Method for improving precipitation efficiency and strength of high-manganese light steel through thermal-mechanical coupling

Abstract

The invention provides a method for improving precipitation efficiency and strength of high-manganese light steel through thermal-mechanical coupling. According to the method, cold rolling treatment is conducted on the high-manganese light steel, then solution treatment and stress aging are conducted, the solution temperature ranges from 900 DEG C to 1100 DEG C, the aging temperature ranges from 450 DEG C to 650 DEG C, and the applied stress accounts for 20%-120% of the yield strength at the aging temperature, so that the precipitation efficiency of the high-manganese light steel is improved, rapid intragranular precipitation is achieved, and the strength is improved. According to the method, the precipitation process is accelerated by utilizing the synergistic effect of temperature and stress, the precipitation efficiency is effectively improved, and the strength is remarkably improved. The process is simple and convenient, saves resources and energy, and is suitable for industrial large-scale application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new materials, in particular to a method for improving the precipitation efficiency and strength of high-manganese lightweight steel by thermal coupling. BACKGROUND

[0002] With the rapid development of aerospace, power machinery and other fields, the service environment of key load-bearing parts is becoming increasingly harsh, and the performance of materials is becoming more stringent. Lightweight has become one of the most important design indicators of structural materials. Under the premise of meeting safety and reliability, the load efficiency is improved by reducing the self-weight of the component. At present, typical lightweight alloys such as aluminum alloy and titanium alloy are widely used in aerospace and other fields. Aluminum alloy has low density and good machinability, but its strength and high-temperature performance are limited, making it difficult to meet the use requirements of key stress parts under extreme working conditions. Titanium alloy has low density and high strength, and has good corrosion resistance and high-temperature performance, and is one of the ideal load-bearing structural materials. However, its raw material cost is high, and its processing is difficult, resulting in high overall manufacturing cost, which restricts its promotion in mass production and large-scale application.

[0003] High-manganese steel is a lightweight steel that has been widely concerned due to its low density, low cost and high toughness. However, its insufficient strength limits its application in extreme service environments. Precipitation strengthening is considered an effective strategy to improve the strength of high-manganese lightweight steel: on the one hand, long-term aging treatment can promote the precipitation of carbides; on the other hand, the addition of alloying elements can introduce various precipitates (such as carbides, intermetallic compounds, etc.), thereby achieving synergistic strengthening. However, long-term aging can improve the strength to some extent, but often accompanied by a significant decrease in plasticity; at the same time, long-term heat treatment has high energy consumption and long cycle, which is not conducive to green manufacturing and sustainable development. In addition, the addition of large amounts of noble metal elements such as Ni in high-manganese lightweight steel can improve the precipitation behavior and improve the strength-plasticity match, but will significantly increase the material cost, making it difficult to realize its economic value. Therefore, it is an urgent need to develop a low-cost, low-energy method to promote the rapid precipitation of strengthening phases in high-manganese lightweight steel. SUMMARY

[0004] In order to overcome the problems existing in the prior art, the present application provides a method for improving the precipitation efficiency and strength of high-manganese lightweight steel by thermal coupling; the method is to perform solid solution treatment and stress aging on the cold-rolled high-manganese steel to precipitate rapidly in the crystal, so as to rapidly increase the strength of high-manganese lightweight steel in a short aging time.

[0005] The present application provides a method for improving the precipitation efficiency and strength of high-manganese lightweight steel by thermal coupling, the preparation method comprising the following steps: S1, multi-pass axial cold rolling treatment is performed on high-manganese lightweight steel; S2, high-temperature solid solution treatment is performed on the high-manganese light steel after the cold rolling treatment; S3, stress aging is performed on the high-manganese light steel after the high-temperature solid solution treatment along the cold rolling direction.

[0006] Preferably, the multi-pass axial cold rolling treatment in step S1 is performed by using a double-roller rolling machine; the cold rolling reduction per pass is 10-20 %, the total cold rolling reduction is 60-90 %, and the thickness of the high-manganese light steel plate after the multi-pass axial cold rolling is 1-10 mm.

[0007] Preferably, the temperature of the solid solution treatment in step S2 is 900-1100 °C, the holding time is 5-60 min, and water quenching is performed to room temperature.

[0008] Preferably, in the stress aging process in step S3, the temperature is 450-650 °C, the holding time is 0.5-100 h, and after the holding is completed, the furnace is cooled to room temperature; the stress applied is 20-120 % of the yield strength at the aging temperature. Preferably, in the stress aging process in step S3, the stress is applied when the aging temperature is reached, and the stress is unloaded after the aging time.

[0009] Preferably, after the stress aging treatment in step S3, in the microstructure of the high-manganese light steel, nanoscale long-range ordered domains are formed in the austenitic matrix, and the size of the long-range ordered domains is 2.6-5 nm.

[0010] Compared with the prior art, the present application has the following beneficial technical effects: The method for improving the precipitation efficiency and strength of high-manganese light steel by thermal coupling provided by the present application can make the nanoscale long-range ordered domains precipitate rapidly in the grains of the high-manganese light steel by cold rolling, solid solution treatment and stress aging, so as to rapidly increase the strength of the high-manganese light steel in a short aging time. The method can rapidly induce precipitation in a short time by using the synergistic effect of temperature and stress, improve the precipitation efficiency, and is simple in processing technology, saves resources and energy, and is suitable for industrialized large-scale application. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below. It should be known that the drawings described below only relate to some embodiments of the present disclosure, and are not a limitation on the present disclosure, wherein: Figure 1 is a preparation process flowchart provided by the present application.

[0012] Figure 2 is a Vickers microhardness distribution diagram of the high-manganese light steel obtained by the examples 1-5 and comparative examples 1-5 of the present application.

[0013] Figure 3 These are transmission electron microscopy (TEM) images of the high-manganese lightweight steel obtained in Example 2 and Comparative Example 2 of the present invention, wherein (a) is the TEM image of Comparative Example 2 and (b) is the TEM image of Example 2. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0015] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the specification and in the relevant art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein. As used herein, the statement of “connecting” or “coupling” two or more parts together shall mean that these parts are directly joined together or joined through one or more intermediate components.

[0016] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0017] This invention provides a method for improving the precipitation efficiency and strength of high-manganese lightweight steel through thermo-coupling, the preparation method comprising the following steps: S1. High-manganese lightweight steel is subjected to multi-pass axial cold rolling using a twin-roll mill. During the multi-pass axial cold rolling process, the cold rolling reduction in each pass is 10-20%, and the total reduction of the high-manganese lightweight steel by the twin-roll mill is 60-90%. The thickness of the high-manganese steel after cold rolling is 1-10 mm, for example, it can be 1.5 mm, 5 mm, or 8.5 mm. S2. The cold-rolled high-manganese light steel is subjected to high-temperature solution treatment. The solution treatment temperature is 900 ℃~1100 ℃, for example, 900 ℃, 950 ℃, 1000 ℃, 1050 ℃, 1100 ℃, etc., and the holding time is 5~60 min. The steel is then water-quenched to room temperature, for example, 10 min, 20 min, 30 min, 40 min, 50 min, etc. S3. Stress aging of the high-manganese lightweight steel after high-temperature solution treatment along the cold rolling direction; the aging temperature is 450℃~650℃, for example, 450℃, 500℃, 550℃, 600℃, 650℃, etc.; the applied stress is 20%~120% of the yield strength at the aging temperature, for example, 20%, 40%, 60%, 80%, 100%, etc.; during the stress aging process, stress is applied at the aging temperature and unloaded after the aging time is reached. The heat preservation time is 0.5 h to 100 h, for example, it can be 1 h, 5 h, 10 h, 20 h, 50 h, 70 h, 90 h, etc. After the heat preservation is completed, it is cooled to room temperature with the furnace. After stress aging treatment, the size of the long-range ordered domain formed in the austenite matrix in the microstructure of high manganese lightweight steel is preferably 2.6 nm to 5 nm, for example, it can be 2.6 nm, 3.1 nm, 3.5 nm, 4.1 nm, 4.5 nm, 5 nm.

[0018] The following is an explanation with reference to specific embodiments: Example 1 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a plate thickness of 1.5 mm. The cold-rolled plate was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniform grain size distribution. Subsequently, the specimens were subjected to stress aging treatment along the cold-rolling direction at 550 ℃ in a high-temperature creep furnace. During stress aging, a stress of 160 MPa (80% of the yield strength of high-manganese lightweight steel at 550 ℃) was applied for 5 h.

[0019] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length. After electrolytic polishing, Vickers hardness tests were performed. (The results are as follows...) Figure 2 As shown, the Vickers microhardness test results showed that the Vickers hardness of the sample after stress aging for 5 hours was 205.86 HV.

[0020] Example 2 High-manganese lightweight steel (Fe-21Mn-6Al-1C (wt.%)) was axially cold-rolled with a reduction of 70%, resulting in a thickness of 1.5 mm. The cold-rolled sheet was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniformly distributed grain size. Subsequently, the specimens were subjected to stress aging treatment along the cold-rolling direction at 550 ℃ in a high-temperature creep furnace. During stress aging, a stress of 160 MPa (80% of the yield strength of high-manganese lightweight steel at 550 ℃) was applied for 20 h.

[0021] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length. After electrolytic polishing, Vickers hardness tests were performed. (The results are as follows...) Figure 2 As shown, the Vickers microhardness test results revealed that the Vickers hardness of the sample after 20 hours of stress aging was 210.15 HV. TEM observation of the sample after 20 hours of stress aging showed... Figure 3 As shown, the results indicate that the size and volume fraction of the long-range ordered domain within the austenite grains in the sample after stress aging for 20 h are 3.1 ± 0.5 nm and 9.82%, respectively. Stress aging increases the size of the long-range ordered domain by 287.5%, while the volume fraction remains essentially unchanged. Therefore, stress aging promotes amplitude modulation decomposition through thermo-mechanical coupling, thereby inducing the growth of the size of the long-range ordered domain and significantly enhancing the mechanical properties of the material.

[0022] Example 3 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a plate thickness of 1.5 mm. The cold-rolled plate was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniformly distributed grain size. Subsequently, the specimens were subjected to stress aging treatment along the cold-rolling direction at 550 ℃ in a high-temperature creep furnace. During stress aging, a stress of 160 MPa (80% of the yield strength of high-manganese lightweight steel at 550 ℃) was applied for 100 h.

[0023] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length. After electrolytic polishing, Vickers hardness tests were performed. (The results are as follows...) Figure 2 As shown, the Vickers microhardness test results revealed that the Vickers hardness of the sample after stress aging for 100 h was 229.18 HV.

[0024] Example 4 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C-1.5Si (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a thickness of 1.5 mm. The cold-rolled sheet was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniformly distributed grain size. Subsequently, the samples were subjected to stress aging treatment along the cold-rolling direction at 550 ℃ in a high-temperature creep furnace. During stress aging, a stress of 240 MPa (80% of the yield strength of high-manganese lightweight steel at 550 ℃) was applied for 1 h.

[0025] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length, and after electrolytic polishing, Vickers hardness tests were performed; Figure 2 As shown, the Vickers microhardness test results showed that the Vickers hardness of the sample after stress aging for 1 h was 248.80 HV.

[0026] Example 5 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C-1.5Si (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a thickness of 1.5 mm. The cold-rolled sheet was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniformly distributed grain size. Subsequently, the samples were subjected to stress aging treatment along the cold-rolling direction at 550 ℃ in a high-temperature creep furnace. During stress aging, a stress of 240 MPa (80% of the yield strength of high-manganese lightweight steel at 550 ℃) was applied for 5 h.

[0027] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length, and after electrolytic polishing, Vickers hardness tests were performed; Figure 2 As shown, the Vickers microhardness test results showed that the Vickers hardness of the sample after stress aging for 5 hours was 256.20 HV.

[0028] Comparative Example 1 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a thickness of 1.5 mm. The cold-rolled sheet was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniform grain size distribution. Subsequently, the samples were aged in a high-temperature creep furnace at 550 ℃ for 5 h without stress.

[0029] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length. After electrolytic polishing, Vickers hardness tests were performed. (The results are as follows...) Figure 2 As shown, the Vickers microhardness test results revealed that the average Vickers hardness of the sample after aging for 5 hours was 176.09 HV, while the Vickers hardness of the sample in Example 1 after stress aging for 5 hours was 205.86 HV, an increase of 29.77 HV compared to Example 1. The results indicate that the increase in Vickers hardness is due to the stress aging promoting amplitude modulation decomposition through thermo-mechanical coupling, thereby inducing the rapid generation of long-range ordered domains, which significantly enhances the mechanical properties of the material.

[0030] Comparative Example 2 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a thickness of 1.5 mm. The cold-rolled sheet was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniformly distributed grain size. Subsequently, the samples were aged in a high-temperature creep furnace at 550 ℃ for 20 h without stress.

[0031] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length. After electrolytic polishing, Vickers hardness tests were performed. (The results are as follows...) Figure 2 As shown, the Vickers microhardness test results revealed that the Vickers hardness of the sample after aging for 20 hours was 178.79 HV, while the Vickers hardness of the sample after stress aging for 20 hours in Example 2 was 210.15 HV, representing an increase of 31.36 HV compared to Example 2. TEM observations were performed after a 20-hour timeframe, such as... Figure 3As shown, the results indicate that the size and volume fraction of long-range ordered domains within the austenite grains in the sample aged for 20 h were 0.8 ± 0.1 nm and 9.11%, respectively, while in Example 2, the size and volume fraction of long-range ordered domains within the austenite grains in the sample aged for 20 h were 3.1 ± 0.5 nm and 9.82%, respectively. The results suggest that the increase in Vickers hardness is due to the rapid generation of long-range ordered domains induced by stress aging through thermo-coupling, which promotes amplitude modulation decomposition and significantly enhances the mechanical properties of the material.

[0032] Comparative Example 3 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a thickness of 1.5 mm. The cold-rolled sheet was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniformly distributed grain size. Subsequently, the samples were aged in a high-temperature creep furnace at 550 ℃ for 100 h without stress.

[0033] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length. After electrolytic polishing, Vickers hardness tests were performed. (The results are as follows...) Figure 2 As shown, the Vickers microhardness test results revealed that the Vickers hardness of the sample after aging for 100 h was 192.33 HV, while the Vickers hardness of the sample in Example 3 after stress aging for 100 h was 229.18 HV, an increase of 36.85 HV compared to Example 3. The results indicate that the increase in Vickers hardness is due to the stress aging promoting amplitude modulation decomposition through thermo-mechanical coupling, thereby inducing the rapid generation of long-range ordered domains, which significantly enhances the mechanical properties of the material.

[0034] Comparative Example 4 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C-1.5Si (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a thickness of 1.5 mm. The cold-rolled sheet was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniformly distributed grain size. Subsequently, the samples were aged in a high-temperature creep furnace at 550 ℃ for 1 h without applying stress.

[0035] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length. After electrolytic polishing, Vickers hardness tests were performed. (The results are as follows...) Figure 2As shown, the Vickers microhardness test results revealed that the average Vickers hardness of the sample after aging for 1 hour was 183.88 HV, while the Vickers hardness of the sample in Example 4 after stress aging for 1 hour was 248.80 HV, an increase of 64.92 HV compared to Example 4. The results indicate that the increase in Vickers hardness is due to the stress aging promoting amplitude modulation decomposition through thermo-mechanical coupling, thereby inducing the rapid generation of long-range ordered domains and significantly enhancing the mechanical properties of the material.

[0036] Comparative Example 5 Hot-rolled high-manganese lightweight steel (Fe-21Mn-6Al-1C-1.5Si (wt.%)) was subjected to axial cold rolling with a reduction of 70%, resulting in a thickness of 1.5 mm. The cold-rolled sheet was wire-cut into dog-bone-shaped tensile specimens with gauge lengths of 50×17×1.5 mm. These specimens were then held at 1050 ℃ for 30 min and water-quenched to room temperature to obtain fully recrystallized high-manganese lightweight steel samples with uniformly distributed grain size. Subsequently, the samples were aged in a high-temperature creep furnace at 550 ℃ for 5 h without stress.

[0037] The high-manganese lightweight steel samples after aging were cut into 8×6×1.5 mm blocks within the gauge length. After electrolytic polishing, Vickers hardness tests were performed. (The results are as follows...) Figure 2 As shown, the Vickers microhardness test results revealed that the Vickers hardness of the sample after aging for 5 hours was 205.10 HV, while the Vickers hardness of the sample after stress aging for 5 hours in Example 5 was 256.20 HV, an increase of 51.10 HV compared to Example 5. The results indicate that the increase in Vickers hardness is due to the stress aging promoting amplitude modulation decomposition through thermo-mechanical coupling, thereby inducing the rapid generation of long-range ordered domains, which significantly enhances the mechanical properties of the material.

[0038] The embodiments given above are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions or substitutions made by those skilled in the art based on the technical features of the present invention are within the protection scope of the present invention.

Claims

1. A method for improving the precipitation efficiency and strength of high-manganese lightweight steel through thermo-coupling, characterized in that, Includes the following steps: S1. High-manganese light steel is subjected to multi-pass axial cold rolling. S2. The cold-rolled high-manganese light steel is subjected to high-temperature solution treatment. S3. Stress aging of high-manganese lightweight steel after high-temperature solution treatment along the cold rolling direction.

2. The method for improving the precipitation efficiency and strength of high-manganese lightweight steel through thermo-coupling according to claim 1, characterized in that, The multi-pass axial cold rolling process in step S1 is carried out using a twin-roll mill; the cold rolling reduction per pass is 10~20%, the total cold rolling reduction is 60~90%, and the thickness of the high-manganese lightweight steel plate after multi-pass axial cold rolling is 1~10 mm.

3. The method for improving the precipitation efficiency and strength of high-manganese lightweight steel through thermo-coupling according to claim 1, characterized in that, The solution treatment in step S2 is performed at a temperature of 900 ℃ to 1100 ℃, with a holding time of 5 to 60 min, followed by water quenching to room temperature.

4. The method for improving the precipitation efficiency and strength of high-manganese lightweight steel through thermo-coupling according to claim 1, characterized in that, In the stress aging process described in step S3, the aging temperature is 450 ℃~650 ℃, the holding time is 0.5h~100h, and after the holding time is completed, the furnace is cooled to room temperature; the applied stress is 20%~120% of the yield strength at the aging temperature.

5. The method for improving the precipitation efficiency and strength of high-manganese lightweight steel through thermo-coupling according to claim 1, characterized in that, In step S3, stress is applied at the aging temperature and then unloaded after the aging time is reached.

6. The method for improving the precipitation efficiency and strength of high-manganese lightweight steel through thermo-coupling according to claim 1, characterized in that, After the stress aging treatment described in step S3, nanoscale long-range ordered domains are formed in the austenite matrix of the high-manganese lightweight steel microstructure, and the size of the long-range ordered domains is 2.6 nm to 5 nm.

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