Corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology and preparation method of corrosion-resistant high-nitrogen steel strip

Abstract

The invention discloses a corrosion-resistant high-nitrogen steel strip based on a pressurized electroslag technology and a preparation method of the corrosion-resistant high-nitrogen steel strip. The high-nitrogen steel strip comprises the following chemical components in percentage by mass: 0.28%-0.32% of C, 0.55%-0.65% of Si, 0.45%-0.55% of Mn, 15.0%-16.0% of Cr, 0.95%-1.05% of Mo, 0.38%-0.50% of N, less than or equal to 0.005% of P, less than or equal to 0.005% of S and the balance of Fe and inevitable impurities. According to the preparation method, the pressurized electroslag remelting technology is adopted, the precise nitrogen increasing technology is combined, the slag system design is optimized, and the follow-up rolling-heat treatment integrated technology is adopted, so that uniform solid solution and fine regulation and control of nitrogen elements in steel are achieved. The nitrogen content of the prepared high-nitrogen steel strip is stably controlled in a target range, and the high-nitrogen steel strip has excellent corrosion resistance, high strength and high hardness, can be widely applied to the fields of kitchen cutters, medical instruments, aerospace and the like, and solves the problems of non-uniform nitrogen content, insufficient corrosion resistance and high industrial production difficulty in the existing high-nitrogen steel preparation.

Description

Technical Field

[0001] This invention relates to the field of metal metallurgical materials, and in particular to a corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology and its preparation method. Background Technology

[0002] High-nitrogen stainless steel, due to the solid solution strengthening and precipitation strengthening effects of nitrogen, possesses both excellent mechanical properties and corrosion resistance, making it promising for applications in aerospace, food and chemical industries, medical devices, and kitchen knives. However, nitrogen has extremely low solubility in steel, making it difficult to achieve stable control of high nitrogen content under normal pressure, and defects such as nitrogen segregation and nitrogen porosity are prone to occur, severely affecting material properties and industrial production. Existing high-nitrogen steel preparation technologies mainly include pressure induction melting and pressure electroslag remelting. Among them, pressure electroslag remelting technology combines the refining advantages of electroslag remelting with the nitrogen-enhancing characteristics of pressure metallurgy, effectively suppressing nitrogen escape and increasing nitrogen solubility in steel, making it the preferred solution for the industrial production of high-nitrogen steel. However, existing pressurized electroslag remelting technology still has the following problems: First, the unreasonable addition method of nitriding alloys leads to uneven nitrogen content distribution; second, the desulfurization and deoxidation capacity of the slag system is insufficient, resulting in high sulfur and oxygen impurity content in the steel; third, the subsequent heat treatment process is imperfect, with excessively high residual austenite content, affecting the material's strength and corrosion resistance; and fourth, there is a lack of integrated preparation processes for steel strip products, making it difficult to meet the demand for thin-gauge high-nitrogen steel in the precision manufacturing field. Therefore, developing a high-nitrogen steel strip with precisely controllable nitrogen content, uniform microstructure, and excellent corrosion resistance and mechanical properties, along with its efficient preparation method, is of great significance for promoting the industrial application of high-nitrogen steel. Summary of the Invention

[0003] The main technical problem solved by this invention is to provide a corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology and its preparation method, which can accurately control the nitrogen content of the steel strip and has excellent mechanical properties and corrosion resistance.

[0004] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is to provide a corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology. The chemical composition of the corrosion-resistant high-nitrogen steel strip, by mass fraction, is as follows: C 0.28%~0.32%, Si 0.55%~0.65%, Mn 0.45%~0.55%, Cr 15.0%~16.0%, Mo 0.95%~1.05%, N 0.38%~0.50%, P≤0.005%, S≤0.005%, with the remainder being Fe and unavoidable impurities.

[0005] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is: to provide a method for preparing a corrosion-resistant high-nitrogen steel strip, wherein the method for preparing the corrosion-resistant steel strip includes the following steps: Step 1: Preparation of consumable electrode: According to the target chemical composition, the consumable electrode is prepared by vacuum induction melting, controlling the N content in the electrode to be 0.20%~0.30%, P≤0.003%, and S≤0.003%; The second step is pressurized electroslag remelting: The consumable electrode is placed in a pressurized electroslag furnace, and remelting is carried out under a nitrogen pressure of 0.7~1.0MPa using a CaF2-CaO-Al2O3-Na2O slag system. During the remelting process, a Si3N4 and FeCrN composite nitride alloy is added through a screw feeder, and the addition rate of the nitride alloy is dynamically matched with the melting rate. The melting rate is 0.5~1.0kg / min, and a high-nitrogen steel ingot is obtained. The third step is forging and shaping: the high-nitrogen steel ingot is homogenized at 1150~1200℃ for 2~3 hours, and then three-dimensional forging is carried out at a forging temperature of 1050~1150℃, and finally forged into a forging billet with a thickness of 60~80mm. The fourth step is hot rolling into strip: the forging billet is heated to 1140~1160℃, held for 1~2 hours and then hot rolled in multiple passes. The final rolling temperature is 1030~1100℃, and finally rolled into a steel strip with a thickness of 1.0~5.0mm. Step 5 heat treatment: Heat the hot-rolled steel strip to between 980 and 1010°C, hold for 1 hour, then quench in water, followed by deep cryogenic treatment at -190°C for 20 hours, and finally temper at 200°C for 3 hours, and air cool to room temperature. Step 6 Finishing: The heat-treated steel strip is pickled, leveled and precision-cut to obtain the finished corrosion-resistant high-nitrogen steel strip.

[0006] In a preferred embodiment of the present invention, the mass composition of the CaF2-CaO-Al2O3-Na2O slag system in the second step is: CaF2 40%~50%, CaO 20%~25%, Al2O3 20%~25%, Na2O 3%~5%.

[0007] In a preferred embodiment of the present invention, the mass ratio of Si3N4 to FeCrN in the composite nitride alloy in the second step is 1:2 to 1:3, the nitrogen content of Si3N4 is ≥30%, and the nitrogen content of FeCrN is ≥8%.

[0008] In a preferred embodiment of the present invention, during the pressurized electroslag remelting process in the second step, the pressure difference between the cooling water and the gas in the furnace is controlled to be ≤0.1MPa by a water-gas dynamic balance system to avoid porosity defects in the ingot.

[0009] In a preferred embodiment of the present invention, the heating and cooling rate of the cryogenic treatment in the fifth step is 0.5~1.0℃ / min.

[0010] The beneficial effects of this invention are as follows: By combining pressurized electroslag remelting technology with precise nitrogen enrichment using composite nitriding alloys, this invention solves the problems of uneven nitrogen content and nitrogen porosity defects in high-nitrogen steel. It stably controls the nitrogen content in the raw steel strip within the range of 0.38% to 0.50%. Furthermore, the use of an optimized slag system (CaF2-CaO-Al2O3-Na2O) during the pressurized remelting process significantly improves the system's desulfurization capacity, ensuring that the sulfur content in the steel is ≤0.005%, while simultaneously inhibiting the aluminization reaction, preventing the formation of AlN inclusions, and improving the purity and toughness of the final product. Moreover, through an integrated heat treatment process of "quenching-deep cryogenics-tempering," a raw steel strip with high strength, high hardness, and excellent corrosion resistance is obtained, meeting the demand for high-performance stainless steel materials in fields such as kitchen knives and medical devices, and showing broad prospects for industrial application. Detailed Implementation

[0011] The preferred embodiments of the present invention will be described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0012] The embodiments of this invention include: Example 1 A corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology has the following chemical composition by mass fraction: C 0.30%, Si 0.60%, Mn 0.50%, Cr 15.6%, Mo 1.0%, N 0.42%, P 0.003%, S 0.002%, with the remainder being Fe and unavoidable impurities.

[0013] Example 2 A corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology has the following chemical composition by mass fraction: C 0.29%, Si 0.58%, Mn 0.48%, Cr 15.3%, Mo 0.98%, N 0.47%, P 0.004%, S 0.003%, with the remainder being Fe and unavoidable impurities.

[0014] Example 3 A corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology has the following chemical composition by mass fraction: C 0.31%, Si 0.64%, Mn 0.55%, Cr 15.7%, Mo 1.04%, N 0.39%, P 0.002%, S 0.004%, with the remainder being Fe and unavoidable impurities.

[0015] Example 4 A corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology has the following chemical composition by mass fraction: C 0.28%, Si 0.61%, Mn 0.46%, Cr 15.1%, Mo 0.98%, N 0.43%, P 0.002%, S 0.004%, with the remainder being Fe and unavoidable impurities.

[0016] The preparation methods of Examples 1-4 include the following steps: Step 1: Preparation of consumable electrode: According to the target chemical composition, the consumable electrode is prepared by vacuum induction melting, controlling the N content in the electrode to be 0.25%, P 0.002%, and S 0.002%; The second step is pressurized electroslag remelting: The consumable electrode is placed in a pressurized electroslag furnace. The electroslag furnace uses a CaF2-CaO-Al2O3-Na2O slag system. High-purity nitrogen gas is introduced into the furnace to pressurize and form a high-pressure nitrogen atmosphere before remelting begins. At the same time, a water-gas dynamic balance control system is activated to adjust the cooling water pressure in real time, keeping the pressure difference between the cooling water and the gas in the furnace within ±0.1 MPa to prevent porosity defects in the ingot. During the remelting process, a Si3N4 and FeCrN composite nitride alloy is added by a screw feeder at a mass ratio of 1:2.5. The addition rate of the nitride alloy is dynamically matched with the melting rate to obtain a high-nitrogen steel ingot. The nitrogen content of the Si3N4 used is ≥30%, and the nitrogen content of the FeCrN is ≥8%. The third step is forging and shaping: the high-nitrogen steel ingot is homogenized at 1180℃ for 2.5 hours, and then three-dimensional forging is carried out at a forging temperature of 1100℃, finally forging into a forging billet with a thickness of 70mm; The fourth step is hot rolling into strip: the forging billet is heated to 1150℃, held for 1.5h and then hot rolled in 7 passes with a final rolling temperature of 1030~1100℃, and finally rolled into a steel strip with a thickness of 3.0mm. Step 5: Heat the hot-rolled steel strip to between 980 and 1010℃, hold for 1 hour, then quench in water, then cool to -190℃ at a rate of 1.0℃ / min for 20 hours for cryogenic treatment, then heat to room temperature at a rate of 0.5℃ / min, and finally temper at 200℃ for 3 hours and air cool to room temperature. Step 6 Finishing: The heat-treated steel strip is pickled, leveled and precision-cut to obtain the finished corrosion-resistant high-nitrogen steel strip.

[0017] In Example 1, the pressurized electroslag furnace contained the following mass fractions: CaF₂ 45%, CaO 22%, Al₂O₃ 23%, and Na₂O 4%; the nitrogen pressure was 0.8 MPa; the alloy nitride addition rate was 0.8 kg / min; the melting rate was 0.7 kg / min; and the quenching temperature was 990 °C. In Example 2, the mass fraction of the pressurized electroslag furnace is the same as in Example 1, the nitrogen pressure is 1.0 MPa, the composite nitride alloy addition rate is 0.9 kg / min, the melting rate is 0.8 kg / min, and the quenching temperature is 1000℃.

[0018] In Example 3, the mass fraction of the pressurized electroslag furnace is the same as in Example 1, the nitrogen pressure is 0.7 MPa, the composite nitride alloy addition rate is 0.7 kg / min, the melting rate is 0.6 kg / min, and the quenching temperature is 1000℃.

[0019] In Example 4, the mass fraction of the pressurized electroslag furnace is the same as in Example 1, the nitrogen pressure is 1.0 MPa, the composite nitride alloy addition rate is 1.0 kg / min, the melting rate is 0.9 kg / min, and the quenching temperature is 990℃.

[0020] The test results above show that the mechanical properties and corrosion resistance of the high-nitrogen steel strip prepared using the technical solution of this invention are significantly better than those of ordinary martensitic stainless steel. It can be used as raw material steel strip for high-end kitchen knives and medical devices, and can meet the demand for thin-gauge high-nitrogen steel in the precision manufacturing field.

[0021] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A corrosion-resistant high-nitrogen steel strip based on pressurized electroslag technology, characterized in that, The chemical composition of the corrosion-resistant high-nitrogen steel strip, by mass fraction, is as follows: C 0.28%~0.32%, Si 0.55%~0.65%, Mn 0.45%~0.55%, Cr 15.0%~16.0%, Mo 0.95%~1.05%, N 0.38%~0.50%, P≤0.005%, S≤0.005%, with the remainder being Fe and unavoidable impurities.

2. A method for preparing the corrosion-resistant high-nitrogen steel strip according to claim 1, characterized in that, The method for preparing the corrosion-resistant steel strip includes the following steps: Step 1: Preparation of consumable electrode: According to the target chemical composition, the consumable electrode is prepared by vacuum induction melting, controlling the N content in the electrode to be 0.20%~0.30%, P≤0.003%, and S≤0.003%; The second step is pressurized electroslag remelting: The consumable electrode is placed in a pressurized electroslag furnace, and remelting is carried out under a nitrogen pressure of 0.7~1.0MPa using a CaF2-CaO-Al2O3-Na2O slag system. During the remelting process, a Si3N4 and FeCrN composite nitride alloy is added through a screw feeder, and the addition rate of the nitride alloy is dynamically matched with the melting rate. The melting rate is 0.5~1.0kg / min, and a high-nitrogen steel ingot is obtained. The third step is forging and shaping: the high-nitrogen steel ingot is homogenized at 1150~1200℃ for 2~3 hours, and then three-dimensional forging is carried out at a forging temperature of 1050~1150℃, and finally forged into a forging billet with a thickness of 60~80mm. The fourth step is hot rolling into strip: the forging billet is heated to 1140~1160℃, held for 1~2 hours and then hot rolled in multiple passes. The final rolling temperature is 1030~1100℃, and finally rolled into a steel strip with a thickness of 1.0~5.0mm. Fifth step heat treatment: Heat the hot-rolled steel strip to between 980 and 1010℃, hold for 1 hour, then quench in water, followed by deep cryogenic treatment at -190℃ for 20 hours, and finally temper at 200℃ for 3 hours, and air cool to room temperature. Step 6 Finishing: The heat-treated steel strip is pickled, leveled and precision-cut to obtain the finished corrosion-resistant high-nitrogen steel strip.

3. The method for preparing corrosion-resistant high-nitrogen steel strip according to claim 2, characterized in that, The mass fraction of the CaF2-CaO-Al2O3-Na2O slag system in the second step is as follows: CaF2 40%~50%, CaO 20%~25%, Al2O3 20%~25%, Na2O 3%~5%.

4. The method for preparing corrosion-resistant high-nitrogen steel strip according to claim 2, characterized in that, In the second step, the mass ratio of Si3N4 to FeCrN in the composite nitride alloy is 1:2 to 1:3, the nitrogen content of Si3N4 is ≥30%, and the nitrogen content of FeCrN is ≥8%.

5. The method for preparing corrosion-resistant high-nitrogen steel strip according to claim 2, characterized in that, In the second step of pressurized electroslag remelting, the pressure difference between the cooling water and the gas inside the furnace is controlled to be ≤0.1MPa through a water-gas dynamic balance system to avoid porosity defects in the ingot.

6. The method for preparing corrosion-resistant high-nitrogen steel strip according to claim 2, characterized in that, In the fifth step, the heating and cooling rates for cryogenic treatment are 0.5~1.0℃ / min.

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