Effect of warm cross-wedge rolling on microstructure and mechanical property of high carbon steel rods

Abstract

High carbon steel rods with a microduplex structure was fabricated by warm cross-wedge rolling (WCWR) using fully lamellar pearlite starting material. The microstructures and mechanical properties at different locations over the cross-section of the rolled rod were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and mini-tensile tests. The results show that after WCWR, the microstructure from the surface to 1/4 R of the rod was refined, and the sizes of cementite particles and equiaxed ferrite grains were about 0.1–0.2 and 0.3–0.4 μm, respectively. The spheroidization/recrystallization of cementite/ferrite was non-uniform from the surface to the center, and the cementite/ferrite near the surface experienced more complete spheroidization/recrystallization. After WCWR, the change in strength and microhardness over the cross-section of the rod was not so distinct from the surface to the center. However, the elongation (EL) and the percentage of reduction in area (RA) of the rod decreased gradually from the surface to the center. This change can be linked to the non-uniform distribution of equivalent strain and strain rate, which also decreased from the surface to the center.