NITROGEN ALLOYING OF HIGH CHROMIUM STEELS BY GAS INJECTION IN THE LADLE

There is a steadily increasing demand for steel grades with increased nitrogen content in a certain range. Nitrogen is an important alloying element and it has a beneficial effect on mechanical and corrosion properties of stainless steel. Increased nitrogen content has a positive effect on the increasing of the pitting resistance equivalent in case of duplex stainless steels. Nitrogen can also substitute expensive nickel that strongly supports its use. There are several ways to increase nitrogen content in the steel. One of the most used ways is the nitrogen gas injection in the ladle. Solubility of nitrogen is significantly influenced by the chemical composition of the steel. However, due to nitrogen enrichment in the remaining liquid, gas pores can be formed during solidification of nitrogen-rich stainless steels. This article describes the results obtained during production of high nitrogen steels at steel plant VITKOVICE HEAVY MACHINERY a.s., mainly during production of martensitic 9% chromium steels and super duplex stainless steels.