Bake hardening - (Hardening after baking)

This particular case of ageing after work-hardening mainly concerns cold-rolled and annealed thin sheets, then deformed by drawing, and painted with paint baked in at between 100 and 200°C.

Bake hardening combines easy shaping of highly ductile, low yield strength steel with significant hardening of the part, making it sufficiently resistant to impact.

The growing use of very low-carbon steels such as interstitial-free (IF) or ultra-low-carbon (ULC) steels, which are very soft, has made this mechanism very useful for meeting indentation resistance requirements in the automotive industry.

What's more, hardening is virtually "free", since it uses only a few ppm (parts per million) of carbon, but this aspect needs to be put into perspective because of the manufacturing constraints due to the precision required for the right carbon content, and the special annealing conditions that entail additional costs.

This mechanism can also be applied to certain types of steel packaging boxes.

This phenomenon has both mechanical and metallurgical aspects.