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balance control) to clean or remove the oxide layer on the workpiece surface. An AC/DC inverter also quickly initiates an arc at low beginning amperages, which helps minimize heat input to the workpiece and reduces the size of the heat-affected zone (HAZ). It also reduces the probability of burnthrough. For optimal performance, consider adding a remote current control, which allows a welder to optimally adjust and manage heat input.
3]What are the recommended parameters for welding thin materials?
As a general rule, use 1 A for every 0.001 in. of material being welded by the GTAW process. For example, when welding materials 1⁄4 in. thick, set welding current at 200 to 250 A. When welding aluminum, the welder can adjust the amount of oxide cleaning and the width of the arc. While experience will guide his judgment, start with an AC balance of 70 to 75 percent electrode negative (EN) and 120 Hz of AC frequency. Those settings should accommodate the surface oxide layer while providing a smooth, stable arc with good directional control.
4]How important is part fitup when welding thin materials?
Fitup is critical. To minimize heat input when GTA weld- ing thin materials, ensure that the materials fit as closely together as possible. Gaps require the use of additional filler metal and heat input, which increases the likelihood of burnthrough or warping. If necessary, the welder can place small tack welds along the joint to keep the materials in place during final welding, or he can clamp them together to hold a tight joint. Fixturing offers yet another method to maintain fitup integrity during welding, and the mass from the fixture helps pull heat from the weld. This improves weld puddle control and minimizes the concentration of heat in the workpiece material.
5]What type of welding torch is best for thin materials?
For welding 1⁄4-in. and thinner materials, select a GTAW torch rated 150-300 A. Air-cooled models cost less than do water-cooled torches, and do not require a separate cooler, which improves process portability. Air-cooled torches do, however, tend to be larger and heavier, and more difficult to maneuver. When using a power source with a water cooler— integrated or separate—instead select a water-cooled torch. These units, compared to air-cooled torches, boast a small- er handle and body, weigh less, and provide easier access into tight weld joints.
6]Are there any recommendations
for optimum torch angle when welding?
Welders should position the GTAW torch nearly perpen- dicular to the weld joint. The most common technique is to tilt the torch back about 15 deg. and push the weld puddle along the joint. This technique results in a symmetrically
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