Volgograd State Technical University (Volgograd, Russia)

A. A. Shuklin, Postgraduate Student, Dept. of Materials Technology
D. V. Rutskii, Cand. Eng., Associate Prof., Head of the Dept. of Materials Technology, drutskii@vstu.ru
N. A. Zyuban, Dr. Eng., Prof.

Volzhsky Pipe Plant, Branch of TMK (Volzhsky, Russia)
A. N. Kuznetsov, Chief Steelmaker, vtz@vtz.ru

This paper presents the results of a metallographic examination of ladle samples taken during the production of continuous cast billets from titanium-containing austenitic stainless steel grades. Using optical and electron microscopy, it was established that the steel contains oxides (Al-Ca-Mg-Si-Ti-Cr)O, nitrides (Ti-Cr)N, sulfides (Ti-Cr)S, and complex non-metallic inclusions following decarburization and vacuum treatmentreleased after decarbonization and vacuuming at a vacuum oxygen decarburization plant (VOD). The identification of non-metallic inclusions in samples collected during the stages of ladle treatment and casting revealed that the presence of chromium oxides (AlTiCrO) in these inclusions indicates their formation is due to insufficient deoxidation of the steel conducted after the decarburization stage. The high content of titanium nitrides (TiN) naturally arises during the alloying of steel with titanium. The analysis of the composition and nature of the non-metallic inclusions has allowed for the determination of key directions for improving the production technology. Unlike the previously used production scheme for obtaining similar steel, which included VD and was characterised by the precipitation of refractory oxide and oxynitride inclusions in deposits on the walls of the steel-teeming channel [1], the present work introduced changes to the process equipment: a vacuum-oxygen decarburisation (VOD) unit was commissioned, and the production technology, including secondary steelmaking, was revised. Implementation of the proposed technological scheme ensured stable casting with minimal fluctuations of the metal level in the mould.

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