JPS6411081B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention solidifies (sinters) powder such as superalloy by HIP.
The present invention relates to a method for manufacturing capsules filled with powder when the capsules are filled with powder. (Prior art) HIP has recently begun to be widely used as a solidification technology for powders such as superalloys, but capsules filled with powder are usually made of thin sheets of mild steel or stainless steel, as shown in Figures 8 and 9. A bottom wall 20 serving as a bottom plate, a barrel wall 21, a top wall 22 serving as an upper lid, and a small-diameter degassing pipe 23 located in the center of the top wall 22 and communicating with the inside.
It is manufactured by assembling four members (elements) by welding. TIG welding is usually used for this welding, and thin plates and pipes with a thickness of several millimeters or less are used to facilitate deformation during HIP. (Problems to be solved by the invention) As is clear from FIGS. 8 and 9, the welded portion 2
Reference numeral 4 indicates each corner where the above four members intersect, and as shown in Fig. 11, air is sucked in during welding, making the weld metal part brittle and prone to micro defects such as pinholes. . To explain this point in more detail, since the materials of the four members are thin, even if welding is done from the outside, the welding heat input will cause the welded part and the inner base metal part in the vicinity to reach a high temperature state. Oxidize. The scale generated by this oxidation is quite severe even if the material is stainless steel, as shown in the photograph in FIG. Capsules are usually cleaned before use to remove foreign matter adhering to their interior surfaces, but scale created by high-temperature oxidation cannot be completely removed. If this is mixed into the powder, the required characteristics of the powder solidifying material will be impaired. Furthermore, when the capsules shown in FIGS. 8 and 9 are filled with powder and subjected to HIP, deformation as shown in FIG. 10 occurs. At this time, a large stress concentration occurs in the highly rigid part of the corner, which is the welding part 24, due to the deformation of the capsule, and together with the aforementioned embrittlement structure and micro defects, gas as a pressure medium intrudes during HIP. It may inhibit the solidification and sintering of the powder. (Means for Solving the Problems) The present invention, when welding and assembling the above four members (elements) constituting the capsule, separates the welded part from the corner part, so that the welded part can be removed during HIP. It was designed to reduce the stress applied to the pipe and prevent the pressure medium from entering during HIP, and the following configuration was adopted as a means to achieve this purpose. That is, in forming a metal capsule consisting of a bottom wall, a barrel wall, and a top wall having a degassing tube, the present invention provides a position slightly closer to the barrel wall than the bottom wall and the top wall, and a position closer to the top wall of the degassing tube. The four elements of the bottom, cylinder body, top, and degassing tube are prepared, which are separated by a plane perpendicular to the axial direction at slightly distant positions, and these four elements are assembled by welding. (Example) FIG. 1 is a sectional view of a capsule obtained by the method of the present invention. In the figure, 1 is a bottom part, 2 is a barrel part, 3 is a top part, and 4 is a degassing pipe part. In a capsule consisting of a bottom wall, a barrel wall, and a top wall with a degassing pipe, these four elements are located at a position slightly closer to the barrel wall than the bottom wall and top wall, and at a position slightly farther from the top wall of the degassing pipe. It has a shape divided by a plane perpendicular to the axial direction (not in a strict sense). Therefore, the dividing planes are the welded portions 5, and in other words, these welded portions 5 are located slightly away from the corner portions 6 of the capsule. In the figure, l is the distance from the end face of the corner part 6 to the welding part 5, preferably 5 < l < 35 (mm), if it is more than 35 mm, it is economically disadvantageous, and if it is less than 5 mm, there is no difference from the conventional one. Therefore, the purpose of the present invention cannot be achieved. Note that the materials of the four elements used in the present invention can be exemplified by stainless steel, mild steel, etc., and the welded portion 5 is formed with a groove etc. according to a usual method and is performed by TIG welding or the like. Next, the welding is carried out while an inert gas such as Ar is flowing into the capsule during welding and for a while after welding (until the temperature of the welding part decreases), or while the atmosphere is replaced with Ar, or Alternatively, the entire capsule is welded in vacuum or in an inert gas atmosphere. This type of welding is performed because the material is a thin plate, so the welding heat heats the weld and its surrounding area to a high temperature and oxidizes it, causing the weld to become brittle and cause HIP.
This is to prevent Ar gas from entering the powder, and to prevent oxide scale from entering the powder and impairing its mechanical properties. The present invention will be described below along with more specific examples and comparative examples. As shown in Figure 1, the outer diameter is 101.6φ.
SUS304TP steel pipe (tube body part 2), bottom plate (bottom part 1) and top cover (top part 3) cut from SUS304 plate,
And the degassing pipe part 4 was TIG welded at each welding part 5. The distance between the corner 6 of the bottom part 1 and the welded part 5 of the cylinder body 2 is 15 mm, the distance between the corner 6 of the top part 3 and the welded part 5 of the cylinder body 2 is 10 mm, and the distance between the corner 6 of the top part 3 and the welded part 5 of the cylinder body 2 is 10 mm. The distance between the degassing pipe part 4 and the welded part 5 was 10 mm, and the material used for each part had a wall thickness of 3 mm. FIG. 2 shows a conventional capsule of the same material and shape as the capsule of the present invention, which was manufactured by a conventional method for comparison. Figure 3 shows a capsule for testing the condition of welds when welding is performed in an atmospheric oxidizing atmosphere and in an inert gas atmosphere. W ₁ as shown,
Take the groove of W ₂ , and apply Ar gas to the inner surface of W ₁ .
W ₂ was welded from the outside in an oxidizing atmosphere of the air while flowing at a rate of 10 min, and the oxidation state near the weld on the inside was compared. The results are shown in the enlarged photographs (x1) in Figures 4 and 5. Figure 4 shows the welded part in _W2 , and Figure 5 shows the welded part in _W1 , and the inner surface of the former is normal. It is clearly seen that in the case of an oxidizing atmosphere, the welded part is severely oxidized, whereas in the latter Ar atmosphere, oxidation is prevented. Next, in order to confirm the effects of the present invention, a super heat-resistant alloy was used as the powder, and a low cycle fatigue test was conducted on the HIP solidified material. The table below shows the chemical composition of Ni-based superalloy (AF115 alloy), which is a powder produced by argon atomization. A HIP capsule was manufactured using the method shown in Figures 1 and 2.

[Table] Both HIPs were performed under the conditions of 1160℃ x 1000Kg/cm ² x 3hr, followed by heat treatment at 1180℃ x
The specimens were subjected to solution treatment and aging at 2 h/AC, 760°C x 16 h/AC to obtain test materials A (Fig. 1) and B (Fig. 2).
The fatigue test was conducted using a smooth test piece with a parallel portion of 7φ x 16, and under strain-controlled swing conditions at a strain rate of 760° C. and a strain rate of ε=0.4%/S. The results are shown in FIG. As shown in FIG. 6, the fatigue life of the HIP solidified material obtained using the capsule of the present invention is high and its variation is small. On the other hand, conventional capsules vary widely, and in extreme cases, the lifespan of conventional capsules is less than 1/10 that of healthy materials. As shown in the micrograph (×100) in Figure 7, in the case of conventional capsules, the pressure medium is released from the welded part during HIP.
Because Ar gas entered and existed as pores,
This resulted in a notch effect, resulting in a short life. From the above, it was found that the present invention is a very effective method in terms of fatigue life reliability. (Effect of the invention) The capsules produced by the method of the present invention have HIP
At times, the stress applied to the welded part can be reduced, and the occurrence of defects in the welded part can be prevented, so the intrusion of pressure medium during HIP can be prevented, and the fatigue properties of the HIP solidified material are not impaired, and the HIP solidified material of various other materials can be used. This is an excellent method for improving the reliability of important characteristic values.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a capsule manufactured by the method of the present invention, Fig. 2 is a sectional view of a conventional capsule, Fig. 3 is a sectional view of a capsule for comparison test, and Fig. 4 is a cross-sectional view of a capsule manufactured by the method of the present invention _.
Figure 5 is a micrograph comparing the oxidation state of the surface metal structure of the _W1 weld in Figure 3, Figure 6 is a fatigue test graph, and Figure 7 is a graph of Figure 2. using conventional capsules of
A micrograph of the metallographic structure showing defects in the HIP solidified material is shown. Figures 8 and 9 are explanatory diagrams of conventional capsules;
Fig. 10 is an explanatory diagram of the deformed capsule after HIP, and Fig. 11 is an explanatory diagram of air entrainment during welding. DESCRIPTION OF SYMBOLS 1... Bottom part, 2... Cylinder body part, 3... Top part, 4... Degassing pipe part, 5... Welding part, 6... Corner part.

Claims (1)

[Scope of Claims] 1. In forming a metal capsule consisting of a bottom wall, a barrel wall, and a top wall having a degassing pipe, a position slightly closer to the barrel wall than the bottom wall and the top wall, and a position of the degassing pipe. It is characterized by preparing four elements, a bottom, a cylinder body, a top, and a degassing pipe, which are divided in a plane perpendicular to the axial direction at a position slightly away from the top wall, and assembling these four elements by welding. A method for manufacturing capsules for HIP. 2. Claim 1, which is characterized in that welding is carried out while an inert gas is flowing inside the welding area until the temperature of the welded part falls during and after welding, or while the inside is replaced with an inert atmosphere. 2. Method for producing HIP capsules as described in Section 1. 3. The method for manufacturing a HIP capsule according to claim 1, wherein the welding is performed in a vacuum or in an inert gas atmosphere.