Abstract
Effects of pre-heattreatment on the anisothermal relaxation of S30C, S45C, SUP3 and quasi-SUP6 during annealing were studied.
In order to investigate the relaxation behavior, the changes of load of variously heat-treated steels, which were made to keep the constant deflection in the 4-points-support bending tests, were measured continuously during heating and cooling. In annealed steel, the load remained, to some extent, upto temperature Ac1, but in quenched or quenched and tempered steel, a sharp decrease of the load was recognized with progress of tempering process. These phenomena can be explained by considering the high-deformability of steel during its structural change. It is necessary to consider these facts in the discussion of the mechanism of stress-relief-annealing.
