JPS5933549B2 - Monolithic refractories - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a monolithic refractory for lining various types of kilns and molten metal containers, and its purpose is to prevent explosions and peeling even when rapidly heated and dried after pouring. It is an object of the present invention to provide a castable monolithic refractory using fireclay as a binder that does not cause a collapse phenomenon.

Conventionally, castable castable refractories that use alumina cement as a binder have been the main type of castable refractories used for pouring. As a result, the hot properties in the high temperature range of 1200°C or higher are poor, and furthermore, in the intermediate temperature range of 800°C to 1000°C, strength deterioration due to dehydration is particularly significant.

In order to correct these shortcomings, castable refractories for pouring have recently been developed using fireclay as a binder and adding deflocculants and flocculants. Because it has superior mechanical strength and volume stability compared to conventional hydraulic castable refractories,
It is used as lining material for various kiln walls, ceilings, hearths, etc.

However, since this castable refractory has a maximum of 20% by weight of fireclay added to the fine powder part, the permeability of the constructed body is extremely reduced, and it is difficult for water vapor to escape during dry heating, and it often explodes. cause target spalling.

In order to prevent such explosions, it is necessary to wait for curing after construction, remove the frame, and then dry it according to a constant temperature rise curve after curing for at least 24 hours, which takes a long time.

Furthermore, since hardening is expected to occur due to the coagulation effect of the fireclay and coagulant, the coagulation effect decreases especially in winter, and it takes a long time (48 hours or more) to remove the frame, and the construction material after the frame is removed. It has drawbacks such as extremely low strength.

The present invention solves the various drawbacks of castable refractories using fireclay as a binding material as described above.

To explain the present invention in more detail below, the present invention is a refractory 1 in which fireclay is added to refractory aggregate whose particle size has been adjusted in advance.
00% by weight, the above fireclay is 3 to 12% by weight.
, a peptizer of 0.02 to 0.5% by weight, aluminate lime of 0.5 to 5% by weight, and a purity of 90% or more, 0
．． 0.1 to 5.55% by weight of metal aluminum powder containing 50% by weight or more of powder with a particle size of 0.074 mm or less
It is a monolithic refractory for pouring.

In Table 1, 80 parts by weight of fire-resistant aggregate (50 parts by weight of clayey chamotte coarse grains, 20 parts of medium grains, 10 parts of fine alumina powder), 10 parts by weight of fire-resistant aggregate,
Parts by weight A total of 90 parts by weight of refractories were weighed and mixed, and to this were added deflocculant, flocculant, metal aluminum powder, etc. in the parts by weight shown in Table 1.

The above weight percentage is 100 parts by weight of the above total refractory material.
As a percentage, fireclay is internally removed, and others are externally removed, converted to weight percent.

Deflocculants include sodium humate, sodium hexa-metaphosphate,
Sodium pyrophosphate and the like are used, and lime aluminate is used as the flocculant.

Refractory aggregates include bauxite, clay shale, kyanite, sillimanite, sintered alumina, fused alumina,
Synthetic mullite, seawater magnesia clinker, zircon,
Fused silica, artificial graphite, chromite ore, silicon carbide, silicon nitride, etc. can be used.

As the fireclay, relatively coarse-grained, white, poorly plasticized kaolin-based clay is effective from the viewpoint of fluidity for pouring, fire resistance, etc.

If the amount of clay added is more than 12.0% by weight, the viscosity during pouring will be too high and the hot properties will deteriorate.

If it is less than 3.0% by weight, the strength of the cured product will be low in the low to high temperature range.

As for the effects of aluminum metal powder, when added to castable refractories for pouring using water as a kneading liquid, the above (
The reaction of formula 1) occurs, and the added water is partially decomposed into aluminum hydroxide and hydrogen gas.

At the same time as the reaction starts, the construction body generates heat and the temperature rise inside the construction body accelerates the solidification of the clay and hardens with the effect of water evaporation.

The reaction start time and the amount of hydrogen gas generated at this time are related to the purity and particle size of the metal aluminum powder.
If it is less than 0%, the reaction time will vary widely, and if the particle size is less than 50% by weight of powder with a particle size of 0.074 mm or less, the reaction start time will be slow and the strength after curing will be weak, which is not preferable.

If the amount added is less than 0.1% by weight, it may explode if heated and dried rapidly, and if it is more than 5.6% by weight, a large amount of hydrogen gas will be generated, resulting in swelling of the cast body after casting. This is undesirable as it increases the size of the cracks, causes many cracks, and weakens the strength.

Addition of metallic aluminum powder within the above range can prevent explosion during rapid heating and drying.

Although the mechanism for preventing this explosion is not clear, it is thought to be due to a decrease in moisture content due to heat generation during curing and an increase in air permeability due to gas generation.

When fire-resistant aggregate, fire-resistant clay, and metal aluminum powder are mixed based on the appropriate addition ratio as described above, and water is poured as a kneading liquid, it will take 2 to 8 hours after pouring is complete.
It is possible to remove the frame in rs (hours), and during curing, (
1) The material starts to generate heat at the same time as the reaction of formula starts.

This exothermic temperature rises to 100℃, and the exothermic time is 3 hours.
The process continues for rs~8Hrs (hours), during which time the water in the material is dehydrated by 60~70% by weight.

When a reaction that generates heat starts from inside the material, the moisture in the material is gradually dissipated from the castable refractory, and at the same time, the material undergoes 3H due to its own exothermic reaction during curing.
Since it is left in a dry state for rs to 8 hours (hours), the cohesive force of the fireclay increases and approaches its dry (110° C.) strength.

Furthermore, this drying is not caused by external heating;
Since the fireclay aggregates while being gradually dried from the inside of the material, it hardens without causing any internal distortion of the hardened material.

These reasons are also considered to be one reason why explosions do not occur due to rapid heat drying.

Further, the time required from the start to the end of the exothermic reaction is desirably within 24 hours when used for actual lining of a kiln or molten metal container.

The purpose of the present invention is to complete the deframing exothermic reaction within 24 hours after the completion of casting, and to make it possible to immediately begin heating and drying. , low temperature drying for a long time (400
℃ or lower), and even if the temperature is rapidly raised to 500° C. to 800° C. at the same time as drying starts, operation can be carried out in a short time without causing any explosion or peeling/collapse phenomena.

Furthermore, when subjected to rapid heating and drying, a remarkable deterioration in strength is observed in ordinary hydraulic castable refractories and conventional fireclay-bonded castable refractories, but the product of the present invention does not have such drawbacks and is superior to ordinary castable refractories.・Exhibits strength comparable to acid strength.

Examples of the present invention are shown below.

As shown in the above examples, the product of the present invention solves the various drawbacks of conventional fireclay bonded castable refractories and provides castable refractories for pouring that do not explode even when subjected to rapid heating and drying with high curing strength. By incorporating highly corrosion-resistant materials such as fused alumina, sintered alumina, magnesia clinker-1 silicon carbide, and silicon nitride raw materials, we have created castable fireproof linings for molten metal containers that are directly exposed to molten slag, molten steel, hot metal, etc. It can be applied as a physical object.

Claims (1)

[Claims] 1. 3 to 12% by weight of the above fireclay and 0.02 to 0.5% by weight of deflocculant to 100% by weight of refractory made by adding fireclay to fireproof aggregate with particle size adjustment %, 0.5 to 5% by weight of lime aluminate, and 0.1 to 5.55% by weight of metallic aluminum powder with a purity of 90% or more and 50% by weight or more of powder with a particle size of 0.074 mm or less. Monolithic refractories for lining various furnaces and molten metal containers, characterized by the addition of % by weight.