| The current intercritical annealing process applied on ordinary commercial C-Mn steel has successfully increased its yield-strength, ay from-105 MP a to 807 MP a, and its tensile strength, au, from 523 MPa to be 1007 MPa, with insignificantly altered the uniform elongation, eu. The impact strength at room temperature increases from 2.850 J/mm2 to 3.587 J/mm2 on the longitudinal direction and from 1.625 J/mm to 3.612 J/mm2 on the transversal direction. Other important result from this research work, the intercritical annealing a/so has successfully eliminated "discontinuous yielding" the unwanted metallurgical phenomenon during metal forming process upon automotive body production Experimentally, this research work proved disappearance of the discontinuous yielding was due to a residual stress and high dislocation density built up within Ferrite grains. Reappearance of the discontinuous yielding is calculated to be 31 years, therefore, application of Dual Phase Steel produced by intercritical annealing is free from strain aging phenomena for a normal automotive life time. |