JPH02160657A - Cao-containing refractory - Google Patents

Abstract

PURPOSE:To prevent cracking from occurring and reduce attrition rate by forming an MgO-CaO-based clinker having the surfaces of particles coated with MgO layers. CONSTITUTION:A slurry prepared from Ca(OH)2 of >=99% purity and Mg(OH)2 of >=98% purity so as to provide (100/0)-(20/80) ratio of CaO/MgO is calcined at 1500-1700 deg.C to afford a primary clinker, which is then pulverized so as to provide <=2mm particle diameter. The obtained powder is then changed into a nonaqueous solvent containing the Mg(OH)2 of 98% purity dispersed therein, dried and then calcined at >=1800 deg.C to afford an MgO-CaO-based clinker with >=98% total content of CaO and MgO, containing 5-70% CaO component therein and having the surfaces of raw material particles coated with MgO layers of 10-500mum thickness. A nonaqueous binder (e.g. tar) is subsequently added to the resultant clinker and the obtained mixture is kneaded, formed and calcined at 1600-1700 deg.C to provide a CaO-containing refractory.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to CaO-containing refractories, particularly MgO-CaO
Regarding quality refractories.

[Prior art]

MgO-CaO refractories are widely used as refractory lining materials for converters, molten steel pots, cement rotary kilns, and the like.

MgO, which is the main component of MgO-CaO refractories, has low reactivity with steelmaking slag and Franks components in cement kilns, making it difficult to erode.
The voids between the grains are easily filled with foreign components such as slag, which causes differences in the coefficient of thermal expansion and other physical properties between the original brick structure and the part that has been infiltrated by foreign components, resulting in the disadvantage that cracks are likely to occur inside the brick. have. On the other hand, CaO has the property of being more easily deformed in response to stress at high temperatures than MgO, and CaO, which is the main component of steelmaking slag, or
5i02SKzO1, the main component of cement kiln interior
It reacts with foreign components such as Na and 01SO to convert them into high-melting point compounds, which has the effect of preventing penetration into the interior of the brick, thereby inhibiting the introduction of cracks into the MgO--CaO refractories.

In other words, CaO has the effect of overcoming the disadvantages of single MgO refractories, which are poor heat spalling resistance and structural spalling resistance, and by combining both components, these characteristics can be effectively exhibited. It is something that will be done.

[Problem to be solved by the invention]

However, as mentioned above, while CaO has excellent thermal and chemical properties at high temperatures, at low temperatures around room temperature CaO + Hz
It is known that it has the disadvantage of causing a digestion phenomenon (pulverization and disintegration) due to the O-Ca(OH)z reaction. For this reason,
CaO-containing raw materials are exposed to Hz during the brick manufacturing process or during use.
If there is a chance of contact with O, cracks will appear in the brick,
Not only does it fail to achieve the intended purpose due to expansion and pulverization, but 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 or moisture generated by secondary reactions with binders and other substances. , it was extremely difficult to completely prevent digestion.

That is, the CaO-containing raw material is CaO alone or MgO
However, all the raw materials to date have been adjusted so that CaO and MgO are homogeneously distributed. Therefore, CaO and M on the surface and inside of the raw material particles
There is no difference in the distribution state of gO, and there is always Ca on the grain surface.
This means that O is exposed. 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.

This invention was proposed in view of the above-mentioned conventional circumstances, and the CaO is not affected by moisture during the manufacturing process, and therefore, CaO is less susceptible to cracking and has a lower wear rate.
The purpose is to provide refractories containing refractories.

[Means for Solving the Problems] In order to achieve the above object, the present invention contains a total of CaO and MgO of 98% or more, of which the CaO component is 5 to 70%, and the surface of the raw material particles is 10 to 500 II m. It is characterized by using a MgOCaO talin car covered with an MgO layer.

[For production]

The MgO-CaO quaclinker composition used in the present invention has a total content of CaO and MgO of 98% or more, preferably 99%.
or more, and the CaO component is 5 to 70%, preferably 10%.
It is preferable to set it to 60%.

Components other than CaO and MgO are usually Sin, A
T-O! , Fe, O, etc. These substances combine with CaO at relatively low temperatures to form low-melting substances, thereby significantly reducing the effect of CaO, so it is desirable to minimize the amount of these substances. It is applicable if the total amount is 98% or more.

When the CaO content is less than 5%, stress is relaxed by deformation, and it also reacts with Stow and other components in the foreign components,
It is not possible to raise the melting point to a sufficiently high level, and if it exceeds 70%, the MgO layer on the surface of the particles will be substantially less than 10 μm in most cases, and there are cases where the surface of CaO is not sufficiently covered by MgO. , which causes problems in terms of digestion resistance.

The MgO--CaO-based linker used in the present invention may be produced, for example, by the following method.

Using Ca(OH)z with a purity of 99% or more and Mg(OH)z with a purity of 98% or more as starting materials, a slurry with a Cab/MgO ratio adjusted to a range of 10010 to 20/80 was charged into a rotary kiln and heated at 1500°C. Calcinate at ~1700°C to create a primary clinker.Then, this primary clinker is crushed into 2 pieces ~ OB and poured into Mg (OH) with a purity of 98% or more dispersed in a non-aqueous solvent.
Mix and make a dried cake with a solvent content of around 10%.

This cake is put into a rotary kiln and fired at a temperature of 1800° C. or higher, the resulting secondary clinker is sieved in an unpulverized state, and the granular bones are packaged.

The MgO--CaO clinker produced as described above has CaO particles wrapped in Mg0, as shown in FIG. On the other hand, the conventional clinker shown in FIG. 2 is simply a mixture of CaO and MgO.

In the CaO-containing refractory of the present invention, the above amount of MgO-CaO quaclinker may be used, or fused magnesia,
Alternatively, sintered magnesia may be used in combination.

The CaO-containing refractory of the present invention is obtained by adding a known non-aqueous binder such as tar, liquid phenol resin, polyurethane, polypropylene, wax, etc. to each of the above raw materials, kneading, molding, and firing. Firing conditions are not particularly specified, but are preferably about 1,600 to 1,700°C.

〔Example〕

Average composition Mg040%, Ca059%, other components 1
%, and the particle surface layer has an average thickness of about 200 pm.
A MgO-Ca03i clinker covered with an O layer was fired under conditions of a primary tallinker firing temperature of 1600°C and a secondary tallinker firing temperature of 1950°C.

This Talinker has an average porosity of 3.7% and an average specific gravity of 3.7%.
No. 17, Talin force was a milky white particle with a maximum particle size of about 10 m.

Using the obtained clinker and seawater magnesia clinker with a purity of 98%, fired MgO--CaO bricks shown in Examples 1 to 3 shown in Table 1 were manufactured.

Comparative Example Existing MgO-CaO tawata linker consisting of 41% Mg, 37% CaO, and 2% other components - purity 98%
Baked MgO--CaO bricks shown in Comparative Examples 1 to 3 shown in Table 1 were manufactured using the seawater magnesia clinker.

The properties of the obtained bricks are also listed in Table 1.

〔Effect of the invention〕

Table 1 shows that the fired MgO-CaO trade bricks of Examples 1 to 3 according to the present invention not only have significantly better digestion resistance than Comparative Examples 1 to 3, but also have excellent corrosion resistance and spalling resistance. , it is obvious that it is useful as a refractory for steelmaking furnaces or cement rotary kilns.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a MgO--CaO clinker used in the present invention, and FIG. 2 is a sectional view of a conventional MgO--CaO.

Claims (1)

[Claims] (1) The total amount of CaO and MgO is 98% or more, of which C
Contains 5 to 70% aO component, and the surface of the raw material particles is 10 to 70%.
MgO-C covered by 500μm MgO layer
A CaO-containing refractory characterized by using an aO clinker.