JPH1119780A - Hip joining method of beryllium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent peeling due to difference in a thermal expansion coefficient of materials in use by covering the surface of different kinds of material with tile- shaped beryllium pieces, whose sides are in contact with each other in the bottom only, with the parts other than the bottom forming a space of a specific width between the adjacent pieces, and making an HIP joined body under specific conditions. SOLUTION: On the surface of a stainless steel plate, copper plate or their composite material 1, tile-shaped beryllium pieces are laid, whose sides are in contact with each other, with the parts other than the bottom forming a space g of 0.2-2.5 mm between the adjacent pieces. This entirety, after being covered with a sheath material, is given an HIP processing under the conditions, a temperature of 430-650 deg.C and a pressure of 80-130 MPa, joined and made a beryllium joined body. Consequently, it enables, in the case of a neutron reflector for example, omission of the grooving on a joined body beryllium plate face which is performed for the purpose of relaxing a thermal stress by the difference in a thermal expansion coefficient between the top and bottom materials used. Incidentally, at the time of the HIP processing, the thickness of the sheath material is made larger in the side face than in the top/bottom faces, reducing pressure transmission from the side face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a beryllium,
The present invention relates to a beryllium HIP bonding method capable of effectively bonding with a dissimilar alloy such as a copper alloy or stainless steel.

[0002]

2. Description of the Related Art Recently, beryllium has been used for applications such as neutron reflectors for material testing furnaces and reflectors for large neutron accelerators. In such applications, beryllium pebbles are usually used in large-sized structural members, but in order to simplify the structure, beryllium plates are dispersed in stainless steel such as SUS 304 or alumina dispersion. A copper alloy such as reinforced copper (DSCu) and a composite material joined to a laminate of both are being studied. Also, as the bonding method, the HIP bonding method is receiving attention.

In the case of using such a beryllium joined body, if the temperature rises or falls during its use, separation occurs at the joint interface due to the difference in the coefficient of thermal expansion between beryllium and stainless steel or a copper alloy. Because of the possibility, a slit is formed in the beryllium plate for the purpose of relieving the thermal stress between dissimilar metals resulting from the difference in the coefficient of thermal expansion.

[0004]

Conventionally, such slit processing has been performed by machining, electric discharge machining or the like after HIP processing. However, in the above method, deep groove processing of a narrow groove is required, and in addition to the fact that Be is a difficult-to-cut material, the difficulty in working is high, and a problem remains where a great amount of time is required. Was.

[0005] The present invention advantageously solves the above-mentioned problems. In addition to devising the shape of a Be piece as a bonding material and optimizing HIP processing conditions, slit processing in a post-process can be performed. An object of the present invention is to propose a new beryllium HIP bonding method which is unnecessary.

[0006]

That is, the present invention provides:
When beryllium and dissimilar materials are HIP-bonded, the sides of the dissimilar materials are in contact with each other only at the bottom at the bottom, and the sides other than the bottom have a side shape that forms a gap of 0.2-2.5 mm between adjacent sides. After covering with a piece of beryllium and covering the whole with a sheath material, temperature: 430 to 650 ° C, pressure: 80
This is a beryllium HIP bonding method, characterized in that HIP processing is performed under conditions of up to 130 MPa.

In the present invention, typical dissimilar materials include stainless steel, copper alloys, and composites thereof.

In the present invention, the thickness of the sheath material is
It is advantageous to reduce pressure transmission from the side surface by making the material to be processed thicker on the side surface than on the upper and lower surfaces.
Here, the thickness of the sheath material on the side surface side of the material to be treated is preferably 1.5 to 3.0 times that of the upper and lower surface sides. Can be increased to 180 MPa.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. Now, in order to omit the slit processing after the HIP processing, as shown in FIG. 1A, it is conceivable to arrange Be pieces 2 on the surface of a dissimilar material 1 such as stainless steel or a copper alloy with a gap. However, in the normal case, due to the pressure during the HIP, the gap between the Be pieces disappears as shown in FIG. In addition, number 3 in the figure is a sheath material.

Therefore, in the present invention, the shape of the Be piece 2, particularly the shape of the side, is processed into a shape as shown in FIG. That is, each side contacts each other only at the bottom, and other than the bottom is processed into a tile shape having a side shape in which an appropriate gap g is formed between adjacent ones. Here, the bottom thickness t as a contact area of each Be piece 2 is preferably about 0.5 to 5.0 mm. That is, if the bottom thickness t is less than 0.5 mm, the above-mentioned gap g formed by the lateral pressure at the time of pressurization may disappear, while if it exceeds 5.0 mm, it may be caused by a difference in thermal expansion. This is because thermal stress between dissimilar metals cannot be sufficiently reduced. The thickness of the Be piece is usually about 10 to 100 mm. Also, the gap g
Is preferably about 0.2 to 2.5 mm. This is because if the gap g is less than 0.2 mm, the thermal stress between dissimilar metals cannot be sufficiently alleviated.
If the thickness exceeds 2.5 mm, the function as a neutron reflector deteriorates.

Further, the planar shape of the Be piece 2 is shown in FIG.
Squares, triangles, and parallelograms, as shown in (a), (b), and (c), are particularly advantageous, but are not limited thereto. Any shape can be used as long as it can be formed.

If the above-mentioned Be piece shape is used, H
Even if lateral pressure acts during IP processing,
Be pieces do not shift. Nevertheless, even with such a structure, if the processing conditions during HIP are too high and high pressure, plastic deformation of Be also occurs, and the gap may be filled as shown in FIG.

However, in this regard, HIP
This can be advantageously solved by suppressing the temperature and pressure during the processing from the stress-strain curve of Be within a range allowable as strain. FIG. 5 shows a stress-strain curve of Be containing about 1 wt% of BeO. According to FIG. 5, when the allowable strain of Be after the treatment is 0.01.
Under conditions of a temperature of 427 ° C, 19.2 KSI or less, ie 13
If the pressure is 2.2 MPa or less, Be does not warp any more, so that a narrow groove can be left.

Here, if the HIP temperature is lower than 430 ° C., the joining of Be to stainless steel and copper alloy is extremely difficult even if the intermediate insert layer is used, while 6
If the temperature exceeds 50 ° C, the pressure must be reduced to 79.2 MPa or less, but at such a low pressure, sufficient bonding reliability cannot be ensured.

Therefore, in the present invention, the HIP processing conditions are limited to the range of temperature: 430 to 650 ° C. and pressure: 80 to 130 MPa. In addition, when joining conventional Be with stainless steel and copper alloy, higher temperature and higher pressure conditions are adopted from the viewpoint of joining efficiency, usually 750 to 850 ° C,
Joining has been performed under a considerably high temperature-pressure condition of 180 to 220 MPa, and there has been no trial of joining at relatively low temperature and low pressure as in the present invention.

When a Be piece and a different material such as DSCu are joined at a relatively low temperature as described above, pure Cu, Al—Ti, Ti—Cu, and Al—Ti— It is preferable to provide a soft intermediate layer (about 2 μm to 2 mm) of Cu or the like. If necessary, a barrier layer (several Å to 0.2 mm) of Ti or Ni—Ti may be provided in order to suppress the growth of the intermetallic compound due to excessive diffusion of Be. In addition, as a method for forming the intermediate layer, any conventionally known method such as a method for inserting a foil and a method for forming a film by PVD is suitable.

By the way, as is apparent from the above description, when the narrow groove slit of Be is formed from the initial state by a combination of the shape of the Be piece and the HIP processing conditions, the plastic deformation of Be in the lateral direction is reduced. Due to the need to minimize it, the HIP processing conditions for achieving sufficient bonding are relatively narrow. However, in this regard, the allowable pressure range can be increased by increasing the thickness of the sheath material on the side surface side compared to the upper and lower surface sides.

That is, as shown in FIG. 6, the thickness of the sheath material on the side surface is increased with respect to the upper and lower surfaces. Here, a description will be given by taking a typical SUS 304 as an example of the sheath material.
In the case of mm, by increasing the thickness of the side surface to about 4 to 6 mm, the pressure from the side surface can be effectively reduced. Therefore, when such a different thickness sheath material is used,
The additional pressure can be raised to 180 MPa.

[0019]

Example 1 In order to HIP-bond Be (grade S65C) to one surface of DSCu, a tile-shaped Be piece having the shape shown in FIG. 7 was prepared. An Al-Ti-Cu composite film (thickness: 40 µm) was previously formed on the bottom surface of each Be piece by a PVD method. After arranging such Be pieces in 5 rows each on the length and width on the DSCu and sheathing the whole with SUS 304 having a thickness of 2 mm, the temperature is 55
HIP treatment was performed for 2 hours under the conditions of 0 ° C. and a pressure of 110 MPa.

After the HIP treatment, the sheath material was peeled off and the appearance was observed. As a result, the same appearance as the initial stage was obtained. That is, the slit groove formed before the bonding remains with almost the same slit width, and the change in the slit width was suppressed to 0.1 mm or less. The joining strength between the Be piece and DSCu was 220 MPa in shear strength, and a sufficiently satisfactory joining strength could be obtained in practical use.

Example 2 As in Example 1, a square having a side of 25 mm and a bottom thickness t was used.
Is 1.0mm and the gap g is 1.0mm.
A piece was prepared. On the bottom surface of the Be piece, a Cu thin film (thickness: 20 μm) was previously formed by a PVD method. After arranging such Be pieces in four rows vertically and horizontally on DSCu and sheathing the whole with SUS 304, temperature: 540 ° C, pressure:
HIP treatment was performed for 2 hours under the condition of 120 MPa. At this time, the thickness of the sheath material was 3 mm for the upper and lower surfaces and 5 mm for the side surfaces.

After the HIP treatment, the sheath material was peeled off and the appearance was observed. The change in the slit width was 0.1 mm or less, and the joint strength between the Be piece and DSCu was 200 MPa in shear strength.
a was good.

[0023]

As described above, according to the present invention, when HIP bonding of beryllium to a dissimilar material is performed, the HIP process can be performed effectively without losing the slits provided in the beryllium. This eliminates the need for slit processing in the post-process, which is advantageous in terms of process saving and cost reduction.

[Brief description of the drawings]

FIG. 1 shows a state before HIP processing when HIP processing is performed in a state in which Be pieces are arranged on a surface of a dissimilar material simply with a gap therebetween (a).
FIG. 9 is a diagram showing a comparison of differences in the arrangement of Be pieces after processing and (b).

FIG. 2 is a diagram showing a preferred side shape of a tile-shaped Be piece according to the present invention.

FIG. 3 is a diagram showing a preferred planar shape of a tile-shaped Be piece according to the present invention.

FIG. 4 is a diagram showing an aggregation state of Be pieces when HIP processing is performed under high temperature and high pressure.

FIG. 5 is a stress-strain curve diagram of Be.

FIG. 6 is a schematic diagram showing a case where the thickness of a sheath material is larger on the side surface than on the upper and lower surfaces of the material to be processed.

FIG. 7 is a diagram illustrating a preferred side shape of the tile-shaped Be piece in the first embodiment.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B23K 103: 18

Claims (4)

[Claims] When a beryllium and a dissimilar material are HIP-bonded to each other, the sides of the dissimilar material are in contact with each other only at the bottom, and the sides other than the bottom form a gap of 0.2 to 2.5 mm between adjacent parts. The beryllium HIP contact is characterized in that a tile-shaped beryllium piece to be shaped is laid, and the whole is covered with a sheath material, and then subjected to HIP treatment under the conditions of temperature: 430 to 650 ° C and pressure: 80 to 130 MPa. legal. 2. The method of claim 1, wherein the dissimilar material is one of stainless steel, a copper alloy, and a composite thereof. 3. The HIP contact of beryllium according to claim 1, wherein the thickness of the sheath material is made thicker on the side surface than on the upper and lower surfaces of the material to be processed to reduce pressure transmission from the side surface. legal. 4. The method of claim 3, wherein the upper limit of the additional pressure during the HIP process is increased to 180 MPa.