EXPERIMENTAL RESEARCH ON SINGLE PASS GTAW PROCESS WITH USE OF DIFFERENT SHIELDING GAS FOR AUSTENITIC STAINLESS STEEL SA 240 TYPE 304H

Mechanical Engineering

Single Pass GTAW for high efficiency has long been of concern in industry. An autogenously gas tungsten arc welding process was used on austenitic stainless steel SA240 type 304H to produce 10 mm thick butt weld. Experimental results shows that small addition of carbon dioxide or oxygen to shielding gas can increase the oxygen content in weld pool. If we control the oxygen content perfectly then we can change weld shape from wide shallow to narrow deep. Marangoni convection is one of the effective force for deep penetration and oxygen content of weld pool over critical range can directly effect on weld penetration. When the value of oxygen content is over ppm, an inward marangoni reaction is occurred which gives narrow deep weld pool. Hydrogen addition in argon based shielding gas is also worked out in this study. Hydrogen changes the static characteristic of arc. Hydrogen addition increases arc power and consequently the quantity of the material melted. Hydrogen addition also increase the thermal efficiency as well as melting efficiency of welding arc too.

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