Also consider whether an air- or water-cooled GTAW torch is best suited to the application. Air-cooled models prove useful for low-amperage applications, below 200 A, for welding materials less than 3⁄16 in. thick, or for shops where welders tend to move around a lot, since these torches do not require an external cooler. Conversely, consider a water-cooled GTAW torch for applications in excess of 200 A. These torches help prevent overheating and allow welders to achieve faster travel speeds.

When selecting a GTAW torch, also consider the angles at which the welders must weld, since maneuvering around difficult joints can be time-consuming, not to mention uncomfortable. Most GTAW-torch manufacturers offer models with flexible necks that make the job easier in awkward positions.

Some torch-body styles also feature a modular design, which allows the welder to add a flexible neck and different head angles to an existing torch. These kits provide good joint access and can lower downtime associated with changing over different torches for multiple applications. Plus, you can save money on extra inventory.

Tip #3: Cover Yourself

When possible, use a gas lens to replace the collet body of a standard GTAW torch. A gas and creates the electrical contact necessary for proper current transfer. It also provides two other functions that can help improve efficiency: It improves shielding-gas coverage (see photos) and improves weld-joint accessibility.

Gas lenses typically consist of a copper or brass body that contains a layered mesh of stainless-steel screens. These screens distribute the shielding gas evenly around the tungsten electrode and along the weld puddle and arc to help prevent oxygen contamination that could lead to weld defects. As in any welding application, minimizing defects and their associated rework ensures that the welder can spend more time in production and less time fixing defects.

Gas lenses also allow the welder to extend the tungsten electrode further out from the nozzle. This additional electrode extension gives the welder a clearer look at the joint and arc, allowing him to have greater torch control and achieve better weld quality, particularly on critical applications or in hard-to-reach areas such as T, K and Y joints.

Gas lenses—which can be used with any shielding gas and are available for air- and water-cooled torches—also prove particularly helpful when welding on alloys highly reactive to atmospheric contaminants or for materials used in high-temperature applications. 

Tip #4: Less can be More

Taking steps to prevent overwelding will significantly improve GTAW efficiency, and save money. Overwelding occurs when the welder deposits more weld metal in a joint than is required to obtain the necessary weld strength. It often results from poor joint fitup or preparation, improper welding parameters or from simple overcompensation —the welder believing that he needs more weld metal to fill the joint than is necessary. 

Overwelding wastes shielding gas and filler metal, and increases welding time. For example, overwelding a fillet weld by a mere 1⁄16 in. can increase arc-on time by as much as 36 percent for a 3⁄8-in. fillet weld and 125 percent for a 1⁄8-in. weld. In addition, overwelding increases the amount of heat input into the base material, raising the risk of burnthrough or distortion and leading to costly and time-consuming rework. It may even increase the need for grinding and finishing. 

To prevent overwelding, avoid over-designing weld joints–do not use a larger joint than is necessary to gain the appropriate strength for the application. A good rule of thumb: Make the leg of a fillet weld no wider than the thickness of the thinnest workpiece, and weld accordingly. For example, when joining a 1⁄8-in. thick plate to a ¼-in. plate, a 1⁄8-in. weld bead suffices. 

Also, know the size of the joint being welded. When in doubt, don’t guess—use a fillet gauge. 

Lastly, proper joint preparation and tight fitup provide good defenses against overwelding, as does welding in the vertical-down position on thin materials.

Tip #5: Get to the Point

The type of tungsten used—which depends on the kind of power source selected and the type of material being welded—as well as the shape of the electrode tip can significantly impact process efficiency. 

For AC and DC welding using an inverter power source and either a ceriated, lanthanated or thoriated tungsten electrode, grind the electrode to create a pointed or truncated tip. This provides the stable arc needed to achieve good welding performance and quality, while preventing contamination or arc wandering. To achieve this shape, grind the tungsten on a borazon or diamond grinding wheel specially designated for the job. Next, grind the taper on the electrode tip to a distance no more than 2.5 times the electrode diameter. For example, using a 1⁄8-in. electrode, grind a surface 1⁄4 to 5⁄16 in. long. This tip design will ease arc starting and help create a more focused arc. 

When welding with low amperage on thin materials (0.005 to 0.040 in. thick), grind the tungsten to a point. This allows welding current to transfer in a focused arc and helps prevent distortion. In particular, a pointed, ceriated tungsten electrode works well when welding aluminum, as it provides 30 to 40 percent more amperage capacity than does pure tungsten before it begins to melt. Note: Do not use a balled tungsten-electrode tip for such an application.

On higher-current applications, grinding the tungsten to a truncated tip can help improve welding performance by preventing the tungsten from balling. First grind the tungsten to a taper (as explained above), then grind a 0.010- to 0.030-in. flat land on the end of the tungsten.

Note: When grinding thoriated tungsten, be sure to control and collect any grinding dust, provide operators with an adequate ventilation system at the grinding station, and follow any manufacture’s warnings, instructions and material-safety datasheets. MF

 

See also: Weldcraft

Technologies: Welding and Joining

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