Failure Analysis on Fracture of High Temperature Fastening Bolts of 20Cr1Mo1VTiB Steel

The high temperature fastening bolts of 20 Cr1 Mo1 VTiB steel for steam turbine of a thermal power plant broke during installation.The fracture causes of bolts were analyzed by means of macro examination,chemical composition analysis,metallographic examination,fracture analysis and mechanical property test.The results show that in the smelting process of materials of the high temperature fastening bolts,the carbon content was seriously exceeded due to the improper control of the chemical elements content,resulting in the decrease of impact absorption energy and plasticity of the bolts,which eventually led to bolt fracture.