Effect of Pre-heat Treatment on Microstructure and Mechanical Properties of Cryorolled Low Carbon Steel

Abstract

Abstract Low carbon steel cannot meet the requirements of most manufacturing and production industry in modern society due to its limited strength. In recent years, ultrafine-grained (UFG) structure steel with grain size below 1 µm has been studied aggressively, because they are expected to provide superior mechanical properties. The present works aim at producing UFG in low carbon steel using cryorolling and investigated its effect on microstructure, mechanical properties and corrosion behaviour. The samples were prepared by pre-annealed at different annealing temperatures (550°C, 750°C and 900°C) followed by cryorolling at 50% thickness reduction. Microstructure and mechanical properties of the cryorolled low carbon steel at different pre-heat treatment were investigated by means of optical, scanning electron microscope (SEM), X-ray Diffraction (XRD), Vicker microhardness and tensile test. The grain aspect ratio decreases for both annealed and cryorolled samples. However the cryorolled samples have the higher grain aspect ratio as compared to annealed sample. All the cryorolled samples have lower crystallite size and higher lattice strain than annealed sample. Among the cryorolled, sample pre-annealed at 500°C has the highest grain aspect ratio, lowest crystallite size, and the highest lattice strain. The high hardness (162.3 Hv) recorded for sample annealed at 550°C followed by cryorolling with 58.1% increment. The cryorolled sample pre-annealed at 550°C showed a remarkable increase in both tensile and yield strength with the value of 567 MPa and 566.6 MPa respectively.