Heat treatment method for improving hydrogen embrittlement resistance of martensitic stainless steel

Abstract

The invention relates to the technical field of stainless steel heat treatment, in particular to a heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel, which comprises the following steps: a, solution treatment; the solid solution treatment comprises high-temperature solid solution treatment, low-temperature solid solution treatment and medium-temperature solid solution treatment which are sequentially carried out, so that the martensitic block interface proportion in the martensitic stainless steel is the maximum, and due to the fact that the orientation difference of the martensitic block interface is larger than that of other interfaces, more energy is needed when hydrogen-induced cracks penetrate through the type of interface, and the hydrogen-induced cracks are not prone to cracking. The martensite block interface has higher hydrogen capture capacity, the hydrogen embrittlement resistance of the martensite stainless steel is simply and effectively improved on the premise that material components are not changed, and the service life of the martensite stainless steel is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of stainless steel heat treatment technology, and in particular to a heat treatment method for improving the resistance of martensitic stainless steel to hydrogen embrittlement. Background Technology

[0002] Martensitic stainless steel, with its excellent comprehensive properties, has become a core research direction in the field of high-strength stainless steel. It possesses high strength and also boasts outstanding advantages such as ease of processing, corrosion resistance, and oxidation resistance. It is widely used in key fields such as aviation, aerospace, marine engineering, and new energy. For example, core components of aircraft engines, landing gear load-bearing structures, spacecraft outer shell protective layers, and major load-bearing components such as satellite gyroscopes have all adopted this type of stainless steel to achieve performance upgrades. However, a key contradiction emerges: the higher the strength of martensitic stainless steel, the stronger its hydrogen embrittlement susceptibility and the worse its resistance to hydrogen embrittlement. Currently, a common composition of martensitic stainless steel is as follows (by mass percentage): C: ≤0.05%, Ni: 5.00–7.80%, Cr: 15.50–17.20%, Mo: 0.15–0.40%, Nb: 0.20–0.50%, Cu: 3.00–4.20%, Si: ≤0.80%, Mn: ≤0.50%, P: ≤0.020%, S: ≤0.008%, with the balance being Fe and unavoidable impurities. After heat treatment involving solution treatment and aging, the hydrogen embrittlement susceptibility of this martensitic stainless steel, calculated using elongation loss as plasticity loss, is 79.3%–88.6%. This high susceptibility and poor resistance to hydrogen embrittlement severely impact its service life. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a heat treatment method that can improve the hydrogen embrittlement resistance of martensitic stainless steel.

[0004] The technical solution adopted by this invention to solve its technical problem is: a heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel, wherein the composition of the martensitic stainless steel is: by mass percentage, C: ≤0.05%, Ni: 5.00~7.80%, Cr: 15.50~17.20%, Mo: 0.15~0.40%, Nb: 0.20~0.50%, Cu: 3.00~4.20%, Si: ≤0.80%, Mn: ≤0.50%, P: ≤0.020%, S: ≤0.008%, with the balance being Fe and unavoidable impurities; The heat treatment method includes the following steps: a) solution treatment; b) aging treatment, wherein the solution treatment includes sequential high-temperature solution treatment, low-temperature solution treatment and medium-temperature solution treatment. The high-temperature solution treatment is specifically as follows: the temperature of the high-temperature solution treatment is 1020℃-1040℃, the high-temperature solution treatment time is 45min-60min, and the high-temperature solution treatment is followed by cooling to room temperature; The low-temperature solution treatment is specifically as follows: the temperature of the low-temperature solution treatment is 850℃-880℃, the low-temperature solution treatment time is 20min-30min, and the solution is cooled to room temperature after the low-temperature solution treatment. The intermediate-temperature solution treatment is as follows: the temperature of the intermediate-temperature solution treatment is 930℃-960℃, the treatment time is 5min-10min, and the solution is cooled to room temperature after the intermediate-temperature solution treatment.

[0005] Furthermore, after high-temperature solution treatment, the solution is cooled to room temperature using 0°C ice water.

[0006] Furthermore, after low-temperature solution treatment, the solution is cooled to room temperature using 0°C ice water.

[0007] Furthermore, after medium-temperature solution treatment, the solution is cooled to room temperature using 0°C ice water.

[0008] Furthermore, the aging treatment is specifically as follows: the aging temperature is 450℃-480℃, the aging time is 1h-4h, and after aging treatment, the temperature is cooled to room temperature.

[0009] The beneficial effects of this invention are as follows: The microstructure of the martensitic stainless steel of this invention is mainly divided into martensitic bundles, martensitic blocks, and lath martensite. The solution treatment in the heat treatment method of this invention is sequentially high-temperature solution treatment, low-temperature solution treatment, and medium-temperature solution treatment, which regulates the internal microstructure morphology of the material, so that the martensitic block interface accounts for the largest proportion in the martensitic stainless steel. Since the orientation difference of the martensitic block interface is larger than that of other interfaces, hydrogen-induced cracks require more energy to pass through this type of interface, which hinders the propagation of microcracks and the formation of macrocracks. At the same time, the martensitic block interface has a stronger hydrogen capture capacity. Without changing the material composition, the hydrogen embrittlement resistance of the martensitic stainless steel is simply and effectively improved, ensuring the service life of the martensitic stainless steel.

[0010] Martensitic stainless steel treated by the heat treatment method of this invention has relatively low hydrogen embrittlement sensitivity. Under the same hydrogen charging conditions, the hydrogen embrittlement sensitivity of this martensitic stainless steel is reduced from 79.3% to 88.6% to 37.5% to 42.3%, while the comprehensive mechanical properties remain basically unchanged. Detailed Implementation

[0011] A heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel, wherein the composition of the martensitic stainless steel is as follows (by mass percentage): C: ≤0.05%, Ni: 5.00~7.80%, Cr: 15.50~17.20%, Mo: 0.15~0.40%, Nb: 0.20~0.50%, Cu: 3.00~4.20%, Si: ≤0.80%, Mn: ≤0.50%, P: ≤0.020%, S: ≤0.008%, with the balance being Fe and unavoidable impurities; The heat treatment method includes the following steps: a) solution treatment; b) aging treatment, wherein the solution treatment includes sequential high-temperature solution treatment, low-temperature solution treatment and medium-temperature solution treatment. The high-temperature solution treatment is specifically as follows: the high-temperature solution treatment temperature is 1020℃-1040℃, the high-temperature solution treatment time is 45min-60min, and the high-temperature solution treatment is followed by cooling to room temperature; The low-temperature solution treatment is specifically as follows: the low-temperature solution treatment temperature is 850℃-880℃, the low-temperature solution treatment time is 20min-30min, and the solution is cooled to room temperature after the low-temperature solution treatment. The intermediate-temperature solution treatment is as follows: the intermediate-temperature solution treatment temperature is 930℃-960℃, the intermediate-temperature solution treatment time is 5min-10min, and the intermediate-temperature solution treatment is followed by cooling to room temperature.

[0012] Solution treatment refers to heating an alloy to a high-temperature single-phase region and holding it at that temperature for a certain period of time. High-temperature solution treatment involves heating martensitic stainless steel to 1020℃-1040℃ and holding it at that temperature for 45-60 minutes. Low-temperature solution treatment involves heating martensitic stainless steel to 850℃-880℃ and holding it at that temperature for 45-60 minutes. Medium-temperature solution treatment involves heating martensitic stainless steel to 930℃-960℃ and holding it at that temperature for 45-60 minutes.

[0013] Specifically, the preferred embodiments of the heat treatment method of the present invention are: high-temperature solution treatment followed by cooling to room temperature with ice water at 0°C; low-temperature solution treatment followed by cooling to room temperature with ice water at 0°C; and medium-temperature solution treatment followed by cooling to room temperature with ice water at 0°C. Cooling with ice water at 0°C ensures the cooling rate and avoids incomplete microstructure transformation.

[0014] The aging treatment is as follows: the aging temperature is 450℃-480℃, the aging time is 1h-4h, and after aging treatment, the air is cooled to room temperature.

[0015] The microstructure of the martensitic stainless steel of this invention is mainly divided into martensitic bundles, martensitic blocks, and lath martensite. The solution treatment in the heat treatment method of this invention consists of high-temperature solution treatment, low-temperature solution treatment, and medium-temperature solution treatment, which regulates the internal microstructure of the material, so that the martensitic block interface accounts for the largest proportion in the martensitic stainless steel. Since the orientation difference of the martensitic block interface is larger than that of other interfaces, hydrogen-induced cracks require more energy to pass through this type of interface, which hinders the propagation of microcracks and the formation of macrocracks. At the same time, the martensitic block interface has a stronger hydrogen capture capacity. Without changing the material composition, the hydrogen embrittlement resistance of the martensitic stainless steel is simply and effectively improved, thus ensuring the service life of the martensitic stainless steel.

[0016] Martensitic stainless steel treated by the heat treatment method of this invention has relatively low hydrogen embrittlement sensitivity. Under the same hydrogen charging conditions, the hydrogen embrittlement sensitivity of this martensitic stainless steel is reduced from 79.3% to 88.6% to 37.5% to 42.3%, while the comprehensive mechanical properties remain basically unchanged.

[0017] The heat treatment method provided by this invention is simple and low-cost, and can be directly applied to the technological upgrade of existing stainless steel production lines. The treated martensitic stainless steel exhibits significantly improved resistance to hydrogen embrittlement while maintaining excellent comprehensive mechanical properties. It can meet the needs of key fields such as aerospace, marine engineering, and new energy for high-strength, hydrogen-embrittlement-resistant stainless steel components, and has broad industrial application prospects and significant economic and social benefits.

[0018] Example 1 A heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel, wherein the composition of the martensitic stainless steel is as follows (by mass percentage): C: 0.03%, Ni: 5.85%, Cr: 16.00%, Mo: 0.15%, Nb: 0.35%, Cu: 3.52%, Si: 0.50%, Mn: 0.34%, P: 0.0018%, S: 0.005%, with the balance being Fe and unavoidable impurities; The heat treatment method includes the following steps: a) solution treatment; b) aging treatment, wherein the solution treatment includes sequential high-temperature solution treatment, low-temperature solution treatment and medium-temperature solution treatment. The high-temperature solution treatment is as follows: the high-temperature solution treatment temperature is 1040℃, the high-temperature solution treatment time is 60min, and after the high-temperature solution treatment, it is cooled to room temperature by 0℃ ice water. The low-temperature solution treatment is specifically as follows: the low-temperature solution treatment temperature is 850℃, the low-temperature solution treatment time is 20min, and after the low-temperature solution treatment, it is cooled to room temperature by 0℃ ice water. The medium-temperature solution treatment is as follows: the medium-temperature solution treatment temperature is 930℃, the medium-temperature solution treatment time is 10min, and after the medium-temperature solution treatment, it is cooled to room temperature by 0℃ ice water.

[0019] The aging treatment is as follows: the aging temperature is 480℃, the aging time is 1 hour, and after aging, the temperature is cooled to room temperature by air.

[0020] Performance testing: Hydrogen embrittlement sensitivity (elongation loss) is 37.5%, and the overall mechanical properties meet the relevant industry standards.

[0021] Example 2 A heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel, wherein the composition of the martensitic stainless steel is as follows (by mass percentage): C: 0.05%, Ni: 7.80%, Cr: 17.00%, Mo: 0.32%, Nb: 0.50%, Cu: 3.78%, Si: 0.40%, Mn: 0.50%, P: 0.020%, S: 0.006%, with the balance being Fe and unavoidable impurities; The heat treatment method includes the following steps: a) solution treatment; b) aging treatment, wherein the solution treatment includes sequential high-temperature solution treatment, low-temperature solution treatment and medium-temperature solution treatment. The high-temperature solution treatment is as follows: the high-temperature solution treatment temperature is 1040℃, the high-temperature solution treatment time is 45min, and after the high-temperature solution treatment, it is cooled to room temperature by 0℃ ice water. The low-temperature solution treatment is specifically as follows: the low-temperature solution treatment temperature is 850℃, the low-temperature solution treatment time is 30min, and after the low-temperature solution treatment, it is cooled to room temperature by 0℃ ice water. The medium-temperature solution treatment is as follows: the medium-temperature solution treatment temperature is 930℃, the medium-temperature solution treatment time is 5min, and after the medium-temperature solution treatment, it is cooled to room temperature by 0℃ ice water.

[0022] The aging treatment is as follows: the aging temperature is 480℃, the aging time is 1 hour, and after aging, the temperature is cooled to room temperature by air.

[0023] Performance testing: Hydrogen embrittlement sensitivity (elongation loss) is 40.4%, and the overall mechanical properties meet the relevant industry standards.

[0024] Example 3 A heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel, wherein the composition of the martensitic stainless steel is: C: 0.03%, Ni: 6.50%, Cr: 16.8%, Mo: 0.40%, Nb: 0.45%, Cu: 4.20%, Si: 0.30%, Mn: 0.20%, P: 0.0012%, S: 0.003%, with the balance being Fe and unavoidable impurities; The heat treatment method includes the following steps: a) solution treatment; b) aging treatment, wherein the solution treatment includes sequential high-temperature solution treatment, low-temperature solution treatment and medium-temperature solution treatment. The high-temperature solution treatment is as follows: the high-temperature solution treatment temperature is 1020℃, the high-temperature solution treatment time is 60min, and after the high-temperature solution treatment, it is cooled to room temperature by 0℃ ice water. The low-temperature solution treatment is specifically as follows: the low-temperature solution treatment temperature is 880℃, the low-temperature solution treatment time is 20min, and after the low-temperature solution treatment, it is cooled to room temperature by 0℃ ice water. The medium-temperature solution treatment is as follows: the medium-temperature solution treatment temperature is 960℃, the medium-temperature solution treatment time is 10min, and after the medium-temperature solution treatment, it is cooled to room temperature by 0℃ ice water.

[0025] The aging treatment is as follows: the aging temperature is 450℃, the aging time is 4 hours, and after aging treatment, the temperature is cooled to room temperature by air.

[0026] Performance testing: Hydrogen embrittlement sensitivity (elongation loss) is 42.3%, and the overall mechanical properties meet the relevant industry standards.

[0027] Comparative Example 1 Martensitic stainless steel with the same composition as in Example 1 was subjected to conventional heat treatment.

[0028] The heat treatment method includes the following steps: a) solution treatment; b) aging treatment; The solution treatment is specifically as follows: the solution treatment temperature is 1040℃, the solution treatment time is 60min, and after the solution treatment, it is cooled to room temperature by 0℃ ice water. The aging treatment was specifically carried out at a temperature of 480℃ for 1 hour, followed by air cooling to room temperature. The martensitic stainless steel was subjected to a hydrogen embrittlement sensitivity test, and its hydrogen embrittlement sensitivity was calculated by the loss of elongation, with a result of 88.6%.

[0029] Comparative Example 2 Martensitic stainless steel with the same composition as in Example 1 was subjected to conventional heat treatment.

[0030] The heat treatment method includes the following steps: a) solution treatment; b) aging treatment; The solution treatment is specifically as follows: the solution treatment temperature is 1040℃, the solution treatment time is 20min, and after the solution treatment, it is cooled to room temperature by 0℃ ice water. The aging treatment was specifically carried out at a temperature of 480℃ for 1 hour, followed by air cooling to room temperature. The martensitic stainless steel was subjected to a hydrogen embrittlement sensitivity test, and its hydrogen embrittlement sensitivity was calculated by the loss of elongation, with a result of 82.1%.

[0031] Comparative Example 3 Martensitic stainless steel with the same composition as in Example 1 was subjected to conventional heat treatment.

[0032] The heat treatment method includes the following steps: a) solution treatment; b) aging treatment; The solution treatment is specifically as follows: the solution treatment temperature is 1040℃, the solution treatment time is 60min, and after the solution treatment, it is cooled to room temperature by 0℃ ice water. The aging treatment was specifically carried out at a temperature of 480℃ for 4 hours, followed by air cooling to room temperature. The martensitic stainless steel was subjected to a hydrogen embrittlement sensitivity test, and its hydrogen embrittlement sensitivity was calculated by the loss of elongation, with a result of 79.3%.

Claims

1. A heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel, wherein the composition of the martensitic stainless steel is as follows (by mass percentage): C: ≤0.05%, Ni: 5.00~7.80%, Cr: 15.50~17.20%, Mo: 0.15~0.40%, Nb: 0.20~0.50%, Cu: 3.00~4.20%, Si: ≤0.80%, Mn: ≤0.50%, P: ≤0.020%, S: ≤0.008%, with the balance being Fe and unavoidable impurities; The steps of the heat treatment method include: a) Solution treatment; b) Aging treatment, characterized in that: the solution treatment includes sequential high-temperature solution treatment, low-temperature solution treatment and medium-temperature solution treatment; The high-temperature solution treatment is specifically as follows: the high-temperature solution treatment temperature is 1020℃-1040℃, the high-temperature solution treatment time is 45min-60min, and the high-temperature solution treatment is followed by cooling to room temperature; The low-temperature solution treatment is specifically as follows: the low-temperature solution treatment temperature is 850℃-880℃, the low-temperature solution treatment time is 20min-30min, and the solution is cooled to room temperature after the low-temperature solution treatment. The intermediate-temperature solution treatment is as follows: the intermediate-temperature solution treatment temperature is 930℃-960℃, the intermediate-temperature solution treatment time is 5min-10min, and the intermediate-temperature solution treatment is followed by cooling to room temperature.

2. The heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel as described in claim 1, characterized in that: After high-temperature solution treatment, it is cooled to room temperature by 0°C ice water.

3. The heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel as described in claim 1, characterized in that: After low-temperature solution treatment, it is cooled to room temperature by 0°C ice water.

4. The heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel as described in claim 1, characterized in that: After medium-temperature solution treatment, the solution is cooled to room temperature by ice water at 0°C.

5. The heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel as described in any one of claims 1 to 4, characterized in that: The aging treatment is specifically as follows: the aging temperature is 450℃-480℃, the aging time is 1h-4h, and after aging treatment, the air is cooled to room temperature.