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Title: Modeling of ferrite formation in nodular cast iron: Influence of silicon content

Silicon is commonly used in nodular cast iron due to its graphitizing and ferritizing effect. A usual silicon content is 2.2 to 2.7%. Nodular cast iron is often alloyed with pearlite-promoting elements, such as Mn, Cu or Sn, to increase the strength. The result is usually a casting with a considerable variation in ferrite/pearlite ratio in different parts due to the variation in thermal history. When increasing the silicon content up to a level of about 3.5 to 4%, the structure will usually be predominantly ferritic. However, due to the solution hardening of ferrite by silicon, a good strength is obtained. This is a promising way to obtain nodular iron castings with desirable and predictable properties. Plate castings (3 to 50 mm) have been cast with five different silicon contents (1.7 to 4.9%). The cooling curves were analyzed by thermal analysis in order to derive the transformation kinetics for the ferrite growth. The results have been the basis for the derivation of a new growth model for the ferrite during an interface controlled stage. It is shown that the action of silicon on the ferrite growth only is related to the transformation temperature, which drastically increases when the silicon contentmore » is raised. To verify the models, a redesigned plate casting was cast with a nodular iron containing 4.00 % silicon. The filling sequence, solidification and solid state transformation in this casting have been simulated using a FDM-program with models for nucleation and growth of all relevant phases. It is shown that the presented models can be used to predict the structure development in the complex situation of continuous cooling in a sand mould.« less
Authors:
 [1]
  1. Royal Inst. of Tech., Stockholm (Sweden)
Publication Date:
OSTI Identifier:
227796
Report Number(s):
CONF-9509118-
ISBN 0-87339-297-3; TRN: IM9622%%73
Resource Type:
Conference
Resource Relation:
Conference: 7. Conference on modeling of casting, welding and advanced solidification processes, London (United Kingdom), 10-15 Sep 1995; Other Information: PBD: 1995; Related Information: Is Part Of Modeling of casting, welding and advanced solidification processes, 7; Cross, M. [ed.] [Univ. of Greenwich, London (United Kingdom). Centre for Numerical Modeling and Process Analysis]; Campbell, J. [ed.] [Univ. of Birmingham (United Kingdom). School of Metallurgy and Materials]; PB: 1030 p.
Publisher:
Minerals, Metals and Materials Society, Warrendale, PA (United States)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 99 MATHEMATICS, COMPUTERS, INFORMATION SCIENCE, MANAGEMENT, LAW, MISCELLANEOUS; CAST IRON; SOLIDIFICATION; MATHEMATICAL MODELS; SILICON ADDITIONS; MICROSTRUCTURE; PEARLITE; AUSTENITE; GRAPHITE; CHEMICAL COMPOSITION; PHASE TRANSFORMATIONS; INTERFACES; PHASE DIAGRAMS; KINETICS; DIFFUSION; THERMAL ANALYSIS; ACTIVATION ENERGY; SIMULATION