Method for improving nitrogen yield of ferrosilicon nitride

Abstract

The invention provides a method for improving the nitrogen yield of ferrosilicon nitride. Based on the steelmaking processes of molten iron pretreatment, converter blowing, RH vacuum treatment and continuous casting, a ferrosilicon nitride core-spun yarn is fed before converter tapping is finished or before refining, and the molten iron is stirred by using nitrogen or argon at the same time; the molten iron condition when the ferrosilicon nitride core-spun yarn is fed is that the oxygen activity is less than 50ppm; and the ferrosilicon nitride core-spun yarn consists of a wrapping and core powder; the core powder is prepared from the ferrosilicon nitride and has the granularity of less than or equal to 0.5mm, particles with the granularity of more than 0.5mm account for no more than 10 percent of all particles, and the diameter of the core-spun yarn is 9 to 16mm. Through the method, the nitrogen yield of the ferrosilicon nitride is improved to over 75 percent from below 30 percent, the fluctuation of the yield is small, and the repeatability is high; and the nitrogen content of the molten iron can be accurately controlled in the subsequent refining process.

Description

[0001] Field [0002] The invention belongs to the field of silicon steel smelting technology. Provided is a method for improving the yield of nitrogen in ferrosilicon nitride. Background technique [0003] The nitrogen-increasing agents used in smelting grain-oriented silicon steel mainly include ferrosilicon nitride, silicon-manganese nitride, etc. Silicon-manganese nitride has a high manganese content, and some grades of grain-oriented steel cannot use silicon-manganese nitride to increase nitrogen, while silicon nitride Iron is widely used because it is not limited by steel types. The traditional way of adding is to add bulk ferrosilicon nitride into the ladle along with the steel flow during the tapping process, which is characterized by convenient and simple operation. However, this method results in low nitrogen absorption rate and instability in ferrosilicon nitride due to the following reasons. [0004] 1. Ferrosilicon nitride has a high melting point and can be us...

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Problems solved by technology

[0006] The above two factors lead to low and unstable yield of nitrogen element in ferrosilicon nitride, and the pressure of nitrogen addition in refining is high. Due to the unstable nitrogen content of molten steel at the refining station, the refining process has large variables, resulting in the refining cycle cannot be accurately estimated, and it is difficult to achieve Standardized operation

Secondly, changes in the refining cycle will affect the precise control of composition (such as Als) and temperature, and affect the refining rate of grain-oriented silicon steel