Difficulties in the Production of Ausferritic Nodular Cast Iron without Heat Treatment

Abstract

The paper presents results of tests carried out on ausferrite carbide matrix alloyed ductile cast iron. The ausferrite was obtained via addition of Cu and Mo alloying elements. This eliminated heat treatment from the alloy production cycle. The article presents results of tests of the quality of the obtained material. Emphasis was put on metallographic analysis using light and scanning microscopy. Works also included chemical composition tests and EDS analysis. Strength tests were executed in an accredited laboratory. It is possible to create a raw ausferrite carbide matrix without subjecting an alloy to heat treatment. However, it turned out that quality parameters of cast iron were insufficient. The obtained material hardness was 515 HB, while Rm strength and A5 ductility were very low. The low tensile strength of the analyzed alloy resulted from the presence of degenerate graphite secretion (of flake or vermicular shape) in the cast iron. The tests also demonstrated that the alloy was prone to shrinkage-related porosity, which further weakened the material. Alloys made of alloyed ductile iron of ausferrite matrix micro-structure are very attractive due to elimination of the heat treatment process. However, their production process and chemical composition must be optimized.

Keywords

• ausferrite
• nodular cast iron
• alloyed cast iron
• casting quality
• vari-morph cast iron