STUDY ON THE SPRING MATERIALS (VII)

Abstract

Many materials were studied hitherto by the author as the spring materials for high temperatures, and these results were reported in Tetsu-to-Hagané as the 1st to the 6th reports.
In the 6th. report, (Tetsu-to-Hagané Vo. 42 No. 4. p. 333-337), it was recognized that with the material corresponding to a die steel No. 5, the treatment in a hot bath at 600°C and quenching from 1100°C was confirmed as the best heat-treatment. In the impact hardness test of ordinary quench-tempered Si-Mn steel, the almost linearly descending inclination of impact hardness was recognized with ascent of testing temperature.
In this report, the test was made on thermal expansion coefficient, impact hardness at high temperature and HRC hardness, impact value, fatigue test at room temperature with Si-Mn steel, and thermal expansion coefficient and torsional test at high temperature with die steel No. 5, and the results were summerized as follows.
(1) The maximum hardness value in Rockwell C scale of Si-Mn steel, was obtained by quenlching at 900°C and tempering at 350°C.
(2) The Izod impact value at room temperature of die steel No. 5, austempered at 600°C was superior to that of Si-Mn steel.
(3) The number of repeatings by fatigue test with the Upton Lewis testing machine of die steel No. 5 austempered at 600°C was superior to that of Si-Mn steel.
(4) The maximum torsional stress of die steel No. 5, was recognized by the isothermal treatment at 600°C×1h. in a constant bath and quenching from 1, 100°C