High-strength stainless steel and preparation process thereof

Abstract

The invention relates to the technical field of stainless steel, and provides high-strength stainless steel and a preparation technology thereof.The high-strength stainless steel is prepared from, by mass, 1.0%-2.0% of Co, 0.8%-1.2% of Al, 1.0%-1.2% of Ti, 0.6%-1.1% of Mo, 6.0%-9.0% of Ni, 10.0%-12.5% of Cr, 0.8%-1.0% of Mn, 0.08%-0.2% of Si, smaller than or equal to 0.03% of C, smaller than or equal to 0.035% of P, smaller than or equal to 0.030% of S and the balance Fe and inevitable impurities; wherein the mass content relation of Ni, Cr and Co is as follows: (Ni + Co) / Cr = 0.7-1. Through the technical scheme, the problem of low mechanical strength of stainless steel in related technologies is solved.

Description

Technical Field

[0001] This invention relates to the field of stainless steel technology, specifically to a high-strength stainless steel and its preparation process. Background Technology

[0002] Stainless steel, with its excellent corrosion resistance, formability, and aesthetics, has been widely used in various fields such as machinery manufacturing, construction engineering, aerospace, and marine engineering. With the continuous improvement of material performance requirements in modern industry, its application scenarios, especially in heavy-duty machinery, high-end equipment, and extreme working conditions (such as high humidity, high salt spray, and high-stress environments), are increasing. Traditional stainless steel is gradually revealing its critical weakness of insufficient strength. Although it can meet the basic usage requirements of general working conditions, its mechanical properties are difficult to meet the standards in scenarios that require high load, deformation resistance, and fatigue resistance. This leads to the need to increase the thickness of the plate or adopt a reinforced structure when designing the product structure, which not only increases the overall weight and manufacturing cost of the equipment, but may also limit the development of lightweight and miniaturized equipment.

[0003] Therefore, developing a high-strength stainless steel can effectively solve the problem of insufficient mechanical strength of stainless steel, expand the application range of stainless steel, and improve the safety of stainless steel during use. Summary of the Invention

[0004] This invention proposes a high-strength stainless steel and its preparation process, which solves the problem of low mechanical strength of stainless steel in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a high-strength stainless steel, which, by mass percentage, is composed of the following components: Co 1.0%~2.0%, Al 0.8%~1.2%, Ti 1.0%~1.2%, Mo 0.6%~1.1%, Ni 6.0%~9.0%, Cr 10.0%~12.5%, Mn 0.8%~1.0%, Si 0.08%~0.2%, C≤0.03%, P≤0.035%, S≤0.030%, with the balance being Fe and unavoidable impurities; the mass content relationship of Ni, Cr, and Co is (Ni+Co) / Cr=0.7~1, preferably (Ni+Co) / Cr=0.75.

[0006] As a further technical solution, the mass content relationship between Ni and Co is: Ni / Co = 3.5~8, preferably Ni / Co = 5.

[0007] This invention also proposes a preparation process for high-strength stainless steel, comprising the following steps: S1. Select raw materials according to the mass percentage of each component in the stainless steel composition, and then melt, refine, and cast them to obtain ingots. S2. After rolling the ingot, a slab is obtained; S3. After heat treatment, the slab is made into stainless steel.

[0008] As a further technical solution, in step S2, the rolling process is as follows: the ingot is heated to 1150~1250℃, held for 24 hours, hot rolled and then cooled to obtain a slab.

[0009] As a further technical solution, the initial rolling temperature of the hot rolling is 1000~1100℃, the final rolling temperature is ≥950℃, and the total reduction rate of hot rolling is 50%~60%.

[0010] As a further technical solution, the cooling is as follows: after being placed in an environment of 150~250℃ and cooled to 300℃, it is then cooled to 20~30℃ at a cooling rate of 1.5℃ / s.

[0011] As a further technical solution, the cooling is as follows: after being placed in an environment of 200°C and cooled to 300°C, it is then cooled to 20~30°C at a cooling rate of 1.5°C / s.

[0012] In this invention, the cooling process of the slab during rolling is adjusted and limited. When the cooling process involves cooling from 200°C to 300°C and then cooling at a rate of 1.5°C / s to 20-30°C, the impact resistance of stainless steel is further improved. The limitation of the cooling process during rolling in this invention can generate more fine reinforcing phases and precipitates, which can improve the effect of preventing rapid crack propagation and improve the overall impact resistance.

[0013] As a further technical solution, in step S3, the heat treatment process is as follows: after holding the slab at 1150~1200℃ for 60~80 minutes, it is then cooled to obtain stainless steel.

[0014] As a further technical solution, the cooling process is as follows: the heat-insulated slab is subjected to a first stage of cooling and a second stage of cooling in sequence, and after cooling to 300°C, it is cooled to room temperature in the air. The cooling rates of the first stage of cooling and the second stage of cooling are different.

[0015] As a further technical solution, the first stage of cooling is carried out to 500°C before the second stage of cooling is performed.

[0016] As a further technical solution, the cooling rate of the first stage of cooling is 25℃ / h, and the cooling rate of the second stage of cooling is 5~15℃ / h.

[0017] As a further technical solution, the cooling rate of the first stage of cooling is 25℃ / h, and the cooling rate of the second stage of cooling is 10℃ / h.

[0018] The stainless steel composition defined in this invention, combined with the dual limitations on the cooling process during rolling and the cooling process during heat treatment, can further improve the impact resistance of stainless steel. The precise limitation of the cooling conditions during rolling can inhibit grain growth and refine the grains. Furthermore, through the precise control of the cooling rate in the cooling process during heat treatment, residual stress from cold work hardening can be eliminated, stress concentration can be reduced, crack propagation can be prevented, and the impact resistance of stainless steel can be further improved.

[0019] The working principle and beneficial effects of this invention are as follows: In this invention, by limiting the mass content of each component and the mass content relationship of Ni, Cr, and Co as (Ni + Co) / Cr = 0.7~1, the tensile strength of stainless steel is improved. Specifically, the Co component in the stainless steel composition can improve the tensile strength of stainless steel through solid solution strengthening, and forms a synergistic effect with Mo through precipitation strengthening, further improving the tensile strength of stainless steel. Furthermore, the limitation of the mass content relationship of the three components (Ni, Cr, and Co) allows for better formation of strengthening phases in the stainless steel composition, further enhancing the tensile strength of the stainless steel. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] In the following embodiments and comparative examples: Silicon-calcium alloy: grade Ca24Si60, manufactured by Yinchuan Weite Metal Products Co., Ltd. Silicon-zirconium alloy: model ZrSi20010, manufactured by Hunan Huwei Jingcheng Materials Technology Co., Ltd.

[0022] Example 1 A high-strength stainless steel, by mass percentage, comprises the following components: Co 1.0%, Al 0.8%, Ti 1.0%, Mo 0.6%, Ni 6.0%, Cr 10.0%, Mn 0.8%, Si 0.08%, C 0.02%, P 0.01%, S 0.02%, with the balance being Fe and unavoidable impurities; satisfying: (Ni + Co) / Cr = 0.7, Ni / Co = 6; A process for preparing high-strength stainless steel includes the following steps: S1. Raw materials are selected according to the mass percentage of each component in the stainless steel composition for smelting, refining, and casting to obtain ingots; wherein: during the refining process, deoxidation is carried out by first using aluminum pre-deoxidation, and then using silicon-calcium alloy and silicon-zirconium alloy with a mass ratio of 1:1 for deoxidation. S2. The ingot is heated to 1200℃ and held for 24 hours. After hot rolling, it is cooled to 300℃ at 250℃ and then cooled to 20℃ at a cooling rate of 1.5℃ / s to obtain a slab. During hot rolling, the initial rolling temperature is 1050℃, the final rolling temperature is 950℃, and the total hot rolling reduction rate is 50%. S3. After holding the slab at 1150℃ for 60 minutes, perform the first stage of cooling at a cooling rate of 25℃ / h, and then perform the second stage of cooling at a cooling rate of 5℃ / h, and finally cool it to room temperature in the air to obtain stainless steel.

[0023] Example 2 A high-strength stainless steel, by mass percentage, comprises the following components: Co 1.5%, Al 1.0%, Ti 1.0%, Mo 0.8%, Ni 7.5%, Cr 12.0%, Mn 0.9%, Si 0.15%, C 0.02%, P 0.012%, S 0.015%, with the balance being Fe and unavoidable impurities; satisfying: (Ni + Co) / Cr = 0.75, Ni / Co = 5; A process for preparing high-strength stainless steel includes the following steps: S1. Raw materials are selected according to the mass percentage of each component in the stainless steel composition for smelting, refining, and casting to obtain ingots; wherein: the deoxidation in the refining process is to first use aluminum for pre-deoxidation, and then use silicon-calcium alloy and silicon-zirconium alloy with a mass ratio of 1:1 for deoxidation. S2. The ingot is heated to 1200℃ and held for 24 hours. After hot rolling, it is cooled to 300℃ at 250℃ and then cooled to 30℃ at a cooling rate of 1.5℃ / s to obtain a slab. The initial rolling temperature is 1050℃, the final rolling temperature is 950℃, and the total hot rolling reduction rate is 50%. S3. After holding the slab at 1150℃ for 60 minutes, perform the first stage of cooling at a cooling rate of 25℃ / h, and then perform the second stage of cooling at a cooling rate of 5℃ / h, and finally cool it to room temperature in the air to obtain stainless steel.

[0024] Example 3 A high-strength stainless steel, by mass percentage, comprises the following components: Co 2.0%, Al 1.2%, Ti 1.2%, Mo 1.1%, Ni 9.0%, Cr 12.5%, Mn 1.0%, Si 0.2%, C 0.02%, P 0.010%, S 0.01%, with the balance being Fe and unavoidable impurities; satisfying: (Ni + Co) / Cr = 0.88, Ni / Co = 4.5; A process for preparing high-strength stainless steel includes the following steps: S1. Raw materials are selected according to the mass percentage of each component in the stainless steel composition for smelting, refining, and casting to obtain ingots; wherein: the deoxidation in the refining process is to first use aluminum for pre-deoxidation, and then use silicon-calcium alloy and silicon-zirconium alloy with a mass ratio of 1:1 for deoxidation. S2. The ingot is heated to 1200℃ and held for 24 hours. After hot rolling, it is cooled to 300℃ at 250℃ and then cooled to 30℃ at a cooling rate of 1.5℃ / s to obtain a slab. The initial rolling temperature is 1050℃, the final rolling temperature is 950℃, and the total hot rolling reduction rate is 50%. S3. After holding the slab at 1150℃ for 60 minutes, perform the first stage of cooling at a cooling rate of 25℃ / h, and then perform the second stage of cooling at a cooling rate of 5℃ / h, and finally cool it to room temperature in the air to obtain stainless steel.

[0025] Example 4 A high-strength stainless steel, by mass percentage, is composed of the following components: Co 1.5%, Al 1.0%, Ti 1.0%, Mo 0.8%, Ni 7.5%, Cr 10.0%, Mn 0.9%, Si 0.15%, C 0.02%, P 0.012%, S 0.015%, with the balance being Fe and unavoidable impurities; satisfying: (Ni + Co) / Cr = 0.9, Ni / Co = 5; the preparation process of this high-strength stainless steel is the same as that in Example 2.

[0026] Example 5 A high-strength stainless steel, by mass percentage, is composed of the following components: Co 1.5%, Al 1.0%, Ti 1.0%, Mo 0.8%, Ni 7.5%, Cr 12.5%, Mn 0.9%, Si 0.15%, C 0.02%, P 0.012%, S 0.015%, with the balance being Fe and unavoidable impurities; satisfying: (Ni + Co) / Cr = 0.72, Ni / Co = 5; the preparation process of this high-strength stainless steel is the same as that in Example 2.

[0027] Example 6 A high-strength stainless steel, by mass percentage, is composed of the following components: Co 1.0%, Al 1.0%, Ti 1.0%, Mo 0.8%, Ni 8.0%, Cr 12.0%, Mn 0.9%, Si 0.15%, C 0.02%, P 0.012%, S 0.015%, with the balance being Fe and unavoidable impurities; satisfying: (Ni + Co) / Cr = 0.75, Ni / Co = 8; the preparation process of this high-strength stainless steel is the same as that in Example 2.

[0028] Example 7 A high-strength stainless steel, by mass percentage, is composed of the following components: Co 2.0%, Al 1.0%, Ti 1.0%, Mo 0.8%, Ni 7.0%, Cr 12.0%, Mn 0.9%, Si 0.15%, C 0.02%, P 0.012%, S 0.015%, with the balance being Fe and unavoidable impurities; satisfying: (Ni + Co) / Cr = 0.75, Ni / Co = 3.5; the preparation process of this high-strength stainless steel is the same as that in Example 2.

[0029] Example 8 Compared with Example 2, the only difference in this example is the preparation process of a high-strength stainless steel. This example of a high-strength stainless steel preparation process includes the following steps: S1. Raw materials are selected according to the mass percentage of each component in the stainless steel composition for smelting, refining, and casting to obtain ingots; wherein: the deoxidation in the refining process is to first use aluminum for pre-deoxidation, and then use silicon-calcium alloy and silicon-zirconium alloy with a mass ratio of 1:1 for deoxidation. S2. The ingot is heated to 1200℃ and held for 24 hours. After hot rolling, it is cooled to 300℃ at 200℃ and then cooled to 30℃ at a cooling rate of 1.5℃ / s to obtain a slab. The hot rolling temperature is 1050℃, the final rolling temperature is 950℃, and the total hot rolling reduction rate is 50%. S3. After holding the slab at 1150℃ for 60 minutes, perform the first stage of cooling at a cooling rate of 25℃ / h, and then perform the second stage of cooling at a cooling rate of 5℃ / h, and finally cool it to room temperature in the air to obtain stainless steel.

[0030] Example 9 Compared with Example 2, the only difference in this example is the preparation process of a high-strength stainless steel. This example of a high-strength stainless steel preparation process includes the following steps: S1. Raw materials are selected according to the mass percentage of each component in the stainless steel composition for smelting, refining, and casting to obtain ingots; wherein: the deoxidation in the refining process is to first use aluminum for pre-deoxidation, and then use silicon-calcium alloy and silicon-zirconium alloy with a mass ratio of 1:1 for deoxidation. S2. The ingot is heated to 1200℃ and held for 24 hours. After hot rolling, it is cooled to 300℃ at 150℃ and then cooled to 30℃ at a cooling rate of 1.5℃ / s to obtain a slab. The hot rolling temperature is 1050℃, the final rolling temperature is 950℃, and the total hot rolling reduction rate is 50%. S3. After holding the slab at 1150℃ for 60 minutes, perform the first stage of cooling at a cooling rate of 25℃ / h, and then perform the second stage of cooling at a cooling rate of 5℃ / h, and finally cool it to room temperature in the air to obtain stainless steel.

[0031] Example 10 Compared with Example 8, the only difference in this example is the preparation process of a high-strength stainless steel. This example of a high-strength stainless steel preparation process includes the following steps: S1. Raw materials are selected according to the mass percentage of each component in the stainless steel composition for smelting, refining, and casting to obtain ingots; wherein: the deoxidation in the refining process is to first use aluminum for pre-deoxidation, and then use silicon-calcium alloy and silicon-zirconium alloy with a mass ratio of 1:1 for deoxidation. S2. The ingot is heated to 1200℃ and held for 24 hours. After hot rolling, it is cooled to 300℃ at 200℃ and then cooled to 30℃ at a cooling rate of 1.5℃ / s to obtain a slab. The hot rolling temperature is 1050℃, the final rolling temperature is 950℃, and the total hot rolling reduction rate is 50%. S3. After holding the slab at 1150℃ for 60 minutes, perform the first stage of cooling at a cooling rate of 25℃ / h to cool to 500℃, then perform the second stage of cooling at a cooling rate of 15℃ / h to cool to 300℃, and finally cool it to room temperature in air to obtain stainless steel.

[0032] Example 11 Compared with Example 8, the only difference in this example is the preparation process of a high-strength stainless steel. This example of a high-strength stainless steel preparation process includes the following steps: S1. Raw materials are selected according to the mass percentage of each component in the stainless steel composition for smelting, refining, and casting to obtain ingots; wherein: the deoxidation in the refining process is to first use aluminum for pre-deoxidation, and then use silicon-calcium alloy and silicon-zirconium alloy with a mass ratio of 1:1 for deoxidation. S2. The ingot is heated to 1200℃ and held for 24 hours. After hot rolling, it is cooled to 300℃ at 200℃ and then cooled to 30℃ at a cooling rate of 1.5℃ / s to obtain a slab. The hot rolling temperature is 1050℃, the final rolling temperature is 950℃, and the total hot rolling reduction rate is 50%. S3. After holding the slab at 1150℃ for 60 minutes, perform the first stage of cooling at a cooling rate of 25℃ / h to cool to 500℃, then perform the second stage of cooling at a cooling rate of 10℃ / h to cool to 300℃, and finally cool it to room temperature in the air to obtain stainless steel.

[0033] Comparative Example 1 Compared with Example 1, the only difference in this comparative example is that the high-strength stainless steel does not contain Co in its composition.

[0034] Comparative Example 2 Compared with Example 1, the difference in this comparative example is that, in the composition of the high-strength stainless steel, Mo is 0.2% by weight.

[0035] Comparative Example 3 Compared with Example 1, the difference in this comparative example is that, in the composition of the high-strength stainless steel, Mo is 2% by weight.

[0036] Comparative Example 4 Compared with Example 1, the difference in this comparative example is that, in the composition of the high-strength stainless steel, Cr is 9% by weight.

[0037] Comparative Example 5 Compared with Example 1, the difference in this comparative example is that, in the composition of the high-strength stainless steel, Cr is 13% by weight.

[0038] Experimental Example The properties of the stainless steels in Examples 1-11 and Comparative Examples 1-5 were determined according to the following test methods: (1) Tensile strength: The tensile strength was tested in accordance with GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test at room temperature", with a test rate of 0.008s. -1 ; (2) Impact resistance: The absorbed energy KV2 at room temperature was tested according to GB / T 229-2020 "Metallic Materials Charpy Pendulum Impact Test Method". A V-notch specimen was used and a 2mm pendulum hammer blade was used for the test. The measurement results are shown in Tables 1 and 2 below.

[0039] Table 1. Tensile strength test results of stainless steel in Examples 1-7 and Comparative Examples 1-5

[0040] As shown in Table 1, the tensile strength of stainless steel in Examples 1-7 of the present invention is higher than that in Comparative Examples 1-5, indicating that the tensile strength of stainless steel can be improved by limiting the mass content of each component in stainless steel in the present invention.

[0041] Table 2. Results of impact resistance tests on stainless steel in Examples 2, 8-11

[0042] As shown in Table 2, the present invention improves the impact resistance of stainless steel by limiting the cooling process conditions of rolling and heat treatment.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength stainless steel characterized by, By mass percentage, consisting of: Co 1.0%~2.0%, Al 0.8%~1.2%, Ti 1.0%~1.2%, Mo 0.6%~1.1%, Ni 6.0%~9.0%, Cr 10.0%~12.5%, Mn 0.8%~1.0%, Si 0.08%~0.2%, C≤0.03%, P≤0.035%, S≤0.030%, the balance is Fe and inevitable impurities, the mass content relationship of the Ni, Cr, Co is: (Ni+Co) / Cr=0.7~1.

2. A high strength stainless steel according to claim 1, characterized in that The mass content relationship of the Ni and Co is: Ni / Co=3.5~8.

3. A process for producing a high-strength stainless steel for producing the high-strength stainless steel according to any one of claims 1 to 2, characterized by, Comprising the following steps: S1, according to the mass percentage of each component in the stainless steel component, the raw materials are selected to carry out smelting, refining and casting to obtain ingots; S2, after the ingot is rolled, a slab is obtained; S3, after the slab is heat treated, a stainless steel is obtained.

4. The process for producing a high-strength stainless steel according to claim 3, characterized by, In step S2, the rolling process is: the ingot is heated to 1150~1250℃, and after holding for 24h, hot rolling is carried out and then cooled to obtain a slab.

5. The process for producing a high-strength stainless steel according to claim 4, characterized by, The open rolling temperature of the hot rolling is 1000~1100℃, the final rolling temperature is ≥950℃, and the total reduction rate of the hot rolling is 50%~60%.

6. The process for producing a high-strength stainless steel according to claim 4, characterized by, The cooling is: cooling to 300℃ under the environment of 150~250℃, and then cooling to 20~30℃ at a cooling rate of 1.5℃ / s.

7. The process for producing a high-strength stainless steel according to claim 3, wherein In step S3, the heat treatment process is: the slab is held at 1150~1200℃ for 60~80min, and then cooled to obtain a stainless steel.

8. The process for producing a high-strength stainless steel according to claim 7, characterized by, The cooling process is: the slab after holding is sequentially subjected to first-stage cooling and second-stage cooling, cooled to 300℃, and then cooled to room temperature in air, the cooling rates of the first-stage cooling and the second-stage cooling are different.

9. The process for producing a high-strength stainless steel according to claim 8, characterized by, The first-stage cooling is carried out to 500℃, and then the second-stage cooling is carried out.

10. The process for producing a high-strength stainless steel according to claim 9, characterized by, The cooling rate of the first-stage cooling is 25℃ / h, and the cooling rate of the second-stage cooling is 5~15℃ / h.

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