Ultrafine bainite wear-resistant steel capable of rapidly completing phase transformation and preparation method thereof

Abstract

The application relates to the technical field of alloy production and manufacturing, in particular to a superfine bainite wear-resistant steel capable of rapidly completing phase change and a preparation method thereof, wherein the superfine bainite wear-resistant steel capable of rapidly completing phase change comprises the following components in percentage by weight: C: 0.20-0.30%, Si: 1.15-1.35%, Mn: 0.85-1.05%, Cr: 0.95-1.24%, Ni: 1.05-1.18%, Al: 0.80-1.20%, and the rest is Fe and inevitable impurities. The preparation method comprises the following steps: S1, melting and casting; S2, hot rolling; S3, secondary warm rolling; S4, low-temperature phase change; and S5, high-temperature phase change. The application solves the technical problem that the isothermal phase change time is too long in the existing superfine bainite preparation process, which is not conducive to industrialized production.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of alloy production and manufacturing, in particular to a super-fine bainite wear-resistant steel capable of rapidly completing phase change and a preparation method thereof. BACKGROUND

[0002] In recent years, super-fine bainite is often used as wear-resistant material due to its good high-strength and high-toughness characteristics, and has attracted extensive attention of researchers and industrial application. However, the super-fine bainite steel needs to be isothermally phase-changed in a relatively low bainite phase change temperature range, and the required time is as long as 10 hours, which restricts the large-scale production and application of the super-fine bainite steel. Therefore, shortening the isothermal phase change time and accelerating the bainite phase change process are the key to solving the industrial production of the super-fine bainite steel.

[0003] The prior art such as the Chinese patent with the publication number CN110527794A provides a heat treatment method of micro-nano structure bainite steel, which realizes the shortening of the bainite steel heat treatment cycle and the refinement of blocky residual austenite by controlling the contents of carbon and silicon and assisting with a multi-step isothermal process, and improves the performance of the bainite steel.

[0004] However, although the above prior art has shortened the bainite steel heat treatment cycle to several hours, there is still a problem of too long production time in industrial production, which is not conducive to the industrial production and large-scale application of the bainite steel. SUMMARY

[0005] The application provides a super-fine bainite wear-resistant steel capable of rapidly completing phase change and a preparation method thereof, and aims to solve the technical problem of too long isothermal phase change time in the existing super-fine bainite preparation process, which is not conducive to industrial production.

[0006] The application provides the following technical scheme, a super-fine bainite wear-resistant steel capable of rapidly completing phase change, which contains the following components by weight percentage: C: 0.20-0.30%, Si: 1.15-1.35%, Mn: 0.85-1.05%, Cr: 0.95-1.24%, Ni: 1.05-1.18%, Al: 0.80-1.20%, and the rest is Fe and inevitable impurities.

[0007] The application also includes a preparation method of the super-fine bainite wear-resistant steel capable of rapidly completing phase change, which comprises the following steps.

[0008] S1 smelting and casting: according to the component design of the bainite wear-resistant steel part, the corresponding raw materials are weighed and smelted and cast into a steel ingot;

[0009] S2 hot rolling: the ingot is heated to 1180-1250 DEG C at a constant heating rate, then homogenized for 2 hours, and then cooled to 1020-1080 DEG C at a constant speed, and then multi-pass hot rolling is carried out;

[0010] S3 secondary warm rolling: the hot rolled blank is cooled to a certain temperature and then warm rolled, the single-pass warm rolling reduction is greater than or equal to 10%, and the total deformation amount of warm rolling is 20-40%.

[0011] S4 low-temperature phase transformation: the warm-rolled rolled steel plate is immediately put into a low-temperature salt bath furnace for 10-30 minutes;

[0012] S5 high-temperature phase transformation: the steel plate obtained in step S4 is immediately put into a high-temperature salt bath furnace and kept for 10-20 minutes, and then air-cooled to room temperature to obtain an ultra-fine bainite wear-resistant steel.

[0013] Principle of the present application:

[0014] In the present application, the steel blank after high-temperature homogenization treatment is hot rolled at a single-phase austenite temperature range, and a relatively large single-pass reduction is used in a relatively low rolling temperature range, which can ensure full recrystallization of austenite, avoid grain growth caused by high temperature during rolling, and eliminate part of the casting defects.

[0015] The rapid cooling to the warm rolling temperature range after hot rolling is to prevent the steel from undergoing other phase changes, such as pearlite phase change. Warm rolling of the steel blank before bainite phase transformation can produce a large number of crystal defects in the deformed steel, increase the dislocation density in the steel, promote the nucleation of bainite ferrite, and significantly shorten the incubation period of bainite phase transformation. After warm rolling, the steel blank is immediately subjected to bainite isothermal transformation at a relatively low temperature range, and the bainite phase transformation occurs immediately, a large number of bainite ferrite nucleates to refine the bainite lath, the original austenite grains are fully divided, and the probability of generating bulk residual austenite is reduced. After isothermal transformation at low temperature bainite phase transformation for a period of time, the steel blank is placed in a salt bath furnace at a relatively high temperature for isothermal transformation, which can accelerate the transformation of bainite without generating coarse bainite. This is because the increase in temperature can accelerate the diffusion speed of carbon atoms, and thus accelerate the phase transformation time, and because the bainite generated in the first step divides the austenite grains, the remaining austenite is fine and limits the growth of bainite.

[0016] Advantages of the present application:

[0017] 1. The present application adopts a multi-step isothermal process in the isothermal transformation of bainite, first at a lower temperature, and then at a higher temperature for the second step, which can significantly shorten the completion time of bainite transformation. Combined with the secondary warm rolling process, it can increase the nucleation rate and growth rate of bainite, significantly shorten the completion time of bainite transformation, shorten the completion time of bainite transformation from several hours to 50 minutes, and greatly improve the production efficiency of ultra-fine bainite.

[0018] 2. Through the secondary warm rolling process, the nucleation rate and growth rate of bainite can be increased, and the completion time of bainite transformation can be significantly shortened. At the same time, the secondary warm rolling process can refine the bainite lath, and the prepared bainite lath is close to nanoscale, so that a large amount of ultra-fine bainite structure is obtained, the fine grain strengthening and solid solution strengthening mechanisms are fully utilized, and the comprehensive mechanical properties of the steel are improved.

[0019] 3. The method of the present application uniformly treats the steel billet at a lower rolling temperature range with a larger pass reduction, which can ensure full recrystallization of austenite and avoid grain growth caused by high temperature during rolling.

[0020] Further, the ultra-fine bainite wear-resistant steel for rapidly completing phase transformation comprises the following components by weight percentage: C: 0.25%, Si: 1.25%, Mn: 0.96%, Cr: 1.12%, Ni: 1.1%, Al: 1.05%, and the rest is Fe and unavoidable impurities.

[0021] Further, the ultra-fine bainite wear-resistant steel for rapidly completing phase transformation comprises the following components by weight percentage: C: 0.29%, Si: 1.32%, Mn: 1.03%, Cr: 1.12%, Ni: 1.15%, Al: 1.16%, and the rest is Fe and unavoidable impurities.

[0022] Further, the ultra-fine bainite wear-resistant steel for rapidly completing phase transformation comprises the following components by weight percentage: C: 0.21%, Si: 1.15%, Mn: 0.88%, Cr: 0.97%, Ni: 1.09%, Al: 0.85%, and the rest is Fe and unavoidable impurities.

[0023] Further, the heating rate in S2 is 65-80℃ / h, and the cooling rate is 10℃ / s.

[0024] In this application, controlling the heating rate and cooling rate can ensure that the material is fully preheated during the heating process, and ensure the uniformity and consistency of the material.

[0025] Further, the number of hot rolling in S2 is 3-5 times, the single hot rolling reduction is ≥15%, and the total deformation of hot rolling is 60-80%.

[0026] In the present application, the single hot rolling with high deformation can fully recrystallize the austenite, and can avoid the grain growth caused by high temperature in the rolling process.

[0027] Further, the cooling speed in S3 is ≥20℃ / s, the number of warm rolling is 1-2 times, the warm rolling opening rolling temperature is 400-450℃, and the finish rolling temperature is ≥330℃.

[0028] In the present application, controlling the warm rolling temperature can effectively reduce the generation of martensite and refine the bainite grains. If the warm rolling temperature is high, the bainite grains will continue to grow, resulting in too large bainite lath thickness and reducing the mechanical properties of the material. If the warm rolling temperature is low, the bainite phase change will not be complete to generate martensite, reducing the impact toughness of the material.

[0029] At the same time, the large cooling speed can prevent other phase change processes such as pearlite phase change from occurring in the phase change.

[0030] Further, the low-temperature salt bath furnace temperature in S4 is 300±20℃.

[0031] In the present application, controlling the low-temperature phase change temperature can control the bainite grain size and the generation of martensite. If the low-temperature phase change temperature is too low, martensite phase change will occur in the phase change process, causing residual austenite to transform into martensite and reducing the impact toughness of the material. If the low-temperature phase change temperature is too high, the generated bainite grains are coarse, resulting in large bainite lath thickness and reducing the strength and hardness of the material.

[0032] Further, the high-temperature salt bath furnace temperature in S5 is 400±30℃.

[0033] In the present application, controlling the high-temperature phase change temperature can inhibit the excessive generation of bainite grains. If the high-temperature phase change temperature is too high or too low, it will cause excessive growth of bainite grains, and further cause the bainite lath thickness to be too large, thereby reducing the mechanical properties of the material. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The process flow chart of the present application;

[0035] Figure 2 The metallographic structure chart of the ultra-fine bainite wear-resistant steel in Example 1 of the present application;

[0036] Figure 3 The SEM (scanning electron microscope) chart of the ultra-fine bainite wear-resistant steel in Example 1 of the present application;

[0037] Figure 4 The metallographic structure chart of the ultra-fine bainite wear-resistant steel in Comparative Example 1 of the present application;

[0038] Figure 5 Microstructure of the ultra-fine bainite wear-resistant steel in the present application comparative example 2;

[0039] Figure 6 Microstructure of the ultra-fine bainite wear-resistant steel in the present application comparative example 3;

[0040] Figure 7 SEM image of the ultra-fine bainite wear-resistant steel in the present application comparative example 4;

[0041] Figure 8 SEM image of the ultra-fine bainite wear-resistant steel in the present application comparative example 5;

[0042] Figure 9 SEM image of the ultra-fine bainite wear-resistant steel in the present application comparative example 7;

[0043] Figure 10 SEM image of the ultra-fine bainite wear-resistant steel in the present application comparative example 9. DETAILED DESCRIPTION

[0044] The following is further described in detail through specific embodiments:

[0045] Example 1

[0046] An ultra-fine bainite wear-resistant steel capable of completing phase transformation quickly, wherein the chemical composition of the ultra-fine bainite wear-resistant steel is 0.25% C, 1.25% Si, 0.96% Mn, 1.12% Cr, 1.10% Ni, 1.05% Al, and the rest is Fe and inevitable impurities. The preparation process of the ultra-fine bainite wear-resistant steel capable of completing phase transformation quickly is as shown in the following table, which includes the following steps: Figure 1

[0047] S1 Melting and casting: according to the component design of the bainite wear-resistant steel, the raw materials are melted and cast into ingots in a vacuum induction furnace.

[0048] S2 Hot rolling: the ingot is heated to 1250℃ at a heating rate of 80℃ / h for homogenization treatment for 2h, and then cooled to 1120℃ at a speed of 10℃ / s for transfer. The ingot is transferred to the rolling workpiece for rolling, the opening rolling temperature is 1050℃, the hot rolling times are 4, and the single hot rolling reduction rate is 17.5%. The final rolling temperature is 920℃, and the total deformation of hot rolling is 70%.

[0049] S3 Secondary warm rolling: the above hot rolled blank is cooled to 500℃ at a speed of 30℃ / s for warm rolling. The hot rolled blank is transferred to the rolling workpiece for rolling, the opening rolling temperature is 425℃, and the final rolling temperature is 340℃. During the period, two rollings are carried out, the single hot rolling reduction rate is 15%, and the total rolling deformation is 30%.

[0050] ​S4 low temperature phase transformation: the warm-rolled steel plate obtained is immediately placed into a 300℃ salt bath furnace for 20 minutes;

[0051] S5 high temperature phase transformation: the steel plate obtained in step S4 is immediately placed into a 400℃ salt bath furnace for 15 minutes, and then air-cooled to room temperature to obtain the ultra-fine bainite wear-resistant steel.

[0052] The microstructure of the ultra-fine bainite wear-resistant steel in this embodiment is shown in FIG. 1. Figure 2 and 3 as shown.

[0053] Example 2

[0054] An ultra-fine bainite wear-resistant steel capable of rapidly completing phase transformation, wherein the chemical composition of the ultra-fine bainite wear-resistant steel is as follows: 0.29% C, 1.32% Si, 1.03% Mn, 1.12% Cr, 1.15% Ni, 1.16% Al, and the balance of Fe and inevitable impurities. The preparation process of the ultra-fine bainite wear-resistant steel capable of rapidly completing phase transformation comprises the following steps:

[0055] S1 smelting and casting: according to the component design of the bainite wear-resistant steel part, the raw materials are smelted and cast into an ingot in a vacuum induction furnace.

[0056] S2 hot rolling: the ingot is heated to 1180℃ at a heating rate of 65℃ / h for homogenization treatment for 2h, and then cooled to 1120℃ at a rate of 10℃ / s for transfer rolling. The rolling temperature is 1050℃, the hot rolling times are 4, and the single hot rolling reduction rate is 15%. The final rolling temperature is 920℃, and the total deformation of hot rolling is 60%.

[0057] S3 secondary warm rolling: the above hot-rolled blank is cooled to 500℃ at a rate of 30℃ / s for warm rolling. The rolling temperature is 425℃, and the final rolling temperature is 340℃. During the rolling, two rolling processes are performed, the single hot rolling reduction rate is 10%, and the total deformation of rolling is 20%.

[0058] S4 low temperature phase transformation: the warm-rolled steel plate obtained is immediately placed into a 300℃ salt bath furnace for 20 minutes;

[0059] S5 high temperature phase transformation: the steel plate obtained in step S4 is immediately placed into a 400℃ salt bath furnace for 15 minutes, and then air-cooled to room temperature to obtain the ultra-fine bainite wear-resistant steel.

[0060] Example 3

[0061] The application discloses a superfine bainite wear-resistant steel capable of rapidly completing phase transformation, and a preparation process thereof.

[0062] S1 smelting and casting: raw materials are smelted and cast into a steel ingot in a vacuum induction furnace according to the component design of the bainite wear-resistant steel part.

[0063] S2 hot rolling: the steel ingot is heated to 1250 DEG C at a heating rate of 80 DEG C / h, then uniformly treated for 2 h, and then cooled to 1120 DEG C at a speed of 10 DEG C / s, and then transferred for rolling. The rolling temperature is 1050 DEG C, the hot rolling times are 4, and the single hot rolling reduction is 20%. The final rolling temperature is 920 DEG C, and the total hot rolling deformation is 80%.

[0064] S3 secondary warm rolling: the hot-rolled blank is cooled to 500 DEG C at a speed of 30 DEG C / s, and then warm rolling is performed. The rolling temperature is 425 DEG C, and the final rolling temperature is 335 DEG C. The rolling is performed twice, the single hot rolling reduction is 20%, and the total rolling deformation is 40%.

[0065] S4 low-temperature phase transformation: the warm-rolled rolling steel plate is immediately placed into a 320 DEG C salt bath furnace for heat preservation for 20 min.

[0066] S5 high-temperature phase transformation: the steel plate obtained in the step S4 is immediately placed into a 430 DEG C salt bath furnace for heat preservation for 15 min, and then air-cooled to room temperature to obtain the superfine bainite wear-resistant steel.

[0067] Comparative Example 1

[0068] With reference to the accompanying drawings, Figure 4 the superfine bainite wear-resistant steel of the comparative example 1 and the example 1 is the same in chemical composition and mass percentage, and the difference lies in that the step S3 secondary warm rolling is not performed, and the specific production steps are as follows.

[0069] S1 smelting and casting: raw materials are smelted and cast into a steel ingot in a vacuum induction furnace according to the component design of the bainite wear-resistant steel part.

[0070] S2 hot rolling: the steel ingot is heated to 1250 DEG C at a heating rate of 80 DEG C / h, then uniformly treated for 2 h, and then cooled to 1120 DEG C at a speed of 10 DEG C / s, and then transferred for rolling. The rolling temperature is 1050 DEG C, the hot rolling times are 4, and the single hot rolling reduction is 20%. The final rolling temperature is 920 DEG C, and the total hot rolling deformation is 80%.

[0071] S3 low-temperature phase transformation: the hot-rolled rolling steel plate is immediately placed into a 300 DEG C salt bath furnace for heat preservation for 20 min.

[0072] S4 high temperature phase transformation: the steel plate obtained in step S4 was immediately put into a 400°C salt bath furnace and held for 15 minutes, and after the holding was completed, air cooling was performed to room temperature.

[0073] Comparative Example 2

[0074] With reference to the accompanying Figure 5 , the ultra-fine bainite wear-resistant steel of the present comparative example has the same chemical composition as that of Example 1, except that there is no step of S4 low temperature phase transformation, and the S5 high temperature phase transformation time is increased to 120 minutes. The specific production steps are as follows:

[0075] S1 melting and casting: according to the component design of the bainite wear-resistant steel, the raw materials were melted and cast into ingots in a vacuum induction furnace.

[0076] S2 hot rolling: the ingot was heated to 1250°C at a heating rate of 80°C / h for homogenization treatment for 2h, and then cooled to 1120°C at a rate of 10°C / s for hot rolling. The rolling temperature was 1050°C, the hot rolling times were 4, and the single hot rolling reduction rate was 17.5%. The final rolling temperature was 920°C, and the total deformation of hot rolling was 70%.

[0077] S3 secondary warm rolling: the hot rolled blank was cooled to 500°C at a rate of 30°C / s for warm rolling. The rolling temperature was 425°C, and the final rolling temperature was 340°C. During the rolling, two rolling were performed, the single hot rolling reduction rate was 15%, and the total deformation of rolling was 30%.

[0078] S4 low temperature phase transformation: the warm-rolled rolled steel plate was immediately put into a 300°C salt bath furnace for 120 minutes of holding, and after the holding was completed, air cooling was performed to room temperature to obtain an ultra-fine bainite wear-resistant steel.

[0079] Comparative Example 3

[0080] With reference to the accompanying Figure 6 , the ultra-fine bainite wear-resistant steel of the present comparative example has the same chemical composition as that of Example 1, except that there is no step of S4 low temperature phase transformation, and the S5 high temperature phase transformation time is increased to 120 minutes. The specific production steps are as follows:

[0081] S1 melting and casting: according to the component design of the bainite wear-resistant steel, the raw materials were melted and cast into ingots in a vacuum induction furnace.

[0082] S2 hot rolling: the ingot was heated to 1250°C at a heating rate of 80°C / h for homogenization treatment for 2h, and then cooled to 1120°C at a rate of 10°C / s for hot rolling. The rolling temperature was 1050°C, the hot rolling times were 4, and the single hot rolling reduction rate was 17.5%. The final rolling temperature was 920°C, and the total deformation of hot rolling was 70%.

[0083] S3 Secondary warm rolling: the hot rolled blank is cooled to 500℃ at a rate of 30℃ / s and then warm rolled. The starting temperature of rolling is 425℃ and the final temperature of rolling is 340℃. Two times of rolling are performed with a single hot rolling reduction of 15% and a total deformation of 30%.

[0084] S4 High temperature phase transformation: the steel plate obtained after step S3 is immediately put into a salt bath furnace at 400℃ and held for 100 minutes. After the holding, the steel plate is air cooled to room temperature to obtain the ultra-fine bainite wear-resistant steel.

[0085] Comparative Example 4

[0086] Reference is made to the accompanying drawings, which show: Figure 7 This comparative example has the same preparation process as Example 1, except that the chemical composition of the ultra-fine bainite wear-resistant steel is different. Specifically, the steel contains 0.25% C, 1.25% Si, 0.96% Mn, 1.12% Cr, 1.10% Ni, and the rest is Fe and inevitable impurities.

[0087] Comparative Example 5

[0088] Reference is made to the accompanying drawings, which show: Figure 8 This comparative example has the same preparation process as Example 1, except that the chemical composition of the ultra-fine bainite wear-resistant steel is different. Specifically, the steel contains 0.25% C, 1.25% Si, 0.96% Mn, 1.12% Cr, 1.10% Ni, and the rest is Fe and inevitable impurities.

[0089] Comparative Example 6

[0090] This comparative example has the same preparation process as Example 1, except that the chemical composition of the ultra-fine bainite wear-resistant steel is different. Specifically, the steel contains 0.25% C, 1.25% Si, 0.96% Mn, 1.12% Cr, 1.10% Ni, and the rest is Fe and inevitable impurities.

[0091] Comparative Example 7

[0092] Reference is made to the accompanying drawings, which show: Figure 9 This comparative example is different from Example 1 in that the warm rolling temperature in S3 is 500℃.

[0093] Comparative Example 8

[0094] This comparative example is different from Example 1 in that the warm rolling temperature in S3 is 300℃.

[0095] Comparative Example 9

[0096] Reference is made to the accompanying drawings, which show: Figure 10 This comparative example is different from Example 1 in that the low temperature isothermal temperature in S4 is 230℃.

[0097] Comparative Example 10

[0098] The difference between this comparative example and Example 1 is that the low temperature phase transition temperature in S4 is 350°C.

[0099] Comparative Example 11

[0100] The difference between this comparative example and Example 1 is that the high temperature phase transition temperature in S5 is 350°C.

[0101] Comparative Example 12

[0102] The difference between this comparative example and Example 1 is that the high temperature phase transition temperature in S5 is 500°C.

[0103] The weight percentages of the components and the preparation parameters of the above examples and comparative examples are summarized in Table 1.

[0104] Table 1: Weight percentages of the components and other data of the examples and comparative examples

[0105]

[0106] Experimental Example 1: Microscopic Experiment

[0107] This experimental example is used to observe the microstructure of the ultra-fine bainite wear-resistant steel prepared in the above examples and comparative examples. The specific steps are: the sample is processed into 10x10x5mm by wire electrical discharge machining, and after polishing and mechanical polishing, it is etched with 4% nitric acid alcohol solution for 15s, and then observed by metallographic (WMJ-9590) and scanning electron microscope (FE-SEM, ZEISS Sigma 500). The specific data are shown in Table 2.

[0108] Table 2: Microstructure of the ultra-fine bainite wear-resistant steel prepared in the above examples and comparative examples

[0109]

[0110] Experimental Example 2: Mechanical Property Test

[0111] This experimental example is used to test the mechanical properties of the ultra-fine bainite wear-resistant steel prepared in the above examples and comparative examples. The specific steps are: the tensile sample is processed into a shape with a gauge length of 25mm, a width of 3mm, and a thickness of 1.5mm by wire electrical discharge machining, and then the tensile test is carried out on a tensile testing machine (Zwick Roell 100kN) with a strain rate of 10 -3 S -1 The impact toughness sample is processed into 10x10x55mm, and the test is carried out on a pendulum impact toughness testing machine. The Brinell hardness is obtained by an electronic Brinell hardness tester. The test results are shown in Table 3.

[0112] Table 3: Mechanical property results of the metal mold cast aluminum alloys prepared in the above examples and comparative examples

[0113]

[0114] From the data table of Table 2 and Table 3, it can be seen that the microstructure of Examples 1-3 is bainite + residual austenite, the volume fraction of residual austenite is 13-18%, and there is no martensite. At the same time, the bainite lath thickness of Examples 1-3 is 106-110 nm, which is close to nanoscale, and the fine bainite lath can play the role of fine grain strengthening to improve the strength and hardness of the steel. In the mechanical property test, Examples 1-3 meet the standard in material strength and hardness, and also have better performance in elongation and impact toughness. This is because there is a sufficient amount of thin film austenite in the microstructure of Examples 1-3, so that the material can occur TRIP effect during deformation, thereby improving the plasticity and toughness of the material.

[0115] Comparative Example 1 differs from Example 1 in that there is no S3 secondary warm rolling step in the preparation process. From the microstructure structure, it can be seen that there is about 23% of martensite in the material, which is due to the fact that the bainite phase change process of Comparative Example 1 has not been completed, and the untransformed austenite occurs martensite phase change in the subsequent cooling process. This part of the martensite is fresh martensite formed during the cooling process after isothermal completion, which is hard and brittle, and contains a large amount of dislocation density, which can improve the yield strength and tensile strength of the steel, but can significantly reduce the elongation and impact toughness of the steel. At the same time, due to the absence of the secondary warm rolling process, the bainite phase change nucleation rate is low, which is beneficial to the growth and coarsening of the lath, and finally the bainite lath thickness of Comparative Example 1 is measured to be 189 nm.

[0116] Comparative Example 2 and Comparative Example 3 differ from Example 1 in that only one step of isothermal is performed. From the microstructure, both parts will produce martensite, which is because one-step isothermal is not enough to complete the bainite phase change. In terms of mechanical properties, it is similar to Comparative Example 1, because the presence of martensite improves the yield strength and tensile strength of Comparative Examples 2 and 3, but the elongation and impact toughness of the material are significantly reduced.

[0117] Comparative Example 4 differs from Example 1 in that no Al element is added. From the attached Figure 7 It can be seen that Comparative Example 4 has cementite precipitation, thus reducing the strength and toughness of the material. From the test results in Table 3, it can also be seen that Comparative Example 4 has a certain degree of decline in strength, hardness and toughness compared with Example 1.

[0118] Comparative Example 5 differs from Example 1 in that the amount of Si element added is small. From the attached Figure 8It can be seen that a small amount of cementite also precipitated in Comparative Example 5, which also affected the strength, hardness and toughness of Comparative Example 5.

[0119] Compared with Example 1, Comparative Example 6 differs in that it has a higher Si content. As shown in Table 2, increasing the Si content leads to excessively large grains during bainite growth, with the bainite lath thickness reaching 164 nm, thus reducing the material's impact toughness.

[0120] Compared with Example 1, the rolling temperature in Comparative Example 7 was 500°C in S3. As can be seen from the attached figures, the microstructure of Comparative Example 7 is coarser than that of Example 1. Therefore, Comparative Example 7 shows a certain degree of decrease in strength, hardness, and toughness compared to Example 1.

[0121] Compared to Example 1, the rolling temperature in Comparative Example 8 was 300°C in S3. Lowering the rolling temperature resulted in incomplete bainitic transformation, leading to the formation of martensite.

[0122] Compared to Example 1, the isothermal temperature in Comparative Example 9 was 230°C in S4. (From Appendix) Figure 10 It can be seen that martensite exists in the microstructure of Comparative Example 9 because the first isothermal temperature is lower than the Ms point, leading to the formation of martensite. This affects the mechanical properties of Comparative Example 9.

[0123] Compared to Example 1, the phase transformation temperature in Comparative Example 10 was 350°C in S4. As shown in Table 2, increasing the low-temperature phase transformation temperature leads to an increase in the thickness of the bainite laths.

[0124] Compared with Example 1, Comparative Examples 11 and 12 changed the phase transformation temperature in S5. The test results show that the high phase transformation temperature affects the grain size of bainite, resulting in an increase in the thickness of the bainite laths.

[0125] The above are merely embodiments of the present invention, and the invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing ultrafine bainitic wear-resistant steel that rapidly undergoes phase transformation, characterized in that: The ultra-fine bainite wear-resistant steel contains the following components by weight percentage: C: 0.20-0.30%, Si: 1.15-1.35%, Mn: 0.85-1.05%, Cr: 0.95-1.24%, Ni: 1.05-1.18%, Al: 0.80-1.20%, and the rest is Fe and inevitable impurities; The preparation method comprises the following steps: S1 melting and casting: according to the component design of the ultra-fine bainite wear-resistant steel, the corresponding raw materials are weighed and melted and cast into ingots; S2 hot rolling: the ingot is heated to 1180-1250 DEG C at a constant heating rate, then homogenized for 2 hours, and then cooled to 1020-1080 DEG C at a constant speed, and then 3-5 times of hot rolling is carried out, the single hot rolling reduction is greater than or equal to 15%, and the total deformation of hot rolling is 60-80%; The heating rate is 65-80 DEG C / h, and the cooling speed is 10 DEG C / s; S3 secondary warm rolling: the hot rolled blank is cooled to a certain temperature at a speed greater than or equal to 20 DEG C / s, and then 1-2 times of warm rolling is carried out, the single warm rolling reduction is greater than or equal to 10%, and the total deformation of warm rolling is 20-40%; the warm rolling opening rolling temperature is 400-450 DEG C, and the final rolling temperature is greater than or equal to 330 DEG C; S4 low-temperature phase change: the rolled steel plate obtained by warm rolling is immediately put into a low-temperature salt bath furnace at 300±20 DEG C for 10-30 minutes; S5 high-temperature phase change: the steel plate obtained in step S4 is immediately put into a high-temperature salt bath furnace at 400±30 DEG C for 10-20 minutes, and then air-cooled to room temperature to obtain the ultra-fine bainite wear-resistant steel.

2. The method of claim 1, wherein the ultra-fine bainite wear-resistant steel is prepared by the following steps: The ultra-fine bainite wear-resistant steel contains the following components by weight percentage: C: 0.25%, Si: 1.25%, Mn: 0.96%, Cr: 1.12%, Ni: 1.1%, Al: 1.05%, and the rest is Fe and inevitable impurities. ​ 3. The method of claim 1, wherein the method of preparing ultra-fine bainite wear-resistant steel with rapid phase transformation is characterized in that: The ultra-fine bainite wear-resistant steel contains the following components by weight percentage: C: 0.29%, Si: 1.32%, Mn: 1.03%, Cr: 1.12%, Ni: 1.15%, Al: 1.16%, and the rest is Fe and inevitable impurities.

4. The method for preparing ultrafine bainitic wear-resistant steel with rapid phase transformation according to claim 1, characterized in that: The ultra-fine bainite wear-resistant steel contains the following components by weight percentage: C: 0.21%, Si: 1.15%, Mn: 0.88%, Cr: 0.97%, Ni: 1.09%, Al: 0.85%, and the rest is Fe and inevitable impurities.

5. The method of claim 1, wherein the ultra-fine bainite wear resistant steel is prepared by the steps of: The microstructure of the ultra-fine bainite wear-resistant steel is bainite + residual austenite, the volume fraction of residual austenite is 13-18%, and there is no martensite. ​ 6. The method of claim 1, wherein the method of preparing ultra-fine bainite wear resistant steel with fast phase transformation is characterized in that: In the ultra-fine bainite wear-resistant steel, the bainite lath thickness is 106-110 nm.

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