20# steel and 45# steel are both commonly used materials for seamless steel tubes and machining. 20# steel and 45# steel have different C, Si, Mn, P, S content, 45# steel material level is higher than 20# steel.

20# steel has good hardenability, low hardenability, good plasticity, toughness, weldability, and better toughness after hot rolling or normalizing. 20# steel can make less important medium and small carburized, carbonitrided parts, forged parts, such as lever shaft, gear shift fork, gear, heavy machinery pull rod, shackle, etc.

45# steel is commonly used medium carbon quenched and tempered steel. 45# steel has good comprehensive mechanical properties, low hardenability, and is prone to cracks during water quenching. Small parts should be quenched and tempered, and large parts should be normalized. 45# steel is mainly used to manufacture high-strength moving parts, such as turbine impellers and compressor pistons. shafts, gears, racks, worms, etc.