JPH01308884A - Material-bonding process and bonded product - Google Patents

Abstract

PURPOSE:To effect the bonding of materials with each other suppressing the generation of cracks, without using an intermediate layer between material elements, by providing a material effective in restricting the extension or contraction of the material element caused by heating and cooling, attaching the material to the outer circumference of the bonding interface of elements having different thermal expansion coefficients and heating the assembled elements at a specific temperature. CONSTITUTION:A Ti foil 8 is inserted between a bonding copper material 6 and a bonding graphite material 7, both materials are made to contact with each other and a Tl layer 9 is placed at the bottom and side faces of the copper material 6. Both material elements are sealed in vacuum in a restriction material 10 made of Mo and having a form of a rectangular cylinder. The material elements maintained in the above state are placed on a specimen table 3 in an HIP furnace 2 and are heated together with the restriction material 10 at a specific temperature. At the same time, Ar gas compressed with a gas compressor 5 is introduced into the furnace 2 to effect the bonding treatment of the materials. The Ti foil 8 interposed between both material elements is melted to effect the mutual diffusion of the copper material 6 and the foil 8 through the formed liquid phase to bond both materials and bond the material 7 by the wetting and reaction with the formed liquid phase. The contraction of the material 6 is restricted with the material 10 in the cooling of the materials to normal temperature and the crack of the material 7 can be prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to material joining in which material elements having different coefficients of thermal expansion, such as graphite material and metal material, are joined to form an integral joined body. The present invention relates to a method and a bonded body thereof, and particularly relates to a material joining method and a bonded body that can be easily manufactured, with less occurrence of defects such as υl during manufacturing or use.

(Prior Art) Composite materials that exhibit high flexibility by combining multiple materials according to usage conditions are becoming popular in many fields for the purpose of enhancing heat resistance, corrosion resistance, weight reduction, etc.

Since graphite material has extremely high heat resistance, its use as a constituent material of nuclear fusion reactors has been considered in recent years. When put into practical use, it is necessary to ensure perfect bonding with the metal structural material and the heat sink material as a cooling member in order to maintain structural strength. However, since the graphite material cannot be wetted at all by the conventionally used vacuum brazing filler metal, sufficient bonding strength with the wrought material cannot be obtained.

As a countermeasure to this problem, a brazing method using an active metal as a brazing material is generally adopted. However, when a bonded body made using a brazing filler metal is used in a high vacuum, components with high vapor pressure contained in the brazing filler metal evaporate over time, greatly inhibiting beam acceleration performance in a fusion reactor. There are other problems. Therefore, in order to eliminate the influence of vaporized gas from the brazing filler metal, it is desired to directly join elements of different materials without using a brazing filler metal.

(Problems to be Solved by the Invention) However, compared to graphite materials, metal materials, particularly copper materials, have a very large coefficient of thermal expansion of about 3 to 4 times, and graphite materials have almost no ductility. For this purpose, in the process of butting and heating and joining the two, and then cooling from the joining temperature to room temperature,
Due to the difference in the amount of thermal expansion, excessive stress acts on the graphite material, which often causes cracks in the graphite material, resulting in a problem that significantly reduces the yield of products.

One way to solve the above problem is to insert a molybdenum plate as an intermediate layer, which has the same coefficient of thermal expansion as the graphite material, on the joint surface between the graphite material and the copper material, and to Japanese Unexamined Patent Publication No. 62-50073 discloses a structure that absorbs the difference in the difference between the molybdenum plate and the copper material at the joint between the molybdenum plate and the copper material and prevents cracks from occurring in the graphite material.

However, when a molybdenum plate is inserted and added as an intermediate layer to alleviate the thermal reaction as described above, the cooling efficiency of the joined body becomes significantly lower because the molybdenum material has lower thermal conductivity than the copper plate used as a heat sink material. There are problems with the decline.

That is, although the molybdenum material generally used to form the intermediate layer in conventional bonding methods has a relatively high scorching conductivity, it still has a thermal conductivity of about 6% compared to that of steel, which is a good thermal conductor.
The value is about 0%. Therefore, in order to maintain cold W efficiency equivalent to that of a bonded body made by direct bonding without inserting an intermediate layer, the thickness of the graphite material that functions as an armor or the copper material that functions as a heat sink must be set thick. It is economical.

The present invention was made in order to solve the above problems, and when joining material elements having mutually different coefficients of thermal expansion, such as graphite material and copper material, to form an integral joined body,
It is an object of the present invention to provide a method for joining materials and a joined body that does not require an intermediate layer between material elements and is less prone to cracking.

[Structure of the invention]

(Means for Solving the Problems) The present invention aims to butt material elements with different coefficients of thermal expansion, such as graphite and a metal material, graphite and a ceramic composite material, and join both material elements by diffusion bonding or chemical bonding to form an integral bond. In the method of joining materials to form a body, a restraining material that restrains expansion and contraction due to heating and cooling of the material elements is attached in advance to the outer periphery of the joining interface, and then the material elements are heated at a predetermined temperature to join the material elements and the material elements and the restraining material. , and then cooled from the bonding temperature to room temperature.

In addition, the joined body according to the present invention is a joined body that is integrally formed by butting and heating material elements having different coefficients of thermal expansion, and at least the outer periphery of the joining interface of the material elements having a large coefficient of thermal expansion is The present invention is characterized in that a restraining material for restraining expansion and contraction is disposed to face the bonding interface, and the outer circumferential side surface of the constraining material is formed to match the outer circumferential side surface of the material element.

(Function) According to the above material bonding method, a restraining material is attached to the outer periphery of the bonding interface between both material elements, and when the material elements are heated in this state to a predetermined bonding temperature and held for a certain period of time, the material elements are bonded to each other. At the same time, the side surface of the material element and the restraining material are joined. After this bonding process is completed and the temperature is cooled from the bonding temperature to room temperature,
A material element with a large coefficient of thermal expansion attempts to contract greatly, but because the material element is joined to a strong restraint material,
Contraction is prevented. At the stage when contraction begins, high stress occurs within the material element, but the material element gradually undergoes plastic deformation in a restrained state, and finally, at the stage when it is cooled to room temperature, the residual thermal stress is significantly reduced. reduced to Therefore, a material element with a small coefficient of thermal expansion does not crack due to contraction of a material element with a large coefficient of thermal expansion.

In addition, in a joined body in which a restraining material is provided around the outer periphery of joining material elements, the expansion and contraction due to heat of the joining surface during heat treatment and cooling is restrained and the binding material prevents the occurrence of cracks. Fewer zygotes can be obtained.

Furthermore, since the outer circumferential side of the above-mentioned restraining material is formed to match the outer circumferential side of the material element, it can be used as a constituent material of the joined body without removing the restraining material, and can be processed after the joining process. The molding process is simplified.

Further, even if shrinkage occurs due to thermal changes during use, the restraint material can effectively prevent cracking, and the life and reliability of the joined body can be greatly improved.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings. Figure 1 shows a hot isostatic pressing apparatus (1.IIP apparatus: Hot
FIG.

The HIP device 1 is a high-pressure container equipped with a heat insulating material.
A furnace 2, a sample stage 3 placed at the bottom of the HIP furnace 2,
A plurality of heater wires 4 which are disposed on the upper side surface of the sample stage 3 and which heat the processing material, and a gas compressor 5 which pressurizes and supplies an inert gas such as argon or nitrogen into the HIP furnace 2 are provided.

The present embodiment will be described below by taking as an example a case where a copper material and a graphite material are bonded as material elements.

First, a titanium foil 8 having a thickness of about 5 μm is inserted between a bonding copper material 6 and a bonding graphite material 7 as material elements, and the two material elements are butted. Bonded copper material 6 with high coefficient of thermal expansion
A tantalum foil 9 having a thickness of approximately 2C1m is placed on the lower part of the bottom surface and side end surfaces of. The matched material elements are vacuum-sealed in a restraining material 10 made of molybdenum and formed into a rectangular tube shape.

Next, the vacuum-sealed material element is placed on the sample stage 3 in the HIP furnace 2, and the heater wire 4 is energized. The material elements and the restraining material 10 are heated to a predetermined temperature, the gas compressor 5 is started, and argon gas is introduced into the HIP furnace 2 as a pressurized medium to perform the bonding process.

The conditions for this joining process vary depending on the type of material element, but
When bonding a steel material and a graphite material, the heating temperature is generally 900° C., the gas pressure is 1 ON gf/m, and the heating temperature is held for 60 minutes.

Under this condition, the titanium foil 8 interposed between both material elements melts to form a liquid phase, and through this liquid phase, mutual diffusion occurs between the bonding copper material 6 and the titanium foil 8, and both are bonded, and the bonded graphite material 7 is bonded by wetting and reaction with the generated liquid phase.

On the other hand, the inner wall surface of the restraining material 10 formed of molybdenum and the side surface portion 11 of the bonding copper material 6 are diffusion bonded under the same conditions. Note that since the tantalum foil 9, which is a melting point metal, is disposed on the lower side and bottom surface of the joining copper material 6, a liquid phase is not formed and the restraining material 10 and the joining copper material 6 are not joined. Therefore, only the side surface portion 11 around the bonding interface between the bonded steel material 6 and the bonded graphite I7 is bonded to the restraining material 10.

After the bonding temperature has been maintained, in the process of cooling the integrated bonded body to room temperature, the bonded steel material 6, which has a large coefficient of thermal expansion, attempts to contract more than the bonded graphite material 7, and a large stress is generated inside the member. Since the copper material 6 is restrained by the restraining material 10 at the side surfaces 11° 11 at both ends of the bonding interface, it does not shrink. Therefore, it is possible to effectively prevent cracking of the bonded graphite material 7 due to the difference in shrinkage.

Note that the lower side and bottom surface of the bonded copper material 6 are not bonded to the restraining material 10, and therefore are easily deformed.

Therefore, while cooling the joining copper material 6, both side parts 11.1
The bonded copper material 6 is plastically deformed in a direction that eliminates the stress generated during the bonding process, and the residual stress in the vicinity of the constrained bonded portion is relaxed.

According to this embodiment, it is possible to restrain the thermal shrinkage of the bonded copper material 6 at the outer periphery of the bonding interface, so that cracking of the bonded graphite vJ7 at the outer periphery of the bonding interface can be prevented.

Also, unlike conventional methods, the graphite material and steel material are directly bonded without providing an intermediate layer to alleviate thermal stress, so thermal conductivity can be significantly improved. Therefore, it becomes possible to reduce the thickness of the copper member serving as a heat sink, and the economical efficiency of the equipment improves.

Next, another embodiment of the method of the present invention will be described with reference to FIGS. 2(a) to 2(d).

In this embodiment, the material element itself having a large coefficient of thermal expansion is used also as a restraining material.

That is, as shown in FIG. 2(a), a titanium foil 8a having a thickness of several μm to several tens of μm is applied to the outer peripheral surface of a bonded graphite material 7a formed into a prismatic shape, and a restraining material is further applied to the outer peripheral surface of the titanium foil 8a. It is assembled so as to surround the joining copper material 6a which also serves as a joint. Joint portion 16a.

(The outer edges of each joining surface of 3a, . . . are seal-welded in a vacuum, and the joining copper materials 6a, 6a, . . . are fixed to each other.

Next, the fixed bonded copper material 6a and bonded graphite material 7a are placed in the LIP furnace 2 shown in FIG. Figure 2 (b)
), pressure is applied from the surroundings as shown by the arrow. The processing conditions are, for example, a heating temperature of 950°C and a gas pressure of 2000°C.
K9 f/cM and heating temperature holding time of about 60 minutes are preferable. Under this condition, the bonded graphite 4
(7a and the bonding copper material 6a are firmly bonded via the titanium foil 8a by mutual diffusion bonding and reaction bonding.

After the joining process by heating is completed, at the beginning of the process of cooling the resulting joined body from the heat treatment temperature to room temperature, the joining steel material 6a has a coefficient of thermal expansion approximately three times or more compared to the joining graphite material 7a. Therefore, the contraction R of the bonded copper material 6a is large, and the bonded steel material 68 compresses the bonded graphite material 7a in the center, as shown in FIG. 2(C).

As cooling progresses further, the temperature of the joined body reaches 400-600℃.
Since the strength of the bonded copper material 6a is extremely low when the temperature reaches this temperature, residual stress in the bonded steel material 6a can be reduced by maintaining the temperature in this temperature range for 1 to 2 hours.

After cooling to room temperature, both side surfaces 1'2a of the joined copper material 6a are joined into a rectangular tube shape as shown in FIG. 2(d).

12b is removed and the bonded graphite material 7a is further cut along the cutting line 13 at the center, thereby obtaining two sets of bonded bodies 14 in which graphite and copper are integrally bonded.

According to the material joining method according to this embodiment, in the process of cooling the joined body after the joining process, the joining copper material 6a, which also serves as a restraining material, always applies compressive stress to the joining graphite material 7a in the center direction. There is no tensile stress or bending stress applied. Therefore, cracks in the graphite material are less likely to occur.

In this example, titanium ff1sa was interposed as a member for forming a liquid phase at the bonding interface, but titanium foil 8
The same applies when a titanium film is formed on the surface of the bonded graphite material 7a or the surface of the bonded copper material 6a by a physical vapor deposition method (PVD method) such as vacuum N deposition, sputter deposition, or ion blating instead of a. It has been proven that effective results can be obtained.

Further, even when titanium powder is used, a dense bonding structure can be formed by the pressurizing action of the isostatic pressure of the HIP device. In addition to titanium (T1), zirconium (Zr) from group Ⅰ of the periodic table can be used as the intervening metal material.
A similar effect can be obtained by using a metal element such as , or hafnium (Hf 2 ).

Furthermore, the material bonding method of this embodiment can be applied to material elements having different coefficients of thermal expansion, such as graphite and graphite composites, graphite and ceramics composites, etc., and can exhibit similar effects.

Next, another embodiment of the method of the present invention will be described with reference to FIG.

In this embodiment, the bonded graphite material 7b and the bonded copper material 6b are butted together via a titanium foil 8b having a thickness of 10 μm, and a restraining material 10b is attached to the outer periphery of the bonded interface via a titanium foil 8C. The restraint material 10b is formed of, for example, a molybdenum material that has a coefficient of thermal expansion similar to that of the bonded graphite material 7b and has excellent high-temperature strength. The bonding material element equipped with the restraining material 10b is placed on the pressurizing table 15.

The side surfaces of the joining material elements are covered with an outer frame plate 16 into which a restraining material 10b is inserted. Furthermore, a pressure plate 17 is placed on the upper surface of the joining material element, and is configured to press the joining material element with a predetermined pressure intensity.

Next, in the above configuration, a bonding process is performed. The bonding process was carried out in an atmosphere with a degree of vacuum of about 2×10' Torr, at a heating temperature of 950° C., a pressure strength of 100 g/d, and a heating temperature holding time of 60 minutes.

Under the above conditions, the bonded copper material 6b and the bonded graphite material 7b are bonded to each other by the pressure applied by the pressure plate 17 and the heat applied, and the upper side surface of the bonded copper material 6b expands thermally and becomes a restraining material. It is joined to the inner surface of 10b.

After the heat treatment is completed, in the process of cooling the resulting bonded body, the bonded copper material 6b, which has a large coefficient of thermal expansion, attempts to contract, but its displacement is restrained by the restraining materials 10b bonded on both side surfaces. Bonded graphite material 7b
The occurrence of cracks at the edges of the material is effectively prevented.

Note that if a restraining material is attached to the entire side surface of the bonded copper material 6b and the contraction of J3 is restrained over the entire side surface, the residual stress inside the bonded copper material 6b increases, and the constraint material 10 after cooling increases.
When removing the bonded graphite material 7b, cracks may occur in the bonded graphite material 7b.

Therefore, it is preferable to attach the restraining material 10b only near the joint interface, as shown in FIG. For example, if the thickness of the bonded copper material 6b is about 10, the bonded copper material 6b is
The width of the restraint part is preferably about 5 shoes.

Further, an embodiment of the joined body according to the present invention will be described with reference to FIG.

The joined body according to this embodiment is a joined body 20 that is integrally formed by abutting and heating a steel material 18 and a graphite material 19 as material elements having different coefficients of thermal expansion through titanium v'I8d, and at least Steel material 1, which is a material element with a large coefficient of thermal expansion
A ring-shaped restraint material 22 for restraining expansion and contraction of the material element is disposed on the outer periphery of the joint interface 21 of No. 8 so as to face the joint interface 21, and the outer peripheral side surface of the restraint material 22 coincides with the outer peripheral side surface of the material element. It is formed to A titanium foil 8e is interposed on the contact surface where the ring-shaped restraining member 22 fits onto the outer peripheral portion of the upper surface of the copper material 18.

The restraining material 22 is preferably formed of molybdenum (MO) or a molybdenum alloy, which has a coefficient of thermal expansion similar to that of the graphite material 19, and has excellent high-temperature strength, such as tungsten or a tungsten alloy.

The front dimension of the restraining material 22 is such that the cross-sectional shape of the graphite material 19 is 25
In the case of aa+ angle, approximately 5#1 angle, cross-sectional shape is 50aI
In the case of an angle, a value of 5 to 10 seconds + angle V1 degree is preferred.

According to the joined body 20 in which the ring-shaped restraining material 22 is arranged, the steel material 18, the graphite material 19, and the ring-shaped restraining material 22 are bonded to each other by heat treatment.

Steel material 18 during cooling of joined body 20 joined together
Since the contraction of the graphite material 19 is restrained by the ring-shaped restraining material 22, cracks in the graphite material 19 are less likely to occur.

Furthermore, according to the present bonded body 20, the ring-shaped restraining material 22 is embedded around the bonding interface, and its outer circumferential surface is formed to match the outer circumferential surfaces of the steel material 18 and the graphite material 19, so that after the bonding process, In this case, it is possible to use the restraining material 22 as it is as a constituent material of the joined body without removing it. Therefore, the processing and forming process after the bonding process is simplified.

Further, since most of the joint interface is occupied by the region where the steel material 18 and the graphite material 19 are directly joined, the heat transfer efficiency is high and the cooling capacity can be set to be large.

〔Effect of the invention〕

As explained above, according to the material joining method and joined body according to the present invention, thermal contraction and deformation of the material elements around the joint can be restrained by the restraining material installed on the outer periphery of the joining interface of the material elements. .

In other words, the generation of stress due to the difference in thermal contraction between material elements whose coefficient of thermal expansion is important is avoided, and a joined body free from defects such as cracks can be obtained.

Further, since both material elements are directly joined without providing an intermediate layer for relaxing thermal stress between the material elements, it is possible to provide a joined body having a high cooling capacity with little reduction in heat transfer efficiency.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of the HrP apparatus used in carrying out the method of the present invention and the state in which material elements are joined by the method of the present invention, and FIGS. FIG. 3 is a cross-sectional view showing a second embodiment of the method of the present invention, and FIG. 4 is a cross-sectional view showing the structure of a joined body according to the present invention. 1... HIP device, 2... HIP furnace, 3... sample stand, 4... heater wire, 5... gas compressor, 6.6a
, 6b... Joined steel material, 7.7a, 7b... Joined graphite material, 8.8a, 8b, 8c, 8d, 8e-...
Titanium foil, 9... Tantalum foil, 10, 10b... Restraint material, 11... Side part, 12a, 12b... Side part, 13... Cutting line, 14... Joined body, 15 ... Pressure table, 16 ... Outer frame plate, 17 ... Pressure plate, 18 ...
・Copper material, 19...Graphite material, 20...Joint body, 21.
...Joining interface, 22...Restraint material. Applicant's agent Hisashi Hatano Figure 1--6α Figure 2

Claims (1)

[Claims] 1. Forming an integral joined body by butting material elements with different coefficients of thermal expansion, such as graphite and a metal material, or graphite and a ceramic composite, and joining both material elements by diffusion bonding or chemical bonding. In the material joining method, a restraining material is attached in advance to the outer periphery of the joining interface to restrain expansion and contraction due to heating and cooling of the material elements, and then the material elements are joined to each other and the material elements and the restraining material by heating at a predetermined temperature. A material joining method characterized by cooling from the joining temperature to room temperature. 2. The material joining method according to claim 1, wherein one of the material elements is graphite and the other is copper or a copper alloy. 3. The material joining method according to claim 1, wherein the restraining material is formed of one kind of material selected from molybdenum, molybdenum alloy, tungsten, and tungsten alloy. 4. It is a joined body formed by abutting and heating material elements with different coefficients of thermal expansion, and at least a restraining material to restrain expansion and contraction of the material elements is placed on the outer periphery of the joint interface of the material elements with a large coefficient of thermal expansion. A joined body, characterized in that the restraining material is disposed so as to face a joining interface, and the outer circumferential side surface of the constraining material is formed to match the outer circumferential side surface of the material element.