Effect Of Mn And Si On Structures And Mechanical Properties Of Heavily Cold-Rolled And Annealed Pearlitic Steels

The changes of microstructures and mechanical properties of heavily cold -rolled and annealed pearlite were investigated by the use of SEM, TEM and XRD etc. in fully pearlitic Fe-0.8C alloys with different contents of Mn and Si. The effect of Mn and Si on the structures and mechanical properties were examined. The following results were obtained:For the as-transformed specimens, the tensile strength and yield strength are increased although the total elongation and uniform elongation hardly change with the addition of Mn or Si.As the rolling reduction increases, the strength of the cold-rolled specimens increases although the ductility remains nearly the same after the drastic decrease by 60% cold rolling. The addition of Mn and Si results in the increase in strength (250~450MPa) whereas their effect on the ductility is negligible.During the annealing at 923K after cold rolling, the growth of cementite is remarkably retarded and the strength is raised by the addition of Mn or Si. The addition of Si is effective for improving the ductility especially while the strength is higher. The combined addition of Mn and Si is more effective for improving the tensile properties of pearlitic alloys heavily cold-rolled and annealed at 650℃For the low temperature (450℃) -short time annealing, tensile strength and yield strength of alloys with added Mn and Si are little changed in comparison with the cold-rolled specimens, but the ductility is obviously improved. The optimal tensile properties in the alloys with Mn or Si are obtained after annealing at 450℃ for 30 to 120s.