SEDL / STP / STP369-EB / STP43740S

Modified Type 316 Stainless Steel with Low Tendency to form Sigma

Spaeader, C. E.
Research engineer, Stainless Steel Products, Applied Research Laboratory, U. S. Steel Corp., Monroeville, Pa.

Brickner, K. G.
Technologist, Applied Research Laboratory, U. S. Steel Corp., Monroeville, Pa.

Pages: 8    Published: Jan 1965

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Abstract

A study was made to determine whether decreasing the chromium or the chromium and molybdenum contents of AISI Type 316 stainless steels would decrease the tendency for sigma-phase formation without impairing the elevated-temperature strength of the steel.

The results of this study showed that in comparison with AISI Type 316, a modified Type 316 steel with about 14 per cent chromium instead of the normal 16 to 18 per cent chromium had about the same coefficient of thermal expansion, similar room- and elevated-temperature tensile properties, similar creep and creep-rupture strengths, and slightly better hot workability. Moreover, the impact strength of modified Type 316 steel after exposure for 6000 hr at 1100, 1300, and 1500 F was markedly superior to that of AISI Type 316 steel. The results of X-ray and metallographic studies indicated that the superior impact strength of the modified Type 316 was the result of lesser amounts of sigma formed in the new steel.