Abstract: Fracture reasons of welded joints in a rotatable bracket were analyzed by chemical composition analysis, macroscopic and microscopic examination, hardness test and heat treatment method. The results showed that: fractures were directly caused by lack of fusion increased by non-standardized welding procedure, by improper formation of hardened structure during welding without heating treatment, and so on. Furthermore, several improvements in welding procedure and heat-treatment management were proposed for prevention.