Řízená modifikace nekovových vměstků pro výrobu oceli s vysokými požadavky na mikročistotu

Abstract

Controlled modification of non-metallic inclusion for steel production with high requirements to microcleanliness. The PhD thesis is focused on a possibility of influencing micropurity by controlled non-metallic inclusion with aluminium killed steels secondary treatment, by ladle furnace with a following vacuum process. The first part contains detailed research of modification of aluminium inclusions by addition calcium. Based on the gained theoretical information, there was made a series of different variation of inclusion modifications by addition of CaSi in an experimental part. The results were evaluating by case hardening steel grades 18CrNiMo7-6, 18NiCrMo5 and quench tempering steel 42CrMo4 casting on bloom continuous casting. The evaluation has used plenty of methods: optical emission spectrometry (method GISS), ternary diagram (CaO-Al2O3-MgO, Ca-S-Al), microcleanliness evaluation by standard ASTM E45 and oxygen determination. The information measured was compared to the results with target of a possible evaluation of micropurity during secondary metallurgy. The findings revealed clarified many processes going on in liquid steel with a proposal of optimal technology with regard to microcleanliness and steel castability.