Carbon content is about 0.05% ~ 0.70%, some can be as high as 0.90%. It can be divided into ordinary carbon structural steel and high quality carbon structural steel.
C45(1.0503) is a kind of medium carbon high-quality steel with higher strength. Due to poor hardenability, it is generally used in normalizing state. When the mechanical performance is required to be higher, it adopts quenching and tempering treatment. Cold deformation plasticity medium, annealing, and normalizing machining are better than the quality. Used for manufacturing parts with high strength requirements, such as gear, shaft, piston pin, etc., and mechanical processing workpiece, forgings, stamping parts and bolts, nuts, pipe joints with low stress.