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<p>This paper investigates the crack failure of a failed weld repair joint in ethylene cracking tubes observed after the weld repair process using visual inspection and micrographic analysis using a light optical microscope and a scanning electron microscope. The results show that the crack originated in the partially melted zone which is characteristic of a typical partially melted zone crack. SEM micrographs reveal dendritic morphology and cleavage fracture of the fracture surface. On one hand, the dendritic morphology found indicates the role of constitutional liquation, which can be presented by the local melting between the matrix and carbide particles. On the other hand, the cleavage fracture signifies the brittleness and significant reduction of ductility of the aged tube. The combined effects of low ductility and brittleness of the aged tube and inappropriate welding procedure are attributed to the crack of the weld repair joint. The improvement of the weldability of the aged tube, such as the removal of the carburization materials and buttering weld, is suggested. In parallel, the reduction of contraction stress, i.e., minimizing heat input, controlling interpass temperature, and using small electrodes, is also recommended.</p>

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Metallurgical Failure Analysis of a Weld Repair Joint in Ethylene Cracking Tubes

  • 期刊论文

  • 发表日期：

    2025年7月5日

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  • Chaiyawat Peeratatsuwan,
  • Dussadee Rattanaphra,
  • Sasikarn Nuchdang,
  • Wilasinee Kingkam,
  • Yingyos Thipsrirach,
  • Thee Chowwanonthapunya

摘要

This paper investigates the crack failure of a failed weld repair joint in ethylene cracking tubes observed after the weld repair process using visual inspection and micrographic analysis using a light optical microscope and a scanning electron microscope. The results show that the crack originated in the partially melted zone which is characteristic of a typical partially melted zone crack. SEM micrographs reveal dendritic morphology and cleavage fracture of the fracture surface. On one hand, the dendritic morphology found indicates the role of constitutional liquation, which can be presented by the local melting between the matrix and carbide particles. On the other hand, the cleavage fracture signifies the brittleness and significant reduction of ductility of the aged tube. The combined effects of low ductility and brittleness of the aged tube and inappropriate welding procedure are attributed to the crack of the weld repair joint. The improvement of the weldability of the aged tube, such as the removal of the carburization materials and buttering weld, is suggested. In parallel, the reduction of contraction stress, i.e., minimizing heat input, controlling interpass temperature, and using small electrodes, is also recommended.