A preparation process of ultra-low sulfur and low-inclusion low-temperature corrosion-resistant steel by converter-LF-RH double smelting

Abstract

The present application relates to the technical field of steel material, and proposes a preparation process of converter-LF-RH duplex smelting ultra-low sulfur low-inclusion low-temperature corrosion-resistant steel, which comprises the following steps: ingredient raw materials are prepared, and then sequentially subjected to converter smelting, LF refining, RH vacuum treatment, continuous casting, rolling, cooling and tempering, so as to obtain the converter-LF-RH duplex smelting ultra-low sulfur low-inclusion low-temperature corrosion-resistant steel, wherein, during the LF refining, the slag system comprises a primary refining slag system with an alkalinity of 4-6 and a secondary refining slag system with an alkalinity of 8-10. Through the above technical scheme, the problem of insufficient low-temperature toughness of the corrosion-resistant steel in the related preparation process is solved.

Description

Technical Field

[0001] This invention relates to the field of steel materials technology, specifically to a process for preparing ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting. Background Technology

[0002] Corrosion-resistant steel, as a special type of steel with the ability to resist corrosion failure, is widely used in many fields such as marine engineering, chemical equipment, and infrastructure in cold regions. Its service environment is often accompanied by harsh conditions such as humidity, salt spray, and low temperature. Therefore, the material not only needs to have stable mechanical properties, but also excellent corrosion resistance and low temperature toughness to resist structural damage caused by media erosion and low temperature impact. Sulfur element easily forms brittle sulfides with metal elements in steel, and inclusions will destroy the continuity of the steel matrix. Both of these factors together lead to a decrease in the low temperature toughness and a deterioration in corrosion resistance stability of the steel, which seriously affects the service life of the steel under extreme working conditions.

[0003] In existing technologies, the smelting of corrosion-resistant steel often employs a single refining slag system for LF refining, making it difficult to balance slag formation efficiency and refining effect. Furthermore, while directly using a high-basicity slag system can improve desulfurization and inclusion adsorption capacity, the slag system has a high melting point and poor fluidity, making it prone to crust formation. This not only prolongs the slag formation cycle but also increases the risk of secondary oxidation of the molten steel, generating more brittle inclusions and resulting in high inclusion density and insufficient low-temperature toughness of the steel. Therefore, a preparation process for corrosion-resistant steel with good low-temperature toughness is urgently needed. Summary of the Invention

[0004] This invention proposes a process for preparing ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH dual smelting, which solves the problem of insufficient low-temperature toughness of corrosion-resistant steel in related preparation processes.

[0005] The technical solution of the present invention is as follows: This invention proposes a process for preparing ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting, comprising the following steps: The raw materials are batched and then sequentially processed through converter smelting, LF refining, RH vacuum treatment, continuous casting, rolling, cooling, and tempering to obtain converter-LF-RH duplex smelting ultra-low sulfur, low inclusion, low temperature corrosion resistant steel. In the LF refining process, the slag system includes a primary refining slag system with a basicity of 4-6 and a secondary refining slag system with a basicity of 8-10.

[0006] As a further technical solution, during the LF refining process, the slag system includes a primary refining slag system with an basicity of 5 and a secondary refining slag system with an basicity of 9.

[0007] As a further technical solution, the primary refining slag system is composed of the following components by weight percentage: CaO 48%~50%, Al2O3 16.7%~19%, MgO 6.4%~10.3%, SiO2 8%~12%, CaF2 11.2%~14.4%, FeO+MnO≤2%; The secondary refining slag system is composed of the following components by weight percentage: CaO 54%~60%, Al2O3 19.6%~20.4%, MgO 5.8%~8%, SiO2 6%~7%, CaF2 7.2%~12%, FeO+MnO≤1%.

[0008] As a further technical solution, during the converter smelting process, the final C content is ≥0.08% by weight percentage.

[0009] As a further technical solution, the tapping temperature during LF refining is 1650~1670℃.

[0010] As a further technical solution, argon gas is introduced for stirring during the LF refining process; The mixing process is divided into primary mixing and secondary mixing. The intensity of the stirring in one pass is 0.5~0.7 L·min. -1 ·t -1 The intensity of the secondary stirring is 0.8~1 L·min. -1 ·t -1 .

[0011] As a further technical solution, during the RH vacuum treatment, the vacuum degree is ≤5Pa and the treatment time is ≥20min; During the RH vacuum treatment, Al wire is added for deoxidation; The amount of Al added is 0.35~0.65 kg / t of molten steel.

[0012] As a further technical solution, the tempering temperature is 550~580℃.

[0013] This invention also proposes a converter-LF-RH duplex smelting ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel, wherein the converter-LF-RH duplex smelting ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel is composed of the following components by weight percentage: C 0.08%~0.12%, Si 0.22%~0.52%, Mn 1.2%~1.5%, Nb 0.02%~0.04%, Mo 0.5%~0.8%, Cr 1%~1.6%, Cu 0.22%~0.52%, Ni 0.5%~1%, Als 0.02%~0.04%, N 0.008%~0.012%, Ce 0.02%~0.04%, S≤0.002%, P≤0.015%, with the balance being Fe and its unavoidable impurities.

[0014] As a further technical solution, the weight percentages of Si, Cr and Cu satisfy the following relationship: 0.36≤(Si+Cu) / Cr≤0.7.

[0015] In this invention, by optimizing the weight percentages of Si, Cr, and Cu, and when the weight percentages of Si, Cr, and Cu satisfy the relationship 0.36≤(Si+Cu) / Cr≤0.7, the corrosion resistance of the produced steel can be further improved. Under the premise of ensuring that Cr provides sufficient basic passivation capability, the combined addition of Si and Cu can synergistically promote the rapid enrichment of Cr on the matrix surface and the formation of a more stable and denser composite oxide passivation layer. This inhibits the activation dissolution in the early stages of corrosion and delays the further intrusion of the corrosive medium, thereby significantly improving the corrosion resistance of the steel from a mechanistic perspective.

[0016] The working principle and beneficial effects of this invention are as follows: In this invention, during refining, a primary refining slag system with a basicity of 4-6 is added first, and then the basicity of the refining slag system is adjusted to 8-10. This reduces the inclusion density and improves the low-temperature toughness of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by converter-LF-RH duplex smelting. The initial addition of a primary refining slag system with a basicity of 4-6 provides a suitable melting point and excellent fluidity, allowing it to melt rapidly after tapping to form a continuous and dense covering slag layer. This effectively isolates the molten steel from air, inhibiting secondary oxidation. Simultaneously, the lower initial basicity avoids the problems of high-basicity slag systems being difficult to melt and forming a crust, shortening the slag formation time. Later, lime is added to adjust the slag basicity to 8-10, forming an ultra-high basicity strong reducing refining system. This reduces the formation of large brittle sulfide inclusions such as MnS and CaS, thereby reducing stress defects and improving the low-temperature impact resistance of the steel. Detailed Implementation

[0017] 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.

[0018] Example 1 A converter-LF-RH duplex smelting ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel is composed of the following components by weight percentage: C 0.08%, Si 0.52%, Mn 1.2%, Nb 0.02%, Mo 0.50%, Cr 1.00%, Cu 0.52%, Ni 0.5%, Als 0.02%, N 0.008%, Ce 0.02%, S 0.002%, P 0.015%, with the balance being Fe and its unavoidable impurities; A method for preparing ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting includes the following steps: S1. Converter Smelting: After the components are weighed according to the above weight percentages, they are smelted in a converter. During smelting, a top and bottom blowing process is adopted, and the oxygen flow rate of the top lance is 250 Nm³. 3 / h, bottom-blown argon flow rate is 50Nm 3 / h, when the molten steel is tapped, the final control point for C content is 0.08wt%; S2. After tapping, the molten steel enters the LF furnace for LF refining. Simultaneously, a primary refining slag system with a basicity of 4 is added at a rate of 6 kg / t of molten steel. Argon gas is introduced for primary stirring at an intensity of 0.5 L / min. -1 ·t -1 After refining for 10 minutes, lime is added to control the alkalinity of the secondary refining slag system to 8. At this point, the stirring intensity is increased to 0.8 L / min. -1 ·t -1 The refining process continued for a total of 40 minutes. At tapping, the molten steel temperature was 1650℃. The primary refining slag system consisted of the following components by weight percentage: CaO 48%, Al₂O₃ 19%, MgO 6.4%, SiO₂ 12%, CaF₂ 12.6%, FeO+MnO 2%. The secondary refining slag system consisted of the following components by weight percentage: CaO 56%, Al₂O₃ 20%, MgO 7%, SiO₂ 7%, CaF₂ 29%, FeO+MnO 1%. S3. After the steel is refined and tapped, it undergoes RH vacuum treatment and Al wire is added for deoxidation treatment. The amount of Al wire added is 0.35 kg / t of steel. During vacuum treatment, the vacuum degree is 5 Pa and the treatment time is 20 min. S4. After vacuum treatment, the molten steel is successively subjected to continuous casting, rolling, cooling, and tempering at 550℃ to obtain ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by converter-LF-RH duplex smelting.

[0019] Example 2 A converter-LF-RH duplex smelting ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel is composed of the following components by weight percentage: C 0.12%, Si 0.52%, Mn 1.5%, Nb 0.04%, Mo 0.80%, Cr 1.00%, Cu 0.52%, Ni 1%, Als 0.04%, N 0.012%, Ce 0.04%, S 0.002%, P 0.015%, with the balance being Fe and its unavoidable impurities; A method for preparing ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting includes the following steps: S1. Converter Smelting: After the components are weighed according to the above weight percentages, they are smelted in a converter. During smelting, a top and bottom blowing process is adopted, and the oxygen flow rate of the top lance is 250 Nm³. 3 / h, bottom-blown argon flow rate is 50Nm 3 / h, when the molten steel is tapped, the final C content is controlled at 0.1wt%; S2. After tapping, the molten steel enters the LF furnace for LF refining. A primary refining slag system with a basicity of 6 is added at a rate of 6 kg / t of molten steel. Simultaneously, argon gas is introduced for primary stirring at an intensity of 0.7 L / min. -1 ·t -1 After refining for 10 minutes, lime is added to control the alkalinity of the secondary refining slag system to 10. At this point, the stirring intensity is increased to 1 L / min. -1 ·t -1 The refining process continued for a total of 40 minutes. At tapping, the molten steel temperature was 1670℃. The primary refining slag system consisted of the following components by weight percentage: CaO 48%, Al₂O₃ 19%, MgO 8.6%, SiO₂ 8%, CaF₂ 14.4%, FeO+MnO 2%. The secondary refining slag system consisted of the following components by weight percentage: CaO 60%, Al₂O₃ 20.4%, MgO 5.8%, SiO₂ 6%, CaF₂ 7.2%, FeO+MnO 0.6%. S3. After the steel is refined and tapped, it undergoes RH vacuum treatment and Al wire is added for deoxidation treatment. The amount of Al wire added is 0.65 kg / t of steel. During vacuum treatment, the vacuum degree is 5 Pa and the treatment time is 25 min. S4. After vacuum treatment, the molten steel is successively subjected to continuous casting, rolling, cooling, and tempering at 580℃ to obtain ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by converter-LF-RH duplex smelting.

[0020] Example 3 A converter-LF-RH duplex smelting ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel is composed of the following components by weight percentage: C 0.1%, Si 0.52%, Mn 1.4%, Nb 0.03%, Mo 0.7%, Cr 1.00%, Cu 0.52%, Ni 0.8%, Als 0.03%, N 0.010%, Ce 0.03%, S 0.001%, P 0.015%, with the balance being Fe and its unavoidable impurities; A method for preparing ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting includes the following steps: S1. Converter Smelting: After the components are weighed according to the above weight percentages, they are smelted in a converter. During smelting, a top and bottom blowing process is adopted, and the oxygen flow rate of the top lance is 250 Nm³. 3 / h, bottom-blown argon flow rate is 50Nm 3 / h, when the molten steel is tapped, the final C content is controlled at 0.1wt%; S2. After tapping, the molten steel enters the LF furnace for LF refining. Simultaneously, a primary refining slag system with a basicity of 5 is added at a rate of 6 kg / t of molten steel. Argon gas is introduced for primary stirring at an intensity of 0.6 L / min. -1 ·t -1 After refining for 10 minutes, lime is added to control the alkalinity of the secondary refining slag system at 9. At this point, the stirring intensity is increased to 0.9 L / min. -1 ·t -1 The refining process continued for a total of 40 minutes. At tapping, the molten steel temperature was 1660℃. The primary refining slag system consisted of the following components by weight percentage: CaO 50%, Al₂O₃ 16.7%, MgO 10.3%, SiO₂ 10%, CaF₂ 11.2%, FeO+MnO 1.8%. The secondary refining slag system consisted of the following components by weight percentage: CaO 54%, Al₂O₃ 19.6%, MgO 8%, SiO₂ 6%, CaF₂ 12%, FeO+MnO 0.4%. S3. After the steel is refined and tapped, it undergoes RH vacuum treatment and Al wire is added for deoxidation treatment. The amount of Al wire added is 0.55 kg / t of steel. During vacuum treatment, the vacuum degree is 4 Pa ​​and the treatment time is 25 min. S4. After vacuum treatment, the molten steel is successively subjected to continuous casting, rolling, cooling, and tempering at 560℃ to obtain ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by converter-LF-RH duplex smelting.

[0021] Example 4 The difference between this embodiment and Embodiment 3 lies only in that an ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by a converter-LF-RH duplex smelting process is composed of the following components by weight percentage: C 0.1%, Si 0.22%, Mn 1.4%, Nb 0.03%, Mo 0.7%, Cr 1.6%, Cu 0.22%, Ni 0.8%, Als 0.03%, N 0.010%, Ce 0.03%, S 0.002%, P 0.015%, with the balance being Fe and its unavoidable impurities.

[0022] Example 5 The difference between this embodiment and Embodiment 3 lies only in that an ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by a converter-LF-RH duplex smelting process is composed of the following components by weight percentage: C 0.1%, Si 0.42%, Mn 1.4%, Nb 0.03%, Mo 0.7%, Cr 1.2%, Cu 0.42%, Ni 0.8%, Als 0.03%, N 0.010%, Ce 0.03%, S 0.002%, P 0.015%, with the balance being Fe and its unavoidable impurities.

[0023] Example 6 The difference between this embodiment and Embodiment 3 lies only in that an ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by a converter-LF-RH duplex smelting process is composed of the following components by weight percentage: C 0.1%, Si 0.27%, Mn 1.4%, Nb 0.03%, Mo 0.7%, Cr 1.5%, Cu 0.27%, Ni 0.8%, Als 0.03%, N 0.010%, Ce 0.03%, S 0.002%, P 0.015%, with the balance being Fe and its unavoidable impurities.

[0024] Example 7 The difference between this embodiment and Embodiment 3 lies only in that an ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by a converter-LF-RH duplex smelting process is composed of the following components by weight percentage: C 0.1%, Si 0.32%, Mn 1.4%, Nb 0.03%, Mo 0.7%, Cr 1.4%, Cu 0.32%, Ni 0.8%, Als 0.03%, N 0.010%, Ce 0.03%, S 0.002%, P 0.015%, with the balance being Fe and its unavoidable impurities.

[0025] Comparative Example 1 The difference between this comparative example and Example 3 lies only in step S2. Step S2 of this comparative example specifically includes the following steps: After tapping, the molten steel enters the LF furnace for LF refining. Simultaneously, a primary refining slag system with a basicity of 5 is added at a rate of 0.55 kg / t of molten steel. Argon gas is also introduced for primary stirring at an intensity of 0.6 L / min. -1 ·t -1 When refining steel, the temperature of the molten steel is 1660℃. The primary refining slag system includes the following components by weight percentage: CaO 50%, Al2O3 16.7%, MgO 10.3%, SiO2 10%, CaF2 11.2%, FeO+MnO 1.8%, and the refining time is 40 minutes.

[0026] Comparative Example 2 The difference between this comparative example and Example 3 lies only in step S2. Step S2 of this comparative example specifically includes the following steps: After tapping, the molten steel enters the LF furnace for LF refining. Simultaneously, a secondary refining slag system with a basicity of 9 is added at a rate of 0.55 kg / t of molten steel. Argon gas is also introduced for secondary stirring at an intensity of 0.91 L / min. -1 ·t -1 When refining the steel, the temperature of the molten steel is 1660℃. The secondary refining slag system includes the following components by weight percentage: CaO 54%, Al2O3 19.6%, MgO 8%, SiO2 6%, CaF2 12%, FeO+MnO 0.4%, and the refining time is 40 min.

[0027] Experimental Example 1 The following performance tests were conducted on the ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steels produced by converter-LF-RH duplex smelting obtained in Examples 1-3 and Comparative Examples 1-2: Low temperature toughness test: The impact energy of the specimen at -40℃ is tested according to the test method specified in GB / T 229-2020 "Metallic Materials Charpy Pendulum Impact Test Method". The specimen specifications are: length 55mm, width 10mm, and thickness 10mm. Inclusion density: Measured using a metallographic microscope (model number required); The results are shown in Table 1; Table 1. Measurement results of inclusion density and low-temperature toughness

[0028] By comparing the data of Examples 1-3 and Comparative Examples 1-2 in Table 1, Examples 1-3, by first adding a primary refining slag system with a basicity of 4-6 and then adjusting the basicity of the refining slag system to 8-10, resulted in a lower inclusion density and a higher impact energy at -40℃ compared to Comparative Examples 1-2. This indicates that by first adding a primary refining slag system with a basicity of 4-6 and then adjusting the basicity of the refining slag system to 8-10, the inclusion density can be reduced and the low-temperature toughness of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by converter-LF-RH duplex smelting can be improved.

[0029] Experiment Example 2 Corrosion resistance: The salt spray corrosion rate of the ultra-low sulfur, low inclusion, low temperature corrosion resistant steel prepared by converter-LF-RH duplex smelting was tested according to the test method specified in GB / T 10125-2021 "Civilized Atmosphere Corrosion Test - Salt Spray Test". The test results are shown in Table 2. Table 2 Corrosion Resistance Test Results

[0030] By comparing the data in Table 2, the corrosion rate of the ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by converter-LF-RH duplex smelting in Examples 5-7 was lower than that in Examples 1-4, thanks to the optimization of the mass relationship of Si, Cu, and Cr. This indicates that by optimizing the mass relationship of Si, Cu, and Cr in Examples 5-7, and when the mass percentages of Si, Cu, and Cr satisfy the formula: 0.36≤(Si+Cu) / Cr≤0.7, the corrosion resistance of the ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by converter-LF-RH duplex smelting can be further improved.

[0031] 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 process for preparing ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting, characterized in that, Includes the following steps: The raw materials are batched and then sequentially processed through converter smelting, LF refining, RH vacuum treatment, continuous casting, rolling, cooling, and tempering to obtain converter-LF-RH duplex smelting ultra-low sulfur, low inclusion, low temperature corrosion resistant steel. In the LF refining process, the slag system includes a primary refining slag system with a basicity of 4-6 and a secondary refining slag system with a basicity of 8-10.

2. The preparation process of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting according to claim 1, characterized in that, During the LF refining process, the slag system includes a primary refining slag system with an basicity of 5 and a secondary refining slag system with an basicity of 9.

3. The preparation process of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting according to claim 2, characterized in that, The primary refining slag system is composed of the following components by weight percentage: CaO 48%~50%, Al2O3 16.7%~19%, MgO 6.4%~10.3%, SiO2 8%~12%, CaF2 11.2%~14.4%, FeO+MnO≤2%; The secondary refining slag system is composed of the following components by weight percentage: CaO 54%~60%, Al2O3 19.6%~20.4%, MgO 5.8%~8%, SiO2 6%~7%, CaF2 7.2%~12%, FeO+MnO≤1%.

4. The preparation process of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting according to claim 1, characterized in that, During the converter smelting process, the final C content is ≥0.08% by weight.

5. The preparation process of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting according to claim 1, characterized in that, During the LF refining process, the tapping temperature is 1650~1670℃.

6. The preparation process of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting according to claim 1, characterized in that, During the LF refining process, argon gas is introduced for stirring. The mixing process is divided into primary mixing and secondary mixing. The intensity of the stirring in one pass is 0.5~0.7 L·min. -1 ·t -1 The intensity of the secondary stirring is 0.8~1 L·min. -1 ·t -1 .

7. The preparation process of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting according to claim 1, characterized in that, During the RH vacuum treatment, the vacuum degree is ≤5Pa and the treatment time is ≥20min; During the RH vacuum treatment, Al wire is added for deoxidation; The amount of Al added is 0.35~0.65 kg / t of molten steel.

8. The preparation process of ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel by converter-LF-RH duplex smelting according to claim 1, characterized in that, The tempering temperature is 550~580℃.

9. A converter-LF-RH duplex smelting method for producing ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel, characterized in that, The ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel prepared by the preparation method according to any one of claims 1 to 8 comprises the following components by weight percentage: C 0.08%~0.12%, Si 0.22%~0.52%, Mn 1.2%~1.5%, Nb 0.02%~0.04%, Mo 0.5%~0.8%, Cr 1%~1.6%, Cu 0.22%~0.52%, Ni 0.5%~1%, Als 0.02%~0.04%, N 0.008%~0.012%, Ce 0.02%~0.04%, S≤0.002%, P≤0.015%, with the balance being Fe and its unavoidable impurities.

10. The ultra-low sulfur, low inclusion, low-temperature corrosion-resistant steel produced by converter-LF-RH duplex smelting according to claim 9, characterized in that, The weight percentages of Si, Cr, and Cu satisfy the following relationship: 0.36 ≤ (Si + Cu) / Cr ≤ 0.7.

Images