Abstract
The effect of working temperature and that of subsequeut low-temperature annealing on the hardness and the magnetic properties have been investigated for low carbon mild steel and pure copper.
Specimens were deformed at temperatures between 75°C and 700°C, and then thier hardness and magnetic properties were measured at room temperature. The higher the working temperature on pure copper the less its hardness, while the hardness of mild steel increases at first, reaching maximum at about 250°C and then decreases in accordance with increasing working temperatures. It is because of diffusion of carbon and nitrogen atoms in α-Fe during deformation.
Though the mild steel is hardened by annealing at low temperature after cold working, it is still more hardened through deformation at elevated temperatures.
When specimens are annealed for 30min. at temperatures at 100°C to 700°C after elevated working temperature, the recovering temperature of mild steel and that of copper slightly increase according to working temperatures, and the hardening phenomena generally observed in annealing cold worked mild steel, were not seen when the working temperature was above 250°C.
