45 steel hardness

Commonly used medium carbon quenched and tempered structural steel. The cold plasticity of the steel is generally good. The annealing and normalizing are slightly better than the quenching and tempering. It has high strength and good machinability. After proper heat treatment, certain toughness, plasticity and wear resistance can be obtained. Convenience. Suitable for hydrogen welding and argon arc welding, not suitable for gas welding. Preheating is required before welding, and stress relief annealing should be performed after welding.
Normalizing improves the cutting performance of blanks less than 160 HBS. After the steel is quenched and tempered, its comprehensive mechanical properties should be optimized for other medium carbon structural steels, but the steel has low hardenability, and the critical hardenability diameter in water is 12~17mm, and there is a tendency to crack when water quenching. When the diameter is more than 80mm, the mechanical properties are similar after quenching or tempering, and the medium and small mold parts can be quenched and tempered to obtain higher strength and toughness, while the large parts are treated with normalizing. Therefore, this steel is usually used in quenched or tempered condition.
Quenching and tempering has a range of hardness, generally between 225-297HB. 45# steel is quenched and tempered, that is, quenching + high temperature tempering, the hardness should be at 297HB, that is, 31 ~ 32HRC! This is the most ideal state. This value may not be reached in general.
45 steel quenching, if water quenching can generally reach 40----60HRC (according to water temperature and material size), quenching with oil is generally between 30----55HRC (depending on the thickness of the material and the type of quenching oil) https://www.supplyforever.com/