Heat treatment process of 40crnimova torsion bar spring

What is the heat treatment process of 40crnimova torsion bar spring?

The manufacturing process route of torsion bar spring: cutting → upsetting → annealing → end processing → quenching → tempering → shot peening → strong torsion treatment → inspection → antirust treatment.

The heat treatment process of 40crnimova torsion bar spring is quenching and tempering treatment (quenching and tempering torsion bar), the quenching diameter is 70mm, the tensile strength after quenching and tempering is 1500 ~ 1700mpa, the quenching heating temperature is 830 ~ 890 ℃ oil quenching. If the low hardness 415 ~ 495hbs (i.e. the working stress reaches 735 ~ 882mpa), the tempering temperature is about 500 ℃; if the high hardness is 47 ~ 52hrc (i.e. the working stress is 883 ~ 932mpa), the tempering temperature is about 400 ℃.

Attention should be paid in heat treatment: surface oxidation and decarburization shall be prevented during quenching and heating, and overheating shall not occur. Tempering shall be timely and sufficient.