Abstract
In the autobody fabrication, both delayed aging properties at room temperature to suppress stretcher-strain and high bake hardenability are required for bake hardening steel sheets. In relation to the requirement, the effect of Mo on aging behavior has been investigated for ultra low carbon steels. Obtained results are as follows. Increase of yield point elongation during aging at 40°C after skinpass rolling is retarded by the addition of 0.025 mass% Mo. The effect of Mo for reducing aging deterioration is enfeebled as aging temperature rises, then bake hardening treatment at 170°C for 20min provides high hardenability. Thus, it is concluded that the addition of Mo is effective to compromise delayed aging properties and high bake hardenability. The effect of reducing aging deterioration is considered to be caused by short-range atomic interaction.
