Hot stamping (also known as press hardening or hot press forming) is a relatively new technology which allows ultra-high strength steels (typically 22MnB5) to be formed into complex shapes, which is not possible with regular cold stamping operations.
Contents
Methods
1) Indirect Process: the blank is formed, trimmed, and pierced in cold condition (i.e., state 1 in below figure). It is later heated and quenched in a die to get high strength properties.
2) Direct Process: the unformed blank is heated in a furnace, formed in hot condition (state 2 in below figure), and quenched in the die to achieve the required properties.
Selection of the process depends on part complexity and blank coating (Zn based coatings typically require indirect process). In either method, the blank is formed in a much softer and formable state and is later hardened in the dies, which have drilled cooling channels. A typical hot stamped components has 1000 MPa (145 ksi) Yield Stress and 1500 MPa (215 ksi) Ultimate tensile strength.
Advantages of Hot Stamping
Higher strength steels may help reducing the weight by downgaging (i.e., use of thinner sheets), while increasing the crashworthiness. However, one problem with many high strength steels is that their formability is generally lower than milder grades. In addition, springback and die wear also cause problems as the forming stresses and contact pressures are higher.