UNDERSTANDING THE MECHANISM OF GRAIN REFINEMENT IN PLAIN CARBON STEELS

摘要

This paper documents a series of plate casting experiments in 1010 steel. A set of castings with various levels of rare earth (RE) silicide and engineered grain refiner were produced via induction melting and green sand molds. One set of castings also contained a high phosphorous content to enable etching for the solidification structure. Metallographic and tensile specimens were examined to determine the resulting microstructure and property changes. Yield strength, ultimate tensile strength and percent elongation significantly increased with the RE additions. This increase appeared to be primarily a function of the cerium content of the final castings. Examination of the phosphorous containing castings revealed the solidification morphology changed from a columnar to equiaxed type. Electron microscopy revealed RE oxides formed in both sets of castings. The strength and solidification morphology changes were likely caused by the nucleation of 5-ferrite on these RE oxides.