Analysis and investigation of the failure elevator induced by dual effects of cyclic alternating load and improper heat treatment

Aiming at the deformation and fracture of slope elevator caused by the cyclic alternating load in service, analyzes and studies the failure reasons and mechanisms from microstructure, physical and chemical properties, and service state. The microstructure of the elevator was lower bainite that preserves the intact of the laths orientation, with high P element content, a certain amount of low harmful low-melting-point elements, and presence of D-type non-metallic inclusions, led to low impact toughness. It indicated that failure of the elevator can be attributed to dual effects of load and improper heat treatment, caused dislocation glide to occur in the crystals, eventually resulting in a mixed-crystal-type brittle fatigue fracture. It was advised to strictly control the content of trace elements, rationally optimize the heat treatment process, and select micro-structure with good resistance to fatigue impact and alternating load, to improve the deformation resistance and critical fracture toughness of the elevator.