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What Are the Causes of Hot Cracks in Pressure Vessel Welding?

Jul. 05, 2019

As an LNG Transport Trailer Factory, let's share the cause of hot cracks in pressure vessel welding.

Thermal cracking occurs and develops along the junction of dendritic crystals in the weld metal. The most common case is cracking along the length of the weld in the middle of the weld, sometimes between the two dendrites within the weld. Hot cracks are generated at the grain boundaries, which indicates that the grain boundary is a weak zone during the crystallization of the weld. The cause of the hot crack in the presence of a liquid interlayer in the weld and the tensile stress of the weld during crystallization. The presence of a liquid interlayer is the root cause of thermal cracking, and tensile stress is a necessary condition for thermal cracking. It is not the late stage of the entire crystallization process, and it is a dangerous temperature zone where hot cracks occur near the solidus line.


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The metal in the near-split area is also heated to a very high temperature (slightly lower than the melting point). If the grain boundary of the base material in the near-split area is present with impurities or low-melting eutectic, it melts under the action of heat and forms at the grain boundary. In the liquid interlayer, the tensile stress that occurs during the process causes thermal cracks in the near-split area. There is an interdependence between the hot cracks in the weld and the hot cracks in the near seam. The hot crack in the near seam may be a continuation of the hot crack in the weld and may also be the origin of the hot crack in the weld.

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