A PARAMETRIC CORRELATION FOR STRESS RUPTURE DATA INCORPORATING HEAT TO HEAT VARIATIONS AND ITS APPLICATION FOR 9CR-1MO STEEL .2. FURTHER CONSIDERATIONS AND APPLICATIONS OF MULTIPLE HEAT CORRELATIONS

The results from the multiple heat correlation of stress rupture data for eleven heats of a 9Cr-1Mo steel described in Part I raise the ques tion whether one (rather than two, as proposed in Pert I) independent heat-indexing constant is adequate for the correlation. Numerical inve stigation detailed in the present paper however shows that this is not fully satisfactory. Empirical correlations are derived which should p rove useful in estimating the values of the heat-indexing constants of a new heat of this material with similar chemistry. Use of the multip le heat correlations for predicting allowable stresses for extended se rvice is discussed. A systematic approach is developed for material qu alification from creep rupture considerations using a small number of rupture tests of short durations with or without prior estimates of he at-indexing constants. Planning of creep rupture tests to economically develop the necessary data base for multiple heat rupture correlation is also discussed.