Porosity and non-metallic inclusions in cast iron produced with a high proportion of scrap

Abstract

The work is devoted to the problem of an increase in the proportion of scrap metal in castings smelted and produced from wear-resistant chromium cast irons. Castings obtained with more than 60% of armor scrap and cracked during solidification and subsequent heat treatment were selected as research objects. Castings of similar mill armor after operation characterized with different wear resistance were selected to compare the characteristics of the structure and properties. The composition, structure, amount of non-metallic inclusion and porosity of samples cut from identical places of castings were studied with the help of the methods of optical and scanning microscopy, metallographic analysis, X-ray fluorescence analysis, and measurement of Vickers hardness. The characteristic localization of non-metallic inclusions of various types in the structure of cast iron samples was considered. An increase in the proportion of non-metallic inclusions in cast irons obtained using a high proportion of scrap was found, and it was shown that non-metallic oxide inclusions with a loose structure had the most negative effect. Along with porosity and primary crystals of carbide (CrFe)3Ctheydo not prevent the propagation of cracks caused by internal stresses arising during crystallization and subsequent polymorphic transformations in castings.