JP2821748B2 - BN normal pressure sintered ceramics with excellent erosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to BN-based ceramics having excellent erosion resistance to a melt of a metal or an inorganic material.

<Conventional technology> While BN ceramics exhibit extremely excellent wettability to molten materials such as metals and glass, they are selectively etched at the portions in contact with the meniscus portion of these molten materials. Disadvantages.

One of the reasons is that BN ceramics are not widely used as furnace materials.

In addition, BN ceramics are usually made by hot pressing because normal pressure sintered products are too low in strength and cannot withstand use at all, which is one of the reasons that they are extremely expensive. .

Therefore, in order to widely utilize the excellent properties of BN ceramics in furnace materials, it is necessary to solve this problem of erosion and the problem of the strength of inexpensive normal pressure sintered products.

<Problems to be Solved by the Invention> The present invention has been made in view of the problems of the state of the art, and has as its object the purpose of the present invention is to sinter a normal-pressure product and to melt the metal or glass in a molten state. An object of the present invention is to provide a new BN ceramic material having excellent loss property.

<Means for Solving the Problems> The means for solving the above problems has the following configuration.

BN 40% or more (SiO2, Al2O3, AlN, B4C, oxides of rare earth elements, TiB2, ZrB2, ZrN, ZrO2, ZrO2 SiO2, Si3
N4, TiO2, oxides of alkaline earth metals), BN-based normal-pressure sintered ceramics containing one or two or more ceramic components as basic components have significantly improved erosion resistance. thing.

Also, the above BN component and (SiO2, Al2O3, AlN, B4C, oxides of rare earth elements, TiB2, ZrB2, ZrN, ZrO2, ZrO2 SiO
2, BN-based normal-pressure sintered ceramics, in which the sum of one or more ceramic components selected from the group of Si3N4, TiO2, oxides of alkaline earth metals) is 60% or more of the total, The erosion resistance is significantly improved.

Further, when the raw material powder of the BN component is an amorphous BN powder alone or a partially amorphous BN powder, and the K value of the amorphous is 0 to 0.6, the above effect is most remarkable. Was found to be represented.

However, S (hkl) is the peak area of (hkl) corresponding to hexagonal BN in the X-ray diffraction pattern.

<Operation> The starting raw material powder of the BN component of the present invention contains at least a part of an amorphous BN powder or an amorphous BN powder during firing.
It is preferred to use a material powder that changes to BN.

The K value is used as a parameter indicating the degree of amorphization of the material. In the present invention, a powder satisfying 0 ≦ K ≦ 0.6 is used.

K is the powder in the above range alone or K ≦ 0.
The crystalline powder of 8 is appropriately mixed and used.

The ratio of crystalline materials that can be mixed is approximately
Up to 80% of BN.

If it exceeds 80%, sinterability deteriorates and strength decreases, which is not preferable.

The K value of the amorphous powder is limited to 0 to 0.6 because the K value is
If it exceeds 0.6, sinterability deteriorates, mechanical strength decreases, and erosion in molten metal increases, which is not preferable.

In addition, the amorphous BN powder includes not only the amorphous BN alone but also a powder that changes into an amorphous BN in a firing process.

Further, the powder containing a part of the amorphous may be a simple mixture of the amorphous powder and the crystalline powder as described above, or the surface of the crystalline BN powder particles may be partially amorphous BN powder. May be present.

Such a powder is obtained by the mechanochemical effect.

 The K value will be described in detail.

h-BN, that is, the X-ray diffraction pattern of hexagonal BN
5 are as shown in FIG.

 FIG. 1 is a typical crystalline pattern.

FIG. 2 to FIG. 5 show patterns when the crystallinity is broken and the crystal is sequentially amorphized.

FIG. 2 → FIG. 3 → FIG. 4 → FIG. 5 shows the progress of the degree of amorphization.

The K value is (PW-1710 manufactured by PHILIPS, line of Cu-Kα). S (102) is a hatched portion (1) of the diffraction pattern.

 S (100) is the portion indicated by oblique line (2).

 S (101) is a portion indicated by oblique lines (3).

 For crystalline materials, K ≧ 0.8 As the amorphization proceeds, this becomes smaller and converges to zero.

It is necessary to add at least 40% or more of the BN component of the present invention.

If the BN content is less than 40%, sufficient erosion resistance cannot be obtained.

Components other than BN (SiO2, Al2O3, AlN, B4C, oxides of rare earth elements, TiB2, ZrB2, ZrN, ZrO2, ZrO2 SiO2, Si3
It is necessary to add one or more components selected from N4, TiO2, and oxides of alkaline earth metals).

These components need to be added together with the BN component at least 60% or more of the whole.

In other words, the components other than the above components are at most 40
It needs to be kept at%.

In order to maintain sufficient corrosion resistance to a molten metal, particularly a molten steel, it is necessary to set the composition in the above range.

Components other than the above components include borides, nitrides,
Ceramic components such as oxide carbide and silicide can be appropriately added according to the purpose.

Note that the oxide of the rare earth element refers to Y2O3, and the oxide of the alkaline earth metal refers to MgO, CaO, BaO, or the like,
These are mutually compatible components.

<Examples> The present invention will be described in detail with reference to examples.

Example 1. In a high-frequency melting furnace, molten steel (SCR4
About 0.1% of Al was added in 20), and a ceramic having the following composition was immersed therein, held for 1 hr, and the amount of erosion was measured.

NO.1 ~ 16 ceramics were molded into a rod state by rubber press, then sintered under normal pressure at 1800 ° C in N2 atmosphere, 10φ × 100
It has been processed into.

In addition, in the compositions of Nos. 1 to 15, all of the BN starting materials were replaced with crystalline BN.
And the normal pressure sintering, in the immersion test of the same conditions,
The diameter after immersion is NO.1 3.8mmφ, NO.2 2.1mmφ, NO.3 2.5mmφ, NO.4 2.8mmφ, NO.5 3.0mmφ, NO.6 3.5mmφ, NO.7 2.3mmφ, NO. 8 2.5mmφ, NO.9 2.8mmφ, NO.10 3.0mmφ, NO.11 2.9mmφ, NO.12 2.1mmφ, NO.13 2.6mmφ, NO.14 3.5mmφ NO.15 3.6mmφ, NO.16 3.1mmφ It was confirmed that the present invention was extremely excellent in erosion resistance despite normal pressure sintering.

Example 2 An immersion test was performed on the ceramic of BN 65% -AlN 15% -SiO2 15% -mullite 5% under the same conditions as in Example 1.

In this example, an amorphous BN powder having K = 0.3 was used for 80% of the BN starting material.

 There was no erosion and no erosion.

When immersed in the molten metal, the ceramics of this example and Example 1 had no affinity with the molten metal and had a property of repelling the molten metal.

<Effects of the Invention> (1) It has the property of repelling molten metal, especially molten steel, and the amount of erosion is extremely small.

(2) Since it is a normal pressure sintered product, a large product and a complicated shaped product can be manufactured at low cost.

(3) High strength.

[Brief description of the drawings]

FIGS. 1 to 5 are diagrams showing changes in the X-ray diffraction pattern up to the crystallinity of hexagonal boron nitride. FIG. 1 shows a crystalline pattern, and FIGS. 2 to 5 show patterns when amorphization has progressed. The vertical axis is the diffraction intensity (cp
s), the horizontal axis is the diffraction angle 2θ (degree).

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-131072 (JP, A) JP-A-63-270359 (JP, A) JP-A-59-169982 (JP, A) JP-A-1 131066 (JP, A) JP-A-1-131106 (JP, A) JP-A-61-132564 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35 / 583-35 / 5835

Claims (2)

(57) [Claims] (1) BN 40% or more and (SiO2, Al2O3, AlN, B4C,
Rare earth oxides, TiB2, ZrB2, ZrN, ZrO2, ZrO2S
iO2, Si3N4, TiO2, oxides of alkaline earth metals) as a basic component, one or more ceramic components selected from the group consisting of amorphous BN
A powder alone or a partly amorphous BN powder,
A BN-based normal pressure sintered ceramic excellent in erosion resistance, characterized in that the amorphous K value is 0 to 0.6. 2. The method according to claim 1, wherein the BN component and (SiO2, Al2O3, AlN, B4C,
Rare earth oxides, TiB2, ZrB2, ZrN, ZrO2, ZrO2S
The sum total of one or more ceramic components selected from the group consisting of iO2, Si3N4, TiO2, oxides of alkaline earth metals) is at least 60% of the total. BN-based normal pressure sintered ceramic described in 1.