Method for deoxidizing molten steel

Abstract

The invention discloses a method for deoxidizing molten steel, which comprises the following steps: after decarbonization and degassing treatments in an RH device, adopting a three-step method to perform deoxidizing treatment on the molten steel; adding low-carbon ferrosilicon first to perform deoxidization to ensure that the silicon content is not higher than the component requirement of the smelted steel type; then adding aluminum to perform deoxidization to ensure that the oxygen content in the molten steel is not more than 0.0020 percent; and finally adding ferrotitanium to perform final deoxidization. The novel method adopted to deoxidize an ultra-low carbon automobile plate steel treated in the RH device can reduce the generation of AL2O3 inclusion which mainly comprises TiO2-coatedAL2O3 tiny inclusions of which the size is less than 10 microns, thereby improving the surface quality of the automobile plate steel and reducing the head blank inclusion rejection rate. Besides, the method improves the performances of yield strength, tensile strength, after-fracture extensibility and the like.

Description

technical field [0001] The invention belongs to the technical field of ferrous metallurgy and relates to an out-of-furnace refining production process, in particular to a deoxidation process for treating ultra-low carbon steel in a vacuum (RH) furnace. Background technique [0002] In the 1990s, with the development of a series of deep-drawing and ultra-deep-drawing steels such as ultra-low-carbon automotive sheet steel, ultra-low-carbon cold-rolled silicon steel, and household appliance panel steel, the surface quality, yield strength, and There are higher requirements for tensile strength and elongation, so how to control the oxide content in molten steel is the key to ensure the quality of cold-rolled coil products. [0003] After the ultra-low carbon automotive sheet steel converter boiling tapping, after the necessary decarburization and degassing treatment in the RH device, the aluminum wire segment is used as a deoxidizer to deoxidize the molten steel to calm the molt...

AI Technical Summary

Problems solved by technology

The disadvantage of this process is that the Al2O3 inclusions generated by aluminum deoxidation are not easy to remove during the vacuum cycle, resulting in some residual Al2O3 inclusions in the steel, and finally forming inclusion defects on the surface of the cold-rolled sheet, resulting in a high scrap rate of cold-rolled inclusions. The scrap rate is nearly 0.7%

In order to control the amount of Al2O3 produced, the following two measures have been tried: one is to reduce the free oxygen content of the RH unit after decarburization. Generally, a good decarburization effect can be guaranteed only when the free oxygen content after decarburization is above 0.02%, so the added If the deoxidized aluminum is above 60kg, more Al2O3 is produced, so the implementation of this measure is limited; the second is to increase the net cycle time after the final deoxidation of aluminum, but the adverse effect is to increase the processing cycle of the RH device and limit the continuous casting The pulling speed of the machine has a great influence on the production capacity, and the extension of the cycle time is not conducive to the floating of inclusions, so the implementation of this measure is also subject to certain restrictions

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