Integrated analysis of the use of chills in high-chromium cast iron plate casting: effects on shrinkage, hardness, and microstructure via computational simulation and DoE

Abstract

High-chromium cast iron parts are widely used in severe wear environments, such as in the mining, cement, and steel industries, due to their high hardness and excellent abrasion resistance. This study investigates the effects of using metallic chills in the mold on the microstructure, hardness, and shrinkage formation in castings according to the ASTM A532 Class III Type A standard. To define the geometry of the chills, the Design of Experiments (DoE) statistical methodology was adopted, allowing the analysis of 525 distinct geometric combinations supported by computational simulation. Four samples were cast, two with and two without chills, and subjected to metallographic, hardness, and microhardness tests. The results demonstrated that the chills act as microstructural refining agents, promoting a hardness increase of up to 100 HB without significant changes to the predominant phases, austenite and $M_7C_3$ carbides, in addition to considerably reducing internal porosity. The application of DoE was essential to identify, in a systematic and statistically robust manner, the most effective dimensions of the chills, highlighting width as the parameter with the greatest influence on defect mitigation. As a result, castings with chills are expected to exhibit superior performance in abrasive applications, with longer service life and reduced need for field replacements, contributing directly to operational efficiency and equipment reliability