Sag Resistance OF Si-Mo and Si-Cr Spring Steels

Sag resistance was determined for a series of standard and experimental spring steels containing varying amounts of silicon, chromium and molybdenum. Of particular interest was the comparison in sag resistance among the SAE 5160, SAE 9260, Mn-Cr-Mo, 1Si-1/2Cr and 1Si-0.1Mo steels quenched and tempered to a common hardness of 50 HRC. The sag resistance was determined by room-temperature relaxation tests in which the specimens were stressed in tension for 150 hours under a given plastic strain. The results showed that in general the sag resistance increased as the silicon content increased. It was also observed that the higher the plastic strain applied in the relaxation tests the more beneficial effect molybdenum additions had on sag resistance.