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B-pillars, door beams, and bumper reinforcements can be made by hot or cold stamping.
## Hot Stamping
Heats boron steel to 900-950C, forms and quenches in water-cooled die. Result: 1500-2000 MPa.
Press requirements:
- Forming speed: 50-150mm/s
- Dwell at BDC: 5-15 seconds for quenching
- Cycle time: 10-20 seconds
## Cold Stamping of UHSS
980-1500 MPa UHSS, no heating required.
Press requirements:
- 2-3x tonnage vs mild steel
- Forming speed: 30-80mm/s
- Dwell at BDC: 100-300ms
## Which to Choose?
Hot stamping: higher strength (1500-2000 MPa), better formability, less springback.
Cold stamping: no furnace ($2-5M saved), faster cycle (3-5s vs 10-20s), lower energy.
B-pillars/door beams: hot stamping. Bumper reinforcements at 980 MPa: cold stamping increasingly preferred.