Abstract
The grinding cracks are frequently found in the medium and high carbon martensite steels such as Fe-C steels, bearing steels, Mo steels, Mn steels, Ni steels and Cr steels. We are decided to go back to the metal structure in the origin of the workpiece to observe the grinding cracks from metallographical standpoint. In this report, the first step of study is investigated the kern and origin of the grinding cracks in the martensite structure. The next step deals with the significance of existence for the grinding cracks of martensite impingement cracks and the shape or size of the minimum unit of it. A summary of the main results are shown below.
(1) The impingement cracks of martensite were observed the lenticular martensite in the many shape of it. And the impingement cracks were become frequently kern of grinding cracks.
(2) The combination of martensite's impingement cracks and grinding cracks were observed in many kinds of the workpiece.
(3) The generation of minimum unit size of grinding cracks are observed in the martensite crystal. And the length of it was shown very high frequency in the range of 4.0-5.0μm.
(4) The stain and impingement cracks of martensite is very high sensitivity of the notch effect or stress concentration.
(5) The generation of microcrack in γ-phase was not observed in the transformation from fcc to bct.
