Hot-Tensile Data and Creep Properties Derived There-from for 316L(N) Stainless Steel with Various Nitrogen Contents

Abstract

Many researchers have proposed equivalence between hot-tensile data and creep rupture properties based on Larson-Miller or similar time-temperature parameter approaches. This is attractive from the point of view economy of time and cost of testing as compared to the long-time creep tests. Basic idea behind such a comparison is that the plastic deformation behavior controlling both the hot-tensile and creep properties are the same, provided the microstructure does not ndergo significant changes for the time periods under consideration. Particularly, such a procedure will be useful in alloy development and preliminary screening. Such a time-temperature parameter approach is adopted in the following for predicting the stress-rupture behavior of 316 L(N) stainless steel from reported hot-tensile properties and the results are compared with actual creep test data for almost a similar steel at two temperatures. It is found that the predicted data follow the ASME Code Case minimum stress-rupture data for 316 SS (stainless steel) and thus are very conservative. Predicted creep rates are also much larger than the actual ones for the one case where comparison has been made. The conclusion drawn is that considering the microstructural stability of the low-carbon nitrogen bearing SSs (at least for lower nitrogen contents), the method of equivalence of hot-tensile and stress-rupture data seems feasible. But test results at different strain rates, rather than the single value considered here, along with the more accurate method suggested would yield better results. In addition, using some old results from the literature, relation for variation of yield stress with temperature, nitrogen content and grain-size for the present heats of steel (with various nitrogen contents) has been derived.