Creep-Rupture Properties of Centrifugally Cast 1 1/4 Cr-1/2 Mo Alloy Steel Pipe

Abstract

The creep-rupture properties of tensile specimens made from 1 1/4 Cr-1/2 Mo centrifugally cast alloy steel pipe, conforming to ASTM A426-CP11, were evaluated at 1000, 1100, and 1200 F. At 1000 F, the pipe was evaluated in two normalized-and-tempered conditions, and at 1100 and 1200 F, in one normalized-and-tempered condition. Specimens were loaded to produce rupture in time ranging from less than 100 to about 2000 hr for determination of the minimum creep rate and the creep-rupture strength, and at lower loads to obtain additional minimum creep rate data. The rupture strength and minimum creep rate of the centrifugally cast pipe were compared to similar properties for the alloy in statically cast and wrought forms. Stresses required to produce a minimum creep rate of 10−5 percent/hr and rupture in 100,000 hr were compared to allowable design stresses specified by the ASME Boiler and Pressure Vessel Code and American Standards Association Specifications B31.1, Pressure Piping, and B31.3, Petroleum Refinery Piping. In both heat-treated conditions evaluated, the minimum creep rate of the pipe compared favorably with published data for the alloy in noncentrifugally cast forms and with the allowable stresses set by the ASME and ASA codes.