Microalloyed bake-hardening steels

A variety of bake-hardenable steels have been developed in the past two decades and implemented by automakers, to achieve good dent-resistance with formability. The evolution of these products is reviewed here as alloy compositions, annealing (and coating) processes, and performance expectations have changed over the years through the progression from traditional low-carbon grades to hot-dip coated ‘bake-hardenable interstitial-free’ type steels, to Advanced High Strength Sheet Steels. The role of microalloying is especially highlighted, with some emphasis on effects of Nb. Mechanistic effects are discussed, and some thoughts are presented related to areas or opportunities for improved understanding in the future. (AU)