cracks mainly exist in the craters of the ring joints. From the shape analysis, most of them are hot cracks. In the process of cooling solidification and subsequent cooling, the weld metal is constrained by the solid metal around the weld, causing tensile stress in the weld metal. This is the external cause of thermal cracking; the presence of low-melting eutectic is the weld seam The internal cause of hot cracks. During the crystallization process of the weld seam, due to the presence of low-melting eutectic in the weld seam, the solidification time is long and is pushed by the columnar crystals to the grain boundary and accumulates on the grain boundary to form a liquid interlayer. Under the action of tensile stress, the columnar crystals The voids increase, and the low-melting eutectic is insufficient to fill the gap, which creates thermal cracks.
