Determination of Nitrogen Content in the Slags of CaO — Al2O3 System by Kjeldahl Method

Abstract

Due to the expansion of the nomenclature of steel grades in the industry and the development of new special alloys with increased strength and corrosion-resistant properties, both in the metallurgical industry and in welding, researchers are very interested in the dissolution of nitrogen in metals and slag. Gas permeability of slag is one of the reasons for the appearance of gases in both the base metal and the weld metal. It is determined by two properties: solubility and mass transfer of gases in slag. In addition, in real conditions, the process of dissolving gases in slag is influenced by the transmission of gases by convection and the initial content of gases in the slag. The transfer of gases to the metal through slag is observed mainly in electroslag processes and welding under flux when there is no direct contact of molten metal with a gas phase. To evaluate the nitrogen permeability of the slag and the mechanism of nitrogen solubility in the high alloys it is necessary to have a reliable, highly sensitive and economical method of gas analysis of nitrogen in metals and slags. A review of nitrogen determination methods in steels is presented. The method of analysis of nitrogen in slags of the CaO — АL2O3 system by the Kjeldahl method was tested. The results of the analysis of slag compositions of the CaO — АL2O3 system allowed us to conclude that it is possible to use the Kjeldahl method (determination of nitrogen content in steels) for the determination of nitrogen content in slags. This technique and installation can be recommended for use by metallurgists and welders as a reliable, simple and inexpensive method for nitrogen content analysis in metals and slags.