Effect of Processing Parameters on the Deformation Behavior of Low Carbon Dual Phase Strip steels at High strain rates

摘要

This study primarily involved the production of dual phase microstructure in low carbon strip steels, via a modified steel-processing route, with the subsequent determination of the dynamic properties of the strip steels. Two dual phase commercial trial grades with compositions 0.094 percentC-0.155 percentSi-1.48 percentMn-0.096 percent V and 0.096 percentC-0.13 percentSi-1.51 percent Mn-0.096 percent V respectively were studied. The steels in the as-received condition had ferrite-pearlite microstructures and were subsequently subjected to intercritical annealing, followed by rapid cooling quenching. A series of ferrite-martensite-bainite structures were developed and the nominal yield strengths of these modified steel microstructures ranged from 280 to 450 MPa, with tensile strengths in the range of 600 to 800 MPa. Low and high-speed tensile testing at strain rates within the range of 0.001, 1 and 100s~(-1) were performed. The results showed that the yield/proof strength and tensile strength increased with increasing volume fraction of martensite and increasing strain rate. In particular, steels with a predominantly ferrite-martensite microstructure showed improved performance, as in terms of the strain rate sensitivity and work hardenability properties are concerned, compared with microstructures with additional non-equilibrium "constituents, characterised mainly as bainite.