Shielding gas

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

The effect of shielding gas composition on welding performance and weld properties in hybrid CO2 laser–gas metal arc welding of carbon manganese steel

Abstract: Metals industries producing large structures currently have a particular interest in hybrid laser welding processes, which possess advantages compared with conventional methods of welding. One major benefit is a reduction in deformation that enables the amount of postweld finishing work to be reduced. Assembly then also becomes simpler because of the greater accuracy that may be achieved. Larger joint tolerances may be accommodated compared with laser welding alone. By using appropriate filler metal, the weld metal composition may be controlled to meet metallurgical criteria. The hybrid CO2 laser–gas metal arc (GMA) welding process was investigated in this study; the aim being to clarify the effects of process gas composition on welding performance, weld cross section, quality, and mechanical properties, when welding carbon manganese steel. Helium, argon, and carbon dioxide were used in varying proportions as shielding gases for welding I-butt and T-butt joints. The composition of the shielding gas was fo...

Physical basis for the transition from globular to spray modes in gas metal arc welding

Abstract: In gas metal arc welding with argon gas, there is a fairly sudden transition current above which diameters of the molten metal drops detached from the welding wire change from being greater than the wire diameter in the 'globular' mode to less than the wire diameter in the 'spray' mode. It is concluded that the primary cause of this transition is that at higher currents the magnetic pinch pressure from current within the molten metal becomes larger than the pressure induced by the surface tension of the molten metal. A formula expressing this condition is I = 2?(?D/?0)1/2, where I is the transition current, D is the diameter of the wire, ? is the surface tension coefficient of the molten metal and ?0 = 1.26 ? 10?6?N?A?2 is the permeability of free space. This formula predicts transition currents in fair agreement with previously published experimental results from various authors for both steel and aluminium, for wire diameters varying from 0.4 to 3.0?mm. The formula is not valid for carbon dioxide, helium or hydrogen where, unlike argon, there is arc constriction at the base of the welding wire. Nevertheless, the formula represents a useful approximation for the change in metal transfer modes using various welding wire materials if, as is usual, argon is the principal component of the welding gas.

TIG welding method and welding apparatus

Abstract: A TIG welding apparatus comprises a welding current supply means for supplying an electric current, a shield gas supply means for supplying shield gases, a tungsten electrode connected to the welding current supply means, a welding torch disposed coaxially around the tungsten electrode and provided with inner and outer double gas shields having gas jetting nozzles through which the gases are jetted, a plurality of wires to be fed to a portion at which the gases are jetted through the gas jetting nozzles, a wire feeding means, and a heating means connected to the wires, except at least one wire, for heating the wires. A TIG welding method is carried out by using such welding apparatus through the steps of supplying shield gases into the inner and outer gas shields and jetting the shield gases through the jetting nozzles to a portion at which a welding arc is generated, feeding continuously wires, except at least one wire, under a condition heated by the heating means to that portion as hot wires through the wire feeding means and feeding continuously the at least one wire under a condition not heated to the portion as cold wire through the wire feeding means substantially at the same time of the feeding of the hot wires.

Hydrogen and molybdenum control on laves phase formation and tensile properties of inconel 718 GTA welds

Abstract: Gas Tungsten arc welding (GTAW) process was employed for welding of Inconel 718 with two different shielding gases, namely argon (Ar) and argon with a 5 vol% hydrogen mixture (ArH) and two fillers viz., ERNiCrMo-10 and ERNiCrMo-4. The effects of gas composition and filler wires on the laves phase formation were studied in detail. The results revealed that hydrogen addition through ArH shielding gas mixture resulted in better grain refinement in the welds than pure Ar. The hydrogen addition induced a steep thermal gradient in the weld, which lowered the segregation of elements like Niobium (Nb) and Molybdenum (Mo) at the interdendritic regions. The laves phase formation in Mo-rich filler addition welds was minimized due to restriction of Nb segregation by Mo at the interdendritic region. Tensile test results indicated that the strength and ductility of the joints of both autogenous and filler added welds of Ar were higher than the ArH shielded welds. In the case of filler added welds, higher Mo content filler exhibited better tensile properties in both shielding gas combinations due to solid solution strengthening of Mo. Nano-sized hydrogen assisted cracks observed in ArH autogenous welds caused a reduction of strength and ductility.