Advantages of Vacuum Quenching in Bearing Manufacturing

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The high-temperature bearing was originally heated by a salt furnace. Due to the large salt spray when the salt furnace is heated, it will not only cause corrosion of the equipment, but also damage the health of the body and pollute the air. More importantly, the product quality cannot be guaranteed, and the salt furnace heating is very prone to corrosion. , resulting in pits, the ferrules treated by the salt furnace, the residual salt in the oil ditch is not clean, causing rust during the processing between the processes, deepening the pits that are heated and corroded, and it is difficult to remove by machining, which greatly reduces the machining efficiency. When cleaning the oil ditch of the ferrule processed by the salt furnace or electric furnace, it takes about one cleaning per shift, and only one qualified product is cleaned, while the ferrule processed by the vacuum furnace is cleaned about one per shift, and all of them are qualified products.

Process flow:

The effective heating area of the vacuum furnace is selected to be 250~300 mm, and the loading capacity of each furnace is 5~6 kg. Before heating, first clean the workpiece with gasoline and alcohol, sprinkle alumina powder between the end faces of the ferrule, and bundle it into a stack with iron wires. The rollers and steel balls are placed on a tray with a layer of each tray, and installed in a cold state. Put it into a vacuum furnace and vacuumize it. When the vacuum degree is normal, it is put into the furnace for heating. After the heat preservation is completed, it is naturally cooled to about 200 °C, and then the can is opened and cooled to room temperature to start tempering.

Characteristics of vacuum heating:

Vacuum heating is above ℃, mainly by radiation heating. Therefore, the method of loading the workpiece and its position in the furnace must consider the characteristics of radiation heating, that is, to minimize the area of the workpiece facing away from the heating body. We tested the ferrule with a closed sleeve, and found that the heating of the inner sleeve was quite slow, and it never reached the temperature of the outer sleeve, the fire color was obviously different, and the hardness structure was different. For this reason, our process regulations do not allow the use of combined heating, and the rolling element adopts layered heating to adapt to the characteristics of vacuum heating.

Degassing phenomenon of vacuum heating:

Under a certain degree of vacuum and temperature, impurities and oxides with high vapor pressure in the gas contained in the workpiece will degas, volatilize and decompose respectively. The degassing and volatilization of harmful gases and impurities is one of the important reasons for the better performance of the workpiece after vacuum heat treatment. The decomposition of oxides on the surface of the workpiece makes the workpiece regain its metallic luster after vacuum heat treatment. We heated the ferrule with rust on the surface and found that the rust would be completely removed.

Vacuum quenching deformation:

The outer ring of the bearing is most likely to be deformed during heat treatment. Electric furnace and salt furnace quenching, The deformation qualification rate is only about 60%, and the vacuum quenching deformation qualification rate is more than 99%.

Equipment selection: The VOGQ series vacuum oil quenching furnace produced by SIMUWU is a high-quality product for processing this type of brazing process. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum brazing process. With more than ten years of sales and manufacturing experience, it is exported to developed regions in Europe, America and Asia. It is a widely acclaimed vacuum furnace product.