Advanced High-Strength Steel and Mixed-Material Handling
Grades and behavior
HSLA, dual phase, TRIP, complex phase, martensitic, and press-hardened (boron) steel gain strength from microstructure, not just thickness. As strength rises, elongation falls, so cold working and heat both reduce the ductility that remains. A kink that would be routine in mild steel can make a high-strength part unfit for service.
Handling rules
- Follow the OEM repair-versus-replace statement; many UHSS and press-hardened parts are replace-only.
- Do not heat unless the procedure explicitly allows it. Heat in the tempering range destroys the microstructure that provides the strength.
- Do not straighten a kink in UHSS; replace the part.
- Cut with methods the OEM permits, generally sawing or shearing rather than processes that add significant heat.
- Join with spot welding, rivet bonding, or adhesive as specified; fusion welding is often restricted.
- Mixed materials: isolate aluminum from steel to prevent galvanic corrosion, and keep dedicated tools, abrasives, and work areas for aluminum so embedded steel particles do not start corrosion.
Worked example
A press-hardened B-pillar has a kink. The reasoning runs in order: the grade is replace-only, so no straightening; heat is prohibited, so no torch work; sectioning is allowed only at the OEM-specified location, if at all. Replacement, correct joining, and full corrosion protection follow from the material, not from the damage size.
Traps that cost marks
Heat shrinking a dent on AHSS; fusion welding where the OEM specifies rivet bonding; using a steel-contaminated disc on aluminum; assuming thicker mild steel is an acceptable substitute.