Shielding gas

About: Shielding gas is a research topic. Over the lifetime, 6697 publications have been published within this topic receiving 58668 citations.

Three-dimensional modelling of arc behaviour and gas shield quality in tandem gas–metal arc welding using anti-phase pulse synchronization

Abstract: The paper presents a transient three-dimensional model of an anti-phase-synchronized pulsed tandem gas–metal arc welding process, which is used to analyse arc interactions and their influence on the gas shield flow. The shielding gases considered are pure argon and a mixture of argon with 18% CO2. Comparison of the temperature fields predicted by the model with high-speed images indicates that the essential features of the interactions between the arcs are captured. The paper demonstrates strong arc deflection and kinking, especially during the low-current phase of the pulse, in agreement with experimental observations. These effects are more distinct for the argon mixture with 18% CO2. The second part of the paper demonstrates the effects of arc deflection and instabilities on the shielding gas flow and the occurrence of air contamination in the process region. The results allow an improved understanding of the causes of periodic instabilities and weld seam imperfections such as porosity, spatter, heat-tint oxidation and fume deposits.

Effect of nitrogen addition on microstructure and fusion zone cracking in type 316L stainless steel weld metals

Abstract: Nitrogen is known to have a significant effect on cracking behaviour of austenitic stainless steel during welding, although reports on its effects have often been controversial. A study was therefore undertaken to examine the effect of nitrogen on the weldability of two type 316L weld metals. Weldability was assessed using the longitudinal moving torch Varestraint test. The brittleness temperature range during solidification was calculated from crack length data. Nitrogen was added through the shielding gas to 316L (base N-0.036%) and 316LN (base N-0.073%) to produce weld metal nitrogen contents in the range 0.04–0.19%. In the primary austenitic solidification mode, nitrogen addition had little effect when the P+S levels were relatively low (316LN with 0.031%P, 0.001%S) while cracking increased for higher impurity levels (316L with 0.035%P, 0.012%S). Nitrogen additions also produced significant coarsening of the primary solidification structure. The study indicates that weldability effects of nitrogen may be influenced by the impurity levels, particularly S. The cracking data showed good correlation with the WRC Cr eq /Ni eq ratio.