Explanation

Cracks occur in castings at the end of solidification due to external force, white stress, or both. hot tear is a serious casting defect in cast steel castings, malleable cast iron castings and some light alloy castings. It is characterized by oxidation on the crack surface, so it is impossible to weld through subsequent hot working. hot tear can be divided into external cracks and internal cracks. The external cracks extend from the surface of the casting to the white part. The surface cracks are wide and the white part is narrow. The oxidation phenomenon is serious. They often occur from the bending of the casting, the abrupt change of the section thickness, or the local stress concentration. The causes are mainly due to the large tensile stress caused by the blocked shrinkage. The edge cracks and corner cracks of the continuous casting billet are also related to the mold design. Internal cracking often occurs at the final solidification point of thick and large castings - oxidation phenomenon is not obvious - often accompanied by dendritic structure.

Classification