Bearing parts quality of quenching heat treatment is mainly dependent on quench heating conditions and cooling conditions, and cooling conditions is mainly dependent on choose corresponding quenching oil and cooling technology.
Bearing parts mainly USES the mineral oil to quenching cooling. Mineral oil is a paraffin wax, bad monosilane, aromatic hydrocarbons and paraffin wax-aromatic series of talk about hydrogen and all kinds of compounds of derivatives. Due to the composition and refining methods of different, form different characteristics, different USES of special quenching oil. Use requirements (including the cooling speed, using temperature, brightness, etc) can be divided into ordinary quenching oil, rapid quenching oil quenching oil, classification, speeding quenching oil, vacuum quenching oil, fast light quenching oil and JiXieYou.
Choose quenching oil, must consider to deal with parts of the materials, shape, size, deformation of hardening layer depth, process, brightness and the heat treatment equipment, and other factors. The fine quenching oil is the high thermal stability of refined base oils (usually paraffin base) and can improve the service life of performance and various additives configuration and into. For rolling bearings components in quenching cooling process, should prevent pearlite type of change, in order to avoid quenching opaque or local appear difference of body, soft spots defects. Therefore, quenching oil cooling speed than the critical bearing steel cooling speed. But the cooling speed shoulds not be too big, lest cause large stress, lead to excessive and quenching cracking deformation. According to the C GCr15 bearing steel that curve of the austenitic most easy transition temperature of about 650 ℃ and 450 ℃ for, in this temperature must be quick cold before, and in the later temperature, then can slow cooling, especially in martensite transformation started to point Ms and Mf slow cold can reduce between the deformation and crack, but not too slow, otherwise the austenitic Chen stable easy cause residual austenitic of body increase. So can choose 650 ℃ and 450 ℃ in cold speed when more than critical cold speed, and in the temperature of cold after a slow for oil quenching oil. In most conditions, due to different site conditions and are difficult to be determined under different conditions of critical steel cooling speed. But in the field can affect the speed of cold according to the critical factors to determine the critical cooling speed the tendency of changes, according to choose the quenching oil. Such as quenching the high temperature, holding time long, thin original organization, the critical cold speed will small a few, this is can choose cooling ability of small quenching oil.
For wall thickness of the big bearing collar, if have enough of hardening layer, quenching oil should have fast cooling speed. And for thin-walled bearing collar, quenching oil shall have a slow cooling speed. For complex shape of parts should choose steam film stage short and the cooling speed faster quenching oil.
Asking for deformation of the bearing collar is small, had better choose the grading quenching oil. Bearing steel rings classification in Ms point temperature above grade is cooling velocity critical cold speed.




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