JP2879255B2 - Molten yttrium oxide molded body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molten yttrium oxide molded article exhibiting excellent corrosion resistance and thermal shock resistance at high temperatures.

<Prior Art> Conventionally, as heat-resistant materials used at high temperatures, ceramics, porcelain, magnesia, alumina, sintered bodies such as zirconia are known, and in recent years, nitrogen silicon,
A sintered body such as aluminum nitride is known. These materials are used, for example, as a metal melting crucible, a firing crucible, a firing case, a furnace wall material, a hearth material, a spark plug insulator, and the like.

However, in recent years, treatment of highly active substances, high-temperature treatment, and highly corrosive atmosphere treatment have been performed, and the life of conventional materials is extremely short. There is a disadvantage that there is no. For example, when an alumina or zirconia crucible dissolves a rare earth metal, it reacts with and contaminates the rare earth metal. There is a disadvantage that the crucible itself is eroded and its life is short. Magnesia crucibles also have the disadvantage that they do not react but are susceptible to thermal shock, crack quickly and cannot withstand multiple uses. Further, a crucible obtained by sintering yttrium oxide that does not melt does not react but is vulnerable to thermal shock, and cracks occur immediately. Further, nitride-based materials are difficult to sinter and are expensive.

<Problems to be Solved by the Invention> It is therefore an object of the present invention to provide a molten yttrium oxide molded article exhibiting excellent corrosion resistance and thermal shock resistance at high temperatures.

<Means for Solving the Problems> According to the present invention, there is provided a molten yttrium oxide molded article obtained by molding, sintering, and then sintering a powder containing yttrium oxide that has been melted, solidified and ground.

 Hereinafter, the present invention will be described in more detail.

The molten yttrium oxide molded product of the present invention is a uniform and dense molded product, and is preferably a molded product containing 50% by weight or more, particularly preferably 90% by weight or more of yttrium oxide. At this time, the content of yttrium oxide was 50% by weight.
If it is less than 1, excellent corrosion resistance and thermal shock resistance cannot be obtained, which is not preferable.

The yttrium oxide used in the present invention has, for example, a purity of 98.
% Or more is particularly preferable, but a commercially available yttrium concentrate containing less than 50% by weight of another rare earth oxide can also be used.

To prepare the molten yttrium oxide molded body of the present invention, first, after the yttrium oxide, for example, electrofusion method, arc imaging furnace, infrared imaging furnace, plasma melting method, electron beam melting method, after the molten state, , Coagulated and pulverized into powder. For the coagulation, it is preferable to coagulate, for example, at 2500 to 1000 ° C. for 30 minutes to 2 hours, and the pulverization is performed using a pulverizer such as a ball mill so that the average particle size is preferably 0.3 mm or less. Pulverization is preferred.

Then, in order to sinter the obtained yttrium oxide powder, for example, water, kerosene, an organic solvent such as polyvinyl alcohol, and a binder such as a water-soluble organic substance such as isopropyl alcohol are preferably added to the powder and mixed. After filling in a desired molding die and press molding, preferably 1200 ~
It can be obtained by sintering in a temperature range of 1800 ° C. for 3 to 24 hours. At this time, the amount of the binder added, when the binder is added to the powder, the amount of the binder is 1 to 4
It is preferable to add so as to be contained by weight%. In addition to the yttrium oxide powder, for example, a group consisting of aluminum oxide (Al ₂ O ₃ ) powder, zirconium oxide (ZrO ₂ ) powder, magnesium oxide (MgO) powder, silicon oxide (SiO ₂ ) powder and a mixture thereof. A selected sintering aid or the like can be further added as a powder component. It is preferable to add the sintering aid so that the content is 10% by weight or less based on the whole powder. If the content exceeds 10% by weight, the excellent high corrosion resistance and thermal shock resistance of molten yttrium oxide are undesirably reduced. When the sintering aid is used, the sintering temperature is preferably from 1000 to 1700 ° C., and the sintering time is preferably from 3 to 24 hours.

<Effect of the Invention> Since the molten yttrium oxide molded article of the present invention uses molten yttrium oxide as a raw material component, it exhibits excellent corrosion resistance and thermal shock resistance at high temperatures and can withstand long-term use. Therefore, the molten yttrium oxide molded article of the present invention is extremely useful, in particular, as an active metal melting crucible, a high-purity material heat treatment case, a spark plug insulating material, a furnace material and the like.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the examples,% indicates% by weight.

Example 1 30 kg of yttrium oxide having a purity of 98% by weight was melted by an electrofusion method, cooled to 1000 ° C. over 1 hour, solidified, and pulverized into a powder having an average particle diameter of 0.3 mm or less using a ball mill. Next, to 350 g of the obtained yttrium oxide powder, 10 ml of kerosene was added as a binder, mixed and stirred well, filled in a crucible mold, pressed, and then pressed at 1250 ° C. for 5 minutes.
After sintering for a time, a crucible was manufactured. The resulting crucible had an outer diameter of 50 mm, an inner diameter of 40 mm, a depth of 80 mm, and a bottom thickness of 8 mm. Then, using this crucible, under an argon atmosphere,
Nd-Fe-B alloy (Nd33.0%, Fe65.8
%, B1.2%) 300g is melted at 1500 ° C for 20 minutes and cast into a mold.
By repeating this operation, the number of times until a crack was formed in the crucible and the number of times until corrosion appeared to the extent that it could be visually confirmed were measured. Table 1 shows the results.

Example 2 As yttrium oxide, commercially available yttrium concentrate (composition Y ₂ O ₃ 60.1%, La ₂ O ₃ 0.2%, CeO ₂ 0.3
_{%, Pr 6 O 11 0.8%} , Nd 2 O 3 1.2%, Sm 2 O 3 1.4%, Gd 2 O 3 2.7
%, Dy ₂ O ₃ 11.3%, Er ₂ O ₃ 1.4%, Ho ₂ O ₃ 3.8%, Yb ₂ O ₃ 3.9
%, Other heavy rare earth 2.1%), a crucible was manufactured in the same manner as in Example 1, and the same measurement was performed. Table 1 shows the results.

Comparative Example 1 A crucible was manufactured in the same manner as in Example 1 except that yttrium oxide having a purity of 98% by weight was pulverized without melting, and the same measurement was performed. Table 1 shows the results.

Examples 3 to 12 Using yttrium oxide and a sintering aid shown in Table 2,
First, yttrium oxide shown in Table 2 was melted by an electrofusion method, cooled to 1000 ° C. over 1 hour, solidified, and pulverized into a powder having an average particle diameter of 0.3 mm or less using a ball mill. Next, the sintering aid shown in Table 2 was mixed with the obtained yttrium oxide powder, and 20 ml of isopropanol was further used as a binder.
Was added, and the mixture was thoroughly mixed and stirred. Next, after filling into a molding die and press molding, 5
After sintering for a time, a crucible having the same shape as in Example 1 was manufactured. Obtained using the crucible under an argon atmosphere, LaNi ₅ alloy (La32.1% by high-frequency heating, Ni67.9
%) Was melted at 1480 ° C. for 20 minutes, and this operation was repeated, and the number of times until a crack was formed in the crucible and the number of times until corrosion appeared enough to be visually observed were measured. Table 2 shows the results.

Comparative Example 2 Crucibles were produced in the same manner as in Examples 3 to 12, except that yttrium oxide having a purity of 98% by weight was pulverized without melting, and the same measurement was performed. Table 2 shows the results.

Examples 13 and 14 Yttrium oxide having a purity of 98% by weight (Example 13) and commercially available yttrium concentrate (Example 14) were used as yttrium oxide, and 10 ml of 3% by weight polyvinyl alcohol was used as a binder. Example 1
Press molding and sintering were performed in the same manner as in the above to prepare a test piece of 10 mmφ × 40 mm. Next, the test piece obtained was heated to about 800 ° C. with a propane gas burner, and a test of dropping water droplets and cooling was repeated 10 times, and chips, cracks and peeling were visually inspected. Table 3 shows the results. In addition, ○ in the table
Indicates a pass and × indicates a reject.

Comparative Examples 3 to 5 Example 13 was repeated, except that insoluble yttrium oxide was used instead of molten yttrium oxide, and 98% by weight of pure yttrium oxide (Comparative Example 3), alumina (Comparative Example 4) and magnesia (Comparative Example 5) were used. A test piece was prepared in the same manner as in Examples 14 and 14, and each test was performed. Table 3 shows the results. In the table, ○ means pass, and × means fail.

Examples 15 to 26 Using yttrium oxide melted by the melting method shown in Table 4, and further using a sintering aid shown in Table 4,
Except for the time sintering, a test piece was prepared in the same manner as in Examples 13 and 14, and each test was performed. Table 4 shows the results. In the table, ○ means pass, and × means fail.

Claims (2)

(57) [Claims] 1. A molten yttrium oxide molded product obtained by molding, sintering, and then molding a powder containing yttrium oxide that has been melted, solidified and ground. 2. The powder according to claim 1, further comprising aluminum oxide (Al ₂ O
₃ ) A sintering aid selected from the group consisting of powder, zirconium oxide (ZrO ₂ ) powder, magnesium oxide (MgO) powder, silicon oxide (SiO ₂ ) powder and a mixture thereof is added to the powder in an amount of 10 wt. % Of the molten yttrium oxide molded product according to claim 1.