Providing for the necessary quantity of delta-ferrite in metal of austenite-ferrite welds

The possibility is studied of controlling the amounts of delta-ferrite in the metal of austenitic seams in gas-blanketed welding by introducing nitrogen into the protective media. The welds have been made with a permanent and a consumable electrode on steel Kh18N9T and on an experimental steel. It is shown that the content of delta-ferrite can be easily reduced to the required level by adding nitrogen to the protective gas. The intensity of the effect of the nitrogen on the content of delta-ferrite in the weld metal increases with the oxidizing ability of the protective gases, which is associated with the intensified penetration of the nitrogen into the weld metal. In the welding of type 18-8 steels the carbon dioxide may reduce the content of delta-ferrite in the weld metal due to an increase in the oxidizing ability of the protective gas and to some carburization of the metal