Solidification macrostructure is of great importance for the properties and the quality of castings made from austenitic grade stainless steels (ASS) because there are limited options to change as-cast macrostructure in the solid condition. A typical cast macrostructure of ASS has a fine surface chilled zone followed by an elongated dendrite zone, columnar to equiaxed transition (CET) zone, and centrally located equiaxed crystals. Several castings from ASS were produced to determine the effects of casting geometry, chilling, and grain refinement on CET. The transient thermal field in solidified heavy castings was simulated and used to determine an isotherm velocity (V) and the thermal gradient (G) in mushy zone at 50% solid fraction. The critical value of the parameter Gn/V was determined from the macrostructure of the cylindrical casting. Using this value, the location of CET was predicted in the heavy rectangular casting and this prediction was in agreement with experimental macrostructure. Two methods of controlling casting macrostructure by using a chilled mold to stimulate extensive columnar zone and by using melt grain refinement to produce fine equiaxed crystals were experimentally verified and simulated.
S. N. Lekakh et al., "Control of Columnar to Equiaxed Transition in Solidification Macrostructure of Austenitic Stainless Steel Castings," ISIJ International, vol. 57, no. 5, pp. 824-832, The Iron and Steel Institute of Japan (ISIJ), Jan 2017.
The definitive version is available at https://doi.org/10.2355/isijinternational.ISIJINT-2016-684
Materials Science and Engineering
Keywords and Phrases
Solidification; CET; Grain refinement; Stainless steel
International Standard Serial Number (ISSN)
Article - Journal
© 2017 The Iron and Steel Institute of Japan (ISIJ)