AN EVALUATION OF THE ELEVATED TEMPERATURE TENSILE AND CREEP-RUPTURE PROPERTIES OF WROUGHT CARBON STEEL
|Publication Date:||1 January 1970|
ABSTRACT: This report seeks to offer a best current assessment of the several elevated temperature properties that commonly form the basis for establishing allowable stresses or design stress intensity values. The results are presented in a form readily usable for that purpose. The data that are evaluated are those that have become available since the publication in 1955 of ASTM Data Series Publication DS 11 (formerly STP No. 180), "Elevated Temperature Properties of Carbon Steels," as well as selected data from that earlier publication. The body of the report provides, in text, tables and figures, details concerning the materials, the evaluation procedures that were employed, and the results.
In evaluating rupture strength, extrapolations to 100,000 hours were performed both by direct extension of isothermal plots of stress and rupture-time for the individual lots, and by a time temperature parameter, scatter-band procedure. Owing to a concern that different populations may be intermixed in a scatter band approach, the rupture strengths shown in the summary Fig. 1 represent the results of the direct individual-lot extrapolations.
A summary of the results of the evaluations is provided in Fig. 1. In this figure, all of the creep and rupture data have been treated as if from a single population, even though there is evidence presented in the body of the report that material produced to specifications that require a minimum tensile strength of 60,000 psi or higher has a greater rupture strength than material produced to specifications that require minimum tensile strengths less than 60,000 psi. Evidence is also offered for a slight superiority in rupture strength at the lower end of the creep range of temperature, of material made to "coarse-grain" practice. The yield and tensile strengths of Fig. 1 represent material that had been tempered after hot working or after normalizing, in practical recognition of the liklihood that material will receive such treatment during fabrication, if not before. The tensile strength curves of Fig. 1 recognize a distinct difference between material made to "coarse-grain" and "fine-grain" practice; however, the differences in yield strength were small, and scatter large, and the curves of Fig. 1 are based on a common trend curve for tempered, coarse- and fine-grain material. Individual trend curves for yield and tensile strength, expressed as strength ratios, are compared in Figs. 2 and 3.