Boron-free low-residual-stress bainite wear-resistant steel and preparation method thereof

Abstract

The invention relates to boron-free low-residual-stress bainite wear-resistant steel and a preparation method, and belongs to the technical field of steel plate manufacturing. The wear-resistant steel comprises the following chemical components in percentage by mass: 0.20%-0.40% of C, 1.80%-2.20% of Mn, 1.40%-1.60% of Si, 0.90%-1.20% of Cr, 0.40%-0.70% of Al, 0.03%-0.06% of Ti, 0.05%-0.12% of V, 0.10%-0.50% of Mo, less than or equal to 0.01% of P, less than or equal to 0.006% of S, 0.010%-0.018% of N and a matrix element Fe, wherein the carbon equivalent is 0.58%-0.75%. Through the design of boron-free alloy components, boron element addition is canceled, the temperature control quenching process is combined to precisely regulate and control the bainite phase change path, and the medium-temperature tempering treatment is assisted, so that the residual stress is remarkably inhibited, and meanwhile, the synergistic improvement of high hardness and high toughness of the bainite wear-resistant steel is realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of steel plate manufacturing, in particular to a boron-free low-residual-stress bainite wear-resistant steel and a preparation method thereof. BACKGROUND

[0002] Traditional martensitic wear-resistant steels rely on low-temperature tempering (usually below 300 DEG C) to circumvent temper brittleness and maintain toughness, but inevitably lead to excessive residual stress, causing cutting deformation and cracking risks; while bainite wear-resistant steels can relieve stress problems through higher tempering temperatures, but the conventional boron-containing design induces severe embrittlement in the range of 300 DEG C to 450 DEG C. The addition of boron element improves hardenability, but significantly hinders the bainite phase transition process and exacerbates the segregation of bainite at grain boundaries, and the isothermal quenching process has poor adaptability to the production line. On the other hand, the bainite steel of high-manganese-silicon-chromium system itself has hardenability to inhibit high-temperature transformation without relying on boron element, but direct quenching to room temperature not only causes insufficient bainite transformation and weakens grain segmentation effect, but also damages performance due to residual stress accumulation and coarse martensite formation.

[0003] Therefore, it is urgent to develop a boron-free alloy design and a temperature-controlled quenching process that adapts to the production line, to circumvent boron embrittlement and precisely control the transformation of complex phase structure, to realize the industrialized production of bainite wear-resistant steel with high toughness and low stress. SUMMARY

[0004] The application provides a boron-free low-residual-stress bainite wear-resistant steel and a preparation method thereof, to solve the technical problem of how to circumvent temper brittleness in a boron-free system and simultaneously realize low stress, stable structure and strength-toughness optimization. In a first aspect, the application provides a boron-free low-residual-stress bainite wear-resistant steel, the chemical composition of the wear-resistant steel includes, in mass fraction: C: 0.20% to 0.40%, Mn: 1.80% to 2.20%, Si: 1.40% to 1.60%, Cr: 0.90% to 1.20%, Al: 0.40% to 0.70%, Ti: 0.03% to 0.06%, V: 0.05% to 0.12%, Mo: 0.10% to 0.50%, P≤0.01%, S≤0.006%, N: 0.010% to 0.018%, and base element Fe; wherein the carbon equivalent is 0.58% to 0.75%.

[0005] Optionally, the wear-resistant steel satisfies at least one of the following properties: yield strength is 1299 MPa to 1379 MPa, tensile strength is ≥1400 MPa, elongation is 10% to 25%, and impact energy is ≥82 J.

[0006] In a second aspect, the application provides a preparation method of the wear-resistant steel in the first aspect, the method includes: The slab has the following chemical composition: C: 0.20%-0.40%, Mn: 1.80%-2.20%, Si: 1.40%-1.60%, Cr: 0.90%-1.20%, Al: 0.40%-0.70%, Ti: 0.03%-0.06%, V: 0.05%-0.12%, Mo: 0.10%-0.50%, P≤0.01%, S≤0.006%, N: 0.010%-0.018%, and base element Fe; The slab is sequentially subjected to heating, rough rolling and finish rolling to obtain a steel plate. The steel plate is sequentially subjected to air cooling, straightening, offline temperature-controlled quenching and medium-temperature tempering to obtain a wear-resistant steel.

[0007] Optionally, the heating temperature is 1130-1160 DEG C, and the heating time coefficient is 1-2 min / mm.

[0008] Optionally, the rough rolling adopts a low-speed large reduction process, and the final pass reduction rate of the rough rolling is ≥15%.

[0009] Optionally, the finish rolling has a roughing temperature of 850-950 DEG C, and a finish rolling temperature of 800-850 DEG C.

[0010] Optionally, the thickness of the steel plate is 6-25 mm.

[0011] Optionally, the air cooling adopts stack slow cooling, the stack has a starting temperature of 400-650 DEG C, and the slow cooling time of the stack is 24-72 h.

[0012] Optionally, the straightening adopts warm straightening and cold straightening.

[0013] Optionally, the warm straightening has a temperature of 100-400 DEG C, and a reduction of 10-20%.

[0014] Optionally, the cold straightening has a temperature of 20-200 DEG C, and a reduction of 5-10%.

[0015] Optionally, the offline temperature-controlled quenching includes austenitizing heating, first-stage fast cooling, air cooling retention and second-stage fast cooling.

[0016] Optionally, the austenitizing heating temperature is 880-930 DEG C.

[0017] Optionally, the first-stage fast cooling has a cooling rate of 20-35 DEG C / s, and a termination temperature of 320-350 DEG C.

[0018] Optionally, the air-cooled residence time is 20s to 60s.

[0019] Optionally, the cooling rate of the second stage rapid cooling is 10℃ / s to 25℃ / s, and the termination temperature of the second stage rapid cooling is 20℃ to 120℃.

[0020] Optionally, the temperature of the intermediate-temperature tempering is 300℃~350℃, and the tempering time is 20min~90min.

[0021] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a boron-free, low residual stress bainitic wear-resistant steel. The chemical composition of the wear-resistant steel, by mass fraction, includes: C: 0.20%~0.40%, Mn: 1.80%~2.20%, Si: 1.40%~1.60%, Cr: 0.90%~1.20%, Al: 0.40%~0.70%, Ti: 0.03%~0.06%, V: 0.05%~0.12%, Mo: 0.10%~0.50%, P≤0.01%, S≤0.006%, N: 0.010%~0.018%, and the base element Fe; wherein the carbon equivalent is 0.58%~0.75%. Through innovative boron-free composition design and a combined process of temperature-controlled quenching and medium-temperature tempering, the fine control of the bainitic / martensite dual-phase structure was achieved: the temperature-controlled quenching stage precisely induces the division of fine bainitic laths into grains, avoiding coarse structural defects; combined with medium-temperature tempering, stress reduction and toughness enhancement are achieved simultaneously, ultimately obtaining bainitic wear-resistant steel with high comprehensive performance and low residual stress. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart illustrating a boron-free, low residual stress bainitic wear-resistant steel and its preparation method, as described in this application. Figure 2 These are microstructure diagrams corresponding to different processes in Example 1 and the comparative example of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges between 1 and 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including" and "contains" used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship. "And / or" indicates that multiple situations can exist individually or simultaneously. Expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0027] In a first aspect, embodiments of this application provide a boron-free, low residual stress bainitic wear-resistant steel. The chemical composition of the wear-resistant steel, by mass fraction, includes: C: 0.20%~0.40%, Mn: 1.80%~2.20%, Si: 1.40%~1.60%, Cr: 0.90%~1.20%, Al: 0.40%~0.70%, Ti: 0.03%~0.06%, V: 0.05%~0.12%, Mo: 0.10%~0.50%, P≤0.01%, S≤0.006%, N: 0.010%~0.018%, and the base element Fe; wherein the carbon equivalent is 0.58%~0.75%.

[0028] The positive effects of limiting the mass fraction of carbon (C) to 0.20%~0.40% include: optimizing toughness and suppressing the brittleness of high-carbon martensite and the accumulation of residual stress, while ensuring the hardness of the bainitic / martensite multiphase structure, thus achieving a synergistic improvement in strength and toughness. For example, the mass fraction of C can be 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, etc.

[0029] The positive effects of limiting the mass fraction of Mn to 1.80%~2.20% include: leveraging the solid solution strengthening effect of Mn to improve steel strength; fully utilizing the dragging effect of Mn at grain boundaries to promote bainite formation; compensating for the loss of hardenability caused by the removal of boron; and lowering the bainite transformation initiation temperature. For example, the mass fraction of Mn can be 1.80%, 1.90%, 2.00%, 2.10%, 2.20%, etc.

[0030] The positive effects of limiting the Si mass fraction to 1.40%~1.60% include: improving matrix strength through solid solution strengthening, suppressing carbide precipitation to stabilize residual austenite, optimizing bainite transformation kinetics and controlling the risk of high-temperature oxidation, thus achieving synergistic regulation of strength, toughness, and process stability. For example, the Si mass fraction can be 1.40%, 1.45%, 1.50%, 1.55%, 1.60%, etc.

[0031] The positive effects of limiting the Cr mass fraction to 0.90%~1.20% include: improving the hardenability of wear-resistant steel, playing a role in solid solution strengthening, and thus improving the strength and hardness of the steel. For example, the Cr mass fraction can be 0.90%, 0.95%, 1.00%, 1.05%, 1.10%, 1.15%, 1.20%, etc.

[0032] The positive effects of limiting the Al mass fraction to 0.40%~0.70% include: optimizing metallurgical purity through deoxidation and nitrogen fixation, suppressing the coarsening of the original austenite grains, synergistically inhibiting carbide precipitation to stabilize residual austenite, and delaying bainite phase transformation to achieve microstructure refinement, while balancing strength, toughness, and continuous casting process stability. For example, the Al mass fraction can be 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, etc.

[0033] The positive effects of limiting the Ti mass fraction to 0.03%~0.06% include: forming high-melting-point TiN through microalloying to refine the original austenite grains, synergistically inducing intragranular ferrite to improve toughness, and simultaneously fixing free nitrogen to suppress aging embrittlement, thus achieving synergistic optimization of grain refinement and toughness. For example, the Ti mass fraction can be 0.03%, 0.04%, 0.05%, 0.06%, etc.

[0034] The positive effects of limiting the mass fraction of V to 0.05%~0.12% include: enhancing matrix strength through carbonitride precipitation, synergistically refining grains to suppress crack propagation, and balancing precipitate size with the risk of over-aging, thereby achieving synergistic optimization of wear resistance and impact toughness. For example, the mass fraction of V can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, etc.

[0035] The positive effects of limiting the Mo mass fraction to 0.10%~0.50% include: synergistically improving the stability of bainitic phase transformation through hardenability compensation and grain boundary segregation suppression, blocking temper brittleness channels, refining the multiphase microstructure, and reducing residual stress, thereby achieving a synergistic leap in strength, toughness, and wear resistance. For example, the Mo mass fraction can be 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, etc.

[0036] The positive effects of limiting the mass fraction of phosphorus (P) to ≤0.01% include: strictly controlling grain boundary segregation sources, blocking tempering embrittlement channels, avoiding a sharp drop in impact energy in the low-temperature-medium-temperature brittle region, and simultaneously improving cleanliness to ensure the toughness and stability of the multiphase microstructure. For example, the mass fraction of P can be 0.004%, 0.006%, 0.008%, 0.010%, etc.

[0037] The positive effects of limiting the mass fraction of sulfur (S) to ≤0.006% are as follows: Since the wear-resistant steel in this embodiment has a high Mn content, it is necessary to strictly control the formation of sulfide inclusions (mainly MnS) to avoid hot brittle cracking and microcrack initiation under impact loads. This also improves material purity and isotropy, ensuring toughness and fatigue life stability under high-strength conditions. For example, the mass fraction of S can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, etc.

[0038] The positive effects of limiting the mass fraction of N to 0.010%~0.018% include: through the synergistic effect of Al, V and N, composite precipitates are formed during the post-rolling air cooling process, laying the foundation for the nucleation-inducing effect of AlN in the subsequent quenching process. For example, the mass fraction of N can be 0.010%, 0.012%, 0.014%, 0.016%, 0.018%, etc.

[0039] Fe is a matrix element, and the specific content / range of Fe can be obtained through the upper and lower limit formulas of the component, that is: The sum of the percentages of all components in a composition should equal 100%, and the content ranges of several components should meet the following conditions: the upper limit of a certain component + the lower limit of other components ≤ 100; the lower limit of a certain component + the upper limit of other components ≥ 100. Furthermore, the specific content of Fe is made up to 100% by the actual detected values ​​of the other chemical components mentioned above, together with any unlisted active elements and / or impurity elements, and Fe must constitute the absolute proportion as a matrix element.

[0040] Carbon equivalent: This is a weighted calculation value of carbon content (wt.%), which represents the influence of various alloying elements (such as Mn, Cr, Mo, V, etc.) on hardenability and weldability in steel, converted into an equivalent value using a specific conversion factor. With a carbon equivalent between 0.58% and 0.75%, precise control of the synergistic effect of alloying elements optimizes hardenability to achieve a balance of strength and toughness in the bainitic / martensitic dual-phase structure, while avoiding excessively high risks of weld cold cracking, and ensuring process adaptability for industrial production. For example, carbon equivalents can be 0.58%, 0.60%, 0.62%, 0.64%, 0.68%, 0.70%, 0.72%, 0.74%, etc.

[0041] In some embodiments, the wear-resistant steel satisfies at least one of the following properties: yield strength of 1299MPa~1379MPa, tensile strength ≥1400MPa, elongation of 10%~25%, and impact energy ≥82J.

[0042] Yield strength: The minimum stress at which a material begins to undergo permanent plastic deformation. Tensile strength: The maximum stress a material can withstand before fracture. Elongation: The ability of a material to undergo plastic deformation at fracture. Impact energy: The ability of a material to absorb energy under impact load. For example, yield strength can be 1299 MPa, 1309 MPa, 1319 MPa, 1329 MPa, 1339 MPa, 1349 MPa, 1359 MPa, 1369 MPa, 1379 MPa, etc.; tensile strength can be 1400 MPa, 1420 MPa, 1440 MPa, 1460 MPa, 1480 MPa, 15000 MPa, etc.; elongation can be 10%, 15%, 20%, 25%, etc.; impact energy can be 82 J, 84 J, 86 J, 88 J, 90 J, etc.

[0043] Figure 1 This is a flowchart illustrating a boron-free, low residual stress bainitic wear-resistant steel and its preparation method, provided as an embodiment of this application.

[0044] Please see Figure 1 Secondly, this application provides a method for preparing the wear-resistant steel described in the first aspect, the method comprising: S1. Obtain a slab with the following chemical composition: C: 0.20%~0.40%, Mn: 1.80%~2.20%, Si: 1.40%~1.60%, Cr: 0.90%~1.20%, Al: 0.40%~0.70%, Ti: 0.03%~0.06%, V: 0.05%~0.12%, Mo: 0.10%~0.50%, P≤0.01%, S≤0.006%, N: 0.010%~0.018%, and the matrix element Fe; S2. The slab is sequentially heated, rough-rolled, and finish-rolled to obtain a steel plate; S3. The steel plate is subjected to air cooling, straightening, offline temperature-controlled quenching and medium-temperature tempering in sequence to obtain wear-resistant steel.

[0045] In some embodiments, the heating temperature is 1130℃~1160℃, and the heating time coefficient is 1min / mm~2min / mm.

[0046] The heating temperature is between 1130℃ and 1160℃ to precisely control the austenite grain size while completely dissolving the V / Ti carbides, providing a uniform and fine phase transformation basis for subsequent temperature-controlled quenching. Examples of heating temperatures include 1130℃, 1140℃, 1150℃, and 1160℃. The heating time coefficient is the heating time (in minutes) required per unit thickness (mm) of the steel plate, used to dynamically calculate the total heating time (total time = thickness × coefficient), ensuring sufficient austenitization in the core while avoiding surface overheating. The heating time coefficient is between 1 min / mm and 2 min / mm, ensuring penetrating austenitization in the core through thickness-adaptive heating, while simultaneously suppressing grain coarsening and surface decarburization in the high-temperature section. Examples of heating time coefficients include 1 min / mm, 1.5 min / mm, and 2 min / mm.

[0047] In some embodiments, the roughing process employs a low-speed, high-reduction process, and the final pass reduction rate of the roughing process is ≥15%.

[0048] Low-speed, high-reduction process: This is a key technical strategy in the hot rolling of steel. Its core lies in the synergistic control of low rolling speed and high single-pass deformation, aiming to overcome the limitations of traditional rolling methods in controlling the core microstructure. The final pass reduction in roughing is ≥15%, forcibly breaking down coarse primary grains through ultra-high strain and triggering dynamic recrystallization. This provides a fine and uniform austenitic microstructure for subsequent temperature-controlled quenching, completely eliminating the risk of mixed grains caused by insufficient core deformation. For example, the final pass reduction in roughing can be 15%, 20%, 25%, etc.

[0049] In some embodiments, the initial rolling temperature of the finishing mill is 850°C to 950°C, and the final rolling temperature of the finishing mill is 800°C to 850°C.

[0050] The initial rolling temperature of the finishing mill is between 850℃ and 950℃. This ensures complete recrystallization of austenite while providing sufficient plasticity reserves and suppressing mixed grains, thus establishing a uniform and fine initial microstructure for subsequent controlled rolling. For example, the initial rolling temperature of the finishing mill can be 850℃, 870℃, 890℃, 910℃, 930℃, or 950℃. The final rolling temperature of the finishing mill is between 800℃ and 850℃. This precisely controls the rolling process to end at the critical point of the non-recrystallization zone, driving the flattening of austenite grains before phase transformation through accumulated distortion energy, providing a high-density nucleation dislocation for subsequent controlled cooling and refinement of bainite laths. For example, the final rolling temperature of the finishing mill can be 800℃, 810℃, 820℃, 830℃, 840℃, or 850℃.

[0051] In some embodiments, the thickness of the steel plate is 6mm to 25mm.

[0052] The steel plate thickness ranges from 6mm to 25mm. By matching the cold penetration limit of temperature-controlled quenching with the stress reduction capability of medium-temperature tempering, the homogeneity of strength and toughness across the entire thickness section is ensured, avoiding the risks of quenching cracks in thin plates and core microstructure / stress runaway in thick plates. For example, the steel plate thickness can be 7mm, 9mm, 11mm, 13mm, 15mm, 17mm, 19mm, 21mm, 23mm, 25mm, etc.

[0053] In some embodiments, the air cooling is performed by stacking slow cooling, the initial temperature of the stack is 400℃~650℃, and the slow cooling time of the stack is 24h~72h.

[0054] Stacking and slow cooling: The cooling rate is controlled by the self-insulating effect created by stacking steel plates. This suppresses residual stress and deformation cracking while ensuring full transformation of the bainitic structure and homogenization of strength and toughness. The use of stacking and slow cooling in air cooling promotes hydrogen removal, preventing microcrack initiation and hydrogen-induced delayed cracking. For example, the initial stacking temperature can be 400℃, 450℃, 500℃, 550℃, 600℃, or 650℃; the slow cooling time can be 24h, 34h, 44h, 54h, or 64h, etc.

[0055] In some implementations, the straightening is performed using warm straightening and cold straightening.

[0056] The straightening process employs both warm and cold straightening to ensure the shape of the rolled steel plate while eliminating residual stress.

[0057] In some embodiments, the temperature of the warm straightening is 100°C to 400°C, and the reduction amount of the warm straightening is 10% to 20%.

[0058] Warm straightening operates at temperatures between 100℃ and 400℃. By precisely matching the temperature range of the material's yield strength trough, straightening is performed within the window of significantly enhanced plasticity in the steel plate, avoiding the fracture risks of cold straightening and the oxidation and discoloration defects of hot straightening. Examples of warm straightening temperatures include 100℃, 200℃, 300℃, and 400℃. The reduction during warm straightening is between 10% and 20%. By applying plastic strain exceeding the critical deformation, wavy bending is forcibly eliminated, while simultaneously suppressing microcracks and residual stress resurgence caused by excessive deformation. Examples of warm straightening reductions include 10%, 12%, 14%, 16%, 18%, and 20%.

[0059] In some embodiments, the temperature of the cold straightening is 20°C to 200°C, and the reduction amount of the cold straightening is 5% to 10%.

[0060] Cold straightening operates at temperatures between 20℃ and 200℃. Through precise plasticity control within the range of room temperature to medium-low temperatures, it ensures the continuous yielding capacity of the steel plate while suppressing the risk of blue brittleness, achieving efficient straightening and avoiding fracture. For example, cold straightening temperatures can be 50℃, 100℃, 150℃, and 200℃. The reduction during cold straightening is between 5% and 10%. By applying strain exceeding the elastic limit but strictly controlling the plastic deformation threshold, it forcibly eliminates plate shape defects while preventing the accumulation of secondary stress caused by work hardening. For example, the reduction rate during cold straightening can be 5%, 6%, 7%, 8%, 9%, and 10%.

[0061] In some embodiments, the offline temperature-controlled quenching includes: austenitizing heating, a first-stage rapid cooling, air cooling hold, and a second-stage rapid cooling.

[0062] Offline temperature-controlled quenching, through the synergistic effect of austenitization treatment and air cooling between two stages of controllable rapid cooling, precisely controls the ratio of bainite / martensite multiphase structures, simultaneously achieving the industrial-scale preparation of low residual stress and high-toughness wear-resistant steel.

[0063] In some embodiments, the austenitizing heating temperature is 880°C to 930°C.

[0064] The austenitizing heating temperature is between 880℃ and 930℃. By fully dissolving carbides and suppressing grain coarsening, it provides a uniform, fine-grained austenitic microstructure for subsequent temperature-controlled quenching, ensuring the synchronicity and integrity of the bainite / martensite multiphase transformation. For example, the austenitizing heating temperature can be 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, etc.

[0065] In some embodiments, the cooling rate of the first stage rapid cooling is 20℃ / s to 35℃ / s, and the termination temperature of the first stage rapid cooling is 320℃ to 350℃.

[0066] The first-stage rapid cooling rate is between 20℃ / s and 35℃ / s. This precise control, exceeding the critical cooling rate for pearlite but below the martensite burst cooling rate, avoids the pearlite transformation region and locks in the bainite nucleation window, laying the kinetic foundation for subsequent isothermal phase transformation. For example, the cooling rate for the first stage can be 20℃ / s, 25℃ / s, 30℃ / s, or 25℃ / s. The first-stage rapid cooling termination temperature is between 320℃ and 350℃ to precisely anchor the cooling endpoint within the bainite phase transformation burst temperature range. This utilizes the phase transformation plasticity to offset quenching stress while suppressing the uncontrolled stress in the microstructure caused by premature martensite formation. For example, the first-stage rapid cooling termination temperature can be 320℃, 330℃, 340℃, or 350℃.

[0067] In some implementations, the air-cooled residence time is 20s to 60s.

[0068] The air-cooling residence time is between 20s and 60s. This ensures that the bainite undergoes a complete phase transformation and prevents excessive coarsening of carbides, thereby synergistically reducing phase transformation stress and regulating the microstructure's refinement and toughness. For example, the air-cooling residence time can be 20s, 30s, 40s, 50s, 60s, etc.

[0069] In some embodiments, the cooling rate of the second stage rapid cooling is 10°C / s to 25°C / s, and the termination temperature of the second stage rapid cooling is 20°C to 120°C.

[0070] The second-stage rapid cooling process operates at a rate between 10℃ / s and 25℃ / s. This critical cooling rate suppresses the decomposition of retained austenite into brittle pearlite while avoiding excessively rapid cooling that could introduce new phase transformation stress, thus ensuring the stability of the multiphase microstructure. For example, the cooling rate for the second-stage rapid cooling can be 10℃ / s, 15℃ / s, 20℃ / s, or 25℃ / s. The final cooling temperature for the second stage is between 20℃ and 120℃, precisely controlling the final cooling temperature below the martensitic transformation completion point and far from the cryogenic brittle region, achieving a synergistic balance between minimal residual austenite and minimized phase transformation stress. For example, the final cooling temperature for the second stage can be 20℃, 40℃, 60℃, 80℃, 100℃, or 120℃.

[0071] In some embodiments, the temperature of the intermediate-temperature tempering is 300°C to 350°C, and the tempering time is 20 min to 90 min.

[0072] The intermediate-temperature tempering temperature is between 300℃ and 350℃. By precisely matching the tempering resistance window of the bainitic / martensite multiphase microstructure, it effectively relaxes residual stress while preventing excessive carbide aggregation and embrittlement, achieving a balance between strength and toughness through synergistic regulation. For example, the intermediate-temperature tempering temperature can be 300℃, 310℃, 320℃, 330℃, 340℃, or 350℃. The intermediate-temperature tempering time is between 20 min and 90 min, relying on cross-scale diffusion kinetics to complete the stress reduction and microstructure stabilization process, simultaneously avoiding stress residue caused by short-time under-tempering and strength collapse caused by long-time over-tempering. For example, the intermediate-temperature tempering time can be 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min.

[0073] The product prepared by the method of preparing wear-resistant steel is the aforementioned wear-resistant steel. Since the method of preparing wear-resistant steel adopts some or all of the technical solutions of the wear-resistant steel embodiments, it has at least all the beneficial effects brought about by the technical solutions of the aforementioned embodiments, which will not be elaborated here.

[0074] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0075] The chemical composition (mass percentage / %) of the steels in the examples and comparative examples is shown in Table 1.

[0076] Table 1

[0077] Example 1 A slab with the chemical composition described in Example 1 of Table 1 was obtained; The slab is heated to 1140℃ with a heating time coefficient of 1.5 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 25%; subsequently, the slab is finish rolled with an initial rolling temperature of 880℃ and a final rolling temperature of 825℃ to obtain a steel plate with a thickness of 14 mm. The steel plate was air-cooled and then slow-cooled by stacking at an initial temperature of 450°C for 48 hours. Next, the steel plate was warm-straightened at 150°C with a reduction of 13%. It was then cold-straightened at 68°C with a reduction of 6%. Subsequently, the steel plate underwent offline temperature-controlled quenching. The austenitizing heating temperature was 890°C, with a first-stage rapid cooling rate of 32°C / s and a final temperature of 324°C, followed by an air-cooling dwell time of 23 seconds. The second-stage rapid cooling rate was 23°C / s, with a final temperature of 43°C. Finally, the steel plate was tempered at a medium temperature of 320°C for 40 minutes to obtain wear-resistant steel.

[0078] Example 2 A slab with the chemical composition described in Example 2 of Table 1 was obtained; The slab is heated to 1150℃ with a heating time coefficient of 1.6 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 26%; subsequently, the slab is finish rolled with an initial rolling temperature of 863℃ and a final rolling temperature of 814℃ to obtain a steel plate with a thickness of 12 mm. The steel plate was air-cooled and then slow-cooled by stacking at an initial temperature of 412°C for 33 hours. Next, it underwent warm straightening at 112°C with a reduction of 12%. Then, it underwent cold straightening at 46°C with a reduction of 6%. Following this, the steel plate underwent offline temperature-controlled quenching at an austenitizing heating temperature of 885°C. The first stage of rapid cooling had a cooling rate of 32°C / s and a termination temperature of 331°C, with an air-cooling dwell time of 20 seconds. The second stage of rapid cooling had a cooling rate of 21°C / s and a termination temperature of 39°C. Finally, the steel plate underwent medium-temperature tempering at 315°C for 35 minutes to obtain wear-resistant steel.

[0079] Example 3 A slab with the chemical composition described in Example 3 of Table 1 was obtained; The slab is heated to 1145℃ with a heating time coefficient of 1.4 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 28%; subsequently, the slab is finish rolled with an initial rolling temperature of 878℃ ​​and a final rolling temperature of 831℃ to obtain a steel plate with a thickness of 13 mm. The steel plate was air-cooled and then slow-cooled by stacking at an initial temperature of 426°C for 32 hours. Next, it underwent warm straightening at 120°C with a reduction of 13%. Then, it underwent cold straightening at 54°C with a reduction of 6%. Following this, the steel plate underwent offline temperature-controlled quenching at an austenitizing heating temperature of 894°C. The first stage of rapid cooling had a cooling rate of 33°C / s and a termination temperature of 348°C, with an air-cooling dwell time of 29 seconds. The second stage of rapid cooling had a cooling rate of 22°C / s and a termination temperature of 57°C. Finally, the steel plate underwent medium-temperature tempering at 315°C for 33 minutes to obtain wear-resistant steel.

[0080] Example 4 A slab with the chemical composition described in Example 4 of Table 1 was obtained; The slab is heated to 1150℃ with a heating time coefficient of 1.4 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 28%; subsequently, the slab is finish rolled with an initial rolling temperature of 884℃ and a final rolling temperature of 813℃ to obtain a steel plate with a thickness of 15 mm. The steel plate was air-cooled and then slow-cooled by stacking, with an initial stacking temperature of 640℃ and a slow cooling time of 58 hours. Next, the steel plate was warm-straightened at 194℃ with a reduction of 15%. It was then cold-straightened at 74℃ with a reduction of 8%. Subsequently, the steel plate underwent offline temperature-controlled quenching, with an austenitizing heating temperature of 894℃. The first stage of rapid cooling had a cooling rate of 28℃ / s and a termination temperature of 349℃, with an air-cooling dwell time of 33 seconds. The second stage of rapid cooling had a cooling rate of 19℃ / s and a termination temperature of 56℃. Finally, the steel plate was tempered at a medium temperature of 315℃ for 38 minutes to obtain wear-resistant steel.

[0081] Example 5 A slab with the chemical composition described in Example 5 of Table 1 was obtained; The slab is heated to 1150℃ with a heating time coefficient of 1.7 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 27%; subsequently, the slab is finish rolled with an initial rolling temperature of 886℃ and a final rolling temperature of 823℃ to obtain a steel plate with a thickness of 14 mm. The steel plate was air-cooled and then slow-cooled by stacking at an initial temperature of 632°C for 47 hours. Next, the steel plate was warm-straightened at 164°C with a reduction of 12%. It was then cold-straightened at 87°C with a reduction of 6%. Subsequently, the steel plate underwent offline temperature-controlled quenching. The austenitizing heating temperature was 879°C, with a first-stage rapid cooling rate of 28°C / s and a final temperature of 339°C, followed by an air-cooling dwell time of 26 seconds. The second-stage rapid cooling rate was 19°C / s, with a final temperature of 48°C. Finally, the steel plate was tempered at a medium temperature of 315°C for 41 minutes to obtain wear-resistant steel.

[0082] Example 6 A slab with the chemical composition described in Example 6 of Table 1 was obtained; The slab is heated to 1155℃ with a heating time coefficient of 1.3 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 28%; subsequently, the slab is finish rolled with an initial rolling temperature of 874℃ and a final rolling temperature of 826℃ to obtain a steel plate with a thickness of 10 mm. The steel plate was air-cooled and then slow-cooled by stacking, with an initial stacking temperature of 413℃ and a slow cooling time of 33 hours. Next, the steel plate was warm-straightened at 105℃ with a reduction of 10%. Then, it was cold-straightened at 23℃ with a reduction of 6%. Subsequently, the steel plate underwent offline temperature-controlled quenching, with an austenitizing heating temperature of 894℃. The first stage of rapid cooling had a cooling rate of 33℃ / s and a termination temperature of 323℃, with an air-cooling dwell time of 24 seconds. The second stage of rapid cooling had a cooling rate of 22℃ / s and a termination temperature of 33℃. Finally, the steel plate was tempered at a medium temperature of 305℃ for 29 minutes to obtain wear-resistant steel.

[0083] Example 7 A slab with the chemical composition described in Example 7 of Table 1 was obtained; The slab is heated to 1140℃ with a heating time coefficient of 1.6 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 29%; subsequently, the slab is finish rolled with an initial rolling temperature of 875℃ and a final rolling temperature of 814℃ to obtain a steel plate with a thickness of 9 mm. The steel plate was air-cooled and then slow-cooled by stacking, with an initial stacking temperature of 463℃ and a slow cooling time of 35 hours. Next, the steel plate was warm-straightened at 230℃ with a reduction of 10%. Then, it was cold-straightened at 45℃ with a reduction of 5%. Subsequently, the steel plate underwent offline temperature-controlled quenching, with an austenitizing heating temperature of 882℃. The first stage of rapid cooling had a cooling rate of 31℃ / s and a termination temperature of 331℃, with an air-cooling dwell time of 32 seconds. The second stage of rapid cooling had a cooling rate of 24℃ / s and a termination temperature of 38℃. Finally, the steel plate was tempered at a medium temperature of 315℃ for 30 minutes to obtain wear-resistant steel.

[0084] Example 8 A slab with the chemical composition described in Example 8 of Table 1 was obtained; The slab is heated to 1150℃ with a heating time coefficient of 1.5 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 26%; subsequently, the slab is finish rolled with an initial rolling temperature of 889℃ and a final rolling temperature of 846℃ to obtain a steel plate with a thickness of 12 mm. The steel plate was air-cooled and then slow-cooled by stacking, with an initial stacking temperature of 472℃ and a slow cooling time of 32 hours. Next, the steel plate was warm-straightened at 156℃ with a reduction of 12%. It was then cold-straightened at 76℃ with a reduction of 7%. Subsequently, the steel plate underwent offline temperature-controlled quenching, with an austenitizing heating temperature of 896℃. The first stage of rapid cooling had a cooling rate of 22℃ / s and a termination temperature of 349℃, with an air-cooling dwell time of 32 seconds. The second stage of rapid cooling also had a cooling rate of 22℃ / s and a termination temperature of 43℃. Finally, the steel plate was tempered at a medium temperature of 345℃ for 35 minutes to obtain wear-resistant steel.

[0085] Comparative Example 1 The slab with the chemical composition described in Comparative Example 1 in Table 1 was obtained; The slab is heated to 1180℃ with a heating time coefficient of 2.3 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 26%; subsequently, the slab is finish rolled with an initial rolling temperature of 905℃ and a final rolling temperature of 845℃ to obtain a steel plate with a thickness of 12 mm. The steel plate was warm-straightened at 166°C with a reduction of 18%; then cold-straightened at 76°C with a reduction of 5%; subsequently, the steel plate was offline quenched at an austenitizing heating temperature of 910°C and directly air-cooled to room temperature at a cooling rate of 32°C / s; finally, the steel plate was tempered at 350°C for 42 minutes to obtain wear-resistant steel.

[0086] Comparative Example 2 The slab with the chemical composition described in Comparative Example 2 in Table 1 was obtained; The slab is heated to 1170℃ with a heating time coefficient of 2.1 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 28%; subsequently, the slab is finish rolled with an initial rolling temperature of 949℃ and a final rolling temperature of 878℃ ​​to obtain a steel plate with a thickness of 12 mm. The steel plate was air-cooled and then slow-cooled by stacking at an initial temperature of 620°C for 46 hours. Next, the steel plate was warm-straightened at 583°C with a reduction of 12%. It was then cold-straightened at 89°C with a reduction of 6%. Subsequently, the steel plate underwent offline temperature-controlled quenching at an austenitizing heating temperature of 899°C, followed by direct quenching to room temperature at a cooling rate of 33°C / s. Finally, the steel plate was tempered at a medium temperature of 320°C for 45 minutes to obtain wear-resistant steel.

[0087] Comparative Example 3 The slab with the chemical composition described in Comparative Example 3 in Table 1 was obtained; The slab is heated to 1165℃ with a heating time coefficient of 1.9 min / mm; then, the slab is rough rolled using a low-speed, high-reduction process with a final reduction rate of 26%; subsequently, the slab is finish rolled with an initial rolling temperature of 945℃ and a final rolling temperature of 869℃ to obtain a steel plate with a thickness of 12 mm. The steel plate was air-cooled and then slow-cooled by stacking at an initial temperature of 650°C for 24 hours. Next, the steel plate was warm-straightened at 230°C with a reduction of 12%. It was then cold-straightened at 98°C with a reduction of 8%. Subsequently, the steel plate underwent offline temperature-controlled quenching at an austenitizing heating temperature of 899°C, followed by direct quenching to room temperature at a cooling rate of 33°C / s. Finally, the steel plate was tempered at a medium temperature of 220°C for 36 minutes to obtain wear-resistant steel.

[0088] The mechanical properties of the embodiments and comparative examples are shown in Table 2.

[0089] Table 2

[0090] The data tables above provide a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn: As can be seen from the data in Table 2, the wear-resistant steel provided in this application embodiment has a hardness of 463HBW~508HBW, a yield strength of 1299MPa~1379MPa, a tensile strength of 1473MPa~1635MPa, an elongation of 21%~28%, and an impact energy of 56J~108J.

[0091] As can be seen from Examples 1 to 8, the combination of process parameters in Examples 1 to 5 is optimal, with Example 1 being the optimal solution. It maintains an impact energy of 108J at a tensile strength of 1543MPa, successfully achieving a synergistic improvement in high strength, high toughness, and high plasticity.

[0092] Comparative Examples 1-3 show that the production scheme of conventional bainitic air cooling and boron-containing conventional martensitic wear-resistant steel with quenching + medium-temperature tempering process results in impact energy ≤54J, verifying the technical defect of boron-induced grain boundary embrittlement.

[0093] Appendix Figure 2 Detailed explanation: Figure 2 These are microstructure diagrams corresponding to different processes in Example 1 and the comparative example of this application. According to... Figure 2 It can be seen that Example 1, through boron-free design and medium-temperature tempering process, achieves a fine matching of bainite / martensite dual-phase microstructure: the bainite laths are refined in size, multi-oriented, and have clear interfaces, fully releasing residual stress and suppressing first-type temper brittleness, ultimately achieving a synergistic leap in ultra-high and low temperature toughness (108J) and strong plasticity. In Comparative Examples 1 and 2, the presence of boron leads to lath coarsening and coarsening after medium-temperature tempering, and a large amount of carbide precipitation, causing brittleness deterioration; although Comparative Example 3 uses low-temperature tempering to avoid carbides, the lack of a temperature-controlled quenching process results in ineffective grain segmentation, presenting a large-sized blocky structure and single-oriented laths, which severely restricts the improvement of toughness.

[0094] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: The temperature-controlled quenching process optimizes microstructure and properties through three stages: the first stage of rapid cooling suppresses coarse granular bainite and forms a fine-grained martensite matrix; the air-cooling stage relies on microalloyed precipitates and the martensite interface to promote the full transformation of bainite; the second stage of rapid cooling blocks lath coarsening and blocky residual austenite formation, significantly improving toughness and anti-peeling properties.

[0095] Temperature-controlled quenching breaks through the bottleneck of traditional quenching: Temperature-controlled quenching achieves grain refinement and lath orientation through microstructure regulation, while avoiding the risk of residual stress accumulation and cracking caused by excessive cooling rate in direct quenching, and ensuring that the stress gradient is released gradually during the cooling process.

[0096] Boron-free design offers dual benefits: it eliminates the hindrance of boron to bainitic phase transformation and simultaneously eliminates boron-induced mid-temperature tempering brittleness.

[0097] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A boron-free low residual stress bainite wear resistant steel, characterized in that, The chemical composition of the wear-resistant steel comprises, in mass fraction, C: 0.20%-0.40%, Mn: 1.80%-2.20%, Si: 1.40%-1.60%, Cr: 0.90%-1.20%, Al: 0.40%-0.70%, Ti: 0.03%-0.06%, V: 0.05%-0.12%, Mo: 0.10%-0.50%, P≤0.01%, S≤0.006%, N: 0.010%-0.018%, and base element Fe; wherein the carbon equivalent is 0.58%-0.75%.

2. The abrasion resistant steel according to claim 1, characterized in that, The wear-resistant steel satisfies at least one of the following properties: yield strength of 1299 MPa-1379 MPa, tensile strength≥1400 MPa, elongation of 10%-25%, and impact energy≥82 J.

3. A method of producing the wear resistant steel according to any one of claims 1 to 2, characterized in that, The method comprises: obtaining a slab with the chemical composition according to any one of claims 1-2; sequentially heating, rough rolling and finish rolling the slab to obtain a steel plate; sequentially air cooling, straightening, offline temperature-controlled quenching and medium-temperature tempering the steel plate to obtain the wear-resistant steel.

4. The method of claim 3, wherein, The heating temperature is 1130°C-1160°C, and the heating time coefficient is 1 min / mm-2 min / mm.

5. The method of claim 3, wherein, The rough rolling adopts a low-speed large reduction process, and the final pass reduction rate of the rough rolling is≥15%.

6. The method of claim 3, wherein, The finish rolling has a roughing temperature of 850°C-950°C and a finish rolling temperature of 800°C-850°C; and / or The thickness of the steel plate is 6 mm-25 mm.

7. The method of claim 3, wherein, The air cooling adopts stack slow cooling, the stack has a starting temperature of 400°C-650°C and a slow cooling time of 24 h-72 h.

8. The method of claim 3, wherein, The straightening adopts warm straightening and cold straightening; wherein The warm straightening has a temperature of 100°C-400°C and a reduction of 10%-20%; and / or The cold straightening has a temperature of 20°C-200°C and a reduction of 5%-10%.

9. The method of claim 3, wherein, The offline temperature-controlled quenching comprises austenitizing heating, first-stage fast cooling, air cooling retention and second-stage fast cooling; wherein The austenitizing heating temperature is 880°C-930°C; and / or The first-stage fast cooling has a cooling rate of 20°C / s-35°C / s and a termination temperature of 320°C-350°C; and / or The air cooling retention has a time of 20 s-60 s; and / or The second-stage fast cooling has a cooling rate of 10°C / s-25°C / s and a termination temperature of 20°C-120°C.

10. The method of claim 3, wherein, The medium-temperature tempering has a temperature of 300°C-350°C and a time of 20 min-90 min.

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