CONTROLLING OF THE NITROGEN CONTENT DURING EAF - TECHNOLOGY AND CONTINUOUS CASTING OF STEEL

摘要

One of the main problem of steel melting in EAF technology are excessive contents of nitrogen in a semi steel products. This concerns in peculiarity these grade of steels from which the good plasticity was required or steels designed to production of the wire rod for welding electrode. The object of investigations was the range of changes of the nitrogen concentrations in the liquid steel immediately before tapping from the UHP - EAF's (105 MVA) in dependence of the kind of metallic charge (scrap and other iron sources). Then the changes of nitrogen content were qualified during steel treatment in a ladle furnace and pick up of nitrogen content during continuous casting of rectangular billets was established. The theoretical description of nitrogen absorption during steel tapping and continuous casting was applied. The dependence among the nitrogen concentration in liquid metal and quantity of the carbon oxidized during oxygen injection was determined. The influence of electric parameters (length of electric arc) on the nitrogen absorption into liquid metal was also considered in the investigations. The influence of different materials bringing carbon into the bath as well as several kinds of scrap on nitrogen content in steel was considered in these investigations. The series of testing heats in the EAF were executed for verification of these settlements. As result of the modification of melting and casting technology, the decrease of the final nitrogen content of about 20 ppm in semi-product was achieved.