Welding Current and Nitrogen Content of Weld Metal (Report 1)

Effect of Sampling Method

Abstract

Effect of welding current and sampling method on the nitrogen content of weld metals in nitrogen and air atmospheres using a pure iron electrode wire was studied.
Three methods i.e. depositing on a mild steel plate, rotating copper disk and water cooled copper block were used for sampling at different current levels.
The main results obtained are summarized as follows;
1. The nitrogen content of weld metals obtained by the bead on mild steel plate method decreases slightly in a nitrogen atmosphere but largely in an air atmosphere with increasing welding current.
2. The rotating copper disk method is not suitable for the study of nitrogen absorption as the weld metal droplets are not so rapidly chilled in water bath and the arc condition is pretty different from that of the conventional arc welding.
3. The water cooled copper block method is more suitable than the rotating copper disk method for studying nitrogen absorption through arc space, though it can not be used at the ionhigher currents.
4. The head on plate method is useful for studying the absorption of nitrogen by molten droplets and weld pool at low welding current.