JP2001323302A - Molybdenum crucible and its manufacturing method - Google Patents

Abstract

(57) [Problem] To provide a molybdenum crucible which can be easily manufactured with a good yield and a method for manufacturing the same. SOLUTION: A crucible-shaped product for melting a high melting point metal oxide or the like is made of molybdenum with a pure content of 99.6% or more, and is formed substantially only by sintering and has excellent practical durability. . In order to manufacture this molybdenum crucible, a molybdenum powder having a pure content of 99.6% or more and a metal core 1 are placed in a rubber container 10.
And a step of obtaining a powder compact by performing CIP treatment and disposing the metal core from the powder compact and sintering the powder compact. This metal core 1 is C
It is configured in a split type so that the powder compact after IP processing can be easily separated and the risk of shape distortion and cracking during sintering can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crucible made of a high-melting-point metal, and more particularly to a crucible made of molybdenum, which is a high-melting-point metal used for melting high-melting-point metal oxides and the like.

[0002]

2. Description of the Related Art Generally, molybdenum products are manufactured by powder metallurgy. The method is that metal molybdenum powder having a particle size of 3 to 10 μm is placed in a rod-shaped or plate-shaped rubber container,
A green compact is produced by CIP (hydrostatic pressing) and sintered at 1800 to 2000 ° C. in a hydrogen atmosphere or vacuum.
Then, a molybdenum product is produced by performing plastic working such as rolling and rolling.

Conventionally, crucible products made of molybdenum are roughly classified into the following two methods based on powder metallurgy: (i) a method by plastic working and (ii) a method by sintering.

First, in the case of a plastically processed product, a sintered molybdenum ingot is hot-rolled to a thickness of 8 to 15 mm.
Make a molybdenum (Mo) plate of mm. The molybdenum plate is hot-worked into a bowl shape as shown in FIG. Thereafter, as shown by a cut-out portion in the reference numeral 52, the surface is externally cut (cut off the scale) to secure a desired vertical rise of the trunk and a bottom corner-R shape. The hot working is based on either forging or knurling, but both are identical in characteristics and cost. This plastically processed product has an advantage that the yield is better than that of a conventional sintered product described below.

On the other hand, a sintered product is obtained by sintering a green compact produced by CIP in a hydrogen atmosphere and thereafter cutting the inner and outer surfaces without performing plastic working. This sintered product has the advantage that the productivity is good and the crystal grains are not enlarged, so that the quality is good and the cost is low because there is no plastic working.

Conventionally, for a molybdenum crucible product having an inner diameter of 80 mm or more, the former method of plastic working is used, and a molybdenum plate having a thickness of 8 to 16 mm is formed by hot rolling a sintered molybdenum ingot. Then, the molybdenum plate is hot drawn or hot forged to form a bowl. In the final step, the surface is trimmed (cut off the black scale) to obtain the desired verticality of the body rising and the bottom corner-R shape. It is made by securing.

However, molybdenum crucible products having an inner diameter of less than 80 mm are usually formed by hot plastic working in a bowl shape because it is cheaper to cut a molybdenum block that has been subjected to hot forging or the like. No fabrication has been done.

[0008]

As described above, the plastically processed product is obtained by hot-drawing or hot-forging a Mo plate produced by hot rolling to form a bowl shape. It is made by cutting. The molybdenum crucible products obtained by the hot comparison process and the hot forging process have the same performance.

However, as shown in FIG. 4, the product portion 51 is indicated by cross hatching. As shown by the hatch, the forged crucible material 50 has many cut portions 52, and the processed product heats a molybdenum plate. After forging, the rising part does not become vertical. Therefore, the R dimension at the bottom of the product had to be large. Furthermore, these plastic working processes take a lot of processing time per product and are not mass production processes, so that productivity is poor, there is a possibility of cracking during working, and quality is poor. This was one of the causes of the high cost. In addition, due to the hot working, it is indispensable to consider the worker in the working environment and it can be said that the process is troublesome.

[0010] More specifically, a molybdenum crucible product formed by a plastic working method undergoes secondary recrystallization when used at a high temperature of 2000 ° C or higher, and the crystal grain size at that time grows to a maximum of about 100 mm. . If the crystal grain size increases and the grain boundary reaches from the inner surface to the outer surface of the crucible, when the metal oxide having a high melting point is melted, the molten metal leaks from the crystal grain boundary portion, and the crucible life is shortened.

On the other hand, the method for producing a sintered product is a method in which a green compact produced by CIP is sintered in a hydrogen atmosphere, and then the inner and outer surfaces are cut without performing plastic working. This manufacturing method has an advantage of being excellent in cost performance by omitting a series of steps of processing into a molybdenum plate material such as the above-mentioned plastically processed product and further processing into a crucible shape. Specifically, after the metal core and the powder are loaded in the rubber container, the upper and lower sides are covered with hard rubber, a green compact is obtained by CIP, and the green compact is sintered.

However, molybdenum powder is liable to crack or chip at the time of press molding, and is a powder having poor press-moldability. In particular, in the case of a crucible-shaped product, the compact is cracked after CIP or the compact and the core Is difficult to separate. Therefore, when a core is used, the taper in the length direction of the core is made 3% or more, that is, it is formed into a truncated cone shape, so that the green compact and the core are easily separated after pressing, and The inner and outer surfaces were cut by setting the size after knotting larger than the product dimensions. The yield at that time was as bad as about 30 to 60%. In addition, the numerical value of the taper described here is the ratio between the vertical diameter difference and the length of the core.

As the taper of the core increases, the compact and the core tend to separate from each other after CIP. However, since the amount of vertical correction in the subsequent process increases, the smaller the core, the better. .

However, as described above, when a core having a taper of less than 3% is used, there are cases where the green compact and the core are difficult to separate.

Accordingly, it is an object of the present invention to provide a molybdenum crucible which can be easily manufactured with good yield and a method for manufacturing the same.

Another technical object of the present invention is to provide a molybdenum crucible which is a sintered product and has the same level of quality as a plastically processed product and has a long life, and a method of manufacturing the same. .

[0017]

SUMMARY OF THE INVENTION In the present invention, a molybdenum crucible product excellent in practicability by using a sintered product which does not undergo plastic working is invented. In addition, the molybdenum crucible as a sintered product was not used because of a problem due to density instability in the process, but in the present invention, the method of the CIP process was changed, and the limitation of the pure content and the result obtained therefrom were obtained. By maintaining the predetermined density, the yield of the raw material powder is improved, and a molybdenum crucible having the same level of quality and life as a plastically processed product has been invented.

According to the present invention, in a crucible-shaped product for melting a high melting point metal oxide or the like, the pure content is made of molybdenum with a purity of 99.6% or more, and is formed substantially only by sintering without a processing step. Thus, a crucible made of molybdenum is obtained, and this crucible has excellent practical durability.

According to the present invention, the molybdenum crucible is a crucible having an inner diameter of at least 80 mm, a bottom corner shape of R10 to 25 mm, a rising body portion being vertical, and substantially no sintering. And a crucible made of molybdenum characterized by having a density of 9.8 g / cm ³ or more, which is excellent in practical durability.

Further, according to the present invention, there is provided a method for producing any of the above-mentioned molybdenum crucibles, wherein a molybdenum powder having a pure content of 99.6% or more and a metal core are placed in a rubber container. Loading the metal core so as to be disposed at the center of the powder, performing a CIP (isostatic pressing) process to obtain a powder compact, and removing and sintering the metal core from the powder compact Wherein the metal core can easily release the powder compact after CIP (isostatic pressing) treatment,
And a method of manufacturing a molybdenum crucible that is configured in a divided type so as to avoid the risk of shape distortion and crack generation during subsequent sintering is obtained.
A method for manufacturing a molybdenum crucible that can be industrially manufactured at low cost can be provided.

Further, according to the present invention, in the method for producing a molybdenum crucible, the metal core has a substantially outer cylindrical surface to facilitate separation of the molybdenum compact from the core. By using a core that does not have a tapered surface (providing a difference in diameter between the upper and lower cores) on the outer peripheral surface, a body with a vertical body is produced and the shape of the inner surface of the crucible is substantially modified. A method for manufacturing a molybdenum crucible characterized by being able to be manufactured without processing is obtained.

Here, in the present invention, the density of the molybdenum crucible is limited to 9.8 g / cm ³ , because the density is limited to 9.6 g / cm ^3.
9.7 g / cm ³ , at the bottom corner-R:
If it is used for a long time, it is easy to crack and there is a problem in practicality,
This is because it has been found that good results can be obtained with a density of at least 9.8 g / cm ³ or more.

In the case of a density of less than 9.8 g / cm ³ , even if the above-mentioned measures were taken, generation of a crack which would immediately end the main life after use was not recognized. However, in some cases, a life equivalent to or 10 to 15% longer than that of the conventional life can be obtained.
The product was not sufficiently stable due to the generation of short-life products.

In the present invention, the reason why the purity of molybdenum is limited to 99.6% is that the inclusion of unavoidable impurities is not particularly detrimental to the results of the present invention.
In the case of containing 0.5 to 0.6% of impurities, according to the experimental results, the contained impurities may react violently with molybdenum or may greatly accelerate the growth of molybdenum particles due to the influence of the impurities, and may be 99.6% or more. This is because it has been found that the use of a molybdenum material having a pure content of

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing a container used in a CIP process for manufacturing a molybdenum crucible according to an embodiment of the present invention. Referring to FIG. 1, a container 10 includes a cylindrical rubber container body 2 having one end sealed, a pedestal disk 3 made of hard rubber on the bottom side, a core 1 having one end embedded therein, and A disc 3 'made of the same hard rubber is provided after the filled molybdenum powder 4 is added. The molybdenum powder 4 is sandwiched by a pair of discs around the core 1. Except that the core 1 is different, the configuration is the same as that of the prior art.

FIG. 2 is a perspective view showing the core 1 arranged in the container of FIG. 3 (a) is a plan view of the core of FIG. 2, FIG. 3 (b) is a cross-sectional view taken along the line IIIB-IIIB of FIG. 3 (a), and FIG. It is a IIIC line sectional view. As shown in FIG. 2, the core 1 is a divided core that is divided into five parts, and includes a central wedge-shaped component 11 and outer first and second outer components 12 and 13, respectively.

As shown in FIGS. 3 (a), 3 (b) and 3 (c), the split core at the center is a wedge-shaped part 1 having a wedge shape.
1, outer shell parts 12, 13 which are other split cores
The portion corresponding to the side surface of the wedge-shaped division core 11 is formed to be inclined with respect to the central axis direction of the division core. In the cross section, the first outer part 1
2 and 12 are formed so that the outside is larger than the inside.

Further, in the present invention, a molybdenum (Mo) crucible product having improved yield and the same level of quality as a plastic processed product has been devised by changing the CIP method from the conventional one. That is, to improve the yield, by suppressing the consumption of expensive molybdenum powder,
It was also important in terms of resources and plant gross profit.

In general, the CIP method for a molybdenum (Mo) crucible-shaped product is performed with a metal core as the center.

In the present invention, in order to improve the phenomenon that the molybdenum compact and the core are not separated after the CIP step,
A split core was used during the CIP process. By using this split type core, the compact can be easily removed after CIP without breaking the compact, and before sintering, it is molded by only slightly modifying the outer diameter of the compact to form a sintered product. can do.

Next, a method of manufacturing a molybdenum crucible according to an embodiment of the present invention will be specifically described.

Referring to FIG. 1, a rubber container body (Shore hardness 50-60) made of natural rubber or neoprene rubber is used.
Put the core 1 in the degree 2). The split core 1 is fixed by a hard rubber pedestal disk 3 (Shore hardness 65 to 75 degrees). Molybdenum powder 4 is filled in the gap,
The packing density is 2.5-3.5 g / cm ³ . The density is such that the bulk density of the molybdenum powder is about 7 to 9 g / c.
m ^3, which is a region where the powder packing has a uniform packing density distribution.

A hard rubber disc (Shore hardness 65-75 degrees) 3 'is laid on the upper part, and the rubber container 10 is
The opening 5 is sealed by tightening a tape or metal fittings.

As shown in FIGS. 2, 3 (a) and 3 (b), the core 1 is made of a hard metal material such as stainless steel which is not easily deformed. The split-type core 1 is constituted by three types of five parts on the outside, each of which includes two pairs of outer parts 12, 12, 13, and 13 and a central wedge-shaped part 11 of the split-type core.

After the CIP of the crucible type product, the core is difficult to be removed from the green compact, but in the split type core 1, the central wedge-shaped part 11 can be easily pulled out. Therefore, as described above, the outer peripheral surface of the core hardly needs to be tapered in the length direction (the ratio between the vertical diameter difference and the length), and the core 1 can be easily extracted from the crucible-shaped green compact.

After the extraction, the inner surface of the green compact is hardly required to be corrected, and the outer surface only needs to be ground with sandpaper or the like.

Further, it is not necessary to increase the dimension of the bottom portion R as in the prior art, and it is possible to increase the volume.
Further, in order to form a green compact, CIP is performed at a pressure of 100 to 200 MPa in a sealed container filled with the powder.

Subsequently, normal sintering is performed to obtain a product.

The inner diameter φ150 obtained by the above method
mm, wall thickness 12mm, bottom R17mm) density 9.97g
In a crucible made of molybdenum having a purity of 99.9% / cm ³ and a temperature of 2,000 ° C. in an inert gas, when used as a melting crucible of a high-melting-point metal oxide, about 1.6 times the life is obtained. Was.

[0041]

As described above, according to the present invention,
Since no hot plastic working is performed, the process can be shortened. Since this plastic working step can be omitted, the production cost can be reduced, and a molybdenum crucible having a stable crystal structure due to the thick-walled portion and a method for producing the same can be obtained. Further, since the yield of the product is improved, a molybdenum crucible product that is less expensive than the conventional method can be provided. Here, increasing the production yield reduces the consumption of rare metal and expensive molybdenum powder, which is also beneficial from the viewpoint of resources and gross profit of the factory.

Further, according to the present invention, a molybdenum crucible having a long life can be provided.

In addition, it takes a long time for the work process per piece of the processed product, and is a troublesome process in which the work environment is indispensable because the work is performed by hot working. Since the production amount per batch depends only on the press and sintering capacity of the factory, it is possible to provide a molybdenum crucible excellent in productivity and a method for producing the same.

[Brief description of the drawings]

FIG. 1 is a sectional view of a container used for manufacturing a molybdenum crucible according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a core used for the container of FIG.

3A is a cross-sectional view of the core of FIG. 2, FIG. 3B is a cross-sectional view taken along the line IIIB-IIIB of FIG. 2A, and FIG.
FIG. 3 is a sectional view taken along line C-IIIC.

FIG. 4 is a diagram which is used to explain the production of a forged product of a crucible made of molybdenum according to the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core 2 Rubber container main body 3 Pedestal disk 3 'disk 4 Molybdenum powder 5 Opening 10 Container 11 Wedge-shaped part 12 First outer part 13 Second outer part 50 Forged crucible material 51 Product part 52 Cutting part

Claims (4)

[Claims] 1. A crucible-shaped product for melting a high melting point metal oxide or the like, which is formed by molybdenum with a pure content of 99.6% or more and formed substantially only by sintering without a processing step. Characteristic molybdenum crucible. 2. The molybdenum crucible according to claim 1, wherein the crucible has an inner diameter of 80 mm or more, a bottom corner shape of R10 to 25 mm, a rising body portion is vertical, and sintering substantially without a post-process. A crucible made of molybdenum, wherein the crucible has a density of 9.8 g / cm ³ or more. 3. The method for producing a molybdenum crucible according to claim 1, wherein the pure content is 99.90% in a rubber container.
Loading a 6% or more molybdenum powder and a metal core such that the metal core is arranged at the center of the powder, and performing a CIP treatment to obtain a powder compact; Removing the core and sintering, wherein the metal core can easily release the powder compact after the CIP treatment,
And a method of manufacturing a molybdenum crucible characterized in that the crucible is configured in a divided type so as to avoid the risk of shape distortion and crack generation during subsequent sintering. 4. The method for manufacturing a molybdenum crucible according to claim 3, wherein the metal core has a substantially outer cylindrical surface and facilitates separation of the molybdenum compact and the core. A crucible made of molybdenum characterized in that a body having a vertical shape can be manufactured by using a material having no tapered surface on an outer peripheral surface of the body, and the shape can be manufactured without substantially modifying the shape of the inner surface of the crucible. Manufacturing method.