Reducing contamination of high-quality steel non-metallic inclusions and the influence of the method of selecting a metal sample on its evaluation

Abstract

The paper presents a literature review on the sources of non-metallic inclusions (NIs) in high-quality steel, as well as studies covering all aspects of this problem, is presented. Modern ways to reduce the contamination of high-quality steel are considered. The objects of the study were candy samples of metal used for express analysis of the chemical composition of steel, special “clean” rod metal samples, as well as metal samples taken from metal products. For a more accurate assessment of the NI content in the liquid metal or for conducting in-depth research and optimization tasks to reduce NIs in the metal, it is recommended to use special samplers that can take a metal sample in an inert atmosphere and without access to air. The task was set to investigate changes in NIs from the steel ladle to the interme-diate ladle and the continuously cast billet, i. e. along the technological chain, and to assess possible sources of NIs in the final metal products. Using scanning electron microscopy and melting in an inert gas flow on a gas analyzer for aluminum-killed pipe steel, the total oxygen content, compositions and morphology of NIs were studied. In order to reduce the content of NIs in high-quality steel, measures aimed at reducing, first of all, inclusions of exogenous nature due to the ingress of slag into the continuously cast metal during casting are considered. NIs are also formed due to the processes of secondary oxidation of the metal during casting on the continuous casting machine and the non-optimal technology of modifying the inclusions with calcium. To eliminate these negative elements of the technology for pro-ducing high-quality steel, effective corrective measures for improving the end-to-end steel production technology are presented