High-Nitrogen Austenitic Stainless Steels

Abstract

The present paper summarizes the results of a number of investigations in which the effects of nitrogen on the mechanical properties of an austenitic stainless steel were evaluated. The results of studies on commercially produced plate indicated that increasing the nitrogen content of Type 304L steel to the range 0.10 to 0.13 percent increased the room and elevated temperature strength of this steel such that its strength was equivalent to that of Type 304 steel in both the welded and unwelded condition. The results of room and elevated temperature tension tests on product from four commercial heats of high-nitrogen (0.12 to 0.16 percent) Type 304 steel indicated that the yield and tensile strength of this steel was significantly increased. Creep-rupture tests were too limited to assess the effect of nitrogen on the creep-rupture strength of the steel. Some failures on punch marks of the creep-rupture test specimens were observed suggesting the possibility of some notch sensitivity in this steel. The results of a limited study on laboratory heats of Type 316L containing nitrogen in the range 0.02 to 0.19 percent indicated a significant increase in the elevated temperature yield and tensile strength of this steel. The creep-rupture strength at 1300 F also increased with increasing nitrogen content.