Since the 1940s, vacuum brazing technology has become a very promising welding technology. Brazing copper and stainless steel parts first appeared in the electronics industry. Later, with the rapid development of the aviation industry, electronics industry, automobile industry, oxygen generator industry and rocket and missile technology, vacuum brazing technology has also been developed accordingly. Vacuum brazing technology is widely used in the manufacture of honeycomb sandwich structure panels, assemblies of jet engines and rocket missile devices, metal filters, waveguides and various radiators.
2. What is vacuum brazing
Vacuum brazing refers to a process method for brazing by using welding metal brazing filler metal without flux in a high vacuum environment.
The brazing filler metal is coated on the surface of the parts to be vacuum brazed, and then put into the vacuum brazing furnace. The vacuum system starts to work and the air is pumped out. When the vacuum degree reaches 10-3Pa vacuum state, the heating starts, and the heating reaches 10-3Pa. At the brazing temperature required by the process, the brazing filler metal begins to melt, and the liquid brazing filler metal wets the base metal and fills the gap between the drill bits under capillary action. At the same time, the solder elements diffuse to the base metal, and the base metal dissolves in the liquid solder to form a high-quality brazing joint.
3. Advantages of vacuum brazing
In the process of vacuum brazing, the workpiece to be brazed is under vacuum conditions, and there will be no oxidation, carbon increase, decarburization and pollution deterioration. The cleanliness of the welded joint is good and the strength is high.
When brazing, the brazing temperature is lower than the melting point of the base metal, which has little effect on the base material, the whole part is heated evenly, and the thermal stress is small, and the deformation can be controlled to a minimum, which is especially suitable for the brazing of precision products.
The low pressure (vacuum) around the base metal and the brazing filler metal can eliminate the volatile gases and impurities released by the metal at the brazing temperature, and can improve the performance of the base metal.
The product design approach has been broadened, and the brazable parts are allowed to have narrow grooves, extremely small transition tables, blind holes, etc. It is especially suitable for parts with closed containers and complex shapes, and can also be brazed in multiple passes at a time. It has high brazing efficiency and does not need to consider the problems of corrosion, cleaning and damage caused by flux, etc.
The heat treatment process of the workpiece can be completed at the same time during the brazing process, the appropriate welding process parameters can be selected, and the brazing can be arranged as the final process to obtain a brazed joint whose performance meets the design requirements.
There are many kinds of metals that can be brazed, especially suitable for aluminum and aluminum alloys, titanium and titanium alloys, stainless steel, high-temperature alloys, etc.; also suitable for brazing connections of titanium, zirconium, niobium, molybdenum, tungsten and other same or dissimilar metals ; Also suitable for composite materials, ceramics, graphite, glass, diamond and other materials.
4.The main application of vacuum brazing technology
Vacuum brazing is widely used in honeycomb structures as sealing components of various types of aero-engines. The brazing process of honeycomb structure is to preset the brazing material in the honeycomb core, then assemble the honeycomb and the shell, and finally adopt the vacuum brazing method For brazing, the strength of the brazed joint is about 50% of the base material. The grouped stator blades of aero-engine compressors are also manufactured by this brazing method. It consists of inner and outer rings and more than 10 blades connected by vacuum brazing. overall.
In addition, vacuum brazing is also used in the manufacture of turbine guides, guide vanes, diffusers, flame tubes, oil filters and other components in aero-engines.
AMB ceramic substrate
The AMB (active metal brazing) process is a further development of the DBC process technology. It uses a small amount of active elements Ti and Zr contained in the brazing filler metal to react with the ceramic to form a reaction layer that can be wetted by the liquid brazing filler metal. A method of joining. It not only has higher thermal conductivity and better copper layer bonding, but also has the advantages of smaller thermal resistance and higher reliability. It is more suitable for the preparation of ceramic copper-clad substrates for IGBT module packaging in electric vehicles and power locomotives. Especially in important fields such as wind energy, solar energy, heat pumps, hydropower, biomass energy, green buildings, new energy equipment, electric vehicles, rail transit, etc., the rapid development of power electronics technology will form a huge impact on ceramic copper clad laminates, the key material for IGBT module packaging. need.
Brazed diamond tools are divided into two types: surface inlay and impregnation. The surface inlay tool is to directly braze the diamond on the surface of the substrate. The impregnated tool is the sintering process of sintering diamond and other materials into a composite diamond composite body. Diffusion brazing process with base material. The brazing of diamond tools is divided into three categories: single-layer diamond tool brazing, diamond bit brazing and PDC composite brazing, which have been widely used in many industries such as stone tools, woodworking tools, aerospace and military industries.
Vehicles and boats
Vacuum brazed plate-fin oil coolers are used in cars and boats. Plate-fin oil cooler has the characteristics of high heat transfer efficiency, compact structure and light weight. It is a replacement product of today's diesel engine coolers and has been widely used in automobiles, tractors, marine diesel engines and other fields.
Air separation equipment
The use of vacuum brazing technology for the impeller in the air separation equipment greatly improves the manufacturing precision of the impeller with narrow flow channels, thus not only ensuring the design performance indicators, but also reducing the manufacturing cost and shortening the production cycle.
5. ACME vacuum brazing process and equipment
After decades of development, ACME occupies an important position in the field of vacuum welding in China and even in the world. It has formed two product series of vacuum brazing and vacuum diffusion welding. At present, nearly 200 vacuum brazing equipments are in operation on customer sites. Applications include vacuum brazing of non-ferrous metals, stainless steel, aluminum alloys, titanium alloys, superalloys, hard alloys, etc., as well as vacuum brazing between metal materials and non-metallic materials, such as vacuum brazing of copper and ceramics Wait.
Application case of ACME vacuum brazing equipment
A photo of the application site of a Japanese-funded enterprise, the AMB ceramic substrate AGV automatic production line adopts ACME 12 horizontal vacuum brazing equipment in batches. The complete set of equipment is an intelligent unmanned production line, covering the MES intelligent control system.
Photo of a domestic aero-engine application site, vertical vacuum brazing equipment, used for vacuum brazing of honeycomb seal rings, turbine guides, guide vanes, diffusers, flame tubes, oil filters and other components.
Technical advantages of ACME vacuum brazing equipment
ACME has the professional qualification of national defense special welding laboratory. In the field of vacuum brazing and diffusion welding, the process and equipment are in a leading position at home and abroad, especially the combination of process and equipment makes our vacuum brazing equipment more practical.
The heating belt adopts the back insulation technology (ACME patent), which not only increases the radiation area, but also reduces the pollution of the insulating material by the metal solder vapor;
The inlet of the vacuum system is equipped with a gas condensing phase converter and a filtering and collecting device to prevent the contamination of the vacuum pump set by the evaporating gas of the flux and brazing material, especially a large amount of lipid pollutants will be generated during the brazing process of the AMB ceramic substrate. Up to 98%, to ensure that the vacuum thermal field is clean and free of contamination;
The unique anti-pollution technology of vacuum regulation ensures long service life of vacuum regulation;
The heating chamber of the metal screen adopts a wide-width molybdenum-lanthanum alloy heating belt, and the heating belt is provided with a rib groove, which has a large radiation area and is not deformed after long-term use;
The furnace liner is optimized by modular design, and the furnace temperature uniformity is good;
Equipped with Ar gas pressurized rapid cooling system to ensure cooling effect and efficient operation.