JPH02120272A - Refractory material of mgo-cao matter containing graphite - Google Patents

Abstract

PURPOSE:To improve slaking resistance and corrosion resistance, etc., by containing MgO-CaO matter clinker having thin layer of MgO on the surface of the particles and graphite in a refractory material containing CaO and MgO as principal components. CONSTITUTION:A MgO-CaO matter clinker containing CaO and MgO in an amount of >=98wt.% in total and 5-70wt.% CaO component within said total and having MgO layer of 10-500mum thickness on the surface of each particle is mixed with graphite to prepare a raw material. An organic binder is added to the raw material, blended, molded and heat-treated to produce graphite- containing MgO-CaO matter refractory material. Besides, MgO-CaO matter clinker having MgO thin layer on the surface of particles is obtained by making primary clinker using Ca(OH)2 and Mg(OH)2, etc., as raw materials, crushing, charging into Mg(OH)2 dispersed in non-aqueous solvent, drying, burning and sieving.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a graphite-containing MgO--CaO refractory, and particularly to a refractory using an MgO--CaO raw material with high digestion resistance.

[Conventional technology]

In recent years, magnesia carbon bricks have been used in various molten metal containers and smelting furnaces as refractory linings that can reduce wear due to slag erosion and spalling and provide high durability.

However, with the remarkable progress and development of iron and steel manufacturing technology, the operating temperatures of molten metal containers and smelting furnaces have become higher in response to special treatments (degassing, alloy injection), and have recently frequently exceeded 1,700°C. It's here. For this reason, existing magnesia carbon bricks are no longer able to provide sufficient durability. That is, magnesia and carbon cause a reaction of MgO+C-Mg+CO at high temperatures, but as a result, magnesia and carbon are simultaneously consumed, the structure deteriorates, and wear increases.

On the other hand, as a means to suppress the increase in wear due to the Mg0-C reaction under high temperature operation,
8. As seen in JP-A No. 61-141663, etc., Ca
It is already known to use O in combination by adding it to MgO raw materials. Here, CaO is CaO+3C-*
Although a reaction of CaC and +CO occurs, CaC maintains its skeleton as a refractory and suppresses tissue deterioration. Also, Mg
2CaO・S ro
It is believed that the formation of high melting point compounds such as z, 3CaO-3ioz reduces wear and tear.

[Problem to be solved by the invention]

However, while CaO has excellent thermal and chemical properties at high temperatures, the CaO content O-Ca (O
H) It is known to have the disadvantage of causing a digestion phenomenon (pulverization and disintegration) due to the z reaction.

For this reason, if the CaO-containing raw material comes into contact with I(to) during the manufacturing process or use of the bricks, the bricks will crack or expand and become powder, not only failing to achieve the intended purpose. On the contrary, there are even cases where the rate of wear and tear is significantly increased.

In the manufacturing process of bricks containing these CaO-containing raw materials, careful attention is paid not only to direct contact with water but also to water vapor in the atmosphere and moisture generated by secondary reactions with binders and other substances. , it was extremely difficult to completely prevent digestion.

Generally, CaO-containing raw materials are used as a single CaO or a composite system with MgO, but all the raw materials to date have been adjusted so that CaO and MgO are homogeneously distributed, as shown in FIG. Therefore, C on the surface and inside of the raw material particles
There is no difference in the distribution state of aO and MgO, and CaO is always exposed on the grain surface. Therefore, when these particles come into contact with water, CaO and water come into direct contact, resulting in a digestive reaction. Even if only a part of the grain surface is digested, cracks will occur in the grains due to expansion and powdering, and the digestion reaction will be further accelerated and the digestion will proceed like a chain reaction.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a refractory with extremely excellent digestion resistance using raw materials in which moisture does not act on CaO. .

[Means to solve the problem]

In order to achieve the above object, this invention
An MgO-CaO refractory raw material containing a total of 98 or more MgO- It is made of CaO quality quake linker.

[For production]

The composition of the MgO-CaO refractory raw material used in the present invention is C
The total amount of aO and MgO is 98% by weight or more, preferably 99% by weight
% by weight or more, and the CaO component is preferably 5 to 70% by weight, preferably 10 to 60% by weight. CaO and Mg
Components other than O are usually 5iOz, Alz 03%
l"ez 03, etc., but these combine with CaO at a relatively low temperature to form a low melting point substance, thereby significantly reducing the effect of CaO, so it is desirable to minimize the amount as much as possible, but at high temperatures of 1700 ° C or more Even under operational conditions, it is applicable if the total amount of MgO and CaO is 98% by weight or more.

If the CaO content is less than 5% by weight, sufficient CaO cannot be supplied to reduce structural deterioration due to the MgOCaO reaction, react with 5in2 in the intruded slag, and increase the melting point.

Furthermore, if the CaO content exceeds 70% by weight, the MgO--CaO clinker produced by the method described below will have an MgO layer on the particle surface of substantially 1011 m or less, causing a problem in terms of digestion resistance.

For example, the MgO--CaO-based linker used in the present invention may be one manufactured by the following method.

C-a (OH)z with a purity of 99% by weight or more and a purity of 98%
Using Mg (OH)2 of a grade higher than that as a starting material, Ca
The slurry with an O/MgO ratio adjusted to a range of 10,010 to 20/80 was put into a rotary kiln, and the O/MgO ratio was adjusted to a range of 1,500 to 1.
The name used to produce primary clinker by firing at 700℃. Then,
This primary clinker is pulverized to a particle size of 2 mm or less and dispersed in a non-aqueous solvent with a purity of 981i.
A cake is prepared by adding and mixing the above Mg(OH)z and drying it to a solvent content of around 10% by weight. This cake is put into a rotary kiln and fired at a temperature of 1800° C. or higher, and the resulting secondary clinker is sieved in an unpulverized state, and the granular bones are packaged.

In the graphite-containing MgO-CaO refractory of the present invention, the above M
0 to 90% by weight of gO-CaO quaclinker and 3 to 40% by weight of graphite are used. In addition, fused magnesia or sintered magnesia can be used. Furthermore,
The graphite-containing MgO-CaO refractory of the present invention is obtained by adding an organic binder to each of the above raw materials, kneading, molding, and heat-treating.

〔Example〕

First, the average composition is Mg054% by weight, Ca045% by weight,
The MgO-CaO Quaclinker is composed of 1% by weight of other components and the particle surface layer is covered with MgO with an average thickness of about 200 μm.The secondary talinker is fired at a firing temperature of 1600°C and a secondary talinker firing temperature of 1950°C. I got it.

In this clinker, as shown in Figure 1, CaO is replaced by MgO.
covered by a layer of 10-500μm, with an average porosity of 3
．． 5%, an average bulk specific gravity of 3.20, and a clinker with a maximum particle size of about 10 mm.

Graphite-containing Mg shown in Examples 1 to 3 shown in Table 1 was prepared using the obtained clinker and natural flaky graphite with a purity of 98% by weight.
O--CaO bricks were produced in a conventional manner.

Further, a conventional MgO-CaO quack linker consisting of 30% by weight of 0Mg0, 68% of Ca0, 2% by weight of other ingredients; an MgO clinker consisting of 99.5% by weight of Mg0, 0.5% by weight of other ingredients; and Examples. Graphite-containing MgOCaO bricks shown in Comparative Examples 1 and 2 shown in Table 1 were produced using the same natural scaly graphite, and the properties of the obtained bricks are also listed in Table 1.

As is clear from Table 1, MgO-C according to the present invention
The graphite-containing MgO-CaO refractory brick using aO clinker has excellent compressive strength (Example 1.2.3), and Example 1.2 using only the MgO-CaO clinker of the present invention has excellent compressive strength. It can be seen that the loss index is also significantly superior. Furthermore, it can be seen that the product of the present invention is significantly superior in dimensional change rate and compressive strength due to digestion of CaO at 40° C. and 80% humidity.

Effects of the invention C] As explained above, the graphite-containing Mgo-C according to the invention
AO-quality bricks have excellent digestion resistance and corrosion resistance, and are useful as refractories for molten metal smelting furnaces.

[Brief explanation of the drawing]

FIG. 1 is a model diagram of the structure of MgO-CaO talin used in the present invention, and FIG. 2 is a model diagram of a conventional MgOCaO clinker.

Claims (1)

[Scope of Claims] [1] Contains a total of 98% by weight or more of CaO and MgO,
Among them, MgO- containing 5 to 70% by weight of CaO component.
CaO-based refractory raw material, the surface of the raw material particles is 10 to 5
MgO-Ca covered by 00μm MgO layer
Graphite-containing M characterized by using O quality clinker
gO-CaO refractory.