Segregation and phase distribution during solidification of carbon, alloy and stainless steels

Description

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 programmingwithin 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:IntroductionTheoryPrinciplesInterface ModellingSecondary Dendrite Arm CoarseningModel ValidityApplication of Peritectic Model to FeCrNi (Stainless) AlloysMacrosegregationAnalytical modelsTheory/Literature ReviewProposed Extensions to Standard FormulationThe Peritectic Reaction Simplified Peri/Eu-Tectic Equilibrium DataSecondary Dendrite Arm Coarsening Numerical modelsLiterature ReviewBasis of Current WorkModel AlternativesModel FacilitiesThe Peritectic ReactionExperimental workScope of StudyLiquidus ExperimentsEquilibration Furnace ExperimentsOptical MetallographyElectron Metallography and Mass SpectroscopyValidation of computed microsegregationComparison with Jernkontoret DataFurther ComparisonDiscussionModelling FeaturesEquilibrium DataValidation of Input DataValidation of ModelComposition GuidelinesAlloy DesignImplications for MacrosegregationModel PropertiesProspects for Future Work Summary and conclusionsReferencesTablesFiguresAppendix