JPS62230674A - Zrb2 composite sintered body - 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] [Field of Industrial Application] The present invention has excellent mechanical properties such as corrosion resistance to molten metals, particularly molten steel and high-temperature metals, high-temperature strength, creep resistance, and abrasion resistance, as well as electrical conductivity. It has excellent properties such as protective tubes for molten metal such as molten steel, crucibles, evaporation source materials, rollers, nozzles, dies, blowing pipes, stirring blades, rotating shafts, corrosion protection rings, inner retiles, This invention relates to a ZrB2 composite sintered body that can be widely applied to heating elements, electrodes, etc.

[Conventional technology]

Conventionally, high melting point oxides such as alumina, magnesia, and zirconia have been used as ceramics for forming members that come into contact with molten metal or high-temperature metal.

However, although members made of such oxide ceramics generally have excellent fire resistance, they are inferior in mechanical properties such as high-temperature strength, creep characteristics, and wear characteristics, and they are also not dense enough in terms of thermal shock resistance. Since it is not possible to use high-quality materials, there is a drawback in that sufficient corrosion resistance cannot be obtained.

For this reason, as described in, for example, JP-A-60-21889 and JP-A-60-46987, ZrB has excellent corrosion resistance against molten metal, slag, etc.
Attempts have been made to apply Z-quality ceramics, but their practical application is far from practical. The reason for this is that ZrB2 itself has poor sinterability and poor oxidation resistance.To overcome these drawbacks, metals such as chromium, nickel, ZrO2, Aj! 20
The addition of oxides such as No. 3, nitrides such as TaN, BN, etc., and the addition of Mo.
Attempts have been made to realize this by adding silicides such as Si2, carbides such as SiC, B÷C, and combinations thereof as sintering aids or subcomponents. In particular, US Pat. No. 3,325,300 teaches that MoSi2 is added in the form of MoSi2 +84C.

In addition, the addition of SiC to US Patent No. 3,775,137, and the addition of MoSi2 + SiC + B to US Patent No. 3,325,300.
4 Addition of C, SiC in JP-A No. 61-21980
+B+C (7) addition is disclosed. These SiC
Addition, SiC+MoSi2 addition, SiC+84G addition, etc. are aimed at improving oxidation resistance by adding SiC and the like.

Moreover, Si C+ B N
(Addition of D is disclosed, but this system also aims to improve oxidation resistance by SiC and thermal shock resistance by BN.

[Problem that the invention seeks to solve]

By adding these sintering aids and subcomponents, the problems of difficulty in sintering and oxidation resistance of ZrBz itself have been considerably improved, and in particular, it has been recognized that MoSi2 has improved oxidation resistance due to the formation of a 5i02 film. Its oxidation resistance is not sufficient, and MoSi2 itself is easily attacked by molten metal.
There is a problem in that the corrosion resistance of the sintered body to molten metal deteriorates. Also, other SiC.

Corrosion resistance against molten metals such as 84C is not very good,
In particular, it is attacked very violently by molten steel. That is, adding these carbides and silicides to improve oxidation resistance causes a problem in that the corrosion resistance of ZrB2 itself to molten metal deteriorates.

Furthermore, if an attempt is made to suppress the amount of such additives to a small amount in order to maintain this corrosion resistance, the oxidation resistance will decrease, and the sinterability will also be inhibited, resulting in a decrease in the corrosion resistance itself.

The problem to be solved by the present invention is to simultaneously solve two opposing problems of oxidation resistance and corrosion resistance to molten metal in ZrB2 ceramics.

c) Means for Solving Problems] The present invention improves the corrosion resistance of SiC added to ZrB2 against molten metal, especially molten steel, by adding an Al compound, thereby providing excellent oxidation resistance and corrosion resistance. A ZrB2 composite sintered body is obtained.

The Affi compound mentioned here can be one or more of aluminum nitride, aluminum carbide, aluminum boride, aluminum oxide, etc., and aluminum nitride (AlN) is particularly effective.

In addition, the addition of this AJ compound improves the sinterability of ZrB2 itself, and a dense sintered body can be obtained, so it has corrosion resistance of 1 strength,
Wear resistance etc. are improved.

The total amount of SiC and Al compounds to be added is 4% by weight of the total amount.
If it is less than 40% by weight, the sinterability and oxidation resistance will be poor, and if it is more than 40% by weight, the corrosion resistance against molten metal will be insufficient.

If the proportion of the AJ compound in the above-mentioned contents of SiC and Al compounds is less than 5% by weight, the effect of improving the corrosion resistance against molten metal will be small, and if it is more than 741%, it will adversely affect the oxidation resistance.

In this SiC and Aj' compound, the preferred range is:
The total amount of SiC and Al compounds is 10 to 30% by weight, and AA
'This is a case where the amount of the compound is 10 to 50% by weight based on the total amount.

The remainder other than SiC and AJ compounds consists essentially of ZrB2, but up to 10% by weight of this ZrB2 is composed of other borides, such as titanium boride, chromium boride, molybdenum boride,
Tungsten boride, niobium boride, lanthanum boride, yttrium boride, hafnium boride.

It can be replaced with a boride such as uranium boride. Further, a small amount of carbon may be included since it promotes sinterability, but it is preferably 5% by weight or less.

The particle size of the raw material powder is preferably small from the viewpoint of sinterability, corrosion resistance, and oxidation resistance, and the average particle size is 10 μm or less, especially 5.
It is preferably less than μm.

It has been experimentally confirmed that the addition of the Al compound improves corrosion resistance to molten metal, especially molten steel.

The cause is not clear, but A7! This is thought to be due to a change in the organizational morphology of the reaction product film due to the addition of the compound.

In other words, this changed reaction product film exhibits excellent corrosion resistance, especially against molten steel, and prevents direct contact between SiC and molten steel, or the form of the reaction product film is so dense that it physically resists S.
It is thought that by preventing direct contact between iC and molten steel, the function of preventing SiC from being decomposed and dissolved into molten steel is increased.

Furthermore, among these Al compounds, AlN is known to form a solid solution with SiC over the entire region, and it is thought that the uniform solid solution in SiC increases this effect. In fact, according to observation using an analytical electron microscope (EPMA), AlN and S
It can be seen that iC is uniformly distributed in the same region except for ZrB2.

In the present invention, when manufacturing a ZrB2 composite sintered body, the raw material mixture is usually prepared using these three types of powder, but Aj
! Substances such as N that form a solid solution with SiC are 5iC-Aj! during the powder synthesis stage! A powder synthesized as a solid solution of N may be mixed.

Sintering can also be carried out by filling a graphite container with a mixture of these materials and performing pressure sintering in an inert or reducing atmosphere such as vacuum, argon, helium, or carbon oxide, but the addition of an Al compound improves sinterability. Because of this, pressureless sintering is possible.

Therefore, even complicated shapes can be easily sintered, which is very economically advantageous for ceramics that are expensive to machine.

Sintering temperature is 1700-2200℃, sintering time is 1-1
0 hours is preferred.

In addition, this ZrB2 composite sintered body has a relatively low electrical resistance in the grain boundary phase formed by SiC and Al compounds.
Electrical discharge machining can be performed very easily without disturbing the electrical conductivity of the material. Therefore, it is very advantageous for processing complex shapes, and can also be used as a corrosion-resistant electrode or heating element.

Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example 1] 82 parts by weight of ZrB2 powder with an average particle size of 3 μm, average particle size of 0
．． 2 parts by weight of novolac resin was added to a mixed powder consisting of 14 parts by weight of SiC powder of 4 μm and 4 parts by weight of AJN powder of 1 μm in average particle size, and the mixture was pulverized and mixed in acetone using a SiC ball mill for 50 hours. This slurry is dried and granulated,
It was molded under a hydrostatic pressure of 3000 kg/c+J.

The obtained molded body was heated in a static gas atmosphere and sintered at 2000° C. for 2 hours. The bulk density of the obtained sintered body was 98.3% and 3
The point bending strength was 61 kg/mm2.

In addition, a square bar-shaped sample was cut out from this sample and subjected to a molten steel immersion test and a cobalt immersion test. Molten steel immersion test
Using a high frequency induction furnace, the pieces were immersed in molten steel at 1600°C for 5 hours, and the erosion speed was measured.

The erosion speed according to this test was 0.05 m+s/hr. In the cobalt immersion test, a resistance furnace was used, and the material was immersed in Ar gas at 1500° C. for 2 hours, and the erosion speed was measured. The erosion speed in this test was 0.1 mm/hr.

In addition, as an oxidation test, 10
After holding for a period of time, the weight change was measured. As a result, the oxidized weight was 0.5 mg/aJ.

[Comparative Example 1] 82 parts by weight of ZrB2 powder with an average particle size of 3 μm, average particle size of 0
．． A mixed powder consisting of 18 parts by weight of 4 μm SiC powder was pulverized and mixed in acetone for 50 hours using a SiC ball mill. This slurry was dried and granulated, filled into a graphite mold, and pressure sintered at a pressure of 400 kg/cd, a sintering temperature of 2050° C., and a holding time of 1 hour. The bulk density of the obtained sintered body was 9
At 7.8%, the three-point bending strength was 42 kg/mm2. A square rod-shaped sample was cut out from this sample and subjected to a molten steel immersion test and a cobalt immersion test. Molten steel immersion test
Using a high frequency induction furnace, the pieces were immersed in molten steel at 1600°C for 5 hours, and the erosion speed was measured.

The erosion speed according to this test was 0.5 mm/hr.

The cobalt immersion test uses a resistance furnace at 150°C in Ar gas.
It was immersed at 0°C for 2 hours, and the melting speed of tjI was measured. The erosion speed according to this test was 0.8 m+m/hr.

In addition, as an oxidation test, 10
After holding for a period of time, the weight change was measured. As a result, the oxidized weight was 1.0 mg/-.

[Example 2] Mixture consisting of 50 to 97 parts by weight of ZrB2 powder with an average particle size of 3 μm, 2 to 40 parts by weight of SiC powder with an average particle size of 0.4 μm, and 1 to 10 parts by weight of AlN powder with an average particle size of 1 μm. 2 parts by weight of novolak resin was added to the powder, and molding and sintering were performed in the same manner as in Example 1 to obtain a sintered body.

Bulk density 1 bending strength of sintered bodies 1 to 13 of Examples.

Table 1 shows the results of the molten steel immersion test and #I conversion test.

The test conditions were the same as in Example 1.

In addition, as comparative examples, samples -1 to -3 that were molded and sintered in the same manner as comparative example 1 are shown in Table 2.

Table 1 Table 2 * indicates the weight percent of the composition other than ZrB2.

[Example 3] 82 parts by weight of ZrB2 powder with an average particle size of 3 μm, average particle size of 0
．． A sintered body was obtained in the same manner as in Example 1 by adding 2 parts by weight of novolak resin to a mixed powder consisting of 14 parts by weight of 4μ-SiC powder and 4 parts by weight of 11 compound powder. Table 3 shows the type, bulk density, erosion speed, and oxidation weight gain of this Al compound.

Table 3 [Example 4] 77 parts by weight of ZrB2 powder with an average particle size of 3 μm, average particle size of 5
μm Ti 825 parts by weight, average particle size 0.4 μm SiC
A sintered body was obtained in the same manner as in Example 1 by adding 2 parts by weight of novolac resin to a mixed powder consisting of 14 parts by weight of powder and 4 parts by weight of AJN powder having an average particle size of 1 μm. The bulk density of the obtained sintered body was 98.0% of the theoretical density, and the three-point bending strength was 70.1.
kg/ff1m''.Furthermore, the melting speed in molten steel was 0.08m+w/hr.

〔Effect of the invention〕

The sintered body of the present invention has improved sinterability, oxidation resistance, and corrosion resistance against molten metal without impairing the excellent mechanical properties of ZrBz itself such as high temperature strength, creep resistance, and wear resistance. It is something.

Claims (1)

[Claims] 1. The total amount of SiC and Al compounds is 4 to 40% by weight, and A
A ZrB_2 composite sintered body, characterized in that the amount of the L compound is 5 to 70% by weight of the total amount of SiC and Al compounds, and the balance other than the SiC and Al compounds consists essentially of ZrB_2. 2. ZrB according to claim 1, characterized in that the total amount of SiC and Al compound is 10 to 30% by weight
_2 Composite sintered body. 3. The total amount of Al compounds is 1 of the total amount of SiC and Al compounds
The ZrB_2 composite sintered body according to claim 1, characterized in that the ZrB_2 composite sintered body contains 0 to 50% by weight. 4. Z according to claim 1, wherein the Al compound is one or more of aluminum nitride, aluminum carbide, aluminum boride, and aluminum oxide.
rB_2 composite sintered body. 5. The ZrB_2 composite sintered body according to claim 1, wherein the balance contains 5% by weight or less of carbon.