A method for adjusting slag of soft magnetic ferrite stainless steel

Abstract

The present invention relates to the field of metallurgy technology, a method for adjusting slag of soft magnetic ferrite stainless steel, comprising the following steps: step one: adjusting slag by transferring the LF refining furnace under the atmosphere to the vacuum of the VOD refining furnace; step two: after the reduction of the VOD refining furnace is completed, at a vacuum degree of ≤2mbar, adding quartz sand, the SiO2 content is 95-98%, and the slag basicity CaO / SiO2 is adjusted from greater than 2 to less than 1.5; step three: stirring 6-8min at the bottom of the ladle with a gas supply intensity of 13-18L / min.t, closing the ladle bottom blowing and then breaking the air. The slag adjustment of the present invention is to transfer the LF refining furnace under the atmosphere to the vacuum of the VOD refining furnace, and after the reduction of the VOD refining furnace is completed, the slag is adjusted at a vacuum degree of ≤2mbar. During the slag adjustment process, the temperature drop of the molten steel is reduced from 3℃ / min to 1℃ / min, the carbon increase during temperature increase is reduced from 0.005% to 0.002%, the T[O] content is reduced from more than 40ppm to less than 30ppm, the nitrogen increase is reduced from more than 30ppm to 0, and the coarseness and fineness series of non-metallic inclusions B, C, D and DS are all no more than level 1.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a method for adjusting slag of soft magnetic ferrite stainless steel. Background Art

[0002] Soft magnetic ferrite stainless steel is used in a variety of control systems with harsh use environments. In addition to good magnetic properties and corrosion resistance, these applications require that the steel be easy to process in order to meet mass production and reduce processing costs. Therefore, by adding sulfur, a more economical easy-to-cut element, to the steel, the sulfur content in the soft magnetic ferrite stainless steel reaches 0.015-0.035%, the steel's easy-to-cut properties are enhanced, the tool life, the dimensional accuracy of the workpiece, and the surface finish are improved.

[0003] Slag basicity (CaO / SiO2) is the most important factor affecting sulfur recovery. In order to improve the sulfur recovery, the slag basicity needs to be adjusted to below 1.5 before adding sulfur content in steel. The current slag adjustment and sulfur adding method is: add slag to the LF refining furnace, and stir it vigorously through the ladle bottom under the atmosphere. The stirring time is more than 8 minutes. In this way, the molten steel is severely exposed, which not only greatly reduces the temperature of the molten steel, but also causes secondary oxidation, resulting in an increase in the carbon, oxygen and nitrogen content in the steel.

[0004] In order to solve the problems of the existing slag adjustment and sulfur addition methods for soft magnetic ferrite stainless steel, the present invention provides a slag adjustment method for soft magnetic ferrite stainless steel. The slag adjustment is carried out by transferring the LF refining furnace under the atmosphere to the VOD refining furnace under the vacuum. During the slag adjustment process, the temperature drop of the molten steel is reduced from 3°C / min to 1°C / min, the carbon increase by heating is reduced from 0.005% to 0.002%, the T[O] content is reduced from more than 40ppm to less than 30ppm, the nitrogen increase is reduced from more than 30ppm to 0, and the coarseness and fineness series of non-metallic inclusions B, C, D and DS are all not more than level 1. Summary of the invention

[0005] The purpose of the present invention is to provide a method for slag adjustment of soft ferrite stainless steel in view of the above problems.

[0006] The object of the present invention is achieved in this way: a method for slag adjustment of soft magnetic ferrite stainless steel, comprising the following steps: step one: slag adjustment is transferred from the LF refining furnace under the atmosphere to the VOD refining furnace under vacuum; step two: after the reduction in the VOD refining furnace is completed, at a vacuum degree of ≤2mbar, quartz sand is added, the SiO2 content is 95-98%, and the slag basicity CaO / SiO2 is adjusted from greater than 2 to less than 1.5; step three: strong stirring for 6-8min at the gas supply intensity of 13-18L / min.t at the bottom of the ladle, and the ladle bottom blowing is closed and then broken.

[0007] The mass percentage of the chemical composition of soft magnetic ferrite stainless steel is: C≤0.025, Si: 1.30-2.10, Mn: 0.20-0.45, P≤0.030, S: 0.015-0.035, Cr: 13.50-15.50, Ni≤0.20, Mo: 0.30-0.50 N≤0.020, and the rest are Fe and unavoidable impurities.

[0008] The beneficial effects of the present invention are as follows: the slag adjustment of the present invention is to transfer the LF refining furnace under the atmosphere to the vacuum of the VOD refining furnace, and the slag adjustment is performed at a vacuum degree of ≤2mbar after the reduction in the VOD refining furnace is completed. During the slag adjustment process, the temperature drop of the molten steel is reduced from 3°C / min to 1°C / min, the carbon increase by temperature is reduced from 0.005% to 0.002%, the T[O] content is reduced from more than 40ppm to less than 30ppm, the nitrogen increase is reduced from more than 30ppm to 0, and the coarse and fine series of non-metallic inclusions B, C, D and DS are all less than level 1. DETAILED DESCRIPTION

[0009] Slag adjustment is carried out by transferring the LF refining furnace under atmosphere to the VOD refining furnace under vacuum. After the reduction in the VOD refining furnace is completed, quartz sand (SiO2 content 95-98%) is added at a vacuum degree of ≤2mbar, and the slag basicity (CaO / SiO2) is adjusted from greater than 2 to less than 1.5. The gas supply intensity at the bottom of the ladle is greater than 12L / min.t and strong stirring is carried out for 6-8min. The bottom blowing of the ladle is closed and the air is broken after the molten steel surface is calm. Specific scheme: The mass percentage of the chemical composition of the soft magnetic ferrite stainless steel is: C: ≤0.025, Si: 1.30-2.10, Mn: 0.20-0.45, P: ≤0.030, S: 0.015-0.035, Cr: 13.50-15.50, Ni: ≤0.20, Mo: 0.30-0.50, N: ≤0.020, and the rest is Fe and unavoidable impurities.

[0010] After the reduction in the VOD refining furnace is completed and the vacuum degree is ≤2mbar, quartz sand (SiO2 content is 95-98%) is added, and the slag basicity (CaO / SiO2) is adjusted from greater than 2 to less than 1.5. The gas supply intensity at the bottom of the ladle is 13-18L / min.t and strong stirring is carried out for 6-8min. After the bottom blowing of the ladle is closed, the air is broken.

[0011] The specific implementation of a method for slag adjustment of soft ferrite stainless steel is described in detail below in conjunction with the embodiments, but the specific implementation of the present invention is not limited to the following embodiments.

[0012] Embodiment 1

[0013] This embodiment is carried out on a 90-ton VOD and LF refining furnace, and the mass percentage of the chemical composition of the soft magnetic ferrite stainless steel is: C: ≤0.025, Si: 1.30-2.10, Mn: 0.20-0.45, P: ≤0.030, S: 0.015-0.035, Cr: 13.50-15.50, Ni: ≤0.20, Mo: 0.30-0.50, N: ≤0.020, and the rest is Fe and unavoidable impurities.

[0014] After the reduction in the VOD refining furnace is completed, quartz sand (SiO2 content is 95%) is added under a vacuum degree of 1 mbar, the slag basicity (CaO / SiO2) is adjusted from 2.3 to 1.2, and the gas supply intensity at the bottom of the ladle is 18L / min.t and strong stirring is carried out for 6 minutes. After the bottom blowing of the ladle is closed, the air is broken.

[0015] The chemical composition of the finished product in mass percentage: C: 0.01, Si: 1.90, Mn: 0.30, P: 0.021, S: 0.026, Cr: 15.00, Mo: 0.45, Ni: 0.10, N: 0.011, and the rest are Fe and unavoidable impurities.

[0016] According to the present invention, slag adjustment is performed by transferring the LF refining furnace under the atmosphere to the VOD refining furnace under the vacuum. During the slag adjustment process, the temperature drop of the molten steel is reduced from 3°C / min to 1°C / min, the carbon increase by temperature is reduced from 0.005% to 0.002%, the T[O] content is reduced from 42ppm to 28ppm, the nitrogen increase is reduced from 36ppm to 0, the coarseness and fineness series of non-metallic inclusions B and C are 0, and the coarseness and fineness series of D and DS are 0.5.

[0017] Embodiment 2

[0018] This embodiment is carried out on a 180-ton VOD and LF refining furnace. The mass percentage of the chemical composition of the soft magnetic ferrite stainless steel is: C: ≤0.025, Si: 1.30-2.10, Mn: 0.20-0.45, P: ≤0.030, S: 0.015-0.035, Cr: 13.50-15.50, Ni: ≤0.20, Mo: 0.30-0.50, N: ≤0.020, and the rest is Fe and unavoidable impurities.

[0019] After the reduction in the VOD refining furnace is completed, quartz sand (SiO2 content is 98%) is added under a vacuum degree of 1 mbar, the slag basicity (CaO / SiO2) is adjusted from 2.2 to 1.3, and the gas supply intensity at the bottom of the ladle is 13L / min.t and strong stirring is carried out for 8 minutes. After the bottom blowing of the ladle is closed, the air is broken.

[0020] The chemical composition of the finished product in percentage by mass: C: 0.011, Si: 1.92, Mn: 0.31, P: 0.020, S: 0.027, Cr: 15.01, Mo: 0.46, Ni: 0.09, N: 0.010, and the rest are Fe and unavoidable impurities.

[0021] The slag adjustment of the present invention is carried out by transferring the LF refining furnace under the atmosphere to the VOD refining furnace under the vacuum. During the slag adjustment process, the temperature drop of the molten steel is reduced from 3°C / min to 1°C / min, the carbon increase by temperature is reduced from 0.005% to 0.002%, the T[O] content is reduced from 43ppm to 26ppm, the nitrogen increase is reduced from 35ppm to 0, the coarseness and fineness series of non-metallic inclusions B and C are 0 level, and the coarseness and fineness series of D and DS are 0.5 level.

[0022] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. A method for slag adjustment of soft magnetic ferrite stainless steel, characterized in that: Includes the following Steps: Step 1: Slag conditioning is carried out by transferring the LF refining furnace under atmosphere to the VOD refining furnace under vacuum; Step 2: After the reduction in the VOD refining furnace is completed, quartz sand with a SiO2 content of 95-98% is added at a vacuum degree of ≤2mbar, and the slag basicity CaO / SiO2 is adjusted from greater than 2 to less than 1.5; Step 3: Stir vigorously for 6-8 minutes at the ladle bottom with a gas supply intensity of 13-18L / min.t, then close the ladle bottom blowing and break the air; The mass percentage of the chemical composition of soft magnetic ferrite stainless steel is: C≤0.025, Si: 1.30-2.10, Mn: 0.20-0.45, P≤0.030, S: 0.015-0.035, Cr: 13.50-15.50, Ni≤0.20, Mo: 0.30-0.50, N≤0.020, and the rest are Fe and unavoidable impurities.