuning of composition and regulation of molten steel temperature to 1580-1610℃; RH vacuum treatment: In the early stage of RH vacuum treatment (vacuum stage of 100-200Pa), add alloy according to Ti:Zr=2-2.5 and fine-tune the alloy composition until Ti reaches the target range; In the later stage of RH vacuum treatment (recovering to a vacuum level of 200-500Pa), a prefabricated Ca-Mg-RE-B composite wire is fed into the ladle at a speed of 2-4m / s using a wire feeder. The mass ratio of its effective components is Ca:Mg:RE:B = 3:2:1:1. The feeding amount is controlled according to the requirement of Ca:S = 5-10. Then, argon blowing and stirring are performed for 3-6 minutes. 3) During the continuous casting stage, the cooling rate of the billet is controlled at 300-450℃ / min until it is completely solidified. It is then cut into blocks, stacked, and slowly cooled to room temperature. The average thickness of the billet is 250mm. 4) Control rolling and cooling: Heat the billet to 1200-1230℃ and hold for 30-55 minutes. During the austenite recrystallization stage, use a cross-rolling method (2-3 passes of transverse rolling followed by longitudinal rolling, depending on the billet size and final plate size). The initial rolling temperature should be controlled at 1080-1120℃, and the deformation rate at 2-4 s. -1 The reduction rate per pass is 20-25%, and the rolling is carried out to a thickness of 100-120mm. After cooling to the non-recrystallized austenite region, the rolling continues to the finished thickness. The final rolling temperature is required to be ≥860℃, and the rolling is carried out rapidly (12-18℃ / s) to room temperature. 5) Quenching and tempering heat treatment: heat the steel plate to 860-880℃ and hold for 10-30 minutes. After taking it out of the furnace, water cool and quench it to room temperature. Then, perform low-temperature tempering. The tempering temperature is controlled at 180-220℃ and the tempering time is controlled at 180-220 minutes. 6) Obtain isotropic high-strength and high-toughness wear-resistant steel plates for later use.

[0042] The specific core process parameters of the embodiments of the present invention are described in detail below: The specific core process parameters for smelting-continuous casting in each embodiment are shown in Table 1, the chemical composition of the cast billet is shown in Table 2, and the specific core process parameters for rolling-heat treatment in each embodiment are shown in Table 3.

[0043] Table 1. Core process parameters for smelting-continuous casting in the examples.

[0044] Chemical composition and inclusion analysis were performed on cast billet samples. The chemical composition is shown in Table 2. The MnO:SiO2 content in the inclusions was within the target range of 0.015-0.045. The oxides also included Ti, Zr, Ca, Mg, RE, etc., forming a diffusely distributed composite granular inclusion with sulfur / nitrogen compounds as the outer layer, centered around the oxide inclusions. Figure 1 As shown, this type of inclusion effectively controls the grain morphology in the cast state. Combined with the rolling-heat treatment process (see Table 3), it ensures the mechanical properties and isotropy of the wear-resistant steel of this patent (see Table 4).

[0045] Table 2. Composition of the Examples and Comparative Examples (percentage by mass %)

[0046] Table 3. Core rolling-heat treatment process parameters used in the examples and comparative examples

[0047] The mechanical properties and microstructure test results of the wear-resistant steels obtained in each embodiment and comparative example are shown in Table 4.

[0048] Table 4 Characterization results of wear-resistant steels obtained in each embodiment and comparative example

[0049] As can be seen from point 3, the wear-resistant steel plate of the present invention has a thickness of 30mm-50mm, a hardness ≥HB450, a tensile strength ≥1450MPa, an elongation A ≥9%, an impact energy of -20℃ ≥85J, and the performance difference in the longitudinal, transverse, and 45° directions is ≤8%.

[0050] The embodiments described above are merely illustrative of the core concept of the present invention and do not constitute a limitation on the technical solutions of the present invention. Those skilled in the art can make various changes or optimizations to its form, structure, parameters, or process steps without departing from the basic design concept of the present invention, and such changes, optimizations, or equivalent substitutions should all fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. An isotropic, high-strength, high-toughness, wear-resistant steel plate, characterized in that, The main chemical components and their mass percentages include: C 0.31-0.44%, Mn 0.2-1.5%, Si 0.01-0.15%, Cr+Mo 0.65-1.25%, V 0.15-0.43%, Ti 0.012-0.043%, Zr 0.011-0.023%, Ca 0.012-0.031%, Mg 0.011-0.025%, B 0.005-0.011%, RE 0.005-0.009%, P≤0.015%, S≤0.005%, Al≤0.0015%, with the remainder being Fe and unavoidable impurity elements.

2. The high-strength, high-toughness, wear-resistant steel plate according to claim 1, characterized in that, The RE is one or more of La, Ce, Pr, Nd, and Y.

3. The high-strength, high-toughness, wear-resistant steel plate according to claim 1, characterized in that, The isotropic high-strength and high-toughness wear-resistant steel plate has a main metallographic structure of lath martensite with no obvious orientation, and the proportion of original austenite grains with an aspect ratio ≤1.11 is ≥92%; the average diameter of the inclusions is 0.13-0.55µm, and the number of inclusions per unit area is 8500-11000 / mm. 2 .

4. The high-strength, high-toughness, wear-resistant steel plate according to claim 1, characterized in that, Its thickness is 30-50mm; hardness ≥HB450, tensile strength ≥1450MPa, elongation A ≥9%, impact energy at -20℃ ≥85J; and the difference in mechanical properties in the longitudinal, transverse, and 45° directions is ≤8%.

5. A method for producing the isotropic high-strength, high-toughness, wear-resistant steel plate according to any one of claims 1 to 4, characterized in that, Includes the following steps 1) Converter smelting Before tapping from the converter, the O content is controlled at 0.020-0.025%; when the tapping amount reaches 65-71%, ferrosilicon and ferromanganese are added at a ratio of Mn:Si=0.2-0.9 for pre-deoxidation, so that the MnO:SiO2 reaches the target range of 0.015-0.045 and the O content reaches the target range of 0.0075-0.0085%, and other alloys are added according to the steel composition requirements. 2) Perform Ar-LF-RH treatment sequentially. Key control requirements include the following: Argon blowing; LF treatment, adjusting the molten steel temperature to 1580-1610℃; RH vacuum treatment; In the early stage of RH vacuum treatment, alloys were added according to the ratio of Ti:Zr=2-2.5 and the alloy composition was fine-tuned until Ti reached the target range; In the later stage of RH vacuum treatment, a prefabricated Ca-Mg-RE-B composite wire is fed in, and the feeding amount is controlled according to the requirement of Ca:S=5-10, and then argon blowing and stirring are performed. 3) Continuous casting Control the cooling rate of the cast billet to 300-450℃ / min until it is completely solidified, cut it into blocks, stack them, and slowly cool it to room temperature; 4) Controlled rolling and controlled cooling The cooled billet is heated, and the austenite recrystallization zone is rolled using a cross rolling method. The initial rolling temperature, deformation rate, pass reduction rate and rolling thickness are controlled. The billet is cooled to the non-recrystallization zone of austenite and rolled to the finished thickness. The final rolling temperature is ≥860℃, and then it is rapidly cooled to room temperature. 5) Quenching and tempering heat treatment The cooled steel plate is heated, water-quenched to room temperature, and then tempered at low temperature to obtain the isotropic high-strength, high-toughness, and wear-resistant steel plate.

6. The production method according to claim 5, characterized in that, In the RH vacuum treatment process, the initial stage of RH vacuum treatment involves evacuating to a vacuum level of 100-200 Pa; the later stage involves restoring the vacuum level to 200-500 Pa; and the period between the initial and later stages is a high vacuum stage with a vacuum condition ≤67 Pa.

7. The production method according to claim 5, characterized in that, In the Ca-Mg-RE-B composite line, the mass ratio of the effective components Ca, Mg, B, and RE is (2.8-3.2):(1.8-2.2):(0.8-1.2):

1.

8. The production method according to claim 5, characterized in that, The thickness of the cast billet obtained in step 3) is 220-300mm; in step 4), the thickness after rolling is 100-120mm.

9. The production method according to claim 5, characterized in that, In step 4), the initial rolling temperature is controlled at 1080-1120℃, and the deformation rate is 2-4 s. -1 The pass reduction rate is 20-25%; the rapid cooling rate is 12-18℃ / s.

10. The production method according to claim 5, characterized in that, In step 5), the steel plate is heated to 860-880℃ and held for 10-30 minutes; the low-temperature tempering step uses a temperature of 180-220℃ and a tempering time of 180-220 minutes.

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