Analysis and Solution for Abnormal Retained Austenite of 20CrMnTi Steel Gear
The microstructure and hardness of the white area on 20CrMnTi steel gear were observed and te-seted by metallographic microscope and hardness tester.The main reason for the white area after vacuum low-pressure carburizing heat treatment was analyzed,and the solution was put forward.The results showed that large amount of residual austenite in the white area with depth of 45 to 170 μm on the tooth surface,and there were large-sized carbides on the tooth surface.The hardness at a distance of 0.05 mm from the surface was only 505 HV1,which was far below the technical requirements characteristics of 660 to 750 HV1.It was found that the main reason for excessive retained austenite on the surface of gears was that the leakage of acetylene into transfer channel,which caused secondary carburization on the surface of the surface of workpiece during transfer process.
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