A517 Grade H in between 350 ~ 500 ℃ tempering.
The purpose is to make A517 Grade H has higher flexibility and the yield point, the appropriate toughness. Get tempered troostite, after tempering refers to martensite tempered formed when there are extremely small globular carbide distribution in the ferrite matrix (or cementite) complex organization.
Mechanical properties: 35 ~ 50 HRC, high elastic limit, yield point, and certain toughness.
Application: mainly used for springs, clockwork springs, forging die, impact tools etc.