A method for denitrification in vd furnace using CO2 steelmaking

Abstract

The invention relates to the technical field of the steelmaking industry, in particular to a method for steelmaking and denitrification of a VD furnace through CO2. The method for steelmaking and denitrification of the VD furnace through CO2 is suitable for the VD refinement of 30-350 t of steel ladles. According to the refinement process, bottom blowing of CO2 or CO2-Ar is performed through the steel ladles; different bottom blowing modes are adopted in all stages, the small-flow gas mixing bottom blowing is adopted in the liquid steel composition even-mixing stage, and liquid steel oxidationis prevented and the vacuumizing speed is increased; the high-flow bottom blowing of pure CO2 is adopted in the high vacuum decarburization stage, decarburization of CO2 is promoted, and then deep denitrification is achieved and dehydrogenation is enhanced; normal operation of a bottom blowing component is ensured by switching bottom blowing of Ar and high-pressure spraying and blowing in the bottom blowing repetition stage; and in the liquid steel purifying stage, bottom soft blowing of CO2-Ar mixed gas is performed, rapid flotation of nonmetal inclusions is promoted, and at the same time, CO2 gas is the main part of blowing, heat impact on a bottom blowing nozzle is reduced, the bottom blowing service life is prolonged, and finally low-cost smelting of low-nitrogen steel through the VDfurnace is achieved.

Description

technical field [0001] The invention relates to the technical field of steelmaking technology, in particular to a VD furnace utilizing CO 2 A method of denitrification in steelmaking. Background technique [0002] At present, VD refining is widely used. By blowing Ar gas at the bottom under vacuum conditions, it can basically meet the refining requirements of most steel types such as dehydrogenation, uniform molten steel composition and temperature, and promote the floating of non-metallic inclusions, but the nitrogen content of molten steel is high. The problem has always limited the improvement of the quality of many steel grades. Most iron and steel enterprises carry out deep deoxidation treatment of molten steel in the process before VD, so pure bottom blowing Ar cannot decarburize molten steel in VD process, and because CO bubbles have stronger denitrification ability than Ar bubbles, bottom blowing Ar also This limits the possibility of rapid and deep denitrification...

AI Technical Summary

Problems solved by technology

Although this method can effectively denitrify, Al will undergo deep deoxidation reaction in molten steel at the same time, which greatly increases the cost of smelting.

[0004] Chinese patent CN201010598281.7 discloses a method for producing low-carbon and ultra-low-carbon steel using the VD+LF+VD process. VD vacuum carbon-oxygen interleaving is used, followed by LF+VD refining. Although this process has achieved the first Decarburization in the VD furnace treatment process, but the treatment process is relatively complicated, and the final VD treatment process still has not achieved deep denitrification, and it increases the cost of smelting and slows down the rhythm of smelting

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