Directional Properties of a Modified 5% Cr Tool Steel Ausformed by Torsion
Report Number: AFOSR-4012 Author: Toth, R. G. Author: Polakowski, N. H. Corporate Author: Illinois Inst. of Tech. Dept. of Metallurgical Engineering Date of Publication: 1962 Pages: 9 Contract: AF 49(638)308
Abstract: A modified 5% Cr tool steel (0.35% C, 5% Cr-Mo-W-V) was quenched into a hot bath at 800° to 900° F, twisted in the austenitic bay range and air cooled to produce martensite. Room-temperature torsion tests in the pretwist direction showed a nominal fracture shear stress of up to 320,000 psi compared with 245,000 after ordinary hardening. The fracture changed from brittle (45°) to the shear type after pretwisting in excess of γp = 1. Reversed torsion or axial tension on pretwisted material invariably gave brittle fractures and a lower fracture stress than quenching alone. These results are indicative of a transverse weakness of ausformed steel. On the other hand, strengthening by torsion may be useful in applications involving substantially unidirectional torsional loads.
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