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Vacuum Heat Treatment Furnace

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SUC bearing vacuum heat treatment

The SUC bearing is a spherical bearing with a top wire and has the function of self-aligning. It is easy to install and disassemble, so it is widely used in food machinery, transportation equipment, etc.

The inner ring of the SUC bearing made of high carbon chromium stainless steel 9Cr18 has two threaded holes. As shown in the figure, if only the overall quenching is used, the hardness of the threaded hole is the same as the hardness of the raceway ≥58HRC. The hole is prone to cracks or chipping due to stress concentration. Therefore, it is necessary to use a local annealing process to reduce the hardness at the threaded hole of the SUC inner ring to avoid cracking or chipping.

Reasons to choose vacuum quenching

If an intermediate frequency induction hardening machine or a salt bath furnace is used, only one end of the inner ring raceway of the SUC is partially quenched, and one end of the threaded hole remains annealed. The hardness of the quenched area is high, and the hardness of the unquenched part is too low, which is easy to be crushed and bruised during the grinding process, resulting in low grinding efficiency and high rejection rate. Annealing makes one end of the screw hole also have a certain hardness. This avoids cracks or chipping at the threaded hole, and at the same time improves the grinding efficiency and reduces the scrap rate.

The equipment uses vacuum furnace overall quenching + flame heating partial annealing to heat treat the SUC bearing inner ring, because the thread of the SUC bearing inner ring has been processed before heat treatment, in order to avoid oxidation and decarburization, the overall quenching uses a double-chamber vacuum quenching furnace.

Process flow:

The process flow chart of vacuum integral quenching is as follows:

Because of the poor thermal conductivity of 9Cr18 steel, the composite carbide in the steel dissolves slowly in austenite at high temperature. The surface temperature of the ferrule heated by the vacuum furnace is fast, and the temperature of the core is slow. In order to prevent deformation and cracking, two times are required. The heating temperature of preheating and quenching is selected from 1060 to 1070 ℃, and the heating time is determined according to the specific furnace load and the effective wall thickness of the ferrule.

The 9Cr18 ferrule contains a lot of retained austenite after quenching. The retained austenite is further transformed into martensite during use, resulting in poor dimensional stability. Therefore, after quenching, it is placed at room temperature for cold treatment to reduce the content of retained austenite. , to improve the dimensional stability of the ferrule. The hardness of the 9Cr18 ring after tempering is ≥58HRC, and the structure is composed of cryptocrystalline, fine martensite, residual primary carbides, secondary carbides and retained austenite.

flame heated partial annealing

Flame heated partial annealing is heated in air using an oxygen-acetylene flame. The mixing ratio of oxygen and acetylene is in the range of 1 to 1.2, the flame is a neutral flame, the oxygen and acetylene of the neutral flame are fully burned, the flame is stable and powerful, the heating speed is fast, and basically no oxidation and decarburization occur when the workpiece is heated.

Although flame heating is not easy to accurately control the temperature, the hardness of the threaded hole of the high-carbon chromium stainless steel SUC inner ring only needs to be controlled below 45HRC to avoid the problem of cracks and chipping when the overall quenched threaded hole is too high in use. At the same time, due to the high hardness of the threaded hole surface, the problems of bumping, crushing, low grinding efficiency and high rejection rate during grinding are avoided.

Selection of vacuum heat treatment furnace equipment: The VOGQ series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment process of tooling and molds. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum heat treatment process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.