INTEGRATED CASTING-HEAT TREATMENT PROCESS ROUTE FOR NEAR NET SHAPE ADI CASTING PRODUCTION

摘要

This paper focuses on developing an innovative process route for Austempered Ductile Iron (ADI) casting production. The innovative process route introduces an integrated approach towards casting and heat treatment practices for the production of near-net shape light-weight ADI casting in a permanent mould. It is based on the fundamental correlation between the production parameters and its combined influences on the microstructure to get the desired mechanical properties and performance in ADI castings. Casting and heat treatment practices are implemented efficiently in a control manner using thermal analysis adaptive system (melt quality) and fluidized bed heat treatment facility (controlled and uniform heat treatment) respectively to optimize the foundry practices for ADI production. The influence of austempering time on the microstructural characteristics, mechanical properties, and strain hardening behaviour of ADI was studied. Optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses were performed to correlate the mechanical properties with microstructural characteristics. It was observed that the mechanical properties of resulting ADI samples were influenced by the microstructural transformations and varied retained austenite volume fractions obtained due to different austempering time. The results indicate that the strain-hardening behaviour of the ADI material is influenced by the carbon content of retained austenite.