JPS6356281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In hot isostatic pressing (hereinafter referred to as HIP), the present invention uses a metal powder-filled container in which the internal gas is sucked and degassed after filling the powder to be processed. This relates to a method of sealing while maintaining a high level of quality.

HIP is a powder filling container, a so-called capsule, filled with metal powder, etc., and after the gas inside is degassed,
This is a method in which metal powder is densified and sintered by sealing a capsule and isotropically compressing it with high-pressure inert gas at high temperatures, and has recently attracted deep interest in the field of powder metallurgy. Metals, glass, etc. are used as capsule materials because they need to be gas-impermeable even at high temperatures and exhibit plasticity under pressure, but metal is the most commonly used material because of its ease of processing and handling. has been done.

Conventionally, methods for sealing such metal capsules include:
The pressure method is commonly used.

As shown in Fig. 1, this method is as follows: (a) The gas in a metal capsule 1 (hereinafter simply referred to as a capsule) filled with the powder to be treated is removed through a degassing pipe 2.
(b) When the inside of the capsule reaches a predetermined degree of vacuum, the degassing tube 2 is sealed at a suitable position by hot pressure using a pair of hammers 5 and 5'. ) The pressure section is cut using an appropriate means such as a gas burner, hacksaw, shearing machine, etc., and (d) the cut section is welded and sealed. It is virtually impossible to completely crimp the head pressure part, and when the head pressure part is cut, some gas leakage is unavoidable.

In particular, if the degassing tube is made of a material that tends to form a strong oxide film on its surface, such as aluminum or stainless steel, the presence of the oxide film makes it impossible to achieve a perfect seal, and powder may get caught in the pressure area. If this occurs, the crimping at the pressure part tends to be incomplete, which increases the vacuum breakage during cutting.
In many cases, it became impossible to maintain a predetermined degree of vacuum inside the capsule. If the HIP process is performed with incomplete degassing in the capsule, pores will be generated in the product due to residual gas, which will lead to a decrease in product quality. In addition, when welding a cut part, welding defects are likely to occur if powder gets caught in the pressure part, and the weld part breaks during HIP processing, allowing high-pressure pressure medium gas to enter the capsule, and the HIP process This can lead to failure.

The incidence of HIP failure or defective products due to such degassing and sealing failures is by no means small during HIP processing, and this is a major factor in lowering yields and increasing costs of HIP products.

Therefore, ensuring that the capsule is completely sealed at all times is one of the important problems in HIP processing.

In view of the above-mentioned problems, instead of the conventional sealing by blow pressure, the plug is screwed to the degassing pipe and the bottom edge of the plug is tightly caught in the degassing pipe to stabilize the sealing. A sealing method has already been proposed in which the two are integrated by welding so that the seal can be maintained even in the case of However, this method requires complicated machining of the degassing tube, strict tolerances are required in the design and manufacture of the plug, and it is difficult to completely seal the vacuum container containing the degassing tube.
The complexity of the structure and the complexity of handling are the causes that hinder its practical application.

The present invention aims to provide a method for easily and reliably performing stable and complete sealing at all times using a jig that is extremely easy to handle and has a simple structure. Powder Filling Container (Capsule) In the step of filling a powder filling container with the powder material to be processed and performing hot isostatic press molding after degassing and sealing, when degassing and sealing the powder filling container, the degassing tube of the container is The method involves flattening the flat part by pressing, cutting the upper end of the flat part with the flat part being pressed with a clamping jig, and welding the cut part to weld the narrow gap in the cross section.

Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 2 is a schematic diagram showing the steps of the method of the present invention. First, in step A, the capsule 1 is inserted into the degassing pipe 2.
Through this, suction and degassing is performed by the vacuum pump 4 to reach a predetermined degree of vacuum.

In process step 2, the degassing tube 2 of the vacuum capsule is pressed at a proper position with hammers 5 and 5' to make it flat and crimped. In this process, it is difficult to completely close the inner tube conduit in the flat portion of the degassing tube.
In step C, the flat part of the degassing pipe is firmly clamped and caulked using the clamping jig 3 to completely close the pipe hole. , hacksaw, shears, etc. In this step, since the flat portion caulked by the clamping jig 3 is completely sealed, there will be no vacuum leakage due to cutting. In step 2, the cut surface is welded while it is still being clamped with the clamping jig 3, and the narrow gap in the cross section is closed by welding.
By doing so, a seal that can withstand HIP treatment is completed. In process E, the clamping jig 3 is removed. The capsule is now ready to be subjected to HIP processing.

FIG. 3 is a perspective view showing a clamping jig applied to the method of the present invention. In the figure, a pair of opposing flat plates 3a, 3a' are connected by four tightening bolts 3c provided through them.
In addition, a pair of clamping pressure bars 3b, 3b' made of a hard material are provided at corresponding positions on the opposing sides of both flat plates 3a, 3a'.
They are fixed so that their respective protruding ridge lines coincide in parallel. If you use this clamping jig to clamp the flat part of the degassing pipe so that its longitudinal direction and the clamping bar are perpendicular to each other, and tighten it with the tightening bolt 3c, the ridgeline portion of the clamping bar 3b, 3b' The flat part is strongly caulked and sealed.

Next, examples of the method of the present invention will be shown.

(Example) High speed steel powder was filled into a stainless steel capsule having a degassing tube with an outer diameter of 20 mm and an inner diameter of 10 mm, and the degassing tube was connected to a vacuum pump to perform degassing at room temperature. Furthermore, the capsule is heated to 300℃ while suction is continued to increase the vacuum level.
The air was degassed to 0.02 torr. Next, the degassing pipe was flattened by hot pressing with a hammer, and the flat part was made into a width of 100 mm.
After clamping with a clamping jig with a length of 60 mm, the upper end of the flat part was cut with a hacksaw, and the cut surface was closed by welding.
When the clamping jig was removed and the vacuum inside the capsule was measured, the initial level of 0.02 torr was maintained.

On the other hand, the same stainless steel capsule as above was degassed to 0.02 torr under the same conditions and hot-pressed using the usual hot-pressing method, and then the pressed part was cut with a hacksaw without using a clamping jig. , the cut surfaces were welded. When we measured the internal vacuum of the capsule in this case, we found that
The degree of vacuum had decreased to 0.2 torr.

As described above, according to the method of the present invention, it is possible to stably and reliably seal the capsule completely by using a jig that has an extremely simple structure and is easy to handle, and the cut end of the deaeration tube is also welded and closed. Since it is double-sealed, the degree of vacuum is maintained sufficiently even during HIP processing, and there is no concern about insufficient degassing or poor sealing. Therefore, the yield of HIP products is significantly improved compared to conventional sealing methods. and stabilize quality, etc.
This is the key to contributing to the improvement of HIP technology.

[Brief explanation of the drawing]

FIG. 1 is a schematic process diagram showing the conventionally known capsule sealing method, FIG. 2 is a schematic diagram showing the steps of the method of the present invention, and FIG. 3 is a perspective view of a clamping jig used in the method of the present invention. . 1... Powder filling container, 2... Deaeration pipe, 3... Clamping jig, 4... Vacuum pump, 5, 5'... Hammer.

Claims (1)

[Claims] 1. In the process of filling a powder material to be processed into a metal powder filling container having a degassing tube, degassing and sealing, and then performing hot isostatic press molding, when degassing and sealing the metal powder filling container, the container The degassing pipe is forged and flattened, the upper end of the flat part is cut while the flat part is pressed with a clamping jig, and the cut part is welded to weld the narrow gap in the cross section. A method for sealing a metal powder filler using the hot isostatic pressing method.