JPH01131047A - Production of refractory container - Google Patents

Abstract

PURPOSE:To obtain a refractory container slightly causing cracks, having excellent durability, by blending a refractory having a specific adjusted particle size with an inorganic binder and an organic binder in a given weight ratio, press molding and calcining. CONSTITUTION:About 10-40wt.% based on total amount of aggregates of coarse aggregate having a particle size in a range of about onethird - fifteenth of the thickness of a container is blended with an ordinary aggregate (e.g., electromelting alumina) to prepare a refractory having an adjusted particle size. Then 93-99wt.% of the refractory is blended with 7-1wt.% inorganic binder (e.g., aluminum phosphate) and organic binder (e.g., phenolic resin). Then the blend is press molded and calcined to give a refractory container. Consequently, since the coarse aggregate is added, particulate boundary is lessened, spalling resistance can be raised and the prepared refractory container can be suitably used as a pouring ladle.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to crucibles, ladles, general heating containers, etc. used for melting metals, glass, slag, etc., or for holding their molten metals. The present invention relates to a method for manufacturing a refractory container and a product thereof.

(Prior Art and Problems) Conventional refractory containers such as induction furnaces or ladles are generally made of alumina, magnesia, zirconia, silica, mullite,
Fireproofing made by blending one or more types of refractory materials such as calcia, silicon carbide, clay, silica, glassy substances, natural or artificial graphite, coke, and other carbonizable substances according to the melting metal, melting method, etc. using things. Small induction furnaces use shaped refractories formed into a crucible shape and fired, but they have poor spalling resistance and tend to crack early during use, making it difficult to manufacture and use large containers. In addition, it is impossible to use it many times, and the molten metal leaks, causing a major accident. For this reason, in large induction furnaces and the like, it is common to use monolithic refractories with lining molding. In this case, the shaping of the container is
In many cases, molding is carried out on-site by inserting a former into these devices at the site of use. In the induction furnace, dry ramming material is charged and filled little by little while pressing against the head of the balk pull-by-break. Although the filling operation is repeated several times along the circumference of the container, there are cases where sufficient filling is not obtained or there are variations in the degree of filling. In areas with poor filling properties, cracks may develop during use, or corrosion resistance may be insufficient, resulting in insufficient durability. In addition, the portable vibrator weighs as much as 10 kg, and the filling operation takes a long time, resulting in a heavy labor load.

An object of the present invention is to provide a method for manufacturing a refractory container that is stable over a long period of time and is free from cracks.

(Means for solving the problem) A refractory material whose particle size is adjusted by mixing coarse aggregate with a particle size of about 1/3 to 1/15 of the wall thickness of the container with normal aggregate is 93% by weight. ~99%, inorganic binder and organic binder 1
~7% is mixed, press-molded, preferably rubber press-molded, and fired in various atmospheres such as air or a reducing atmosphere to produce a refractory container.

If the particle size of the refractory material is adjusted so that the coarse aggregate accounts for 10 to 40% by weight, the so-called refractory material containing many coarse particles can be made into a homogeneous structure, which is preferable.

It is preferable to sinter the press molded body of the refractory material at a temperature of 300'C to 1800 I'C depending on the type of the refractory material.
A temperature of 00'C or higher is undesirable because over-firing tends to occur.

(Function) Resistance to thermal stress during heating and cooling, which is one of the important factors governing the durability of refractories, that is,
Thermal spall resistance is often due to the particle size composition of the refractory. For example, in the case of fine grains having a uniform grain size, they are easily sintered and have many grain boundaries, so that cracks propagate through the boundaries and are easily destroyed, that is, the spall resistance decreases.

In the present invention, the coarse aggregate has fewer grain boundaries in the aggregate,
Improves spall resistance. A small amount of organic binder disappears in part or in its entirety during the firing process, reducing the bonding force at the grain interface, while a small amount of inorganic binder provides the necessary strength as a structure through moderate bonding force between aggregate particles. Express most of the

Furthermore, the disappearance of the organic binder filled in the grain boundaries increases the degree of freedom for expansion and contraction of the particles constituting the refractory container during heating and cooling applied from the outside, and reduces the stress generated at the grain boundaries. suppress. In this way, the manufacturing process of the present invention makes it possible to suppress stress interference between particles while maintaining bonding strength as a structure.

(Example) As shown in the table below, high purity fused alumina powder of 99.7% or more was mixed and kneaded, and the outer diameter was 240 m.
, mφ, a height of 430 mmφ, and a wall thickness of 20 mm t.

The typical physical properties of the crucible are shown in the table below.

When the quality variation in each part of this crucible was investigated by porosity measurement, it was 23 ± 0.5% in the crucible manufactured based on the present invention, compared to 22 ± 5% in the conventional product, which made it possible to fill the crucible uniformly. It can be seen that

When this crucible was used in an experiment in a high-frequency induction furnace, the life of the crucible according to the present invention was 62 channels, which was 1.7 times longer than that of the conventional product with 36 channels.

Various molding methods can be used to mold the refractory material mixed with the above materials, but if rubber press molding is used, uniform pressure can be applied and a dense and homogeneous structure can be created.

The refractory container thus formed can be used as a crucible, ladle, or other general heating container.
Filling the outside of a refractory container with dry stamp material and using it as an induction furnace or ladle will further strengthen the refractory container and prevent it from cracking, making it possible to manufacture large refractory containers. , and the refractory container can be used many times.

An example of using a refractory container in an induction furnace is as follows. That is, the dry stamp material 2 is put into the bottom of the inside of the outer shell 1 made of a heat insulating material and hardened, and the crucible 3 molded with the above structure and method is placed on top of the dry stamp material 2 in the cassette crucible and L7.
The gap between the inner surface of the outer shell 1 and the outer periphery of the crucible 3 is filled with dry stamp material 2 and solidified, and the opening edge of the crucible 3 and the upper edge of the dry stamp material 2 are stamped with a Uso I type stamp. It is hardened with a material 4, and a coil 5 is provided around the outer periphery of the outer shell 1.

(Effects) According to the method for manufacturing a refractory container according to the present invention, the spalling resistance is good, cracks do not occur early during use, and there is no risk of a major accident due to the spillage of molten metal. It has the excellent effect of producing refractory containers that can also be used.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of an induction furnace in which a refractory container is used. 1... Outer shell 2... Dry stamp material 3... Crucible 4... Wet type stamp material 6... Coil

Claims (1)

[Claims] 1. Mixing coarse aggregate with a particle size of approximately 1/3 to 1/15 of the wall thickness of the container and comprising approximately 10 to 40% of the total aggregate with normal aggregate. 1. A method for producing a refractory container, which comprises mixing 93 to 99% by weight of a refractory material whose particle size has been adjusted by weight, and 1 to 7% by weight of an inorganic binder and an organic binder, press molding, and firing.