Repair of welds as it is Material affected
American Iron and Steel Institute (AISI) studies conducted in cooperation with North American OEM’s to understand the influences of “in field” repair practices on some AHSS have been completed for DP (Dual Phase), Martensitic and TRIP (Transformation Induced Plasticity) steels. In particular, the effects of MIG (Metal Inert Gas) welding and a practice called “flame straightening” were examined. Flame straightening consists of heating a portion of the body or frame structure which has been deformed in a collision to 650ºC (dull cherry red) for 90 seconds and then pulling the deformed portion of the structure to its original position. This heating cycle then could be applied twice. Test results indicate that “flame straightening” should NOT be used to repair AHSS such as DP, Martensitic and TRIP. The heating cycle does cause degradation to the mechanical properties of as-formed (work hardened) body part.
Test results indicate that MIG welding is acceptable as a repair method for AHSS such as DP, Martinsite and TRIP. Mechanical properties are within the expected range for each material in close proximity to the repair weld and therefore, acceptable.
Therefore, replacement of AHSS parts in the field as outlined above is acceptable. In any event, the OEM’s specific recommendations for the material and vehicle should be followed.