Method for controlling tapping nitrogen content of converter

Abstract

The invention is a method for controlling the nitrogen content of converter tapping. The requirements for molten iron are: P≤0.150%, T≥1250°C, sulfur content is lower than 0.015%, and the molten iron ratio is increased by 85-90%; 30- 40kg / t iron ore; End point control: C: 0.08-0.12%, P≤0.015%, S≤0.020%, T: 1650-1690℃; 1-2 minutes before tapping, blow argon at the bottom of the ladle in advance, and the whole process of tapping Argon blowing, at the same time, during the tapping process, the bottom blowing argon volume is turned down for soft blowing so as not to expose the molten steel surface; the tapping process adopts two-step deoxidation. The invention does not need to add new equipment or modify equipment, and reduces the nitrogen content after the converter is tapped to 25ppm without increasing the cost, thereby reducing the nitrogen content of the finished product and improving the quality of the steel.

Description

technical field [0001] The invention belongs to the technical field of steelmaking technology, and relates to a method for controlling the nitrogen content of converter tapping. Background technique [0002] The nitrogen content in the steel has a great influence on the properties of the steel, and its nitrides (Fe x The precipitation of N) will lead to aging and blue brittleness of the steel, resulting in an increase in the yield limit, strength limit and hardness of the steel, and a decrease in toughness, plasticity, deep drawing performance, HAZ performance, hot workability, electrical conductivity and welding performance. It is easy to cause the slab to crack and cause intergranular corrosion. In addition, the nitrogen in the steel is very easy to form angular inclusions with titanium, aluminum and other elements in the steel, which reduces the cleanliness of the steel and affects its drawing performance. If the dissolved nitrogen content in the steel exceeds a certain...

AI Technical Summary

Problems solved by technology

Patent 201110403469.6 improves the order of adding deoxidized alloys by controlling the oxygen content of tapping and the timing of adding strong deoxidizers, thereby reducing the nitrogen content of finished products; however, it is difficult to control the oxygen content of tapping. The degree of deoxidation of molten steel increases, and the amount of nitrogen added to molten steel increases. The main reason is that ferroalloy, as an alloy, will be involved in air to varying degrees during the process of adding molten steel; The reduction of oxygen content in the steel reduces the inhibitory effect of oxygen in the steel on nitrogen absorption; in addition, after aluminum enters the molten steel, it is very easy to react with the nitrogen in the steel to form AlN inclusions, resulting in nitrogen fixation and nitrogen increase in molten steel; when the deoxidized alloy When the addition amount is high, its influence on the nitrogen content of molten steel is difficult to control, and the nitrogen content in molten steel fluctuates greatly

[0005] Patent 201010195201.3 discloses a method for denitrification of molten steel during the tapping process of the converter. During the tapping process of the converter, carbonate, coke and metal aluminum are successively added to the ladle, and the kinetics and thermodynamics of the molten steel are used to denitrify the molten steel during tapping. Decompose or promote its reaction with oxygen in molten steel to generate CO2 or CO, and remove it by adsorbing N, but carbonate is prone to splashing and has an erosive effect on the ladle