Preparation method of Ti-containing low-nitrogen stainless steel

Abstract

The invention provides a preparation method of Ti-containing low-nitrogen stainless steel. The preparation method comprises the following steps: subjecting raw materials to mixing, electric furnace coarse smelting, AOD (argon oxygen decarburization) furnace refining, tapping treatment, ladle treatment and continuous casting, thus obtaining Ti-containing low-nitrogen stainless steel, wherein the step of tapping treatment at least comprises the sub-steps of blowing argon into a ladle after AOD furnace refining is completed, tapping molten steel and steel slag from an AOD furnace to the ladle 5-10 minutes later, and continuously blowing argon into the ladle until tapping is completed. The nitrogen uptake of the molten steel after AOD furnace tapping can be effectively reduced by adopting the preparation method, thus reducing precipitation of inclusions such as TiN and the like so as to improve the continuous casting level and improve the surface quality of the stainless steel.

Description

technical field [0001] The invention relates to a method for preparing Ti-containing low-nitrogen stainless steel, and belongs to the technical field of stainless steel smelting in the field of metallurgy. Background technique [0002] Adding Ti to stainless steel grades can effectively prevent intergranular corrosion. Typical stainless steel grades are 321 and 409L stainless steel, which contain more than 0.1% Ti. Under current production conditions, Ti content control can be adjusted by inputting Ti alloy. [0003] The preparation of 321 and 409L Ti-containing low-nitrogen stainless steel mainly adopts the dual process of electric furnace + argon oxygen furnace (EAF+AOD). After the molten steel is denitrified, the nitrogen content in the molten steel is much lower than the solubility of nitrogen. In direct contact with air, the nitrogen content increases after absorbing nitrogen. The composition requirement of 321 stainless steel is Ti / (C+N)>5. Therefore, when the N c...

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Problems solved by technology

[0003] The preparation of 321 and 409L Ti-containing low-nitrogen stainless steel mainly adopts the dual process of electric furnace + argon oxygen furnace (EAF+AOD). After the molten steel is denitrified, the nitrogen content in the molten steel is much lower than the solubility of nitrogen. In direct contact with air, the nitrogen content increases after absorbing nitrogen

The composition requirement of 321 stainless steel is Ti / (C+N)>5. Therefore, when the N content in molten steel is high, the proportion of Ti content should be increased accordingly, resulting in high precipitation temperature of TiN, and the precipitation of inclusions such as TiN during casting, which affects The quality of stainless steel

Using the existing AOD smelting method, the nitrogen content of AOD tapping is about 70ppm. After tapping according to the AOD steel slag mixing method, the steel slag is completely removed during ladle processing, and the molten steel is directly exposed to the air for a period of time, resulting in a large amount of nitrogen absorption in the molten steel. And secondary oxidation, so that the nitrogen content in molten steel reaches 130-140ppm

According to the judgment of post-engineering quality, if the nitrogen content in molten steel is > 125ppm, the casting process is likely to contain TiN, TiO 2 Such inclusions are enriched on the surface of the slab, and it is easy to cause surface defects of the plate during steel rolling, such as steel-making scars and cracks.

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