Continuous casting of molten steel for sheet metal

Abstract

Disclosed is a method of continuous casting of aluminum-killed steel, using a refractory martial containing 20 mass % or more of CaO.MgO-based clinker. 60% or more of MgO grains included in the grains of the CaO.MgO-based clinker have a diameter of 50 μm or less. The refractory martial is used at least at a portion to be in contact with molten steel. The present invention can reduce the diameter of MgO grains as inclusions in slabs to suppress the occurrence of flaws in a milled sheet metal.

Description

TECHNICAL FIELD[0001]The present invention relates to continuous casting of molten steel to be formed as a sheet metal, and more particularly to a refractory material for use in the continuous casting.BACKGROUND ART[0002]In late years, the need for strict quality control of steel products has become increasingly prominent. Under these circumstances, in the continuous casting of aluminum-deoxidized steel (hereinafter referred to as “aluminum-killed steel”) to be formed as high-quality steel, such as sheet metal, a good deal of effort has been made to prevent alumina from being attached onto a casting nozzle for pouring molten steel from a tundish into a mold.[0003]The alumina attached onto the casting nozzle will be combinedly accumulated, and formed as a large-size impurity. Then, the alumina will be mixed in molten steel flow, and incorporated into slabs as a large-size inclusion to cause defect in slabs or deterioration in quality thereof.[0004]As one of measures against this prob...

AI Technical Summary

Benefits of technology

[0007]It is therefore an object of the present invention to provide a refractory material for use in a continuous casting nozzle, which contains CaO.MgO-based clinker having CaO as a mineral phase having an anti-alumina-buildup effect, so as to allow the amount of a large-size inclusion in slabs during casting of aluminum-killed steel to be drastically reduced.

[0012]The Al2O3.CaO-based compound released from the surface of the refractory component is readily dispersed over the molten steel, and less apt to be formed as a large-size inclusion. Thus, an adverse affect on the quality of slabs can be minimized.

[0017]According to preparation methods, CaO.MgO-based clinker is classified into three types: synthetic dolomite clinker, natural dolomite clinker and electro-fused CaO.MgO-based clinker. The synthetic dolomite clinker is prepared by burning mixed particles of Ca (OH)2 and Mg (OH)2 at a high temperature. The natural dolomite clinker is prepared by burning dolomite as a natural product at a high temperature. The electro-fused CaO.MgO-based clinker is prepared by arc-melting a material containing CaO components and MgO components, and cooling / solidifying the arc-melted material. The diameter of MgO crystal grains in the synthetic CaO.MgO-based clinker can be changed by controlling the particle size of a starting material. Specifically, Mg (OH)2 particles in the starting material can be arranged to have a small particle size and enhanced dispersibility to reduce the diameter of MgO crystal grains in the clinker.

Problems solved by technology

Then, the alumina will be mixed in molten steel flow, and incorporated into slabs as a large-size inclusion to cause defect in slabs or deterioration in quality thereof.

However, if an excessive amount of argon gas is injected, resulting gas bubbles will be incorporated into slabs to cause the formation of pinholes or defect.

Thus, this method is not exactly a sufficient measure due to the restriction in the allowable injection amount of argon gas.

The inclusion causes occurrence of flaws in a rolling process of the slabs.

In particular, the inclusion has a serious impact on slabs to be formed as a thin sheet metal.

Images