Grain size is an important index to measure the quality of M50 bearing steel.By discussing the effect of annealing process on the grain size of M50 steel

in order to improve the coarse grain size and mixed grain of high temperature bearing steel M50 in the actual production process. The test results show that the grain size of M50 steel is not affected by appropriately increasing the annealing temperature and extending the holding time. It has been verified in actual production that the annealing process is changed from holding heat at 860 ℃ for 5 h to holding heat at 910 ℃ for 8h

which can im- prove the grain size and mixed crystal of M50 steel caused by insufficient uniformity of furnace temperature. In addition

it is verified that when the cooling rate is too fast after annealing and heat preservation

it is easy to cause coarse quenched grain of the finished bearing

which should be paid attention to in the actual production process.