SYMPOSIA PAPER Published: 01 January 1950

Sigma Phase in Several Cast Austenitic Steels


Since there are many applications of modern piping systems that involve metal that will withstand temperatures up to 1750 F., producers of cast austenitic steel valves and fittings have been faced with the problem of structural stability of these castings when operated long periods of time at temperatures ranging from 1000 F. to 1750 F. Six materials commonly used for cast valves and fittings were investigated, three cast 18-8 alloys and three cast 16–35 alloys, with respect to the embrittling effect of the sigma phase after exposure to temperatures of 1000 F. to 1500 F. The chemical compositions of the materials tested are given in Table I. The embrittling effect was determined by means of keyhole notch Charpy impact testing at both room and elevated temperatures. Identification of the sigma phase was made by means of metallographic and X-ray diffraction techniques. The C9 and C9 + Mo material was annealed by water-quenching from 2100 F. The C9 + Cb material was annealed by air cooling from 1850 F. All the 16–35 type material was annealed by water quenching from 1950 F.

Author Information

Malcolm, V., T.
The Chapman Valve Manufacturing Co., Indian Orchard, Mass.
Low, S.
The Chapman Valve Manufacturing Co., Indian Orchard, Mass.
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Developed by Committee: E04
Pages: 38–47
DOI: 10.1520/STP46102S
ISBN-EB: 978-0-8031-6741-4
ISBN-13: 978-0-8031-6506-9