Vacuum brazing technology and vacuum furnace equipment

---

Vacuum brazing technology and vacuum furnace equipment introduction

Brief introduction of vacuum brazing technology development

Vacuum brazing refers to the heating of the workpiece in a vacuum chamber, and is mainly used for welding products that require high quality and easily oxidized materials.

Vacuum brazing technology has become a very promising welding technology since the beginning of the 1940s. It first appeared in the electronic industry for brazing copper and stainless steel parts, and later applied to the aviation industry and the atomic energy industry, and in 1959 began to be applied to the manufacture of stainless steel plate-fin heat exchangers. Now, it is widely used in plate-fin heat exchangers and coolers in industrial sectors such as air separation equipment, petrochemical equipment, engineering machinery, vehicles, ships and household appliances. Due to the unparalleled advantages of vacuum brazing technology, it has been rapidly developed and widely used in industrially developed countries in the world.

Advantages of vacuum brazing technology

1. Vacuum brazing, because no flux is used, significantly improves the corrosion resistance of the product, avoids all kinds of pollution, pollution-free treatment equipment costs, and has good safe production conditions;
2. Vacuum brazing not only saves a large amount of expensive metal flux, but also does not require complicated flux cleaning procedures, which reduces production costs;
3. Vacuum brazing solder has good wettability and fluidity, and can weld more complex and narrow-channel devices. Vacuum brazing improves the yield of products and obtains a firm and clean working surface;
4. Compared with other methods, the internal structure of the furnace and fixtures have a long 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, Inconel, etc., which can be brazed in a vacuum electric furnace. The designer determines the required materials according to the purpose of the brazing device, and aluminum and aluminum alloys are the most widely used.

Application field of vacuum brazing technology
Aircraft engine
In foreign countries, the JT9D engine honeycomb sealing ring of the American company is made of vacuum brazing ring parts and honeycomb sandwich core; the engine fuel main pipe is composed of the main pipe and multiple branch pipes and nozzles using vacuum brazing; the engine is stainless steel The heat exchanger is composed of more than 300 stainless steel tubes, partitions, and shells by vacuum brazing; the stator ring of JT8D engine 12 and 13 stage compressor is made by vacuum brazing of inner and outer rings and dozens of blades. The engine casing of GE in the United States is made by three-step vacuum brazing of more than 240 Inconel alloy parts with a thickness of 0.25-0.7mm. Vacuum brazing furnaces are the main brazing equipment in the manufacture of aero engines. There are more than 200 vacuum brazing furnaces in the United States. In China, Liming Engine Manufacturing Company, Chengdu Engine Company, and Beijing Aviation Technology Research Institute developed medium-sized single-chamber vacuum brazing electric furnaces in the 1970s. In 1964, Beijing Institute of Aeronautical Technology and Tianjin Electric Furnace Factory jointly developed a semi-continuous vacuum brazing furnace. Xi’an Aero Engine Company introduced the horizontal vacuum furnace of IPSEN Company (furnace size 910×610×610mm) and imported vacuum brazing furnaces. It is microcomputer temperature control and automatic program control. Now, Shanghai Gehang Vacuum Technology Co., Ltd., Beijing Institute of Aeronautics Technology, Shenyang Institute of Vacuum Application and other units have developed large-scale high-temperature vacuum brazing electric furnaces that can be controlled by a computer and controlled automatically according to procedures. SIMUWU brand vacuum brazing furnaces are sold all over the world.

Construction machinery field
Vacuum brazing of small and medium drill bits is an example. Small and medium drill bits are widely used in metallurgy, geology, coal, water conservancy, railway, military and other construction industries. According to statistics, in 1978, the country consumed about 10,000 small and medium-sized drill bits, but now the consumption is even greater, playing an important role in the construction of the national economy. SIMUWU high temperature and high vacuum diamond drill bit brazing has served many large and medium customers at home and abroad.

Vehicle industry
Vacuum brazed plate-fin oil coolers are used in vehicles and ships. The plate-fin oil cooler has the characteristics of high heat transfer efficiency, compact structure and light weight. It is an updated product of today’s diesel engine cooler and has been widely used in automobiles, tractors, marine diesel engines and other fields. There are few manufacturers in China that produce this type of plate-fin oil cooler, and they all use silver-copper alloy welding, each costing 150 grams of silver, and the cooler made by the silver-free copper vacuum brazing process is not only for the country It saves a lot of precious silver and has good airtightness. The brazed product has passed the air pressure test of 10kg·f/cm2, and there is no air leakage or leakage. It has high cleanliness and good surface gloss. It is used on diesel engines. The thermal performance meets the requirements of the “t·diesel engine plate-fin water-cooled oil cooler” promulgated by the Ministry of Machinery Industry. When immersed in water for 115 hours, the surface is free of rust and corrosion, and the production cost is greatly reduced. In 1984, the Czech Republic introduced a small continuous vacuum from the United Kingdom. The brazing electric furnace produces aluminum radiators on Skoda trucks, with an annual output of more than 10,000 units. The Ford Motor Company of the United States began to use the real brazing process to produce aluminum radiator cores in 1971. Cars produced in 1984 Among the radiators, aluminum accounts for 20%. Later, the two subordinate factories produced aluminum radiator production lines for technical transformation, and it is estimated that after the technical transformation, it will reach 3 million units in 1985. The reason why Ford company has to carry out technical transformation on the production line This is because aluminum radiators are light in weight and have good heat exchange performance. Therefore, in passenger cars, light trucks, and trucks with roofs manufactured by Ford Motor Company, aluminum radiators account for 90% to 95%.

Japan Aluminum Corporation has developed a new type of alloy (CF series) suitable for vacuum brazing of automotive heat exchanger fins, and has been mass-produced. This new CF series alloy is made of aluminum, zinc, and manganese with 0.2~ An alloy composed of 0.3% calcium. It can be used as the heat sink of the heat exchanger. The new alloy improves the corrosion resistance and service life. According to information, aluminum materials for automotive heat exchangers account for 80% to 90% in Europe, 50% in the United States, and 15% in Japan. Therefore, Japan’s Furukawa Aluminum Industry Co., Ltd. only launched the CF series of new aluminum alloys, which will undoubtedly promote the aluminumization of Japanese automobile heat exchangers.

At present, there are more than 20 vacuum brazing parts on a car, which shows that the vacuum brazing technology has great effect, good effect and wide application.

Air separation equipment
The first vacuum brazed turbo oxygen compressor impeller of Hangzhou Oxygen Plant Factory was tested at three speeds of 14500, 16000, and 18060r/min. The three-minute overspeed test was carried out. The entire impeller was still intact.

The success of the vacuum brazed impeller greatly improved the manufacturing accuracy of the factory’s narrow runner impeller, thus not only ensuring the design performance indicators, but also reducing the manufacturing cost, and at the same time shortening the production cycle. The actual breakthrough of vacuum brazing impeller manufacturing technology will play an important role in promoting the technological progress of my country’s air separation equipment industry.

Due to the many advantages of vacuum brazing, the British Marston Company closed the salt bath brazing furnace at the end of 1983 and used large-scale vacuum brazing furnaces to produce low-temperature heat exchangers.

Pertro-chemical industry
Vacuum brazing is widely used in the petrochemical industry to manufacture floor-fin heat exchangers, such as:
(1) gas recovery in petrochemical refineries;
(2) separation and recovery of natural gas and coke oven gas;
(3) natural gas, petroleum Liquefaction of gas. Because the plate-fin heat exchanger has the advantages of large processing 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.

Other field
So far, SIMUWU brand vacuum brazing furnaces have been used in locomotive radiators, compressor intercoolers, freon and alkane, olefin refrigeration systems, excavator oil coolers, gas turbine regenerators, high-power transformer radiators, And the application of household appliances, such as vacuum brazing of domestic air conditioners and heat exchanger core strips of various electric heaters.

Learn More :

Vacuum Brazing Furnace