JPS63139063A - Molten ceramic particle and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is suitable for use in various types of furnaces for steel and non-ferrous metals, molten metal containers, and aggregates used in ZrB2 refractories suitable for molten metal contact members. The present invention relates to ceramic particles and a method for producing the same.

[Prior Art] Refractories with excellent corrosion resistance, spalling resistance, and wear resistance are widely used in furnaces for steel and non-ferrous metals, and many of them are Al2O3, MgO, MgO-C.
r2O3,! 4g0-C:aO, Mg0-C:, Al
It was a composite of oxide refractory particles such as 203-C and Zr02-C and carbonaceous materials such as graphite. In recent years, with the improvement of steel smelting technology, the properties required for refractories have diversified, and Si
Non-oxide refractory particles such as n, 5i3Na, and BN are also used.

Moreover, in patent publication No. 44-14820, ZrB2-5i
Although electrofusion cast refractories such as C-C and ZrB2-CrB2-C have been proposed, they contain a considerable amount of residual C, ZrC, and 84G, and have the drawback of poor oxidation resistance and corrosion resistance when used as aggregates.

[Problems to be solved by the invention] However, these conventional refractories for steel and non-ferrous metals have natural or synthetic A! 203゜MgO, MgO
-Cr2(h, MgO-CaO, Mg0-C, Al2
03-C.

As Zr02-C and additives, 5i3Na, SiC
, BN, etc., have the drawback of insufficient corrosion resistance, permeation resistance, and adhesion resistance against molten metal.

On the other hand, it is known that ZrB2, which has excellent corrosion resistance, penetration resistance, and adhesion resistance against molten metal, will exhibit excellent performance if used as a refractory aggregate, and in recent years it has been used as a sintered material. It is gaining attention.

However, ZrB2 particles have not been reprinted as coarse particles of about 5 cm, which are necessary for use as aggregate, and ZrB2 particles have not been reprinted.
rB2 particles are easily oxidized, and due to the reaction with molten steel and slag, ZrB2 oxidizes and becomes ZrO2 (monoclinic crystal), which cracks into fine pieces and is released in small pieces in the slag, resulting in decreased corrosion resistance and cannot be used as a refractory aggregate. had not been put into practical use.

[Means for Solving the Problems] The present invention was made to solve these problems, and provides ceramic particles characterized by a eutectic structure essentially consisting of ZrB2 and CaB6. It is something to do.

From the purpose of development, the particles of the present invention are ideal as a raw material for refractories (materials) with excellent oxidation and corrosion resistance, especially as a refractory raw material for aggregate, but they can also be used as a general refractory raw material and for various applications. It is also a material widely used as ceramic particles.

The following description will focus on its use as a refractory aggregate.

First, the particles of the present invention are characterized by the following structure.

That is, it is essentially a eutectic structure of Z rB2 and CaB6 crystals, in which CaBb crystals having a smaller grain size than the Z rB2 crystals are uniformly dispersed and bonded around the Z rB2 crystals outside the structure. be.

Furthermore, the proportion of crystals is expressed in weight% (the same applies hereinafter),
The best is 95-80% Zr1h and 5-20% CaB6.

This is because if there is too much CaBb, the oxidation resistance of CaB6 is poor, so when used as a refractory, the corrosion resistance will decrease, and if there is too little CaB6, the desired effect of improving corrosion resistance will be reduced. It is.

The particles of the present invention are thus eutectic particles consisting essentially of ZrB2 and CaBb, and other components may be contained in small amounts as long as they do not impair the characteristics of the 2-82 quality, but they should be kept in as small amounts as possible. It is desirable to keep it at . Note that other components include ZrC, C, and α-Zr.

ZrB+2. Small amounts of ZrO2 etc. are often included.

In addition, the grain size of Z rB2 crystal in the eutectic grain is 100
The particle size of the CaB6 crystals is preferably about 50 mm or less.

Although it is not clear why such eutectic particles of the present invention are desirable as a fireproof material, the following is thought to be the reason.

In other words, since particles in which CaB6 crystals are uniformly formed around ZrB2 crystals are used, when eroded by slag, CaB6 is oxidized and becomes CaO before ZrB2, forming a protective layer with high graininess at the eroded interface. Z r
There is less Zr02 formation due to oxidation of B2, and even if Zr02 formation (monoclinic crystallization) occurs, Zr02 is stabilized by CaO at the temperature during use, so the Zr82 grains are less likely to crack finely. It is thought that this resulted in improved corrosion resistance and penetration resistance.

A preferred method for producing such eutectic particles of the present invention will be described below.

That is, the zirconium raw material, boron raw material, carbon raw material, and calcium raw material are respectively converted into ZrO2, B2O3, C, and CaO, and the weight percentages are 25 to 35% and 25 to 35%.
%, 30-20% and 20-5% mixed raw materials
This method involves melting and resolidifying at a high temperature of 500°C or higher.

Preferred examples of these raw materials are as follows.

The ZrO2 powder can be a natural mineral containing ZrO2, a purified raw material, or a synthesized raw material, but it is particularly desirable to use ZrO2 with a purity of 95% or more and a particle size of 1.
The amount should be 00uL or less.

B2O3 powder is Na2Ba07. BaC,B3O0
Although it is possible to use B2O3 etc., B2O3 is particularly preferable.
As purity is 85% or more and particle size is 100. The following is to be done.

As the carbonaceous material, coke, carbon black graphite, etc. can be used, but desirably, the amount of residual carbon as carbonaceous material should be 95% or more, and the particle size should be 100. The following is to be done. CaO powder is CaCO3, Ca(OH)2
Although it is possible to use CaO, it is preferable to use CaO with a purity of 95% or more and a particle size of 100g or less.

The raw material mixture is usually prepared by uniformly mixing these four kinds of powders in a V-type mixer.

The electrofused aggregate of the present invention can be obtained by charging the mixture into an electric melting furnace lined with graphite and having a water-cooled structure, melting it by arc melting using a graphite electrode, and leaving it in the furnace to cool.

Usually, ZrB2 can be melted at a lower temperature than when synthesized alone, and it can also be cast.

The powders of ZrB2, B2O3, C, and CaO are prepared as a mixture of four types, as described above.
8203 25-35%, 030-20%, Ca02
The content is preferably 0 to 5%, and the reason is as follows.

When Zr02 is less than 25%, the production of ZrB2 is reduced, and when it is more than 35%, the amount remaining as Zr02 increases. Also, if B2O3 is less than 25%, 8203
ZrB2. Production as CaB6 decreases, and if it exceeds 35%, the amount of volatilization increases and the viscosity of the melt increases, making it difficult to continue stable electric melting.If the amount of C is less than 20%, the amount of C required to reduce ZrO2 and CaO is reduced. The amount is small and remains as ZrO2 and CaO.

Moreover, if it exceeds 30%, ZrC, α-Zr, and residual C are generated. If CaO is less than 5%, the intended effect of improving corrosion resistance will be small, and if it is more than 20%, the oxidation resistance of CaB6 will be poor, resulting in a decrease in corrosion resistance when used as a refractory.

Next, to use the particles obtained in this way as a refractory aggregate, it is effective to use them as all or the main component of the refractory particles, or to use them as part of the refractory particles. Furthermore, it can be used as a thermal spray material.

For example, in order to use it as the main raw material for refractory particles of shaped refractories, coarse particles should be 4.76 to 1.00+am, medium particles should be 1.
．． 00~0.1mm, it is best to grind it with a Shaw crusher or a bot mill to fine particles of 0.1m+s or less, and select the particle size necessary to mix it with other refractory particles as part of it. good.

[Example] Table 1 shows examples of melting tests of ZrB2 electrofused aggregate.

The raw materials shown in the table are mixed in a ■-type mixer, and the mixture is put into an electric melting furnace lined with graphite and has a water-cooled structure, synthesized by arc melting using a graphite electrode, and left in the furnace to cool. Ta. This lump was taken out of the furnace, and the produced mineral was fixed by X-ray diffraction.

This lump was crushed into coarse particles of 4,76 to 1. oom+s,
Medium grain 1.00~0. The lO1 fine particles were prepared to be 0.10 mm or less and used as an aggregate for monolithic refractories. Table 2 shows examples of monolithic refractories. The raw materials shown in the table were mixed using a universal mixer, and the amount of water shown in the table was added to obtain a kneaded product. This was poured into a 40X 40X 180I mold while being vibrated with a vibrator, cured for a predetermined period of time, and then removed from the mold and dried for 110'CX 24 hours.

Hot strength is the bending strength of a dry product at 1280℃ (kg/a
m2), and #saponifiable property was determined by firing the dried product in the atmosphere at 1500° C. for 10 minutes and observing the cross section to indicate the thickness of the oxidized layer on the surface. Corrosion resistance, penetration resistance, and adhesion resistance are 155% for dry products.
The amount of erosion (■) is the maximum amount of erosion, the amount of penetration (am) is the maximum depth of penetration, and the adhesion resistance is determined visually by Ox. Indicated.

As a comparative example, stable and Al in non-eutectic Z rB2B2
2O3 castable was shown.

Table 1 (Note 1) Identification by X-ray diffraction indicates the intensity of X-ray diffraction, and in descending order of strength: vS>S>M>W>V
It is W.

(Note 2) Samples 2 to 5 have a texture of 150 to 400
CaB6 crystals of about 1" 5 to 20 hemorrhoids are tightly formed around the ZrB2 crystals of about 1".
It falls within the range of 0%.

(Note 3) In sample 1, a small amount of CaO crystals are formed and slaking occurs during standing.

Table 2 (Note 1) ZrB2 aggregate is not eutectic aggregate but ZrB299
It is a normal synthetic aggregate consisting of %.

(Note 2) ZrB2-CaB6 The eutectic particles of sample 3 in Table 1 were used as the aggregate.
0%, fine particles 30%.

(Note 4) Ultra-fine powder is one with a particle size of 5 l or less, and fine powder is one with a particle size of 0.
It is 1 mm or less.

[Effects of the Invention] As described above, the present invention is a ZrB2-based CaBb eutectic particle, which has excellent corrosion resistance against molten metal when used as an aggregate or powder for ZrB2-based amorphous refractories, fired bricks, ceramic coatings, etc. It has permeation resistance, adhesion resistance, and particularly improves the oxidation prevention, corrosion resistance, and permeation resistance of ZrB2.

Therefore, this aggregate powder can be used appropriately in the steelmaking process, such as container mating materials for hot metal and molten steel, molten metal passing rings, furnace materials for blast furnaces, furnace materials for nonferrous metals, etc., and surface coating materials for these peripheral parts. Not only can it be used appropriately in a wide range of applications, but it can also be used in a wide range of other applications as ceramic particles, and its industrial value is enormous.

Claims (6)

[Claims] (1) Molten ceramic particles characterized by a eutectic structure of ZrB_2 and CaB_6. (2) As a crystal structure, ZrB_2 is 95 to 95% by weight
Ceramic particles according to claim 1, consisting essentially of 80% and 5 to 20% CaB_6. (3) Ceramic particles according to claim 2, in which microscopic CaB_6 crystals having a smaller crystal grain size than the ZrB_2 crystals are uniformly dispersed and bonded around the ZrB_2 crystals. (4) The grain size of ZrB_2 crystals is 100 to 500μ, and C
The ceramic particles according to claim 3, wherein the aB_6 crystal grain size is 50 μm or less. (5) Ceramic particles according to any one of claims 1 to 4, wherein the particles are used as an oxidation-resistant and refractory aggregate. (6) Zirconium raw material, boron raw material, carbon raw material and calcium raw material are ZrO_2, B_2O_3, C and CaO
25 to 35%, 25% by weight, respectively.
A method for producing ceramic particles consisting essentially of ZrB_2 and CaB_6, characterized by melting mixed raw materials containing ~35%, 30-20%, and 20-5% at a high temperature of 2500°C or higher and resolidifying them.