Proposed Modification to Schaeffler Diagram for Chrome Equivalents and Carbon for More Accurate Prediction of Martensite Content

摘要

The austenitizing effect of carbon strongly alters the microstructure of Cr-Ni steels, which is not taken into consideration by the Ni equivalent in the Schaeffler diagram. By determining the austenitizing effect of carbon and the alloying elements, a mathematical formula was devised to calculate a new nickel equivalent, denoted as Ni_(eqB). On the basis of this, the Schaeffler diagram can be improved. A new regression equation was constructed that gives a good estimation of the measured M_s temperatures. It was concluded that M_s temperatures for the hardenable high-alloy creep-resistant steels, depending on the composition of the steel heats, vary over a wide range. That is why the crack sensitivity of weld metal changes strongly during the welding operation.