Bearing steel heat treatment hardness of the problem of knowledge:
Annealed hardness: before heat treatment annealing hardness and microstructure of parts to test. GCr15:179-207HB (88-94HRB), 179-217HB (88-97HRB) if the hardness is not qualified (too high, too low or uneven), has to be carefully analyzed may have an impact on quenching (such as: not enough hardness, carbon dioxide removal, heat, elliptical, etc).
Quenching and tempering hardness: wall thickness is greater than 12mm, hardened 63HRC, 60-65HRC after tempering; customers may face special hardness, such as 61-64HRC, etc, but tempering hardness tolerance range is size from 3HRC; normal when hardening, hardness depends primarily on the tempering temperature.
Uniformity of hardness: standard, the same part hardness uniformity generally 1HRC; diameter greater than 200mm, is less than 400mm for 2HRC is greater than 400mm 3HRC.
Hardness of substandard performance in high hardness: hardening temperature or heating time, cooling rate too fast, high carbon (carbon)
Low hardness: quenching temperature or heating time shorter, slower cooling rate, low carbon (carbon), material for decarburization
Uneven hardness: quenching temperature or heating time shorter, slower cooling rate, material for decarburization, sticks to shadows.
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