Wear-resistant steel plate and method for manufacturing the same

Abstract

The application relates to the technical field of wear-resistant steel, in particular to a wear-resistant steel plate and a preparation method thereof, and solves the technical problems of long production cycle, great process control difficulty and insufficient comprehensive performance of the steel plate in the prior art. The technical scheme adopted by the application is that, on the basis of reasonable design of chemical components, a controlled rolling and controlled cooling process is used to realize fine control of a cooling path, an ideal good strength-toughness matching structure is obtained after cold rolling to room temperature and tempering, and the production does not need to be carried out through quenching and tempering or traditional isothermal quenching and the like, so that the finally obtained bainite wear-resistant steel has good comprehensive performance. The bainite wear-resistant steel plate prepared through the chemical components designed in the application can obtain the wear-resistant steel plate with good hardness, strength and plasticity and toughness on the basis of avoiding quenching and tempering or traditional isothermal quenching means, greatly reducing the production cycle and process control difficulty.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wear-resistant steel, in particular to a wear-resistant steel plate and a preparation method thereof. BACKGROUND

[0002] At present, conventional bainite wear-resistant steel is usually produced by offline quenching and tempering or isothermal quenching and other complex processes, which leads to a long production cycle, great difficulty in process control, and high production cost of the product, and the prepared wear-resistant steel plate usually has defects such as too low hardness, insufficient strength, and poor plasticity and toughness. SUMMARY

[0003] The present application provides a wear-resistant steel plate and a preparation method thereof to solve the technical problems of a long production cycle, great difficulty in process control, and insufficient comprehensive performance of the prepared steel plate in the prior art.

[0004] In a first aspect, the present application provides a wear-resistant steel plate, and the chemical composition of the steel plate comprises:

[0005] C: 0.18wt%-0.22wt%, Mn: 2.00wt%-2.30wt%, Si: 1.50wt%-1.80wt%, Cr: 0.70wt%-1.20wt%, Mo: 0.20-0.50wt%, Ni: 0.2wt%-0.4wt%, Al: 0.02wt%-0.04wt%, Ti: 0.010wt%-0.025wt%, Nb: 0.01wt%-0.04wt%, P: ≤0.02wt%, S: ≤0.02wt%, B: 0.0001wt%-0.0025wt%, Fe.

[0006] In the rolling process, the present application focuses on the decisive role of the mixed structure transformation of bainite / martensite / austenite in the finishing rolling, ensures the cumulative reduction rate of the finishing rolling based on the design of the re-rolled thickness after tempering being more than 4.5 times the finished product thickness, and thus ensures the refinement of the bainite structure in the subsequent cooling process. The present application is different from the general technology which focuses on the refinement of the grain in the rough rolling stage, and ensures the refinement of the bainite lath by the cumulative reduction rate of the finishing rolling to obtain more refined effective grain size.

[0007] Optionally, the metallographic structure of the steel plate comprises at least one of the following: bainite, martensite, austenite, and carbon-containing precipitates.

[0008] Optionally, the carbon-containing precipitates comprise at least one of the following: Ti-containing carbonitride, Nb-containing carbonitride, cementite, and epsilon carbide.

[0009] Optionally, the lath width of the bainite is 200nm-400nm, the lath width of the martensite is 500nm-800nm, and the average diameter of the prior austenite grain is 15μm-25μm.

[0010] Optionally, the content of the bainite is 20vol%-30vol%, the content of the martensite is 70vol%-80vol%, and the content of the austenite is 5vol%-10vol%.

[0011] Optionally, the performance parameters of the wear-resistant steel plate satisfy at least one of the following I-VI:

[0012] I, the surface Brinell hardness is HBW420-480,

[0013] II, the tensile strength is ≥1400MPa,

[0014] III, the elongation A 50 is 15%-25%,

[0015] VI, the carbon equivalent is 0.55-0.85,

[0016] V, the low-temperature V-type impact at-20℃ is ≥50J,

[0017] VI, the unevenness is ≤5mm / m.

[0018] In a second aspect, the application provides a preparation method of a wear-resistant steel plate, for preparing the wear-resistant steel plate of any one of the first aspect, the method comprising:

[0019] subjecting the plate having the chemical composition to temperature rising treatment at a first set heating temperature and a first set heating time, wherein the first set heating time t1 satisfies the relationship: t1=a1×b1, wherein a1 represents a heating coefficient of the first set heating temperature, and b1 represents the thickness of the plate;

[0020] subjecting the plate after the temperature rising treatment to rough rolling at a set reduction rate;

[0021] subjecting the plate after the rough rolling treatment to finish rolling at a set finish rolling temperature and a set finish rolling temperature, and then first straightening at a first set temperature;

[0022] subjecting the plate after the first straightening to strong water cooling treatment at a set cooling speed, so that the plate reaches a second set temperature;

[0023] subjecting the plate after the strong water cooling treatment to air cooling, so that the plate reaches a third set temperature, and then second straightening;

[0024] The second straightened plate is subjected to a temperature rising treatment at a second set heating temperature and a second set heating time, to obtain the wear-resistant steel plate, wherein the second set heating time t2 satisfies a relationship: t2=a2*b1, wherein a2 represents a heating coefficient of the second set heating temperature, and b1 represents a thickness of the plate.

[0025] Optionally, the first set heating temperature is 1150-1180 DEG C, and / or

[0026] The heating coefficient of the first set heating temperature is 1-2 min / mm, and / or

[0027] The set finishing temperature is 820-880 DEG C, and / or

[0028] The set finishing rolling temperature is 800-830 DEG C, and / or

[0029] The first set temperature is 750-800 DEG C.

[0030] Optionally, the set cooling speed is not less than 10 DEG C / s, and / or

[0031] The second set temperature is 200-400 DEG C, and / or

[0032] The third set temperature is 100-300 DEG C.

[0033] Optionally, the second set heating temperature is 150-200 DEG C, and / or

[0034] The heating coefficient of the second set heating temperature is 1-3 min / mm, and / or

[0035] The set reduction is greater than 15% for a set last three passes.

[0036] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages:

[0037] The method provided by the embodiments of the present application, by adding appropriate Ti, Si, Mn and Nb elements, obtains a relatively sufficient complex structure of bainite, martensite and austenite, so that the steel has high strength and high toughness, and the multi-scale Ti(C, N) and Nb(C, N) in the structure have precipitation strengthening effect, so that the steel plate has good processability and wear resistance. The bainite wear-resistant steel plate prepared by the chemical composition designed in the present application can obtain a wear-resistant steel plate with good hardness, strength and plasticity and toughness on the basis of avoiding quenching and tempering or traditional isothermal quenching means, and greatly reducing the production cycle and process control difficulty. BRIEF DESCRIPTION OF DRAWINGS

[0038] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application.

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings required to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0040] Figure 1 SEM photos provided for Example 1 of the present application;

[0041] Figure 2 SEM photos provided for Example 2 of the present application;

[0042] Figure 3 SEM photos provided for Example 3 of the present application;

[0043] Figure 4 SEM photos provided for Example 4 of the present application;

[0044] Figure 5 SEM photos provided for Example 5 of the present application;

[0045] Figure 6 SEM photos provided for Comparative Example 1 of the present application;

[0046] Figure 7 SEM photos provided for Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0047] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the scope of protection of the present application.

[0048] Unless otherwise specifically indicated, all the various raw materials, reagents, instruments and equipment, etc. used in the present application can be purchased from the market or can be prepared by the existing methods.

[0049] Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single values in the described range, such as 1, 2, 3, 4, 5 and 6, which applies to any range. In addition, whenever a numerical range is indicated herein, it refers to any cited number (fraction or integer) in the indicated range.

[0050] In the present application, the orientation words such as "upper" and "lower" are specific to the drawing direction in the drawings unless otherwise stated. In addition, in the description of the present application, the terms "include", "include" and the like mean "include but are not limited to".

[0051] In this paper, the relationship terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. In this paper, "and / or" describes the relationship between the associated objects, which means that there can be three relationships, for example, A and / or B can represent the following cases: A exists alone, A and B exist together, and B exists alone. Where A and B can be singular or plural. In this paper, "at least one" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of the items, including single item or any combination of multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0052] The technical solution provided by the embodiments of the present application solves the above technical problems, and the overall idea provided by the embodiments of the present application is as follows:

[0053] In a first aspect, the present application provides a wear-resistant steel plate, the chemical composition of the steel plate comprises:

[0054] C: 0.18-0.22 wt%, Mn: 2.00-2.30 wt%, Si: 1.50-1.80 wt%, Cr: 0.70-1.20 wt%, Mo: 0.20-0.50 wt%, Ni: 0.2-0.4 wt%, Al: 0.02-0.04 wt%, Ti: 0.010-0.025 wt%, Nb: 0.01-0.04 wt%, P: ≤0.02 wt%, S: ≤0.02 wt%, B: 0.0001-0.0025 wt%; the balance being Fe and inevitable impurity elements.

[0055] In the present embodiment, the C element can ensure the hardness level of the wear-resistant steel plate, and too high C content will cause the hardness of the steel plate to exceed the standard, and at the same time change the phase change rule of the steel plate, affecting the final bainite / martensite ratio and performance results. Too low C content is easy to cause the final hardness of the steel plate to fail to meet the requirements.

[0056] In the present embodiment, the Mn element generally needs to be ensured to be above 2.0 wt%, only by ensuring the addition of sufficient Mn element, can the better interface-like drag effect during high temperature transformation be ensured, the high temperature transformation is inhibited to ensure that there is no ferrite and pearlite structure in the structure, and at the same time, only sufficient Mn element can ensure bainite transformation, and a relatively sufficient bainite / martensite / austenite complex phase structure is obtained. In addition, the solid solution strengthening effect of the Mn element can improve the strength of the steel, and at the same time, the bainite start transformation temperature is reduced.

[0057] In the present embodiment, by adding a certain amount of Si element to inhibit cementite precipitation, the residual austenite is carbon-rich, and at the same time, the condition for the formation of carbide-free bainite is provided. Only when the Si element is ≥1.5 mass%, can it be ensured that the carbide cannot be precipitated in the bainite during the transformation process in the steel, so as to promote the carbon-rich austenite, and further ensure that more residual austenite is retained to meet the sufficient transformation of the bainite wear-resistant steel.

[0058] In the present embodiment, the Cr element can improve the hardenability of the wear-resistant steel, and at the same time, can play a solid solution strengthening role to improve the strength and hardness of the steel,

[0059] In the present embodiment, the Mo element is mainly used to improve the hardenability of the steel, and the Ni element has the effects of enhancing the hardenability and improving the toughness.

[0060] In the present embodiment, the Ni element has the effect of enhancing the low-temperature toughness,

[0061] In the present embodiment, the Al element is used for deoxidation and nitrogen fixation,

[0062] In the embodiment, the Ti element is used to refine the grain, and the TiC is beneficial to improve the wear resistance of the wear-resistant steel structure.

[0063] In the embodiment, the addition of the Nb element is beneficial to ensure the deformation in the non-recrystallization zone in the finish rolling stage and promote the structure refinement in the bainite transformation process.

[0064] In the embodiment, the P and S elements are residual elements.

[0065] In the embodiment, the B element is a hardenability element.

[0066] In some embodiments, the metallographic structure of the steel plate includes at least one of the following: bainite, martensite, austenite, and carbon-containing precipitates.

[0067] In the embodiment, the bainite structure has good impact wear characteristics, and the bainite ferrite and the film-shaped residual austenite between the bainite laths have good impact wear resistance. Meanwhile, the bainite laths are beneficial to the division of the grains, and can effectively refine the grain size under the condition that the original austenite grains are not significantly refined.

[0068] In some embodiments, the carbon-containing precipitates include at least one of the following: Ti-containing carbonitride and Nb-containing carbonitride.

[0069] In the embodiment, the Ti-containing carbonitride is mainly beneficial to improve the cutting resistance of the bainite wear-resistant steel structure and improve the overall wear resistance of the steel plate.

[0070] In some embodiments, the width of the bainite laths is 200 nm-400 nm, the width of the martensite laths is 500 nm-800 nm, and the average diameter of the original austenite grains is 15 μm-25 μm.

[0071] In the embodiment, the fine bainite laths and ferrite laths are beneficial to improve the strength and toughness of the wear-resistant steel, and the division of the bainite laths in the original austenite grains is beneficial to refine the effective grain size of the structure, thereby positively affecting the optimization of the strength and toughness of the steel plate.

[0072] In some embodiments, the content of the bainite is 20 vol% to 30 vol%, the content of the martensite is 70 vol% to 80 vol%, and the content of the austenite is 5 vol% to 10 vol%.

[0073] In the embodiment, the main structure of the martensite can ensure that the steel plate has good hardness and strength levels, a certain amount of bainite can ensure good impact wear performance, and the residual austenite as a ductile plastic phase is beneficial to the improvement of the ductile plasticity of the steel plate.

[0074] In some embodiments, the performance parameters of the wear-resistant steel plate satisfy at least one of the following I-VI:

[0075] I, the surface Brinell hardness is HBW420-480,

[0076] II, the tensile strength is ≥1400MPa,

[0077] III, the elongation A 50 is 15%-25%,

[0078] VI, the carbon equivalent is 0.55-0.85,

[0079] V, the low temperature V-type impact at-20℃ is ≥50J,

[0080] VI, the unevenness is ≤5mm / m.

[0081] In a second aspect, the application provides a preparation method of a wear-resistant steel plate, for preparing the wear-resistant steel plate of any one of the first aspect, the method comprising:

[0082] performing temperature rising treatment on the plate blank with the chemical composition at a first set heating temperature and a first set heating time, wherein the first set heating time t1 satisfies the relationship: t1=a1×b1, wherein a1 represents a heating coefficient of the first set heating temperature, and b1 represents the thickness of the plate blank;

[0083] performing rough rolling on the plate blank after the temperature rising treatment at a set reduction rate;

[0084] performing finish rolling on the plate blank after the rough rolling treatment at a set finish rolling opening temperature and a set finish rolling temperature, and then performing first straightening at a first set temperature;

[0085] performing strong water cooling treatment on the plate blank after the first straightening at a set cooling speed, so that the plate blank reaches a second set temperature;

[0086] air cooling the plate blank after the strong water cooling treatment, so that the plate blank reaches a third set temperature, and then performing second straightening;

[0087] performing temperature rising treatment on the plate blank after the second straightening at a second set heating temperature and a second set heating time, to obtain the wear-resistant steel plate, wherein the second set heating time t2 satisfies the relationship: t2=a2×b1, wherein a2 represents a heating coefficient of the second set heating temperature, and b1 represents the thickness of the plate blank.

[0088] In the embodiment, the production process route is: slab heating-rolling-pre-straightening-ultra-fast cooling + accelerated laminar cooling-cold bed cooling-warm straightening-tempering, and the bainite wear-resistant steel with high strength and toughness matching is obtained by controlled rolling and controlled cooling + tempering, avoiding long processes such as quenching and tempering or isothermal quenching or processes difficult to control. Considering the problem of plate shape caused by low final cooling temperature, pre-straightening is used before water cooling to improve the plate shape before water cooling and reduce the deformation caused by water cooling. Warm straightening is used after cold bed cooling, mainly considering that phase transformation continues to occur during the air cooling process of the cold bed after water cooling, thereby causing deformation of the steel plate.

[0089] In the embodiment, the thickness of the steel plate is preferably 10-30 mm, and it is emphasized that the warm thickness is not less than 4.5 times the thickness of the finished product. If the warm thickness is less than this value, the cumulative reduction of finish rolling will be insufficient, thereby affecting the refinement degree of the bainite structure and the strength and toughness of the bainite wear-resistant steel. If the warm thickness is higher than this value, the reduction during the rough rolling stage will be too low, thereby affecting the performance of the wear-resistant steel.

[0090] In some embodiments, the first set heating temperature is 1150-1180℃, and / or

[0091] The heating coefficient of the first set heating temperature is 1 min / mm-2 min / mm, and / or

[0092] The set finish rolling opening temperature is 830-880℃, and / or

[0093] The set finish rolling temperature is 780-830℃, and / or

[0094] The first set temperature is 780-800℃.

[0095] In the embodiment, the opening temperature of 830-880℃ and the finish rolling temperature of 780-830℃ are mainly used to ensure the sufficient refinement of the bainite laths and the effect of dividing grains in the subsequent phase transformation process by more fully rolling in the unrecrystallized zone. Too high opening and finish rolling temperatures will result in insufficient refinement of the structure, and the toughening and grain division effects cannot be achieved. Too low opening and finish rolling temperatures will result in too large residual stress of the steel plate, which is not conducive to plate shape control.

[0096] In some embodiments, the set cooling speed is not less than 10℃ / s, and / or

[0097] The second set temperature is 200-400℃, and / or

[0098] The third set temperature is 100-300℃.

[0099] In the embodiment, the expected bainite / martensite complex phase structure can be ensured by the set final cooling temperature. If the second set temperature is higher, the overall bainite / martensite proportion of the overall structure of the steel plate will change, which will result in the decrease of strength and the deterioration of toughness. If the second set temperature is lower, the strength will increase and the toughness will deteriorate due to the change of the proportion of the structure, and the plate shape will also deteriorate.

[0100] In some embodiments, the second set heating temperature is 150-200℃, and / or

[0101] The heating coefficient of the second set heating temperature is 1-3 min / mm, and / or

[0102] The set reduction is greater than 15% for the last three passes.

[0103] In the embodiment, the steel plate can obtain the expected structure at the heating temperature. If the temperature is higher, the strength and hardness will decrease, which will result in rejection. If the temperature is lower, the residual stress of the steel plate will not be eliminated completely, which will result in subsequent plate shape problems.

[0104] The application will be further described in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not to limit the scope of the application. The experimental methods in the following embodiments are not specified, and the national standards are generally used for measurement. If there is no corresponding national standard, the international standard, the conventional condition, or the condition suggested by the manufacturer is used.

[0105] Optionally, the first set heating temperature is 1150-1180℃, and / or

[0106] The heating coefficient of the first set heating temperature is 1-2 min / mm, and / or

[0107] The set finishing temperature is 820-880℃, and / or

[0108] The set finishing temperature is 800-830℃, and / or

[0109] The first set temperature is 750-800℃.

[0110] Optionally, the set cooling speed is not less than 10℃ / s, and / or

[0111] The second set temperature is 200-400℃, and / or

[0112] The third set temperature is 100-300℃.

[0113] Optionally, the second set heating temperature is 150-200℃, and / or

[0114] The heating coefficient of the second set heating temperature is 1-3 min / mm, and / or

[0115] The set reduction is greater than 15% in the last three passes.

[0116] Example 1

[0117] The chemical composition of this example is shown in Table 1, and the balance is Fe and trace elements. A slab meeting the above composition is heated, rolled, pre-straightened, ultra-fast cooled + laminar cooled, cooled on a cooling bed, warm straightened, and tempered to obtain a wear-resistant steel plate, wherein the slab is heated at 1150℃, the heating time coefficient is 1 min / mm, then two-stage rolling is performed on a plate mill, coarse rolling is performed at 1050℃, coarse rolling adopts a low-speed large-reduction rolling schedule to ensure that the reduction in the last three passes is greater than 15%, and the thickness after being warmed is 113mm. The finish rolling starts at 870℃, and the finish rolling temperature is controlled at 830℃, the steel plate is immediately pre-straightened after rolling to ensure the shape of the steel plate before water cooling, the steel plate is ultra-fast cooled after rolling, a UFC (ultra-fast cooling) + ACC (accelerated laminar cooling) strong water cooling process is adopted, the final cooling temperature is 390℃, the cooling speed is not less than 10℃ / s, the steel plate is air-cooled on a cooling bed after water cooling, and the steel plate is warm straightened when cooled to 280℃. The steel plate is tempered, the tempering holding temperature is 200℃, and the heating time is 1 min / mm x plate thickness.

[0118] Example 2

[0119] The chemical composition of this example is shown in Table 1, with the balance being Fe and trace elements. A slab meeting the above composition is heated, rolled, pre-straightened, ultra-fast cooled + laminar cooled, cooled on a cooling bed, warm straightened, and tempered to obtain a wear-resistant steel plate, wherein the slab is heated at 1150°C, the heating time coefficient is 1 min / mm, then two-stage rolling is performed on a plate mill, rough rolling is performed at 1050°C, the rough rolling adopts a rolling schedule of low speed and large reduction, so as to ensure that the reduction rate of the last three passes is greater than 15%, and the re-rolled thickness after warming is 113 mm. The finish rolling starts at 870°C, and the finish rolling temperature is controlled at 820°C. The steel plate is immediately sent to a pre-straightening machine for pre-straightening after rolling, so as to ensure the shape of the steel plate before water cooling. The steel plate is immediately subjected to ultra-fast cooling after rolling, and a UFC (ultra-fast cooling) + ACC (accelerated laminar cooling) strong water cooling process is adopted, the final cooling temperature is 370°C, the cooling rate is not less than 10°C / s, and the steel plate is air-cooled on a cooling bed after water cooling. The steel plate is warm straightened when the temperature is cooled to 250°C. The steel plate is subjected to a tempering heat treatment, the tempering holding temperature is 150°C, and the heating time is 1 min / mm x plate thickness. The rolling and heat treatment process parameters are shown in Table 2, and the mechanical properties after tempering are shown in Table 3.

[0120] Example 3

[0121] The chemical composition of this example is shown in Table 1, with the balance being Fe and trace elements. A slab meeting the above composition is heated, rolled, pre-straightened, ultra-fast cooled + laminar cooled, cooled on a cooling bed, warm straightened, and tempered to obtain a wear-resistant steel plate, wherein the slab is heated at 1150°C, the heating time coefficient is 1 min / mm, then two-stage rolling is performed on a plate mill, rough rolling is performed at 1050°C, the rough rolling adopts a rolling schedule of low speed and large reduction, so as to ensure that the reduction rate of the last three passes is greater than 15%, and the re-rolled thickness after warming is 113 mm. The finish rolling starts at 865°C, and the finish rolling temperature is controlled at 820°C. The steel plate is immediately sent to a pre-straightening machine for pre-straightening after rolling, so as to ensure the shape of the steel plate before water cooling. The steel plate is immediately subjected to ultra-fast cooling after rolling, and a UFC (ultra-fast cooling) + ACC (accelerated laminar cooling) strong water cooling process is adopted, the final cooling temperature is 290°C, the cooling rate is not less than 10°C / s, and the steel plate is air-cooled on a cooling bed after water cooling. The steel plate is warm straightened when the temperature is cooled to 240°C. The steel plate is subjected to a tempering heat treatment, the tempering holding temperature is 200°C, and the heating time is 1 min / mm x plate thickness.

[0122] Example 4

[0123] The chemical composition of this example is shown in Table 1, with the balance being Fe and trace elements. A slab meeting the above composition is heated, rolled, pre-straightened, ultra-fast cooled + laminar cooled, cooled on a cooling bed, warm straightened, and tempered to obtain a wear-resistant steel plate, wherein the slab is heated at 1150°C, the heating time coefficient is 1 min / mm, then two-stage rolling is performed on a plate mill, rough rolling is performed at 1050°C, the rough rolling adopts a rolling schedule of low speed and large reduction, so as to ensure that the reduction rate of the last three passes is greater than 15%, and the thickness after being warmed up is 113 mm. The finish rolling starts at 850°C, the finish rolling temperature is controlled at 810°C, the steel plate is immediately sent to a pre-straightening machine for pre-straightening after rolling, so as to ensure the shape of the steel plate before water cooling, the steel plate is immediately subjected to ultra-fast cooling after rolling, a UFC (ultra-fast cooling) + ACC (accelerated laminar cooling) strong water cooling process is adopted, the final cooling temperature is 280°C, the cooling rate is not less than 10°C / s, the steel plate is air-cooled on a cooling bed after water cooling, and the steel plate is warm straightened when the temperature is cooled to 260°C. The steel plate is subjected to a tempering heat treatment, the tempering holding temperature is 200°C, and the heating time is 1 min / mm x plate thickness.

[0124] Example 5

[0125] The chemical composition of this example is shown in Table 1, with the balance being Fe and trace elements. A slab meeting the above composition is heated, rolled, pre-straightened, ultra-fast cooled + laminar cooled, cooled on a cooling bed, warm straightened, and tempered to obtain a wear-resistant steel plate, wherein the slab is heated at 1150°C, the heating time coefficient is 1 min / mm, then two-stage rolling is performed on a plate mill, rough rolling is performed at 1050°C, the rough rolling adopts a rolling schedule of low speed and large reduction, so as to ensure that the reduction rate of the last three passes is greater than 15%, and the thickness after being warmed up is 113 mm. The finish rolling starts at 840°C, the finish rolling temperature is controlled at 800°C, the steel plate is immediately sent to a pre-straightening machine for pre-straightening after rolling, so as to ensure the shape of the steel plate before water cooling, the steel plate is immediately subjected to ultra-fast cooling after rolling, a UFC (ultra-fast cooling) + ACC (accelerated laminar cooling) strong water cooling process is adopted, the final cooling temperature is 250°C, the cooling rate is not less than 10°C / s, the steel plate is air-cooled on a cooling bed after water cooling, and the steel plate is warm straightened when the temperature is cooled to 150°C. The steel plate is subjected to a tempering heat treatment, the tempering holding temperature is 200°C, and the heating time is 1 min / mm x plate thickness.

[0126] Comparative Example 1

[0127] The chemical composition of the comparative example is shown in Table 1, with the balance being Fe and trace elements. The slab is heated at 1150°C, with a heating time coefficient of 1 min / mm, and then two-stage rolling is performed on a plate mill, with the rough rolling stage being performed at 1050°C. The rough rolling uses a low-speed and high-pressure rolling schedule, with the last three passes being ensured to have a reduction of more than 15%, and the re-rolled thickness after being warmed up being 75 mm. The finish rolling stage is started at 880°C, with the finish rolling temperature being controlled at 820°C. After rolling, an ACC water cooling process is used, with the final cooling temperature being 632°C and the cooling speed being not less than 10°C / s. After being discharged from the water, the steel plate is air cooled to room temperature on a cooling bed. Then, the steel plate is heated to 900°C and then air cooled to room temperature. Finally, the steel plate is subjected to a tempering heat treatment, with the tempering holding temperature being 200°C and the heating time being 1 min / mm x plate thickness.

[0128] Comparative Example 2

[0129] The chemical composition of the comparative example is shown in Table 1, with the balance being Fe and trace elements. The slab is heated at 1150°C, with a heating time coefficient of 1 min / mm, and then two-stage rolling is performed on a plate mill, with the rough rolling stage being performed at 1050°C. The rough rolling uses a low-speed and high-pressure rolling schedule, with the last three passes being ensured to have a reduction of more than 15%, and the re-rolled thickness after being warmed up being 75 mm. The finish rolling stage is started at 870°C, with the finish rolling temperature being controlled at 820°C. After rolling, an ACC water cooling process is used, with the final cooling temperature being 645°C and the cooling speed being not less than 10°C / s. The steel plate is then heated to 900°C and quenched, and then isothermal quenched at 250°C and then cooled to room temperature. Finally, the steel plate is subjected to a tempering heat treatment, with the tempering holding temperature being 200°C and the heating time being 1 min / mm x plate thickness.

[0130] Related test methods:

[0131] The test of the type and content of the metallographic structure is performed by SEM analysis.

[0132] The test method of the grain size of the metallographic structure is GB6394-86 metallographic method.

[0133] The test method of the mechanical properties is GB / T228-2002 "Metallic materials tensile test method at room temperature".

[0134] Related experiments and effect data:

[0135] Table 1 (wt%, balance being Fe and unavoidable impurities)

[0136]

[0137]

[0138] Table 2 Rolling and heat treatment process parameters

[0139]

[0140] Table 3 Mechanical properties after tempering

[0141]

[0142] The influence of the process on the microstructure and performance of the steel plate was found to be different under different processes. The final cooling temperature of Example 1 and Example 2 was relatively high, and the microstructure was mainly lath bainite and granular bainite ( Figure 1 and Figure 2 ), which resulted in a relatively low hardness level of the bainite steel plate under this process, which could only meet the hardness requirement of NM400 level, and could not meet the requirement of NM450 level. The final cooling temperature in Example 3-5 was further reduced, resulting in a large amount of lower bainite and martensite in the microstructure ( Figures 3-5 ), so the strength and hardness under this process were higher than those of Example 1 and 2, which could meet the hardness requirement of NM450 level, and the toughness also met the design requirement. This kind of microstructure ensured that the bainite wear-resistant steel plate obtained the best strength and toughness matching, and the overall hardness level met the requirement of NM450 level.

[0143] The overall strength of Comparative Example 1 was relatively low due to the low cooling speed during air cooling. There was a large amount of granular bainite and martensite in the microstructure ( Figure 6 ), and the large amount of granular bainite affected the improvement of the strength and toughness of the steel plate. The toughness of Comparative Example 2 was improved by isothermal quenching, and the bainite lath obtained by isothermal quenching was relatively thin and long ( Figure 7 ), which failed to achieve the most ideal strengthening and toughening effect.

[0144] The above description is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wear-resistant steel plate, characterized in that, The chemical composition of the steel plate includes: C: 0.18 wt% - 0.22 wt%, Mn: 2.00 wt% - 2.30 wt%, Si: 1.50 wt% - 1.80 wt%, Cr: 0.70 wt% - 1.20 wt%, Mo: 0.20 - 0.50 wt%, Ni: 0.2 wt% - 0.4 wt%, Al: 0.02 wt% - 0.04 wt%, Ti: 0.010 wt% - 0.025 wt%, Nb: 0.01 wt% - 0.04 wt%, P: ≤0.02 wt%, S: ≤0.02 wt%, B: 0.0001 wt% - 0.0025 wt%, balance Fe; The method for preparing the wear-resistant steel plate includes: Under a first set heating temperature and a first set heating time, a plate containing the chemical composition is heated, wherein the first set heating time t1 satisfies the relationship: t1=a1×b1, where a1 represents the heating coefficient of the first set heating temperature and b1 represents the thickness of the plate. Under a set reduction rate, the heated sheet is subjected to rough rolling; The plate after rough rolling is subjected to finish rolling at a set finish rolling temperature and a set final rolling temperature, and then straightened at a first set temperature. At a set cooling rate, the first straightened plate is subjected to strong water cooling treatment so that the plate reaches a second set temperature; The plate and container, after being subjected to strong water cooling, are air-cooled until they reach a third set temperature, and then a second straightening process is performed. Under a second set heating temperature and a second set heating time, the straightened plate is heated to obtain a wear-resistant steel plate. The second set heating time t2 satisfies the relationship: t2=a2×b1, where a2 represents the heating coefficient of the second set heating temperature and b1 represents the thickness of the plate. The set finishing rolling temperature is 820℃-880℃, and the set final rolling temperature is 800℃-830℃. The set cooling rate is not less than 10℃ / s, the second set temperature is 200℃-400℃, the third set temperature is 100℃-300℃, and the second set heating temperature is 150℃-200℃. The thickness of the product to be heated should not be less than 4.5 times the thickness of the finished product.

2. The wear-resistant steel plate according to claim 1, characterized in that, The metallographic structure of the steel plate includes at least one of the following: bainite, martensite, austenite, and carbonaceous precipitates.

3. The wear-resistant steel plate according to claim 2, characterized in that, The carbonaceous precipitates include at least one of the following: Ti-containing carbonitrides, Nb-containing carbonitrides, cementite, and ε-carbide.

4. The wear-resistant steel plate according to claim 2, characterized in that, The lath width of the bainite is 200nm-400nm, the lath width of the martensite is 500nm-800nm, and the average grain diameter of the austenite is 15μm-25μm.

5. The wear-resistant steel plate according to claim 2, characterized in that, The bainite content is 20%-30% by volume, the martensite content is 70%-80% by volume, and the austenite content is 5%-10% by volume.

6. The wear-resistant steel plate according to any one of claims 1-5, characterized in that, The performance parameters of the wear-resistant steel plate satisfy at least one of the following I-VI: I. The surface Brinell hardness is HBW420-480. II. Tensile strength ≥ 1400 MPa III. Elongation A 50 It is 15%-25%. VI. Carbon equivalent is 0.55-0.

85. V-shaped impact at -20℃ ≥50J, VI. Unevenness ≤ 5mm / m.

7. A method for preparing a wear-resistant steel plate, characterized in that, The method for preparing the wear-resistant steel plate according to any one of claims 1-6 comprises: Under a first set heating temperature and a first set heating time, a plate containing the chemical composition is heated, wherein the first set heating time t1 satisfies the relationship: t1=a1×b1, where a1 represents the heating coefficient of the first set heating temperature and b1 represents the thickness of the plate. Under a set reduction rate, the heated sheet is subjected to rough rolling; The plate after rough rolling is subjected to finish rolling at a set finish rolling temperature and a set final rolling temperature, and then straightened at a first set temperature. At a set cooling rate, the first straightened plate is subjected to strong water cooling treatment so that the plate reaches a second set temperature; The plate and container, after being subjected to strong water cooling, are air-cooled until they reach a third set temperature, and then a second straightening process is performed. Under a second set heating temperature and a second set heating time, the straightened plate is heated to obtain a wear-resistant steel plate. The second set heating time t2 satisfies the relationship: t2=a2×b1, where a2 represents the heating coefficient of the second set heating temperature and b1 represents the thickness of the plate.

8. The preparation method according to claim 7, characterized in that, The first set heating temperature is 1150℃-1180℃. The heating coefficient for the first set heating temperature is taken as 1 min / mm - 2 min / mm. The first set temperature is 750℃-800℃.

9. The preparation method according to claim 7 or 8, characterized in that, The heating coefficient for the second set heating temperature is taken as 1 min / mm - 3 min / mm. The set reduction rate is set to be greater than 15% for the last three passes.

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