关键词: 应力集中, 强度降低系数, 铁素体, σ相, 超温时长

Abstract: The weld cracking of expander inlet line of FCCU threatens the operation safety seriously. This paper lists the key factors and operation requirements from the aspects of design, welding materials, welding construction and operation. This is helpful for the operators and maintainers in the industry to understand the cracking mechanism, and then to find and solve the problems.

Key words: stress concentration, strength reduction factor, ferrite, σ phase, upset temperature duration