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Analysis on Surface Crack of Steel Ball ( I ) ---- Quenching crack

    Steel balls is an important part in rolling bearing, whose quality directly affects the life of bearing. According to the diameter of steel ball, the main processing method include cold heading, hot rolling, forging. There are many kinds of surface defects, in which the crack is the most common defect. The main cracks on the surface of steel ball of rolling bearings are commonly raw material crack, quenching crack, forged folding crack, cold processing crack and large instantaneous stress cracking during the assembly or operation. The position, micro metallographic structure, ways of analysis and precaution measures of each kind of cracks are different. Here mainly introduce the quenching crack.
    1.Macroscopic morphology characteristics and location: generally showed branch shape, arc shape, mainly in the equatorial part of the steel ball.
    2.Microcosmic morphology characteristics: most of the cracks are deep and no decarburization in both two sides.
    3.Reasons: improper quench method, or processing technology of steel ball lead to large stress in this part.
    4.Ways of analysis: use metallurgical microscope to observe the cracks and metallographic structure in two sides and use hot pickling process to make sure the morphology and location of the cracks.