The chemical composition, surface hardness and microstructure of the failed SLD steel mold were examined and analyzed by direct reading spectrometer, digital Rockwell hardness tester, optical microscope and scanning electron microscope. The results show that the failure reason to place mold is the excessive retained austenite in the matrix and the incomplete transformation of martensite. During the placement of the mold, the unstable retained austenite structure in the matrix continuously transforms to martensite and its volume expands, resulting in the mold to elongate during the placement, in which the eutectic carbides exceeds the standard, and the size increases along the deformation direction of the eutectic carbides. The tempering of the mold is not sufficient, the structural stress can not be eliminated and is continuously released during the placement, which will further promote the deformation and elongation of the mold, and there is microcrack in the matrix structure due to producing stress cracking.
NETL
NSTL
万方数据
维普
