In order to make clear the feasibility of forming of hardened steel during tempering, 4-pointssupport bending tests, acute-angle bending tests and tests on accuracy of forming were performed. Materials tested were S30C, S45C, SUP3 and quasi-SUP6.
The results of tests were as follows:
(1) For the sake of high-deformability of hardened steel during tempering, the steel could be bent in an acute angle without fracture during its heating from room temperature to tempering temperature when there were no defect on its surface.
(2) The load necessary for such working during heating upto the temperature that was used to obtain hardness suitable for springs (c.a. Rc 42), was about 15-times as much as that was required in the usual hot-working at the temperature above Ac1.
(3) The higher the carbon content of hardened steel, the better the accuracy of such forming works.