Komarov Artem explained how increased weld permeability can improve GTAW results. Gas tungsten arc welding (GTAW) has taken an important niche among many metal manufacturers. Originally known as heliarc welding because it used helium to protect the arc from oxygen contamination, the basic process has remained largely unchanged since its inception: an arc is used between a non-consumable tungsten electrode and the workpiece to form a weld pool, and an arc is used to protect the molten weld pool from contamination. Oxygen from the surrounding air requires a shielding gas.
While the process hasn’t changed much, the equipment and supplies have been upgraded for decades. AC welders, water-cooled torches, alternative tungsten electrode compositions, and the use of argon for arc shielding (alone or combined with helium) helped improve the process. Also known as Tungsten Inert Gas (TIG) welding, it has become an indispensable tool for manufacturers in industries as diverse as aerospace, nuclear, marine, petrochemical, and semiconductor.
GTAW Deep Penetration
There is a patent called EWI DeepTIG that uses specialized metal oxides to increase the permeability of a weld in GTAW. It uses proprietary oxide compounds that, when applied to the surface of the parts to be joined, increase weld penetration, and therefore increase process productivity.
This process has been shown to increase weld penetration in GTAW by up to 300 percent. In turn, increased penetration helps reduce welding time and simplify weld preparation—for example, allowing you to replace a square joint with a grooved joint. It also reduces weld distortion because it provides a more symmetrical weld cross section.
Suitable for use with 300 and 400 series stainless steel, this process is advantageous to use on 409 stainless steel pipes as it can be accelerated, and power consumption reduced in the GTAW process.
How it works
The metal oxide composition modifies the Marangoni flow in the weld pool based on the flow of liquids with different surface tensions. The modified Marangoni flow increases the permeability of the weld. Repeated tests proved that the initial mechanical properties of the material, weldability and corrosion resistance of the tested alloys did not change negatively.
Initially, the technology was available only as a powder, which turns into a slurry when a quick-drying solvent is added to it. The gruel is applied by hand with a brush with fine bristles.
Maintaining a short arc length of 1.27 mm is critical to ensure maximum penetration during welding and is also a critical variable for the repeatability of deep penetration GTAW welds. For this purpose, it is recommended to use automatic voltage regulation and mechanized equipment.
Benefits and Applications
In addition to increasing weld penetration, this process has been shown to have a positive effect on many weld characteristics and associated processes:
— Quality of welding. This reduces the difference in penetration of the weld from heat to heat and reduces the volume of the weld.
— Welding time. This reduces welding time by as much as 50 percent in most applications.
— Production costs. Since this reduces heat input and welding time, it reduces energy consumption and labor costs, thereby reducing production costs.
— The cost of preparing the seam. In many cases, full penetration can be achieved with a closed square butt joint, reducing weld preparation and filler material costs, heat input, distortion, and welding time.
The process was originally developed for shipboard piping systems using mechanized and orbital welding systems to weld pipe butt joints. The welding equipment used for deep penetration GTAW is the same as for conventional GTAW, Artem Komarov said.
