On the application of vacuum technology in aerospace

In order to meet the design and manufacturing requirements of aeroengines with high thrust-to-weight ratio, high reliability, long life, and low cost, new materials, new structures, and new processes are increasingly used in the aerospace field, which puts forward the requirements for processing and manufacturing methods. It has met higher requirements and at the same time promoted the continuous development of aerospace manufacturing technology. As a means of aerospace manufacturing technology, welding technology has also developed rapidly. Brazing technology has unique advantages and flexibility for the connection of new materials and the manufacturing of complex precision structural parts. For some refractory welding materials and complex components, brazing is the only feasible and effective connection technology. It can even achieve “perfect” welding effect without processing the brazing joint. Therefore, vacuum brazing technology is increasingly used in the aviation industry and other industrial fields. Many important components on aerospace engines, such as turbine blades, compressor blades, combustion chamber components, honeycomb sealing structures, stainless steel heat exchangers, The manufacturing of components such as fuel main pipes and other pipelines involves vacuum brazing technology.

Vacuum heat treatment is one of the important methods of heat treatment for aerospace engines. It has evolved from early vacuum annealing and vacuum degassing to vacuum quenching, vacuum tempering, vacuum chemical heat treatment and special vacuum heat treatment. Vacuum heat treatment furnace design and manufacturing, components The level and performance have been continuously improved, and a vacuum heat treatment production line has been developed.

Currently commonly used processes include vacuum oil quenching, vacuum pressurized gas quenching, vacuum carburizing, vacuum magnetic field heat treatment, etc. Vacuum oil quenching is the main process of vacuum heat treatment at present. The technical difficulty encountered during the development process is that vacuum oil quenching may produce carburization, which reduces fatigue performance. In the past 30 years, vacuum quenching oil and vacuum oil quenching surface carburization have been solved. Technical key. Vacuum pressurized gas quenching has many advantages such as smooth workpiece surface, no need for cleaning, and avoidance of environmental pollution. It is an important and rapidly developing field of vacuum heat treatment in recent years. At present, in the aviation industry, vacuum pressurized gas quenching plays an important role in the heat treatment of parts such as stainless steel, high-temperature alloys, titanium alloys, precision alloys and some structural steels. Vacuum carburizing can successfully solve the problem of removing the passive film of stainless steel without adding any chemicals, without any operational difficulties and the generation of pollutants; it also solves the requirements for high-quality carburizing of aviation parts without internal oxidation and small holes, The problem of uniform carburizing in blind holes improves the carburizing speed and efficiency. In recent years, the number of vacuum carburizing equipment has increased rapidly, and its application scope has continued to expand. Vacuum magnetic field heat treatment combines vacuum heat treatment technology with electromagnetic field technology to form another branch of vacuum heat treatment.
For titanium alloys commonly used in the aviation field, stress relief annealing of sheet metal parts and castings, solution treatment and aging treatment of fastening standard parts, hydrogen removal annealing, and constrained aging treatment of high-strength titanium alloy sheet metal parts must all be performed in a vacuum. Proceed in the furnace.

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