Listen to a customer to buy a factory Chain Hoists spoken in the use of a few months after the occurrence of the accident chain hoists short loop strand breaks . After the accident, we need to identify 1 phase hoist the cause of the accident is located , in order to avoid the occurrence of similar incidents. Chain hoists manufacturing standards : JB/T7334-94 " hoists ", JB/T8108.1 ~ 8108.2-1999 " crane with a short chain ." Short link chain with a chain heat treatment : 890 ℃ ± 10 ℃ quenching ( water-cooled ); 300 ~ 350 ℃ back to cold (water ) , hardness is HRC32 ~ 38. Chains made of 20Mn2, Φ6mm. From the broken chain , the chain of the welding zone is good, the location of the fracture in the chain to chain arc welding parts of the junction. Subtle observation, broken parts are subjected to severe mechanical damage marks, and can not be completely closed after fracture split , there are gaps. Fracture Analysis of the final results of the chain is a chain of mechanical damage gaps exist ; chains have been subjected to localized stress overload .