Annealed carbon chromium bearing steel

    Spheroidizing carbon chromium bearing steel in order to obtain uniform distribution of the ferrite matrix of thin , small , uniform, round carbide particles organize , prepare for the future and the ultimate cold quenching and tempering for the organization . The traditional ball annealing process is slightly higher than the Ac1 temperature ( eg GCr15 of 780 ~ 810 ℃) after slow cooling in the furnace heat (25 ℃ / h) baked cooled to below 650 ℃ . The heat treatment process for a long time (20h or more ) [ 1 ] , and after annealing carbide particles uniform, cold and final microstructure and properties of quenched and tempered later . After that, according to the characteristics of supercooled austenite transformation , development isothermal spheroidizing : rapid cooling after heating to a temperature within the range of the following Ar1 (690 ~ 720 ℃) ??isothermal , isothermal austenite to complete the process transformation of ferrite and carbide , directly after the transition is completed cooled baked . The advantage of this process is that the heat treatment time saving ( about the process 12 ~ 18h), the treated tissue carbide fine uniform. Another time- saving process is repeated annealing of the ball : the first heated to 810 ℃ cooling to 650 ℃, and then heated to 790 ℃ to 650 ℃ cooling cooled baked . Although this process can save some time , but the process is more complex operations .