Q345B steel belongs to low alloy high strength steel, which contains a small amount of alloy elements and is mainly used in construction and engineering structures. The carbon content of Q345B steel is 0.20%. Due to the effect of alloying elements, the yield strength of low alloy high strength structural steel is 25% - 150% higher than that of carbon structural steel with the same carbon content. Using low alloy high strength structural steel instead of carbon structural steel can reduce the dead weight of structure, save metal materials and prolong the service life of structure.

Chinese No.45 steel belongs to high-quality carbon structural steel. Chinese No.45 steel does not contain alloy elements specially included. Chinese No.45 steel is suitable for manufacturing high strength moving parts, such as air compressor, piston of pump, impeller of steam turbine, rolling shaft, connecting rod, worm, rack, gear and pin in heavy and general machinery.