Effects of Rapid and Low Temperature Annealing on the Microstructure and Properties of Cold Rolled Low Alloy Low-Carbon Steel Sheet

Abstract

In this study, a cold rolled low alloy low-carbon high-strength steel sheet was annealed at a short-term and rapid low-temperature by induction heating. The properties and microstructures of the steel at a heating rate of 50°C/s are studied. The results demonstrated that after low-temperature annealing, the microstructure of cold-rolled low-carbon high-strength steel is mainly composed of recrystallized ferrite, residual deformed pearlite, and spheroidized cementite. Furthermore, a small amount of hard structure is distributed between recrystallized grains. It was also seen that increasing the annealing temperature from 600°C to 700°C, the yield strength decreased from 947MPa to 663MPa, the tensile strength decreased from 948MPa to 702MPa, the elongation after fracture increased from 2.2% to 10.8%, and the microhardness decreased from 307HV to 223HV. The results confirm that increasing the temperature of low-temperature annealing is beneficial for reducing defect density, eliminating banded cold rolled microstructure, and improving uniformity.

Keywords: low-carbon high-strength steel, low-temperature rapid annealing, Mechanical properties, Microstructure