Beyond conventional product development of castings properties predictions for efficient design CastDesign

Purpose and goal

The aim of the project was to improve the static tensile and thermo-mechanical fatigue (TMF) properties of lamellar cast iron components through alloying. The goal was to understand how Mo and alternative alloying elements affect the solidification and microstructure formation including defects to, as far as possible, benefit from the positive effects of Mo alloying. Initially compacted graphite iron was also considered, but was omitted to gain a more compressive understanding of alloying in LGI.

Expected effects and result

The thermal fatigue behaviour for LGI is mainly influenced by Mo content and to a lesser extent by and Nb while for low cooling rate the effect of alloying on the TMF is negligible. Alloying with Nb and/or Mo improves the mechanical properties independent of cooling rate. Titanium promotes the formation of primary austenite and enhances the tensile strength. Models were developed for the prediction of tensile and TMF properties based on the experimental results. The models coupled deferent metallurgical parameters like alloying content and solidification rate with these properties.

Planned approach and implementation

Ultimate tensile strength (UTS) and thermo-mechanical fatigue properties of lamellar graphite irons have been investigated for three different cooling rates and eight different micro alloying levels of Mo and Nb. Additionally casting trials and interrupted solidification investigations performed for studying the influence of Ti and Mo alone on the microstructure and consequently on the UTS of lamellar graphite iron. Finally linear multiple regression analysis were made to determine the simultaneous influences of composition, solidification time and cooling rate on the UTS.