Abstract
Typical AISI alloy steels which are used extensively in the automotive industry were investigated. These steels were studied in order to provide a comparison with the steels now used for piping and elevated temperature service. The results indicate that the Cr-Mo steels now employed for piping are satisfactory in comparison with the AISI alloy steels. The steels were exposed at 900° and 1050° and, in several instances, 1200°F. They were either normalized or annealed before exposure and, in general, two carbon levels were investigated. The microstructure was observed after 34,000 hr exposure. Tensile and creep rupture properties were determined after 10,000 hr exposure. Graphite was observed in the Ni-Mo steels, but not in the chromium bearing steels, which were the most structurally stable of the AISI steels investigated. A slight decrease in tensile strength in the various steels was observed after exposure. The creep rupture strength of the nickel steels was similar to plain carbon steels, but the steels containing molybdenum or vanadium had a higher creep rupture strength.
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