JPH0791112B2 - SiC refractory - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a SiC refractory material mainly composed of SiC.

[Conventional technology]

SiC refractories have excellent fire resistance and heat resistance and occupy an important position industrially. For example, it is often used as a floor plate, shelf plate for firing ceramics, and other firing jigs and sheaths.

Conventional SiC-based refractories are mainly composed of SiC as a main ingredient, and in addition to this, by mixing, kneading and firing a silicate mineral such as clay mineral and an organic binder as a binder, SiC particles of the main ingredient, a bonding portion and a pore portion. Which has high heat resistance as well as mechanical strength. However, when a silicate mineral is used for the joint, soft deformation and oxidation are likely to occur at high temperatures.

Due to recent material innovation and development of new ceramic products,
Further, it is required to have higher strength and higher heat resistance, and a SiC material in which a bond is formed of silicon nitride or silicon dioxide by using a mixture of SiC particles and a trace amount of metal oxide as a raw material. Refractory materials have been proposed. For example, in JP-A-62-21762 and JP-A-62-83371, there have been proposed improvements in SiC-based refractory materials in which a joint portion is formed of silicon dioxide.

[Problems to be Solved by the Invention]

However, a material having high mechanical strength, sufficient heat resistance without causing thermal deformation, and excellent thermal shock resistance has not yet been obtained.

The present invention mainly focuses on research and development of bonding part forming materials and additives as an improvement in thermal strength and thermal shock resistance of conventional SiC refractories, but further excellent heat resistance etc. To complete the present invention by reviewing the SiC raw material aggregate particles from a micro viewpoint in order to obtain, high thermal resistance with little thermal deformation at high temperatures, high thermal shock resistance, high temperature shock and large temperature gradients, etc. It provides a SiC refractory that can be used for.

[Means for Solving the Problems]

According to the present invention, a SiC-based refractory material mainly made of SiC, wherein the raw material SiC particles have a particle size of 1000 to 5000 μm of 10 to 45% by weight,
~ 1000μm has a particle size distribution of 10-35% by weight, less than 500μm 20-80% by weight, at least 65% by weight of raw SiC particles having a particle size of 500μm or more is rounded edge A silicon carbide refractory is provided.

Hereinafter, the present invention will be described in detail.

The SiC refractory of the present invention includes, for example, 82 to 94% by weight of SiC, kaolin, bentonite, and other clay minerals such as silicate minerals or Si.
A SiC grain boundary phase (consisting of a glass phase, a cristobalite phase, an aluminosilicate phase, etc.) based on a metal oxide such as O ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , V ₂ O ₃ , CaO and K ₂ O. Containing 18 to 6% by weight, about 60 to 90% by weight of SiC, silicon nitride (S
i ₃ N ₄ ), which includes a SiC grain boundary phase based on 4 to 36% by weight of i ₃ N ₄ ) and 4 to 15% by weight of a metal oxide, and containing about 60% by weight or more of SiC as a main component. If it is, it will not be specifically limited. These SiC-based refractory materials are the main components of the raw material particles of SiC raw material with a predetermined particle size distribution, mixed with silicate minerals and metal oxides and metal Si, and then kneaded, molded and
It can be obtained by firing.

In the present invention, usually 1000 to 500 as the SiC raw material aggregate particles
0-μm is 10-45% by weight, 500-1000 μm is 10-35% by weight,
Those having a particle size distribution of 20 to 80% by weight less than 500 μm are used.

The SiC raw material aggregate particles of the present invention have the above-mentioned particle size distribution and are rounded so that about 65% by weight or more of particles of 500 μm or more do not have an edge portion. Incidentally, the edge portion in the present invention, SiC by observation with an electron microscope
On the outer peripheral surface of the aggregate particle, it means an angular portion such as a boundary line between a cut surface and a surface or a projection.

Conventionally, SiC raw material aggregate particles have been used by adjusting the particle size distribution, but there were variations due to differences in the thermal shock resistance and bending strength of the SiC-based refractory material obtained depending on the raw material. The present invention has found that the cause of these variations is based on the morphology of the raw material particles, and the raw material SiC aggregate particles that give SiC quality refractory having poor thermal shock resistance and the like are almost particle shapes by visual observation. Also has an edge part under a microscope or electron microscope observation, and in the obtained refractory, aggregate particles with an edge part are observed by a scanning electron microscope (SEM), and the pore distribution is non-uniform, which is good. A large amount of porosity was also observed in comparison with that of N.

Although the edge portion of these SiC raw material aggregate particles does not hinder the obtaining of a SiC-based refractory molded body in a macroscopic view,
As described above, the thermal shock resistance, the bending strength, and the bulk specific gravity are small, which is not preferable. In the present invention, a particle size of 500
The SiC aggregate particles obtained by rounding and removing the edge portions of the SiC aggregate particles having a size of μm or more are used as a raw material.

The rounding process for removing the above edge part was adjusted for particle size distribution.
Of the SiC aggregate particles, it is preferable to remove the edge portion of the particles of 500 μm or more. SiC aggregate particles less than 500 μm
It may be rounded with particles of 500 μm or more,
The edge portion of the SiC aggregate particles of less than m has little effect on the obtained SiC-based refractory material, and there is no problem even if it is used with the edge portion.

The rounding treatment of the above 500 μm or more SiC aggregate particles is preferably such that at least about 65% by weight thereof is rounded, and more preferably at least about 65% by weight of the 1000 μm or more SiC aggregate particles is the edge portion. It is preferable to use the one that has been rounded for removal. When the rounding ratio of SiC aggregate particles of 500 μm or more is less than 65% by weight, the thermal shock resistance of the obtained SiC-based refractory is insufficient. Further, the rounding treatment of the edge portion of the SiC aggregate particles of 500 μm or more may be up to 100% by weight as long as it is 65% by weight or more. Good.

In the present invention, the rounding treatment may be performed by any method and device as long as most of the edge portion of the SiC aggregate particles can be removed by polishing, abrasion, etc., and preferably by a fret mill or a ball mill.

When at least about 65% by weight of the SiC aggregate particles of 500 μm or more in the present invention are rounded, the filling property at the time of molding is improved and the obtained Si
In C-type refractory, the distribution of pores becomes uniform and the bulk specific gravity increases, and the thermal shock resistance and bending strength also increase.
Very little softening deformation at high temperature.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the following examples.

Examples 1 to 3 and Comparative Examples 1 to 4 Rounded SiC aggregate particles rounded by a fret mill, one example of which is shown in the electron micrographs of FIGS. 1 (1) and (2), as SiC aggregate particle raw material, Untreated SiC aggregate particles, an example of which is shown in an electron micrograph in FIGS. 2 (1) and (2), were used. As is clear from FIG. 1 and FIG. 2, the rounded treated SiC aggregate particles are in a state of being rounded and evened out due to the abrasion of the angular portions of the untreated SiC aggregate particles. ing.

10% by weight of bentonite was added to the rounded SiC aggregate particles and untreated SiC aggregate particles having the particle size distribution shown in Table 1, and 6% by weight of water was added and kneaded to the bentonite. 400
It was molded into × 350 × 10 (thickness) (mm). This compact was fired at 1400 ° C. for 10 hours in a nitrogen gas atmosphere. The heating rate and the cooling rate were each 100 ° C./hour.

The thermal shock resistance, bulk specific gravity, and bending strength of the obtained fired body were measured. The results are shown in Table 1.

The thermal shock resistance (ΔT _700-RT ) was shown by the number of repetitions of cracking when the fired body after being used for 50 hours in a 1200 ° C furnace was repeatedly placed at 700 ° C and room temperature.

The room temperature bending strength was measured according to JIS 2205.

Examples 4 to 5 and Comparative Examples 5 to 6 5 wt% of kaolin is added to the particle size distribution shown in Table 1 and SiC aggregate particles which have been rounded by a ball mill or untreated.
A fired body was obtained in the same manner as in Example 1 except that the ingredients were mixed.

The thermal shock resistance, bulk specific gravity, and bending strength of the obtained fired body were measured. The results are shown in Table 1.

As is clear from the above examples and comparative examples, 500 μm
The fired body using 65% by weight or more of the above-mentioned SiC aggregate particles rounded has excellent thermal shock resistance and high bending strength. On the other hand, when the amount of rounded 500 μm or more SiC aggregate particles is less than 65% by weight, both thermal shock resistance and bending strength are small. Further, the rounded product has a good filling property, and in particular, the sintered body of the example obtained by using the rounded product of 65% by weight or more of SiC aggregate particles of 500 μm or more is the same as that of the comparative example. The bulk specific gravity is higher.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY The present invention has excellent thermal shock resistance and bending strength by using, as the raw material SiC aggregate particles constituting the main component of the SiC refractory, particles of 500 μm or more rounded at a predetermined ratio.
SiC refractories can be obtained.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the particle structure of an example of the rounded SiC aggregate particles of the present invention, and FIG. 2 is an electron micrograph showing the particle structure of an example of the untreated SiC aggregate particles of the present invention. is there.

Front Page Continuation (72) Inventor Toshiyuki Ito 81, 5668 Asahigaoka, Asahigaoka-cho, Owariasahi-shi, Aichi 81 (72) Inventor Katsu Hasegawa 65, Ijiri, Mitake-cho, Kani-gun, Gifu (56) References JP-A-55-6070 JP, A)

Claims (3)

[Claims] 1. A SiC-based refractory material mainly composed of SiC, wherein the raw material SiC particles have a particle size of 1000 to 5000 μm of 10 to 45% by weight, and 500 to 1000.
characterized by having a particle size distribution of 10 to 35% by weight of μm, 20 to 80% by weight of less than 500 μm, and at least 65% by weight of raw SiC particles having a particle size of 500 μm or more having rounded edges. SiC quality refractory. 2. The SiC refractory material according to claim 1, wherein at least 65% by weight of the raw SiC particles having a particle size of 1000 μm or more have a rounded edge portion. 3. The rounding process is performed by using a fret mill or a ball mill.
SiC-based refractory described.