High strength steels - stress relaxation and derived creep characteristics at room temperature

Abstract

The room temperature tensile strength and stress relaxation characteristics of 301 stainless, 431 stainless and Vascomax 300 maraging steels in the form of thin strip have been determined. On the basis of Ultimate Tensile Strength (UTS), the maraging and 431 steels (UTS ~ 1.8 GPa) are marginally superior to the 301 steel (UTS ~ 1.75 GPa). Relaxation data show that plastic deformation occurs at ~ 45% UTS in the 301 steel, ~ 60% UTS in the 431 steel and ~ 65% UTS in the 300 steel. These stresses, which define the lower limit above which creep will certainly occur, are significantly lower than 0.1% proof stresses measured directly from stress/strain data. The relaxation data were used to estimate logarithmic creep rates under constant load for these materials. There is a comparative superiority of the maraging steel over the two stainless steels in the range 80-90% UTS.