Heterogeneous medium manganese steel warm-rolled plate with high strength and toughness structure as well as preparation method and application of heterogeneous medium manganese steel warm-rolled plate

Abstract

The embodiment of the invention relates to a high-toughness structure heterogeneous medium manganese steel warm-rolled plate and a preparation method and application thereof, and belongs to the technical field of medium manganese steel. According to the heterogeneous medium manganese steel warm-rolled plate with the high strength and toughness structure, the heterogeneous medium manganese steel warm-rolled plate with the high strength and toughness structure comprises the following components in percentage by mass: 0.15%-0.18% of C, 10.0%-10.32% of Mn, 1.9%-2.1% of Al, 1.8%-2.2% of Cu and the balance of Fe. According to the method, through simple warm rolling treatment and follow-up short tempering, medium manganese steel forms structural heterogeneity, and therefore the warm rolling plate is promoted to have the more remarkable transformation induced plasticity TRIP effect and heterogeneous deformation induced (HDI) hardening capacity; according to the heterostructure medium manganese steel treated through the method, the yield strength is increased to 1113 MPa from 782 MPa; the tensile strength is increased to 1304 MPa from 1099 MPa; and the ductility is increased from 20.8% to 21.7%, and the mechanical property of the medium manganese steel is effectively improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of medium manganese steel, and in particular to a high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate and a preparation method and application thereof. Background Art

[0002] Vehicle weight reduction can effectively reduce vehicle exhaust emissions and save energy. How to achieve vehicle weight reduction without sacrificing safety performance has become a key issue in the current automotive industry. Ways to achieve lightweighting include: (1) lightweight optimization design of vehicle structure, such as structural topology / size / morphology optimization, etc.; (2) application of high-strength and lightweight materials, such as high-strength / advanced high-strength steel and ultra-high-strength steel, aluminum-magnesium alloy, engineering plastics, etc.; (3) use of advanced lightweight processing technology, such as laser welding, high-strength steel hot forming and other technologies. The application of lightweight advanced high-strength steel and lightweight manufacturing process technology are gradually gaining attention. Steel accounts for 65-70% of the vehicle body in China. The excellent performance of advanced high-strength steel (AHSS): high tensile strength characteristics enable it to achieve weight reduction through thinning without sacrificing safety performance.

[0003] The representative materials of the third generation AHSS are medium manganese steel, lightweight steel, quenching and partitioning (Q&P) steel, etc. The strength-plasticity product is expected to be between the first and third generations, but with the optimization of performance, its strength-plasticity product has now surpassed the second generation AHSS. On the basis of traditional TRIP steel, medium manganese steel is improved by increasing the Mn content, with a Mn mass fraction of 3% to 12%. It is usually a dual-phase structure of ferrite + austenite, and 50% austenite is obtained by annealing in the critical zone. During the deformation process, the metastable austenite undergoes a martensitic phase transformation, which is the TRIP effect. The elongation is significantly improved. At the same time, due to the strain hardening of the phase transformation process, the tensile strength is also improved.

[0004] In recent years, the concept of heterogeneous structure has been proposed for the design of new materials to synergistically increase the elongation and strength of materials. The core idea of ​​heterogeneous structure is to design appropriate soft and hard domains in the material. When in the elastic stage, the two domains deform together; when entering the initial stage of elastic-plasticity (stage II1), the soft domain begins to deform plastically first, while the hard domain is still in the elastic stage. The strain compatibility between the two domains forms a strain gradient near the interface, and a large number of geometric necessary dislocations (GNDs) are formed in the soft domain to coordinate the strain gradient to relieve the strain incompatibility. At this time, the long-range stress generated by GNDs is called back stress, which strengthens the soft phase and improves the YS of the material; a large number of GNDs accumulate near the interface to form stress concentration, and at this time the hard domain begins to deform plastically to adapt to the stress concentration, so that the stress and strain near the interface are relaxed (corresponding to stage II2); when the plastic deformation reaches stage III, the hard domain and the soft domain undergo plastic deformation together, and the soft domain undergoes higher plastic deformation than the hard domain. Summary of the invention

[0005] In view of this, the embodiments of the present application provide a high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate and its preparation method and application. Through a simple direct warm rolling-(low-temperature tempering) heat treatment process, the soft and hard domains in the material are reasonably set, and the preparation of high-strength and toughness structural heterogeneous medium manganese steel is completed. The strength of the medium manganese steel is further improved through short-time tempering heat treatment, which can effectively overcome the defects existing in the above-mentioned prior art.

[0006] A first aspect of an embodiment of the present application provides a high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate, wherein the high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate comprises the following components in mass percentage: C 0.15-0.18%, Mn 10.0-10.32%, Al1.9-2.1%, Cu1.8-2.2%, and the rest is Fe.

[0007] The second aspect of the embodiment of the present application also provides a method for preparing the above-mentioned high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate, comprising the following steps:

[0008] (1) Ingot smelting: Each component is melted and cast in vacuum to obtain an ingot;

[0009] (2) High temperature forging: forging the ingot into a slab and air cooling it to room temperature;

[0010] (3) high temperature hot rolling: hot rolling the slab to obtain a hot rolled plate, and air cooling;

[0011] (4) Medium temperature rolling: the hot rolled plate is subjected to double-pass heat preservation and rapid rolling to obtain a medium temperature rolled sample;

[0012] (5) Tempering heat treatment: The medium-temperature rolled sample is subjected to a short-time tempering heat treatment and then water quenched to room temperature to obtain a high-strength and tough structural heterogeneous medium-manganese steel warm-rolled plate.

[0013] In some embodiments that may include the above embodiments, the specific process of step (ii) is: heating the ingot to 1250°C, keeping it warm for 2.5 hours, and then forging it into a slab with a cross-section of 100mm×30mm, and then air-cooling it to room temperature.

[0014] In some embodiments that may include the above embodiments, the specific process of step (3) is: heating the slab to 1250°C, keeping it warm for 2.5 hours and then hot rolling it, with the starting rolling temperature being 1200°C and the final rolling temperature being greater than 950°C to obtain a hot-rolled plate with a thickness of 4mm±0.5mm, and then air cooling it.

[0015] In some embodiments, which may include the above embodiments, the final rolling temperature is 1000°C.

[0016] In some embodiments that may include the above embodiments, in step (3), the hot rolling is performed in 7 passes.

[0017] In some embodiments that may include the above embodiments, the specific process of double-pass insulation and rapid rolling in step (4) is: the hot-rolled plate is reheated to 600°C and kept warm for 15 minutes, and then immediately taken out for warm rolling to 3 mm, and then quickly placed in a heat treatment furnace for continued insulation at 600°C for 15 minutes, and then the sample is taken out for warm rolling to a target thickness of 2 mm, and then air-cooled to room temperature; during the double-pass insulation and rapid rolling, the temperature drop in the entire warm rolling process can be basically ignored.

[0018] In some embodiments that may include the above embodiments, in step (5), the short-time tempering heat treatment temperature is 400-600° C. and the time is 10-30 min.

[0019] The third aspect of the embodiments of the present application also provides the application of the above-mentioned high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate in automobiles.

[0020] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0021] The present application uses a simple warm rolling treatment, coupled with a subsequent short tempering, to form structural heterogeneity in the medium manganese steel, which promotes the warm-rolled plate to have a more significant phase transformation induced plasticity TRIP effect and heterogeneous deformation induced (HDI) hardening ability; the yield strength of the heterogeneous structure medium manganese steel treated by the present application is increased from 782MPa to 1113MPa; the tensile strength is increased from 1099MPa to 1304MPa; the elongation is increased from 20.8% to 21.7%, which effectively improves the mechanical properties of the medium manganese steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 The engineering stress-strain curves of Example 1 and Comparative Examples 1-2;

[0024] Figure 2 The strength / plasticity changes of Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] A first aspect of an embodiment of the present application provides a high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate, wherein the high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate comprises the following components in mass percentage: C 0.15-0.18%, Mn 10.0-10.32%, Al1.9-2.1%, Cu1.8-2.2%, and the rest is Fe.

[0027] The second aspect of the embodiment of the present application also provides a method for preparing the above-mentioned high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate, comprising the following steps:

[0028] (1) Ingot smelting: Each component is melted and cast in vacuum to obtain an ingot;

[0029] (2) High temperature forging: the ingot is heated to 1250° C., kept at this temperature for 2.5 h, and then forged into a slab with a cross section of 100 mm×30 mm, and then air-cooled to room temperature;

[0030] (3) High temperature hot rolling: the slab is heated to 1250° C., kept at this temperature for 2.5 h, and then hot rolled. Preferably, the hot rolling is performed in 7 passes, the starting rolling temperature is 1200° C., the final rolling temperature is greater than 950° C., preferably 1000° C., to obtain a hot rolled plate with a thickness of 4 mm±0.5 mm, and then air cooled;

[0031] (4) Medium-temperature rolling: the hot-rolled plate is reheated to 600°C and kept at this temperature for 15 min, then immediately taken out for warm rolling to 3 mm, and then quickly placed in a heat treatment furnace for further warming at 600°C for 15 min, and then the sample is taken out for warm rolling to a target thickness of 2 mm, and then air-cooled to room temperature; in double-pass warming and rapid rolling, the temperature drop during the entire warm rolling process can be basically ignored;

[0032] (5) Tempering heat treatment: The medium-temperature rolled sample is subjected to a short-time tempering heat treatment at a temperature of 400° C. for 10 min, and then water quenched to room temperature to obtain a high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate.

[0033] The third aspect of the embodiments of the present application also provides the application of the above-mentioned high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate in automobiles.

[0034] Unless otherwise specified, the experimental methods used in the examples of this application are all conventional methods.

[0035] In the following examples and comparative examples, unless otherwise specified, all raw materials can be obtained by commercial purchase or conventional methods.

[0036] Example 1

[0037] The method for preparing the high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate in this embodiment comprises the following steps:

[0038] Each component (C 0.15-0.18%, Mn 10.0-10.32%, Al 1.9-2.1%, Cu 1.8-2.2%, and the rest Fe) is cast by vacuum melting; then the ingot is heated to 1250°C by high-temperature forging, and is kept warm for 2.5 hours before forging into a slab with a cross section of 100 mm×30 mm, which is then air-cooled to room temperature; further high-temperature hot rolling is performed, the obtained slab is heated to 1250°C, and is kept warm for 2.5 hours before hot rolling, with a starting rolling temperature of 1200°C and a final rolling temperature of 1000°C to obtain a hot-rolled plate with a thickness of 4 mm±0.5 mm, which is then air-cooled; further medium-temperature rolling is performed, and the obtained hot-rolled plate is reheated To 600℃ and keep it for 15min, then take it out immediately for warm rolling to 3mm, put it into the heat treatment furnace quickly after rolling and continue to keep it at 600℃ for 15min, then take out the sample for warm rolling to the target thickness of 2mm, and then air cool it to room temperature. In double-pass insulation and rapid rolling, the temperature drop in the whole warm rolling process can be basically ignored; the obtained medium-temperature rolled sample is further subjected to subsequent heat treatment, heated to 600℃ and kept for 30min for short-time tempering heat treatment, and then water quenched to room temperature to obtain high-strength and toughness structural heterogeneous medium manganese steel warm-rolled plate, denoted as WRT.

[0039] According to GB / T 228-2010 "Room Temperature Tensile Test Method for Metallic Materials", the medium manganese steel hot-rolled plate was processed into tensile specimens for mechanical property testing. The obtained engineering stress-strain curve is shown in Figure 1 As shown in Figure 2, the austenite content in the steel before and after stretching is as follows: Figure 2 shown.

[0040] Comparative Example 1

[0041] The preparation method of the manganese steel warm-rolled plate in this comparative example comprises the following steps:

[0042] Each component (C 0.15-0.18%, Mn 10.0-10.32%, Al 1.9-2.1%, Cu 1.8-2.2%, and the rest Fe) is cast by vacuum melting; then the ingot is heated to 1250°C by high-temperature forging, and after being kept warm for 2.5 hours, it is forged into a slab with a cross section of 100 mm×30 mm, and then air-cooled to room temperature; further high-temperature hot rolling is performed, the obtained slab is heated to 1250°C, and after being kept warm for 2.5 hours, hot rolling is performed, the starting rolling temperature is 1200°C, the final rolling temperature is 1000°C, and a hot rolling with a thickness of 4 mm±0.5 mm is obtained. The plate is rolled and air-cooled; further medium-temperature rolling is performed, and the obtained hot-rolled plate is reheated to 600℃ and kept warm for 15 minutes, and then immediately taken out for warm rolling to 3mm. After rolling, it is quickly placed in a heat treatment furnace and kept warm at 600℃ for 15 minutes. Then the sample is taken out for warm rolling to the target thickness of 2mm, and then air-cooled to room temperature. In double-pass insulation and rapid rolling, the temperature drop in the whole warm rolling process can be basically ignored, and the medium manganese steel warm-rolled plate is obtained, which is recorded as WR.

[0043] According to GB / T 228-2010 "Room Temperature Tensile Test Method for Metallic Materials", the medium manganese steel hot-rolled plate was processed into tensile specimens for mechanical property testing. The obtained engineering stress-strain curve is shown in Figure 1 As shown in Figure 2, the austenite content in the steel before and after stretching is as follows: Figure 2 shown.

[0044] Comparative Example 2

[0045] The preparation method of the manganese steel warm-rolled plate in this comparative example comprises the following steps:

[0046] Each component (C 0.15-0.18%, Mn 10.0-10.32%, Al 1.9-2.1%, Cu 1.8-2.2%, and the rest is Fe) is obtained by vacuum melting and casting to obtain an ingot; then the ingot is heated to 1250°C by high-temperature forging, and is kept warm for 2.5 hours before forging into a slab with a cross section of 100mm×30mm, and then air-cooled to room temperature; further high-temperature hot rolling is performed, the obtained slab is heated to 1250°C, kept warm for 2.5 hours, and then hot rolled, the starting rolling temperature is 1200°C, the final rolling temperature is 1000°C, and a hot-rolled plate with a thickness of 4mm±0.5mm is obtained, and the temperature is air-cooled; the obtained medium-temperature rolled sample is further subjected to subsequent heat treatment, heated to 600°C and kept warm for 30 minutes for short-time tempering heat treatment, and then water quenched to room temperature to obtain a medium manganese steel warm-rolled plate, recorded as WRA.

[0047] According to GB / T 228-2010 "Room Temperature Tensile Test Method for Metallic Materials", the medium manganese steel hot-rolled plate was processed into tensile specimens for mechanical property testing. The obtained engineering stress-strain curve is shown in Figure 1As shown in Figure 2, the austenite content in the steel before and after stretching is as follows: Figure 2 shown.

[0048] Test Case

[0049] Table 1 Mechanical properties test results

[0050]

[0051] Compare the engineering stress-strain curves ( Figure 1 ) and mechanical properties (Table 1) found that compared with comparative example 1 (hot rolling-warm rolling only) and comparative example 2 (hot rolling annealing only), embodiment 1 (hot rolling and warm rolling annealing) has obvious improvement in mechanical properties and shows excellent strength and plasticity. The strength-plasticity product is 30.3 GPa%, with a tensile strength of 1330 MPa and an elongation of 22.8%. Figure 2 (YS is yield strength, UTS is tensile strength, and TEL is elongation) shows the strength / plasticity changes between Example 1 and Comparative Examples 1-2.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-strength and high-toughness structural heterogeneous medium manganese steel warm-rolled plate, characterized in that: The high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate comprises the following components in mass percentage: C 0.15-0.18%, Mn 10.0-10.32%, Al 1.9-2.1%, Cu 1.8-2.2%, and the rest is Fe.

2. A method for preparing the high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate according to claim 1, characterized in that: The following steps are involved: (1) Ingot smelting: Each component is melted and cast in vacuum to obtain an ingot; (2) High temperature forging: forging the ingot into a slab and air cooling it to room temperature; (3) high temperature hot rolling: hot rolling the slab to obtain a hot rolled plate, and air cooling; (4) Medium temperature rolling: the hot rolled plate is subjected to double-pass heat preservation and rapid rolling to obtain a medium temperature rolled sample; (5) Tempering heat treatment: The medium-temperature rolled sample is subjected to a short-time tempering heat treatment and then water quenched to room temperature to obtain a high-strength and tough structural heterogeneous medium-manganese steel warm-rolled plate.

3. The method for preparing the high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate according to claim 2, characterized in that: The specific process of step (ii) is: heating the ingot to 1250° C., keeping it at this temperature for 2.5 hours, forging it into a slab with a cross section of 100 mm×30 mm, and then air cooling it to room temperature.

4. The method for preparing the high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate according to claim 2, characterized in that: The specific process of step (3) is: heating the slab to 1250°C, keeping it warm for 2.5 hours and then hot rolling it, with the starting rolling temperature being 1200°C and the final rolling temperature being greater than 950°C, to obtain a hot-rolled plate with a thickness of 4mm±0.5mm, and then air cooling it.

5. The method for preparing the high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate according to claim 4, characterized in that: The final rolling temperature is 1000°C.

6. The method for preparing the high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate according to claim 2, characterized in that: In step (3), the hot rolling is performed in 7 passes.

7. The method for preparing the high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate according to claim 2, characterized in that: The specific process of double-pass heat preservation and rapid rolling in step (4) is as follows: the hot-rolled plate is reheated to 600°C and kept warm for 15 minutes, then immediately taken out for warm rolling to 3 mm, and then quickly placed in a heat treatment furnace for further warming at 600°C for 15 minutes, then the sample is taken out for warm rolling to a target thickness of 2 mm, and then air-cooled to room temperature.

8. The method for preparing high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate according to claim 2, characterized in that: In step (5), the short-time tempering heat treatment temperature is 400-600°C and the time is 10-30 minutes.

9. Application of the high-strength and tough structural heterogeneous medium manganese steel warm-rolled plate according to claim 1 in automobiles.

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