Early failure identification and prevention of welds in 12Cr1MoVG boiler tubes based on case comparison

A comparative analysis was conducted on the cracking of welded joints of 12Cr1MoVG tubes in two power plants. The results showed that although the materials, specifications, and macroscopic morphology of the cracked tubes in the two power plants were the same, they actually had two completely different fracture properties. The crack properties of the tubes in power plant A is reheat cracking, while the crack properties of the tubes in power plant B are stress corrosion cracking caused by alkaline solution, namely caustic embrittlement cracking. The factors that lead to the formation of the two types of cracks are somewhat different. The former is related to the reheating temperature and time experienced after welding, while the latter is related to the alkaline corrosive medium present in the environment. But there are also some common factors that cause the formation of the two types of cracks, which are related to the excessive residual stress caused by the high hardness of the weld seam, the structural constraint stress, and the microstructure type of the parent pipe. After a thorough comparative analysis of the two types of cracking properties, it was pointed out which features engineers can use to distinguish between the two types of cracks without on-site sampling analysis.