Prediction of Austenitic Weld Metal

With advent of new stainless steels, a wider range of alloys must be considered in predicting ferrite BY D. L. OLSON ABSTRACT. Diagrams, such as the Schaeffler and DeLong diagrams, have been used to assist in the proper selec-tion and use of austenitic filler materials and to predict weld metal microstruc-tures and properties. These diagrams have been very successful in predicting the amount of delta ferrite in stainless steel weld metal. This paper is concerned with the predictability of austenitic weld metal microstructure and properties over a larger compositional range. There are two main different types of phase transformations associated with austenitic weld metal. Existing analytical methodology has been successful at pre-dicting quantitatively the nature of the liquid to delta ferrite transformation. But the austenite to martensite transforma-tion for high alloy weld metal needs to be better understood if welding consuma-bles for new high manganese ferrous alloys are to be developed to achieve optimum properties and service behav-ior. In this paper, new expressions are introduced to predict the martensite start room temperature composition or the martensite start temperature. Some of these high manganese ferrous alloys are the basis for the new "no chromium" stainless steel. Various available diagrams, which allow for the prediction of weld metal microstructure, will be given. New mathematical forms for expres-sions to predict weld metal phase stability and microstructure, based on solution thermodynamics and kinetics, will be introduced. These new expressional forms should allow for better predictabil-ity over a larger alloy range. The non-homogeneous (cored) nature of the weld metal composition will also be consid-ered. These new forms can allow funda-mental alloying and solid solution infor-mation to be obtained from the micro-structure or property correlations with the weld metal compositions