Method for reducing nitrogen increment of molten steel in refining process

Abstract

The invention provides a method for reducing nitrogen increment of molten steel in a refining process. The scheme is mainly realized by the following technical measures: (1) after molten steel reaches the refining step, lifting the furnace cover of a finery and starting a buggy ladle to underface of the furnace cover of the finery; (2) reducing the furnace cover of the finery to a lower limit position; (3) meanwhile, inserting argon blowing conduits the original accidental argon gun hole, the original wire feeding hole and a new argon blowing hole, wherein the distance from the argon blowing conduits to the molten steel level is 200-1000mm; and (4) blowing argon to the refinery along the argon blowing conduits, wherein the pressure range of argon is 0.5-1.0Mpa. An argon protective layer is formed on the molten steel surface to increase the reducing atmosphere in the furnace cover, so that the probability of contact of molten steel and air is reduced, and nitrogen increment caused by high temperature ionized air during heating is avoided, therefore, secondary oxidation of the molten steel during stirring is greatly reduced, and the degree of purity of the molten steel is improved.

Description

technical field [0001] The invention belongs to the field of steelmaking, and in particular relates to a method for reducing the amount of nitrogen added to molten steel in the refining process. Background technique [0002] Nitrogen and oxygen elements in steel are harmful elements to most steels. High nitrogen content in steel will easily lead to aging of steel, aggravate the cold and brittleness of steel, and reduce the high temperature toughness, plasticity and welding performance of steel; Various non-metallic inclusions are produced, which affect the performance of steel and reduce the fatigue life of steel. Therefore, for most steel types, oxygen and nitrogen in steel are required to be as low as possible. As the main equipment for refining molten steel outside the furnace, the refining furnace uses high-power electrodes to heat up the temperature during the production process, and at the same time uses large argon gas to stir for desulfurization, uniform temperature...

AI Technical Summary

Problems solved by technology

For the steel grades that require stricter nitrogen content in smelting, the main measures taken by major steel mills in the refining process are submerged arc with large amount of slag and reducing the flow rate of bottom-blown argon as much as possible to reduce the nitrogen increase in molten steel. The effect of this measure is unstable, especially when the sulfur content of the molten steel is high, it is inevitable to stir the molten steel with argon gas to pollute the molten steel, and the nitrogen increase in the molten steel generally reaches 5-10 ppm during the refining process.