JPH08208315A - Basic brick - Google Patents

Abstract

PURPOSE: To improve the structural spalling of a magnesian fired basic brick mainly used to line a refining vessel at the outside of a furnace due to the penetration of slag. CONSTITUTION: A fired brick contg. >=50wt.% MgO is prepd. and 0.2-10.0wt.% NiO is incorporated into the fired brick.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a magnesia-based baked basic brick lined in a refining vessel outside a furnace.

[0002]

2. Description of the Related Art The present invention will be described with reference to a magnesia-chromic brick (hereinafter referred to as magcro brick) used in a VOD pot whose main purpose is to decarburize stainless steel in an out-of-furnace refining furnace. VOD refining is a high temperature exceeding the maximum temperature of 1750 ° C. and is a long-term operation. In addition, it is generally used at a relatively low operating rate for replacement and repair of porous plugs and bricks. Therefore, magro brick, which is the most typical lining brick, has a large damage rate due to all damage mechanisms such as chemical erosion, thermal / structural spalling, and abrasion. From various post-use brick analyzes, it can be concluded that structural spalling, which causes cracks and exfoliation from the slag infiltration layer, is the main factor. And as an improvement measure against this structural spalling, it is important to suppress the penetration of slag, and the chromium composition is increased to raise the melting point of slag and increase the viscosity. Makes the brick dense and reduces the air permeability. However, the porosity tends to increase. However, there are drawbacks such that the thermal spalling property is significantly lowered, and at present, they are not sufficiently satisfied.

[0003]

Therefore, an object of the present invention is to improve structural spalling which is mainly caused by slag infiltration of magnesia-based calcined basic bricks lined in a refining vessel outside the furnace.

[0004]

[Means for Solving the Problems] Focusing on the effect of additives as a means for suppressing slag penetration, a comparison of various additives other than Cr ₂ O ₃ composition was made. As a result of various basic research, the effect of NiO composition was obtained. Therefore, further research was conducted on the addition of NiO composition. NiO forms a complete solid solution with MgO (see FIG. 1). Therefore, it is inferred that the strength is produced at high temperature and the matrix portion is densified. Moreover, the melting points of the main components CaO and SiO ₂ of the slag are relatively high. Various prototypes shown in Table 1 were prepared to investigate the proper additive amount. The porosity decreases and the strength increases along with the addition amount of NiO. Even in the slag penetration test, the penetration thickness became smaller. However, excessive addition causes a large decrease in thermal spalling with a decrease in porosity, so 10%
The following was judged to be an appropriate amount. The minimum amount is set to 0.2% or more in order to minimize the effect. NiO is MgO
Since it forms a solid solution with MgO, if it is a magnesia-based brick containing MgO as a main component, that is, containing 50% or more, it is considered that similar effects can be obtained with MgO-Al ₂ O ₃ -based, MgO-CaO-based, etc. To be

[0005]

EXAMPLE A binder was added and kneaded at the compounding ratio shown in Table 2, press-molded, and then fired in a tunnel kiln at a temperature of 1800 ° C. or higher. The physical properties of the fired product are shown in Table 2 together.

[0006]

[Table 1]

[0007]

[Table 2]

[0008]

[Effects of the Invention] The magrophilic direct bond brick according to the present invention shown in the examples was placed on the slag line of a 30 t VOD pot and tested in a real machine. The result is shown in Figure 2.
Shown in Conventional 12ch (8.3mm / ch) for durability
Was extended to 16 ch (5.5 mm / ch) by the product of the present invention, and a significant improvement effect was recognized. The post-use analysis results also showed that the amount of slag infiltration was significantly reduced, which could suppress the occurrence of structural spalling and greatly contributed to the extension of service life.

[Brief description of drawings]

FIG. 1 is a chart showing the relationship between the composition of MgO and NiO forming a complete solid solution.

FIG. 2A is an explanatory diagram after use of a conventional product showing a result of an actual device test, and FIG. 2B is an explanatory diagram after use of an invention product showing a result of an actual device test.

Claims (1)

[Claims] 0.2 to 10.0 weight percent Ni in a fired brick containing more than 50 weight percent MgO composition.
A baked basic brick characterized by containing O.