Refractory for steel casting, plate for sliding nozzle device, and method for producing refractory for steel casting

Abstract

In order to suppress destruction of a refractory which contains a metal aluminum, the refractory is a refractory for steel casting which includes a refractory material containing a free carbon in the range of 1 to 10% by mass, both inclusive, a metal aluminum in the range of 1 to 15% by mass, both inclusive, and a metal oxide in a balance. The refractory for steel casting satisfies the following Equation 1: 0.31×Al≦(P−4) / D (Equation 1), with a metal aluminum content in the refractory designated by Al % by mass, an apparent porosity thereof designated by P %, and a bulk density thereof designated by D.

Description

TECHNICAL FIELD[0001]The present invention relates to a refractory for steel casting, a plate for a sliding nozzle device using the refractory, and a method for producing the refractory.BACKGROUND ART[0002]A plate for a sliding nozzle device (hereinafter, this is referred to as “sliding nozzle plate”, and a refractory for this plate is referred to as “plate refractory”) is being widely employed in a steel industry as an essential refractory product for a flow control member of a melted metal in the present time when the secondary processing and continuous casting in a ladle have been generalized. This sliding nozzle plate is a component which plays a role to control a flow of a melted metal including a melted steel, so that the sliding nozzle plate is required to have a very high performance, and also in a material quality, the sliding nozzle plate is required to have well-balanced superior properties which can cope with various harsh conditions. That is, the sliding nozzle plate re...

AI Technical Summary

Benefits of technology

The present invention relates to a refractory material for use in steel casting that can withstand thermal shock, corrosion, and erosion, while also being able to control its physical properties for optimal performance under different operation conditions. By controlling the metal aluminum content and the voids in the refractory organization, the refractory is protected from destruction due to the expansion of metal aluminum upon heating. Additionally, the refractory contains a large amount of metal aluminum while still maintaining excellent thermal shock resistance without using large amounts of fire resistant aggregate or carbonaceous raw material. This refractory material can be used for various steel casting members such as upper nozzle, lower nozzle, tuyere, and sliding nozzle plate.

Problems solved by technology

With regard to the method for improving the thermal shock resistance, a large amount of raw material having a low thermal expansion coefficient, which includes a siliceous material, a silicon carbide material, and a carbonaceous material, is generally used; however, because the raw material including the siliceous material, the silicon carbide material, and the carbonaceous material readily reacts with a melted steel or forms a compound having a low melting point, there has been a problem of deterioration of the corrosion and erosion resistances.

For example, in Patent Document 1, a proposal is made with regard to a baked plate refractory which is produced by adding to a fire resistant aggregate an expanded graphite and a metal with the maximum amounts of 10% by mass and 8% by mass, respectively, followed by molding the resulting mixture and then by a heat treatment at a temperature of not lower than 1000° C. In the baked plate refractory thus produced, however, the metal added as an antioxidant does not have an effect to enhance the thermal shock resistance, so that the thermal shock resistance thereof is improved by adding the expanded graphite, but, the expanded graphite causes a deterioration of the oxidation resistance and a decrease in the strength, as well as an increase in roughness of a sliding part, thereby resulting in a decrease in the tolerance.

On the other hand, the organization is excessively densified by a heat which is received upon casting, resulting in a very high modulus; and thus there is a drawback of a low thermal shock resistance.

Accordingly, there have been problems including an edge defect and an easy generation of a crack by a thermal shock.

However, this does not take into an account a volume increase due to the reactions that take place upon a heat receiving of a metal aluminum; an excessive densification causes a large increase in the modulus, and thus, the thermal shock resistance thereof is insufficient.