Segregation and phase distribution during solidification of carbon, alloy and stainless steels 1 July 1986 to 30 June 1989 ; Final report

Technical steel research. — Contract No 7210-CF/801 (1 July 1986 to 30 June 1989). Final report. — Commission of the European Communities, 1989. — 260 p. A major, new computer model of as-cast microsegregation has been created which can be applied to the majority of carbon, alloy and stainless steels because of its ability to handle multicomponent compositions and the peritectic reaction in a rigorous manner. Comparison of computed and experimental data has shown strong correlation. The program can operate on a 1, 2 or 3 dimensional primary (static) or secondary (coarsening) dendrite arm representative basis, as desired, under variable cooling rate or heat extraction control. Subsequent, sub-solidus interface motion and diffusive adjustment is readily considered on the same morphological basis. The finite difference (FD) procedure uses second order interpolation for solute gradients at interfaces, with the interface position independant of nodal planes. A third order interpolation procedure is included for the remeshing of the FD array. The basic concepts and computer model are fairly general to metallic alloys although the emphasis for application is naturally on steel. In addition to the central work on the derivation of new, numerical routines and their programming within a FD formulation, important extensions have also been made on analytical equations for microsegregation and the analysis of secondary dendrite arm coarsening. The implications for macrosegregation have been discussed but only semi-quantitative treatments could as yet be added onto a detailed treatment of microsegregation. Multicomponent equlibrium data have been provided as a computerised database (MTDATA) which has been assessed against experiment and alternative predictive techniques. It is a powerful and flexible system although certain limitations have been highlighted where further work is required. Contents: Introduction Theory Principles Interface Modelling Secondary Dendrite Arm Coarsening Model Validity Application of Peritectic Model to FeCrNi (Stainless) Alloys Macrosegregation Analytical models Theory/Literature Review Proposed Extensions to Standard Formulation The Peritectic Reaction Simplified Peri/Eu-Tectic Equilibrium Data Secondary Dendrite Arm Coarsening Numerical models Literature Review Basis of Current Work Model Alternatives Model Facilities The Peritectic Reaction Experimental work Scope of Study Liquidus Experiments Equilibration Furnace Experiments Optical Metallography Electron Metallography and Mass Spectroscopy Validation of computed microsegregation Comparison with Jernkontoret Data Further Comparison Discussion Modelling Features Equilibrium Data Validation of Input Data Validation of Model Composition Guidelines Alloy Design Implications for Macrosegregation Model Properties Prospects for Future Work Summary and conclusions References Tables Figures Appendix