Vacuum brazing refers to the heating of workpiece in the vacuum chamber, which is mainly used for the welding of high-quality products and easily oxidized materials. The vacuum brazing furnace includes a pressure vessel with a cylindrical side wall and a door, the size and position of which are designed to close one end of the cylindrical side wall. The workpiece processing system is installed on the pressure vessel door to support the metal workpiece for heat treatment or brazing. The workpiece processing system includes a device for rotating the workpiece during the processing. The vacuum system can be connected to the workpiece so that the internal pressure of the workpiece is lower than atmospheric pressure during the brazing process.
Since 1940s, vacuum brazing technology has become a very promising welding technology. First appeared in the electronic industry brazing copper and stainless steel parts, then applied to the aviation industry, atomic energy industry, in 1959 began to apply to the manufacture of stainless steel plate fin heat exchanger. Now it is widely used in plate fin heat exchanger and cooler of air separation equipment, petrochemical equipment, engineering machinery, vehicles, ships and household appliances.
Due to the incomparable advantages of vacuum brazing technology, it has been rapidly developed and widely used in the world’s industrial developed countries
1. Vacuum brazing can improve the corrosion resistance of products, avoid all kinds of pollution and pollution-free treatment equipment cost, and have good safety production conditions because of no flux;
2. Vacuum brazing not only saves a lot of expensive metal flux, but also does not need complex flux cleaning process, which reduces the production cost;
3. Vacuum brazing filler metal has good wettability and fluidity, which can weld more complex and narrow channel devices. Vacuum brazing improves the yield of products and achieves a solid and clean working surface;
4. Compared with other methods, the internal structure and fixture of the furnace have long service life, which can reduce the maintenance cost of the furnace;
5. There are many materials suitable for vacuum brazing, such as aluminum, aluminum alloy, copper, copper alloy, stainless steel, alloy steel, low carbon steel, titanium, nickel, inconei, etc., which can be brazed in vacuum furnace. The designer determines the required materials according to the use of brazing devices, among which aluminum and aluminum alloy are most widely used.
Vacuum brazing furnace is the main brazing equipment in Aeroengine manufacturing.
2. Construction machinery
Vacuum brazing small and medium-sized bit is an example. Small and medium-sized bit is widely used in metallurgy, geology, coal, water conservancy, railway, military and other construction undertakings.
3. Vehicles and vessels
The plate fin type oil cooler of vacuum brazing is used in vehicles and ships. Plate fin engine oil cooler has the characteristics of high heat transfer efficiency, compact structure and light weight. It is an updated product of diesel engine cooler and has been widely used in the fields of automobile, tractor, marine diesel engine, etc.
4. Air separation equipment
The heater is mainly used for the production of oxygen, nitrogen, argon and rare gas. In the past, the plate fin heat exchanger was mainly made by salt bath immersion brazing. This technology not only consumes a lot of energy, has a complex process, but also has strong corrosiveness, serious environmental pollution, high production cost and low product life. Vacuum brazing has many advantages over salt bath brazing, so the development trend is that vacuum brazing will replace salt solution brazing.
5. Petrochemical industry
In petrochemical industry, vacuum brazing is widely used to manufacture floor fin heat exchanger, for example: (1) gas recovery in petrochemical refinery; (2) separation and recovery of natural gas and coke oven gas; (3) liquefaction of natural gas and petroleum gas. The plate fin heat exchanger has the advantages of large capacity, good separation effect, low energy consumption and high purity. Therefore, countries all over the world attach great importance to the development of vacuum brazed plate fin heat exchanger technology.
6. Other aspects
Vacuum brazing technology is used for locomotive radiator, compressor intercooler, freon and alkene refrigeration system, digging oil cooler, gas turbine regenerator, high-power transformer radiator, and the application of household appliances, such as vacuum brazing the core of heat exchanger of household air conditioner and various electric heaters.