Copyright Goodheart-Willcox Co., Inc. 136 Gas Tungsten Arc Welding Handbook Welding Procedure Specifications (WPS) The following eleven procedures have been devel- oped for GTAW practice and production. Any scrap material can be used for practice. The weld joint should fi t properly for good results. Clean all of the materials, as previously discussed, before tack welding and welding. When steel is being welded, a small white dot may form on the weld pool surface. This is a normal condition and does not require any corrective action. The material in the dot is silicon, which separates from the base material and the welding rod. It fl oats on the surface because it is lighter than the metal. Gas nozzle sizes are not specifi ed, since many variables are involved. Always use the largest possible size. However, do not use a size that will obstruct your view of the weld pool. Tooling can be used when welding practice plates. Tools assist in holding the material in the proper plane and prevent warpage and misalignment during the welding sequence. The tooling may also have a gas manifold to permit use of a backing gas, if desired. See Figure 8-11. Welding Procedure Number 8-1 Weld joint type: Flat plate autogenous weld Position: Flat Material type: Cold-rolled steel Thickness: 1/16″ (1.6 mm) Machine setup: DCEN high-frequency start Shielding gas: Argon CFH: 15–25 Tungsten type: 1%, 1.5%, or 2% lanthanated, ceriated, or thoriated Diameter: 1/16″ (1.6 mm) (tapered) Procedure: 1. Prepare and clean the materials. 2. Raise the part to be welded 1/8″ (3.2 mm) above the table with metal blocks. 3. Align the torch to the angles shown in Figure 8-12 (90° work angle and 15°–25° travel angle) and lower the torch until the tip of the electrode is approximately 1/8″ (3.2 mm) from the top surface. 4. Start the arc at low current lower the torch until the electrode tip is approximately 1/16″ (1.6 mm) from the surface. A B Figure 8-11. Tooling can support the weld and provide backing gas. A—Hand-built copper backing plates for providing backing gas to the back side of a butt weld. The weld is positioned on top of the plate and welded. B—This fixture includes a manifold for backing gas. The weldment is clamped and held in place by the top bars. (Mark Prosser)