RH nitrogen-blowing alloying process capable of accurately controlling nitrogen content of nitrogen-containing steel grade

Abstract

The invention discloses an RH nitrogen-blowing alloying process capable of accurately controlling the nitrogen content of a nitrogen-containing steel grade. The RH nitrogen-blowing alloying process capable of accurately controlling the nitrogen content of the nitrogen-containing steel grade comprises the following steps: desulfurized molten iron and scrap steel are smelted in a converter, oxygen is blown from the top, and nitrogen is blown from the bottom; LF refining and RH vacuum refining are sequentially carried out on molten steel, a mechanical pump vacuum system is adopted for RH, specifically, argon/nitrogen switching is carried out on RH circulation gas, the nitrogen flow is 90-150 Nm<3>/h, the nitrogen pressure is 1.0-1.8 Mpa, RH vacuum air-pumping is carried out, the pressure is reduced to 273 Pa or below from atmospheric pressure, and RH air-pumping lasts for 5-10 min; temperature measurement and sampling are carried out, and the chemical components and the nitrogen component content of the molten steel are analyzed; the component content of the molten steel is adjusted according to the sampling analysis result, the RH vacuum degree is adjusted to 4-15 kpa, nitrogen is rapidly increased in the molten steel, and the average nitrogen increasing amount is 3.0-3.50 ppm/min; and after the molten steel meets the technical requirements of the steel grade, the RH is finished, re-pressing is carried out, a steel ladle is opened for blowing argon from the bottom, and calcium treatment in a metal calcium feeding line is carried out. According to the invention, the nitrogen content fluctuation of the molten steel can be accurately controlled to be +/-5ppm, the technical requirements of the steel grade are met, the quality of the steel grade is ensured, and the production cost is reduced.

Description

Technical field [0001] The present invention relates to the field of steel metallurgy, and more particularly to a method of increasing the hit rate of RH refining blown nitrogen-free nitrogen components. Background technique [0002] Blowing nitrogen to molten steel is a low-cost nitrogen-containing steel production, and the application is widely used in steel smelting process. Steel mill has a method of producing nitrogen-containing steel species in a converter bottom blown nitrogen, a steel pucer. RH is a widely used molten steel vacuum refining device (mainly steam jet pump system), with deprophythmic, degassed, warming, removing inclusions, etc., for producing high quality clean steel. However, when RH blown nitrogen is alloyed, the nitrogen component control precision is between 20 and 40 ppm, and there is a problem with a large fluctuation of nitrogen, affecting the production cost of the company and the quality of steel. [0003] The existing RH blown nitrogen-free nitroge...

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Problems solved by technology

However, the method RH uses a steam jet pump vacuum system, and the steel type is limited to oriented electrical steel; at the same time, its production process is: molten iron pretreatment → 210 tons of converter smelting → RH refining → continuous casting, in which the RH refining process is performed twice Switch between argon and nitrogen, and the nitrogen pressure in the RH vacuum nitrogen increase stage is 1.1-1.6MPa, the circulation flow is 200-280Nm3 / h, and the vacuum degree of the RH furnace is 3-5KPa. The defect of the circulation gas flow will lead to vacuum Severe defect of "nodules" inside the groove

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