Method for obtaining low-nitrogen steel by reducing nitrogen content in steel in electric furnace steelmaking process

Abstract

The invention relates to a method for obtaining low-nitrogen steel by reducing nitrogen content in steel in an electric furnace steelmaking process. The method comprises the following steps that in the smelting process of an electric arc furnace, a mode of mixed smelting of waste steel and molten iron is adopted, a rapid slagging technology is assisted, and silicon iron is added in the tapping process to carry out weak deoxidation on molten steel; in the LF refining procedure, a high-temperature-resistant material sealing sleeve is installed at an electrode opening, refining synthetic slag is added in the smelting process for slagging, and the appropriate bottom blowing argon flow is adjusted; in the VD vacuum treatment process, a high vacuum degree, treatment time prolonging and bottom blowing argon flow increasing strong stirring mode is adopted; and in the continuous casting process, protective pouring and immersion type sleeve sealing measures are adopted. According to the method, the nitrogen content in the steel is obviously reduced on the basis of molten steel nitrogen absorption and denitrification mechanisms and in combination with the operation characteristics of all the procedures, the method is easy to operate, nitrogen control of the whole process in the electric furnace steelmaking process is stable, and it can be effectively guaranteed that the nitrogen content in a finally obtained product is smaller than 30ppm.

Description

technical field [0001] The invention belongs to the technical field of electric furnace steelmaking, and in particular relates to a method for reducing the nitrogen content in steel to obtain low-nitrogen steel in the electric furnace steelmaking process. Background technique [0002] In most cases, the existence of nitrogen in steel greatly affects the performance of steel, which will reduce the toughness, welding performance and toughness of thermal stress zone of steel, and improve the brittleness of steel to a certain extent. At the same time, the existence of nitrogen element in the continuous casting process will also cause cracking of the continuous casting slab. Therefore, effective control of nitrogen content in steel has become one of the hot topics that more and more scholars in the industry pay attention to. At present, the main direction of controlling the nitrogen content in steel is to start from two aspects: the source of nitrogen in steel and the denitrific...

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Problems solved by technology

[0004] Nitrogen increase in molten steel is unavoidable in the production of electric furnace steelmaking process. However, with the increase of social demand for high-end steel, the requirements for nitrogen content in steel are becoming more and more stringent, and the nitrogen content of some steel types is even required to reach 30ppm. Below, for this reason, many experts and scholars in the industry have done a lot of research work on the denitrification of molten steel under the electric furnace process

[0005] The method disclosed in Chinese patent application CN111996334A adopts all-scrap electric arc furnace smelting, further optimizes the formation of foamy slag in the furnace, and reduces the degree of nitrogen absorption of molten steel. The nitrogen content of raw materials fluctuates greatly, and the denitrification task is heavy during the smelting process; in addition, the carbon content of the furnace charge is not high, and only a relatively severe carbon-oxygen reaction occurs in the later stage of blowing, and the denitrification effect is not ideal. There is still some instability when the nitrogen content meets the product requirements

The Chinese patent application CN107502702A adopts the whole scrap steel furnace charge for smelting, utilizes high-power power supply to melt scrap steel quickly, and sprays large flow of O after melting 2 and CO 2 Promote the denitrification of molten steel, but the carbon content of molten steel in the later stage of smelting is not enough to carry out severe carbon-oxygen reaction to achieve denitrification; in addition, it does not fully form foamy slag during the smelting process, resulting in poor submerged arc effect and molten steel contact with the atmosphere, so there is some degree of nitrogen uptake

The method disclosed in Chinese patent application CN108715912A controls the oxygen content of molten steel in a relatively high range before tapping, and the molten steel is in a slightly overoxidized state during tapping, which effectively reduces the nitrogen absorption of molten steel during tapping However, the addition of a large amount of slagging material in the subsequent LF refining process will lead to an increase in the nitrogen content of the molten steel, and the denitrification capacity of the process is still insufficient, and the phenomenon of nitrogen absorption in the molten steel during the smelting process has not been greatly improved.

Chinese patent application CN110951937A discloses a method for efficiently smelting low-nitrogen steel using an electric furnace, but it does not control the oxygen content in molten steel during the smelting process, resulting in high carbon content and low oxygen content at the end of smelting. Therefore, it is extremely easy to cause nitrogen absorption of molten steel during the tapping process.

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