| The present study aims at investigating the correlation of carbon content, aging and bake hardening characteristics, and yield point elongation(YPEl) in cold-rolled and annealed sheet steels. It was found that solute carbon content less than 10 weight ppm existed without contributing to both bake hardenability(BH) and aging index(AI). The yield point elongation of as-annealed steels showed a good correlation with carbon content in the range of carbon content less than 10 weight ppm, but showed a weak correlation with carbon content above 10 weight ppm. In contrast, both bake hardenability and aging index which were not observed in the steels with carbon content less than 10 weight ppm, increased with increasing the carbon content above 10 weight ppm. Increasing Mn content from 0.2% to 1.0% in Ti-added ultra-low carbon steels contributed to decrease in BH, AI, and yield point elongation. This was because more Mn content participated in the sulfide precipitation as MnS, resulting in the increase in Ti content available to scavenge solute carbon. |
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