JPS6130292A - Diffusion-joining method by hot isotropic pressure press - Google Patents

Abstract

PURPOSE:To execute diffusion joining with a hot isotropic pressure press which simplifies a joining stage by heating materials to be joined to the extent of preventing the melting thereof in a vacuum, pressurizing the materials to the extent of obviating the generation of plastic deformation to join preliminarily the materials and subjecting the materials to the hot isotropic pressure press treatment. CONSTITUTION:The materials 1 to be joined are attached to face each other via dies 3 for pressurizing in a vacuum vessel 2. The materials are pressurized by a hydraulic unit and is heated by a heater 4 by which the preliminary diffusion joining is executed. The joined materials are then held in the geseous argon maintained at a prescribed temp. and prescribed atm. pressure and are subjected to the hot isotropic pressure press treatment. The diffusion joining is thus made easy without reguiring the outside circumferential welding of the materials to be joined.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved diffusion bonding method for metals and the like by hot isostatic pressing.

In the conventional diffusion bonding method using hot isostatic pressing, a vacuum is created between the joining surfaces of the objects to be joined, and the objects are hot isostatically pressed (hereinafter referred to as HIP). need to be prevented from invading.

In the conventional HIP diffusion bonding method, in order to prevent gas from entering between the bonding surfaces, there are two methods: (1) electron beam welding the outer periphery of the objects to be bonded in a vacuum, or (2) welding the outer circumference of the objects to be bonded by The method used is to seal it in a sealed container that is evacuated to a vacuum.

However, in the method (1) above, cracks tend to occur in the welded portion when dissimilar materials are welded, and it is often difficult to make the jointed portion airtight. In addition, method (2) not only requires complicated enclosing techniques, but also makes it difficult to join hollow parts and parts with complicated shapes, and also prevents mutual diffusion between the materials of the objects to be joined and the materials of the sealed container. Due to the accompanying problems, there are drawbacks such as restrictions on the HIP processing temperature.

Purpose of the Invention The present invention has been made to overcome the drawbacks of the conventional methods, and its purpose is to simplify the joining process by HIP diffusion without using a sealed container or welding the outer periphery of the objects to be joined. To provide a joining method.

Structure of the Invention In the present invention, the objects to be joined are brought into contact with each other, heated in a vacuum to an extent that the objects do not melt, and mechanically pressurized to an extent that no large plastic deformation occurs to perform diffusion bonding. This purpose can be achieved by bonding the materials to the substrate and then diffusion bonding them in a HIP device by applying high temperature and pressure for a certain period of time.

The method of the present invention is characterized in that preliminary bonding is performed by diffusion bonding by mechanical pressure in a vacuum as a method of preventing gas from entering between the bonding surfaces of objects to be bonded by HIP.

Even if the bonding surfaces of objects to be bonded are processed to be flat, there are minute irregularities on the bonding surfaces. Figure 1 shows an enlarged view of the cross section when such surfaces are brought together. When this is mechanically pressurized and heated to an extent that it does not melt, the convex portions are deformed and brought into close contact, and bonding occurs due to the diffusion of atoms at the close contact portions. Since the bonding surface has irregularities, voids formed from the recesses are scattered, as shown in ◎ in Fig. 1. When the bonding area ratio in the diffusion bonding portion becomes 25% or more, the gap in the diffusion bonding portion is cut off from the outside.

In order to make the bonding area ratio at the diffusion bonding part 25% or more,
Although it is also related to the roughness of the bonded surface, the rate of change in the length or the rate of change (increase rate) in the cross-sectional area of the objects to be bonded is 0.05%.
To achieve the above, mechanical pressure may be applied under heating.

When the rate of change exceeds 60%, the voids disappear due to deformation.

Therefore, 005 to 6
If the rate of change of the length or cross-sectional area is set in the range of 0%, the interior of the gap in the diffusion bonding portion is a vacuum, and the gap is isolated from the outside. Next, when this is subjected to HIP processing, the voids in the bonded portion disappear, and complete bonding can be achieved.

Examples of the objects to be joined include metals, alloys, and ceramics, which can be joined in the same way, and the shape thereof may be a cylinder, a prism, a plate, or a hollow product.

Pressure may be applied mechanically through a die, or may be applied using a roll.

Preliminary diffusion bonding in vacuum and H
The IP process may be performed in a separate device, but it also has an exhaust device and a mechanism for mechanically pressurizing (IP device allows continuous bonding).

Furthermore, as shown in FIG. 5, a HIPIP apparatus capable of evacuation to a vacuum can perform preliminary diffusion bonding by heating the objects to be bonded fixed with a jig 7 under vacuum, and then perform HIP to perform diffusion bonding.

FIG. 2 shows an embodiment of the device for applying preliminary mechanical pressure in the method of the present invention, and FIGS. 3 and 4 show variations in the method of contacting objects to be welded. In the figure, 1 is an object to be welded, 2 is a vacuum container, 3 is a pressurizing die,
4 indicates a heating heater. The operation of this device is described in the Examples.

EXAMPLE SUS 304 stainless steel was used as the bonding metal. As a bonding test piece, diameter 12 possible, length 30, rm
A rod with a surface roughness of 2 .mu.m was used, and the surface to be joined was machined using a lathe. Preliminary diffusion bonding was carried out using the apparatus shown in FIG.

The objects 1 to be bonded were placed in a vacuum container 2 facing each other via a pressurizing die 3, pressurized by a hydraulic device, and heated by a heater 4 to perform preliminary diffusion bonding. Next, this joined test piece was subjected to HIP treatment. HIP treatment is 1100℃,
This was carried out by holding in argon gas at 1000 atm for 2 hours. The results were as shown in Table 1 below.

Note that the bonding area ratio was determined from observation of the tensile fracture surface of a joint that was preliminary diffusion bonded under the same conditions as in Example 1.

As shown by these results, all test pieces with a joint area ratio of 25% or more in preliminary diffusion bonding broke at the base material in the tensile test after HIP treatment, indicating that they were firmly bonded. Recognize.

The above results were obtained when the roughness of the joint surface of this test piece was 2 μm, and when the roughness of the joint surface became finer to 0.1 μm,
A bond area percentage of 25% for the preliminary diffusion bond is obtained by making the cross-sectional area or length change percentage 0.05%.

In the above embodiment, the surfaces of the objects to be welded are processed to be flat, but as shown in FIG. 3, only the outer periphery of the surfaces of the objects to be welded can be bonded. That is, it can be obtained by joining an object 1 having a flat joining surface on one side and an object 1 having a protrusion 5 on the outer periphery of the joining portion on the other side. Similar effects can be obtained in this case, and the bonding load during preliminary diffusion bonding can be reduced, making it possible to easily bond products. Alternatively, a foil or a ring 6 may be placed between the objects to be bonded along the outer periphery so that only the outer periphery of the objects to be bonded is bonded, as shown in FIG.

Effects of the Invention According to the method of the present invention, it is possible to eliminate the drawbacks of conventional HIP press diffusion bonding due to sealing in a sealed container, and there is no need to weld the outer periphery of the objects to be welded, making diffusion bonding easy. It is possible to achieve some excellent effects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the bonding state of objects to be bonded using the method of the present invention, (5) is an enlarged view of the cross section of the bonded portion before preliminary diffusion bonding, and (B) is an enlarged view of the cross section of the bonded portion after preliminary diffusion bonding. Figure, 2nd
The figure is an embodiment of a device for preliminarily applying mechanical pressure in the method of the present invention, Figures 3 and 4 are variations in the method of contacting objects to be joined, and Figure 5 is a difference in thermal expansion coefficients. FIG. 2 is a diagram of an embodiment in which the objects to be welded are pressurized using the pressure. 1: Object to be welded 2: Vacuum container 3: Pressure die 4: Heater for heating 5: Protrusion on the contact outer periphery of the object to be welded 6: Foil or ring 7: Fixing jig Patent applicant Director, Metal Materials Technology Research Institute, Science and Technology Agency Ryu Nakagawa - (A) Castle 11 Old No. 21 ¥1 Perforation 4 mouths

Claims (1)

[Claims] The objects to be joined are brought into contact and heated in a vacuum to an extent that the objects do not melt, and mechanically applied in the pressure direction of the objects, the rate of change in length or the rate of change in cross-sectional area at the joint is 0. .0
The feature is that after preliminary diffusion bonding is performed by applying pressure in the range of 5 to 60%, this is diffusion bonded by applying high temperature and isostatic pressure using a hot isostatic press machine. Diffusion bonding method using hot isostatic pressing.