DE-102008058773-B4 - Connection method

Abstract

A diffusion joining process in which, during the heating of a first joining object (W1) and a second joining object (W2) made of metal and in contact with each other, pressure is applied to the first joining object (W1) and the second joining object (W2) and atoms from the first joining object (W1) diffuse into the second joining object (W2), while atoms from the second joining object (W2) diffuse into the first joining object (W1), thereby joining the two joining objects (W1, W2) together, wherein the process comprises the following steps: Inserting the first connecting object (W1) and the second connecting object (W2) into a connecting container (12) and evacuating the connecting container (12) to a pressure on the order of 10⁻¹ Pa, Supplying nitrogen gas to the evacuated connecting vessel (12), wherein the pressure in the connecting vessel (12) is controlled to 3 to 10⁵ Pa, and Heating the first connecting object (W1) and the second connecting object (W2) inside the connecting container (12), in which the nitrogen gas has a pressure of 3 to 10⁵ Pa, whereby pressure is applied to the first connecting object (W1) and the second connecting object (W2), wherein the first connecting object (W1) consists of a steel material, a nickel alloy or a copper alloy, and wherein the second connecting object (W2) consists of a steel material, a nickel alloy or a copper alloy.

Inventors

• Osamu Ohashi
• Keiichi Minegishi
• Yasunori Yoshida
• Kouji Wada

Assignees

• SMC KABUSHIKI KAISHA

Dates

Publication Date

20260513

Application Date

20081124

Priority Date

20071129

Claims (5)

1. A diffusion joining process in which, during the heating of a first joining object (W1) and a second joining object (W2), which are made of metal and are in contact with each other, pressure is applied to the first joining object (W1) and the second joining object (W2), and atoms from the first joining object (W1) diffuse into the second joining object (W2), while atoms from the second joining object (W2) diffuse into the first joining object (W1), thereby joining the two joining objects (W1, W2) together, the process comprising the following steps: placing the first joining object (W1) and the second joining object (W2) into a joining vessel (12) and evacuating the joining vessel (12) to a pressure on the order of 10⁻¹ Pa, supplying nitrogen gas into the evacuated joining vessel (12), the pressure in the joining vessel (12) being controlled to 3 to 10⁵ Pa, and heating the first connecting object (W1) and the second connecting object (W2) within the connecting container (12), in which the nitrogen gas has a pressure of 3 to 10⁵ Pa, wherein pressure is applied to the first connecting object (W1) and the second connecting object (W2), wherein the first connecting object (W1) is made of a steel material, a nickel alloy or a copper alloy, and wherein the second connecting object (W2) is made of a steel material, a nickel alloy or a copper alloy.
2. Procedure according to Claim 1 , characterized in that the heating of the first connecting object (W1) and the second connecting object (W2) is carried out by supplying electric current.
3. Procedure according to Claim 1 , characterized in that the heating of the first connecting object (W1) and the second connecting object (W2) is carried out by high-frequency heating.
4. Method according to one of the preceding claims, characterized in that materials are used for the first compounding object (W1) and/or the second compounding object (W2) which are capable of causing nitrogen to enter a solid solution.
5. Procedure according to Claim 4 , characterized in that nitrogen-doped stainless steel is used for the first connecting object (W1) and/or the second connecting object (W2).

Description

Background of the invention The present invention relates to a bonding method by which objects to be joined are connected by applying negative pressure and heating a plurality of bonding objects that are in contact with each other. Diffusion bonding is a known method for joining such objects. In this process, the objects in contact are heated by applying electrical energy, high-frequency heating, or similar methods, causing atoms to distribute within the contact area. As a result, the two objects are bonded together. When electrical energy is applied, all types of metallic materials, including steel, nickel alloys, and copper alloys, are suitable as objects to be joined (conductive bodies). In the event that diffusion bonding is carried out with the aforementioned metallic components, an oxide layer (oxide film) forms on the surface of the components if there is an excess of oxygen in the bonding environment. The temperature of this layer increases with the application of current. In this case, the diffusion of atoms is hindered by the oxide layer, raising concerns that the bond strength (bonding force) of the bonded area cannot be guaranteed. To address this concern, the electrical current supply and the creation of a vacuum in such metallic compounds are generally carried out in a bonding vessel under a strong vacuum, or in a bonding vessel containing an inert gas atmosphere. In the case where a strong vacuum is created in the bonding vessel, a rotary pump and a diffusion pump are combined to evacuate the vessel. This sets the pressure in the bonding vessel to approximately 10⁻³ Pa. If it is necessary to reduce the pressure further, a turbomolecular pump can be used in addition to the two pump types mentioned above. In cases where an inert gas atmosphere is provided in the connecting vessel, argon, helium, or similar gases were primarily used as the inert gas. Depending on the circumstances, nitrogen was also used (see, for example, the Japanese patent disclosure). JP 2006-315040 A ). If a diffusion pump or a turbomolecular pump is used to generate a strong vacuum in the connecting vessel, the investment in equipment increases significantly due to the high cost of such pumps. If an inert gas atmosphere is used, it is not easy to completely remove the original atmosphere (oxygen) from the connecting vessel. Therefore, the formation of an oxide layer cannot be entirely avoided. Since the cost of argon, helium, or similar gases is comparatively high, the operating costs for carrying out the diffusion connection also increase. Recently, attention has focused on nitrogen-doped stainless steel, which contains a specified amount of nitrogen to improve corrosion resistance. However, when this material is fusion-welded, it has been observed that the nitrogen content in the joint area decreases. This naturally leads to concerns that corrosion resistance may also decrease. The DE 44 30 779 C2 This describes a method for producing a diffusion bond at low pressure. In one embodiment, the diffusion bonding process is carried out in a protective or reducing atmosphere, wherein the workpieces and a plate made of a superplastic alloy are enclosed in a heat-resistant steel chamber, which is filled with protective or reducing gas via a gas cylinder. Subsequently, the plate and the workpieces are heated, and pressure is applied perpendicular to the surface of the plate. Pressure and temperature are maintained until a diffusion bond between the plate and both workpieces is achieved. The DE 29 40 959 C2 This describes a method and a device for creating a shielding gas atmosphere in a welding booth for gas metal arc welding (GMAW). The welding booth is first placed under a relatively low vacuum in the range of 133 to 400 Pa before normal atmospheric pressure is restored by introducing the shielding gas. The shielding gas is not specified. From the DE 101 62 937 A1 This process involves joining dissimilar materials under a protective gas atmosphere. In metal inert gas welding (MIG/MAG welding), an electric arc burns within a shielding gas mantle. Argon and/or helium are used as inert and protective gases. Additionally, an active gas is used, which advantageously influences the process. The active gas components of the protective gas are one of the following gases or a mixture of the gases O₂ , CO₂ , NO, N₂O , or N₂ . The DE 601 10 312 T2 This relates to an electrical joining method and a corresponding device for joining several elements, wherein these are positioned so that their joining surfaces abut each other and a temporary connection is created by applying a pulsed current to the elements under pressure. In a subsequent step, the full connection strength is achieved by subjecting the temporarily joined elements to a heat treatment with mutual diffusion at a desired temperature and in an inert atmosphere. document DE 30 03 186 A1 discloses a method for joining components made of silicon composite materials, which are joined