45# steel is a carbon structural steel, with moderate hardness and easy to machine. It is commonly used to make molds, templates, guide posts, etc., but requires heat treatment.

The 45# steel is considered qualified before tempering and after quenching, with a hardness greater than HRC55 (up to HRC62).

The actual application hardness is HRC55 (high-frequency quenching HRC58).

2. Do not use carburizing and quenching heat treatment process for 45# steel.