JPH0262510B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to improvements in magnesia-based refractory materials used in basic refractories. (Prior art) Magnesia clinker is conventionally known as a typical refractory material for basic refractories.
This magnesia clinker has the advantage of being highly refractory and having low solubility in basic slag, but on the other hand, slag components etc. easily penetrate into the structure, causing deterioration of the structure and having a high coefficient of thermal expansion. There are disadvantages. For this reason, shaped and unshaped refractories formed and constructed using this material absorb slag during use, causing phenomena such as the formation of altered layers and structural deterioration, resulting in heat-resistant spalling and structural damage. Currently, the magnesia material's original characteristics cannot be fully utilized. The microstructure of magnesia clinker produced using conventional manufacturing methods consists of periclase microcrystals and a silicate matrix surrounding them, so periclase and microcrystals have a high melting point of 2800°C and exhibit high resistance to basic slag. However, the silicate matrix portion has a low melting point and is easily dissolved in slag. Therefore, when it comes into contact with slag at high temperatures, it easily and infiltrates into this matrix area, producing a large amount of low-melt liquid, with periclase microcrystals floating in it, loosening the structure, and allowing the slag to penetrate. This results in the formation of a thick altered layer and a fragile layer between the altered layer and the unaltered layer. (Problems to be solved by the invention) As a method to improve the above-mentioned drawbacks, extremely pure magnesite and magnesium hydroxide are used as raw materials, high-pressure granulation, calcining and high-pressure granulation, and high-temperature calcination are performed. By doing this, sintered high purity magnesia clinker is produced. However, even with this increase in purity and density, the quality of the clinker remains basically the same, so the mechanism by which the slag penetrates into tissues during use remains the same, and although some improvement can be seen. However, the current situation is that sufficient effects have not yet been achieved. Therefore, in view of the current situation, this invention maintains the high heat resistance and low solubility in basic slag that are the characteristics of conventional magnesia clinker, while improving its shortcoming of easy slag penetration. The technical challenge is to provide magnesia-based refractory materials of excellent quality. (Means for solving the problem) This invention was made to solve the above-mentioned problems and technical problems, and the method is to coat magnesia particles with a soluble material mainly composed of calcia and/or refractory fine powder. A magnesia-based refractory material with a structure in which a thin sintered layer of coating material is partially formed on the surface layer of magnesia particles and a layer with calcium oxide intervening at magnesia grain boundaries is formed by coating and/or impregnating into the structure and firing. be. This invention will be explained in more detail. In order to interpose calcia on the particle surface and grain boundaries of magnesia clinker, the surface layer of the particles is coated with a refractory fine powder of one or more of a soluble synthetic calcia agent and/or a finely powdered calcia material, and fired at a high temperature. By forming a strong thin sintered layer of some coating materials and a structure containing calcia at the magnesia grain boundaries, we can easily create a new and excellent magnesia-based refractory material with high bonding properties between periclase microcrystals. It's about getting. Next, this invention will be described with reference to embodiments. Example 1

[Table] 〓
surface coating
A rotary kiln product of the present invention is obtained.
(Fired at 1900℃)
A novel magnesia-based clinker was obtained by the method of each of the above examples. This clinker is characterized by a structure in which a layer of calcium oxide is formed at grain boundaries, mainly on the MgO surface layer, and a calcium oxide layer is mainly formed on the surface. (Effects of the Invention) By interposing calcium oxide between the partial coating material thin film sintered layer formed in this way and the magnesia grain boundaries, it was possible to improve the slag penetration resistance and the heat spalling resistance. The quality evaluation test results are as follows. Quality characteristic values

【table】

[Table] Slag erosion resistance and penetration test Slag with a basicity of 3 from a steelmaking converter is melted in a graphite crucible and immersed in the molten slag.

[Table] (Note) - in the amount of erosion loss is due to osmotic swelling.
As shown in the above results, calcium oxide is dissolved in the thin film sintered layer and magnesia grain boundaries of the covering material of the clinker structure according to the invention, which has a great effect on suppressing the penetration of molten slag that comes into contact with it.
It was possible to produce a refractory material that can improve the properties of magnesia clinker without impairing it.

Claims (1)

[Claims] 1. A magnesia-based refractory material having a structure in which a thin sintered coating layer is formed on the surface layer of magnesia particles and a layer in which calcium oxide is present at the magnesia grain boundaries.