Method for controlling tapping nitrogen content of converter

Abstract

The invention relates to a method for controlling the tapping nitrogen content of a converter. Requirements for molten iron are as follows: P is less than or equal to 0.150%, T is more than or equal to 1250 DEG C, the sulphur content is lower than 0.015%, and the hot metal ratio is increased by 85-90%; 30-40kg / t iron ore is added in the blowing period of the converter; terminal control comprises is as follows: C is 0.08-0.12%, P is less than or equal to 0.015%, S is less than or equal to 0.020% and T is 1650-1690 DEG C; steel ladle bottom argon blowing is carried out in advance, argon blowing is carried out in the whole tapping course, the bottom argon blowing amount is reduced and soft blowing is carried out under the condition that a molten steel liquid level is not exposed in a tapping process; and a two-step deoxygenation method is adopted in the tapping process. According to the method provided by the invention, no new equipment is required to be added and the equipment is not required to be modified, and the nitrogen content is 25ppm after tapping of the converter is reduced while the cost is not increased, so that the nitrogen content of the finished product is reduced and the steel quality is improved.

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