Bearing heat treatment technology and equipment (3)

The water-based quenching medium is an aqueous solution composed of an organic polymer, an anticorrosive agent, and other additives. Different cooling characteristics can be obtained by changing the type and concentration of the organic polymer to suit the quenching cooling requirements of different bearing parts. During the quenching and cooling process, organic matter adheres to the surface of the part, which can reduce the risk of quenching and cracking of the part, and does not produce soot, easy to clean, and free of pollution, which is the development direction of the quenching medium.

Gas quenching uses an inert gas as a medium (commonly used nitrogen) to spray compressed gas through a specially designed nozzle onto the surface of the workpiece to achieve quenching and cooling of the workpiece. The cooling characteristics and deformation can be controlled by adjusting the pressure of the gas and the structure of the nozzle. Gas quenching is cleaner and less costly than water-based quenching. The key technology is the structural design of the nozzle. China's gas quenching is still in its infancy in the field of bearings, and there is still a certain gap in the structural design technology of nozzles.

Quenching and cooling equipment is another major factor affecting the quenching effect of the workpiece in addition to the quenching medium. At present, there are few control parameters for quenching and cooling equipment in China, and generally only the oil temperature and oil circulation are controlled. Foreign countries apply multi-parameter control to commonly used quenching oil tanks, such as oil temperature, oil cooling characteristics, oil circulation and agitation direction, and speed, workpiece oil feeding method, etc., in order to obtain the best quenching structure and performance, Reduce distortion to a minimum. Some bearing manufacturers in China are also trying multi-parameter control, especially by controlling the oil inlet mode of the tapered bearing to solve the change of the angle during the quenching process of the bearing parts.

The multi-station automatic quenching press has been applied in China, but the degree of automation cannot keep up with foreign countries.

(6) Cleaning of cleaning equipment is usually an essential process after oil quenching. The cleaning equipment used in the continuous production line generally completes the processes of hot soap water soaking, water spray and hot air drying, and has a water-water separation device. In the advanced cleaning equipment, a secondary cooling device (with refrigeration equipment and temperature between 5 and 10 °C) is added before drying to reduce the content of retained austenite and improve the dimensional stability. At present, the cleaning equipment in our country is mainly cleaned with high-pressure cleaning liquid. This kind of cleaning is ineffective for non-through holes and small oil grooves, which often causes tempering fumes and pollution, and sometimes causes fire.

Vacuum cleaning is a cleaning device developed in recent years. The advantages of this type of cleaning equipment are: good cleaning effect, especially for complex structural parts, the surface of the workpiece is bright after cleaning; safe and clean, the cleaning liquid is clean water, and no harmful chloride and oil are added. Solvent-like; high degree of automation, and can replace low temperature tempering with cleaning heating, saving tempering costs. In recent years, ultrasonic cleaning and eddy current cleaning have also been applied well in heat treatment.

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