Smelting method for reducing nitrogen increase of molten steel in converter process

Abstract

The invention relates to a smelting method for reducing nitrogen increase in molten steel in a converter process. The smelting method comprises the following steps: limiting the nitrogen content and size of a waste steel raw material, changing bottom argon blowing in the early stage of a converter into nitrogen-argon combined blowing, increasing the gas flow, adopting bottom pure argon blowing in the middle and later stages of smelting, and increasing the bottom blowing gas flow; the smelting final temperature is smaller than or equal to 1630 DEG C, an oxygen lance is switched into argon, and argon is blown into the converter for 10-30 s; in the tapping process, 1.0 Kg / t to 1.2 Kg / t of calcium carbide is added to the bottom of a steel ladle in advance before tapping, 0.5 Kg / t to 1.0 Kg / t of calcium carbide is thrown in a steel flow impact area in the tapping process, CO generated by calcium carbide deoxidation is used for forming an air curtain, molten steel is isolated from air, and nitrogen absorption of the molten steel is reduced; the content of [O] in the molten steel in the tapping process is controlled to be (200-400) * 10 <-4 >%; bottom argon blowing of the steel ladle is started 20 seconds before tapping, air in the steel ladle is emptied, argon is stopped immediately after tapping is finished from 20 seconds before tapping to the end of tapping, and the steel ladle is covered for heat preservation to prevent molten steel from being exposed to increase nitrogen; the method is simple and clear in technological process, high in operability and easy to control.

Description

technical field [0001] The invention relates to the technical field of iron and steel metallurgy and converter smelting, in particular to a smelting method for reducing the nitrogen increase of molten steel in the converter process. Background technique [0002] Nitrogen is a harmful element for most steel grades. High nitrogen content is a key factor in a series of problems such as purity, fluidity, surface quality and performance fluctuations of the slab. It is easy to cause cracking of the slab and cause intergranular corrosion. In addition, the precipitation of steel nitrides will lead to aging and blue brittleness, resulting in a decline in the toughness, plasticity, deep drawing, hot working and welding of steel. Since nitrogen will deteriorate the performance of steel, most steel grades have strict control requirements for smelting w[N]. -4 %, w[N]≤50×10 in low nitrogen steel -4 %, or even lower. The partial pressure of nitrogen in the general atmosphere is 0.79Kg / ...

AI Technical Summary

Problems solved by technology

[0002] Nitrogen is a harmful element for most steel types. High nitrogen content is the key factor for a series of problems caused by purity, fluidity, slab surface quality and performance fluctuations, which can easily cause slab cracking and intergranular corrosion. In addition, the precipitation of steel nitrides will lead to aging and blue embrittlement, resulting in the decline of toughness, plasticity, deep drawing, hot working and welding of steel.

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