GTA welding

Details GTA welding GTA welding

1996-12-04

1999-04-06

Shaw, Clifford C.

Electric heating

Metal heating

By arc

219 75, B23K 9167

Patent

active

058921990

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a process and to a welding torch for high current gas-tungsten arc (GTA) welding of metals.
Gas tungsten arc (GTA) welding (known also as tungsten inert gas, or TIG welding) is a precision welding method which has been used for many years to produce high quality joints in a wide variety of materials. It is normally used at low welding currents to weld relatively thin materials, and is a very clean process as no flux is used. When the process is used for welding thicker sections, greater than 4 mm in steels and greater than 6 mm in non-ferrous alloys, careful V- or X-type edge preparation by machining or plasma cutting is required. This edge preparation may add up to approximately 30% to the total fabrication costs, in addition to the costs of storage and handling between the machining and welding areas. In the joining of thin plates in square butt configuration, the process is usually run autogenously without the addition of filler material. When thicker elements requiring the V- or X-type machined preparations are used, filler wire is employed. Furthermore, under these conditions many passes are required to complete the joint and interpass grinding may be necessary, leading to significantly increased joint completion times. Thus, despite the high quality of joints produced by conventional GTA welding, it does not find wide application in the fabrication of thicker materials because of its poor productivity. A significant amount of research has been done on high current (500-1000 A) GTA welding in order to extend the applicability of the process and to improve its productivity. This work has been directed both towards normal elevated arc technology where the electrode tip is above the surface being welded, and to buried arc technology (also know as subsurface or immersed arc GTA welding) where the electrode tip is located below the surface of the material being welded. The advantage of the latter mode of operation is that the deep penetration obtained makes the process attractive for joining relatively thick materials (15-30 mm). However, because of the high arc forces and turbulence generated in the weld pool when operating at high currents, severe defects such as porosity, cracking, humping and inclusions are commonly observed, as well as poor mechanical properties on occasions. Although these effects are not as severe in the buried arc mode because of the shorter arc length used, commercially acceptable welding procedures have not been developed because of an imbalance between the welding conditions, the arc force, the thermal conductivity and density of metals, and convection effects in the weld pool. In addition, the practical application of high current GTA technology has been very limited owing to the unreliability of conventional welding torches. To overcome problems of these types, current densities are typically kept low by employing large diameter electrodes, for example, 9.5 mm, equating to a current density of only 12.7 A/mm.sup.2 at 900 A, and high gas flow rates of about 38 1/min of Ar or 76 1/min of He are used.
The reference to current density in the immediately preceding paragraph, and throughout this specification, is based on the transverse cross-sectional electrode area.
A large number of GTA welding torches have been designed to operate at currents of approximately 350-500 A, incorporating localised chamber cooling (a small chamber at the top of the torch) and an uncooted ceramic gas shroud. During continuous operation the torch body, gas shroud and contact systems are heated significantly, thus causing reduced reliability of the torch elements and tungsten electrode. A very frequent occurrence is the loss of the electrode tip by overheating, and the resultant inclusion of tungsten in the welds. To the best of our knowledge, there is no reliable GTA torch for elevated and buried arc welding at higher currents (500-1200 A), and for use in continuous operation.
The present invention has as its objective the provision of a more productive process for GTA Welding

REFERENCES:
patent: 2468807 (1949-05-01), Herbst
patent: 3007032 (1961-10-01), Whiteman
patent: 3018360 (1962-01-01), Engel
patent: 3309492 (1967-03-01), Fields
patent: 3950629 (1976-04-01), Auzary et al.
patent: 4002878 (1977-01-01), Disney
patent: 4103143 (1978-07-01), Yamauchi et al.
patent: 4142084 (1979-02-01), Torrani
patent: 4788401 (1988-11-01), Kleppen
patent: 5258599 (1993-11-01), Moerke

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