JPS63201067A - Manufacture of metal diboride base ceramics - 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 Application Field> The present invention relates to a method for obtaining metal diboride ceramics having excellent corrosion resistance even by normal sintering at low temperatures.

<Prior art> Niated metals, especially TiJ, ZrB2. HfB2 is
Since it has excellent corrosion resistance against molten metal, it is used in many applications such as containers for molten metal, components of molten metal contact type sensors, and Ti electrodes for molten metal.

However, most of these nimate metals have a high melting point of about 3000°C and are difficult to sinter, and in order to obtain high-density sintering, it is necessary to It is necessary to adopt a sintering method under high pressure of 1,000 atmospheres, or to use a sintering method in which a low melting point substance is added, as shown in Japanese Patent Publication No. 58-3997, which increases the size of the equipment. There may be difficulties in the manufacturing process, or the composition of the sintered body may change due to the addition of different low melting point substances.
As a result, the excellent properties originally possessed by diboron metals are impaired, and furthermore, the above-mentioned low melting point substance remains in the sintered body as it is, and the molten metal comes into contact with this residual part, and from there. There were problems such as corrosion.

<Problems to be Solved by the Invention> The present invention solves the above-mentioned difficulties in the manufacturing process of the high-pressure sintering method, limitations in the dimensions of the resulting product (large-sized products are difficult to obtain), and the method of adding different low-melting substances. To solve the problem of deterioration of product properties, we have developed a method that allows high-density sintered bodies to be obtained by low-temperature sintering, and that does not contain other substances that may cause deterioration of the properties of the sintered bodies. The purpose is to provide.

Means for Solving the Problems> The above object of the present invention can be achieved by employing the following means.

That is, TiB2. ZrBz, HfB
At least one of the Z powders and Ti, Zr, H
This is a method for producing metal diboride-based ceramics, characterized by mixing at least one of ZrB, ZrB, and HfB powders and sintering the mixed powder.

The present invention will be explained in detail below.

Niated metal has a hexagonal crystal structure in which the B content is in the range of 65 to 67 at %. That is, the content of B is
It exhibits a hexagonal crystal system even within a certain range and somewhat away from the stoichiometric range, without losing its corrosion resistance or electrical conductivity. Therefore, TiB2 alone has poor sinterability,
For one or more mixed powders of ZrB2 and HfB2 powder, low melting point metals or compounds such as Ti, Zr,
[(f, one or more of ZrB and HfB powders, the composition of the total mixed powder is such that the B content is 65 to 6 as described above)
The amount is adjusted to 7 at %, or B powder is further added to adjust the B content to 65 to 67 at %.

Or T Kamo Zr, old, TiB, ZrB from the beginning.

[One or more types of HB powder and B powder are the same (B is 65 to 6
If the amount is adjusted to 7 atomic % and then sintered, the low melting point metal or compound contained in these mixed powders will melt and enter a liquid phase sintering state, allowing easy sintering at low temperatures. When the sintering process is completed, all the metals are niated metals containing B in the range of 65 to 67 at %.

Sintering according to the method of the present invention is preferably performed in a non-oxidizing atmosphere in order to prevent oxidation of the powder used as a raw material, and the particle size of the raw material powder used is preferably as fine as possible, usually 4 μm or less. The powder has an average particle size of 1 μm or less, more preferably 1 μm or less. The content of B in these raw material powders should be strictly regulated, and as described above <B:
Of course, if i is outside the range of 65 to 67 at%, it will not be possible to make all of the obtained sintered body hexagonal, and if the amount is greater than 67 at%, the density of the obtained sintered body will be reduced. If the amount is less than -65 at %, metals, monoborides, etc. will remain in the sintered body, reducing corrosion resistance and oxidation resistance.

Next, a typical method of the present invention will be described.

That is, first, a powder composition mixed at a predetermined mixing ratio is filled into a mold, cold-pressed at a press pressure of about 0.5 to 10 ton/cd, and the resulting green compact is pressed with a rubber press))0 ．．
Hydrostatic pressure of about 5 to 10 tons/cd is applied to form a powder compact with uniform pressure distribution, or by the slurry method, which is made into a slurry with a ball mill etc. and then molded using differential pressure or pressurization. The green compact is heated at 1800 to 2600° C. in vacuum or in argon at 30 to 30°C.
There is a method of sintering for 200 minutes.

Other methods include a hot press method and a hot isostatic pressure method, and a sufficiently dense sintered body can be easily obtained by using either method.

<Example> Next, the method of the present invention will be explained in further detail by showing examples.

In this example, after forming 984% by weight of HfB2 powder and 1 kg of Zr powder, a compact was obtained by rubber pressing at 4 tons/c+j, and the compact was heated in an argon atmosphere for 24 hours.
It was heated and baked at 00°C for 90 minutes. The sintered body thus obtained has a very small porosity and a transverse rupture strength of 25 kg/
It was mm'. The surface layer of this sintered body is removed by grinding, and
As a result of testing the corrosion resistance by immersing it in molten aluminum at 50℃ for 24 hours, no change was observed in both shape and mass16.
It was confirmed that the Zr-residue H fB2 sintered body had a corrosion resistance of 12% by weight. This 16% by weight Zr-residue [(
Examples of fB2 sintered bodies are No. 1, and the characteristics of sintering produced from raw material mixed powders with different compositions under the same conditions as in the above example are shown in Table 1 below. However, No. 34 in Table 1 is a comparative example.

As described above, according to the method of the present invention, liquid phase sintering is performed at a low temperature due to the low melting point metals and compounds contained in the raw material mixed powder. A sufficiently dense sintered body can be obtained using the normal sintering method, and the amount of B in the raw material mixture powder is in the range of 65 to 67 at%, so after sintering, low melting point metals and compounds can be obtained. The resulting sintered body exhibits excellent corrosion resistance because all of the metal has a hexagonal crystal system and no residual metal remains.

Patent applicant: Director of the Agency of Industrial Science and Technology (1 other person) Sub-agent Noriharu Ariyoshi

Claims (1)

[Claims] 1. At least one of TiB_2, ZrB_, HfB_2 powder and Ti, Zr, Hf, Zr
B, mixed with at least one or more of HfB powder,
A method for producing metal diboride ceramics, which comprises sintering the mixed powder. 2. TiB_2, ZrB_2, HfB_2 so that the composition of the sintered body after sintering contains 65 to 67 at% of B atoms.
At least one of the powders contains Ti, Zr, Hf, and TiB.
, ZrB, and HfB powder and B powder, and sintering the mixed powder. 3. Ti, Zr, Hf, TiB, ZrB, so that the composition of the sintered body contains 65 to 67 at% of B atoms
A method for producing metal diboride ceramics, comprising mixing at least one type of HfB powder and B powder, and sintering the mixed powder.