1, the bearing ring heat treatment problems
The structure of the bearing ring shown in Figure 1, the characteristics of its parts is a thin-walled, hollow, and has a small hole in the middle. Its performance requirements of having a high hardness, high resistance. Bearing ring material of choice for GCr15, heat treatment process is quenching and tempering, hardness requirements HRC61 to 65. In development of heat treatment process the bearing ring during production, according to the existing equipment and quenching medium. ILlX-75 box-type furnace quenching quenching heating temperature of 840 ° C and incubated for one hour, the quenching medium optional # 2 oil, kerosene injected as a protective atmosphere heat treatment furnace. The quenching process is driven by the motor material basket stirring. 40 bearing ring in the actual operation of each furnace installed parts installed furnace using wire strings installed, 8 per bunch, a furnace installed 5 string. The result of the heat treatment process some parts decarburization and deformed. Resulting in scrapped parts.
The bearing ring decarbonization and deformation analysis
Parts obsolescence There are two reasons: First decarburization, distortion-tolerance. The decarburization reasons: first, due to kerosene as poor protection of the atmosphere, the effect of pyrolysis at 840 "C, rarely produce the activated carbon atoms, but also easy to generate a lot of carbon black, and so cause parts decarburization. second, the use of the box-type furnace heating, should open the door parts every time came out with a hook to pick out the parts per furnace parts during the operation to open the fifth door, furnace door did not fire curtain device, it is easy formation of negative pressure in the furnace, so that the air into the furnace resulting in the decarburization of the parts. third, the use of quenching medium is # 2 oil, the quenching medium use a long time, the cooling capacity also reduces, resulting in the local cooling rate of the workpiece lower than the critical quenching speed shift troostite may cause hardness unqualified local part of the bearing rings after quenching.



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