The AWS Pipe Welding Procedures

Work Slowly

• The first rule in welding alloy steel pipes is to go slow. Moving too quickly will produce incomplete fusion of the metal. You can’t compensate by boosting the welding current because you’ll burn the metal rather than welding it. Before welding, seal the ends of the pipes and keep the interior filled with an inert gas like argon or helium. You also must shield the welding arc with a stream of an inert gas from your welder. The inert gas inside and out will keep oxygen away from the weld. If oxygen contacts the molten weld metal it will form oxides that produce a weak joint. A device called a gas lens concentrates the shielding gas flow around the 1/8 inch alloy welding rod.

DC Welding

• You weld alloy steels using a direct-current welder with the welding wire as the negative pole. Before you start welding, ensure the welding rod is cleaned with solvent and fully dry before use. Bevel the joint to form a wide-angle V groove and clean the joint surfaces with solvent to remove all traces of dirt, grease, oil and chemicals. A dirty joint will be weak. The space between the pipe sections should be just a tiny bit wider than the welding rod.

Get In Tight

• When welding alloys, you must keep the arc as short as possible -- just slightly more than 1/8 inch -- to produce a well-defined pool of molten metal. An arc that’s too long will cause heat to dissipate from the weld pool into the surrounding metal, weakening the joint. Welders often have to assume awkward positions to see the arc to maintain proper arc length.

Vertical Arc

• As you weld the pipe joint, keep your welder nearly perpendicular to the joint, angling it only enough to see the weld. If you angle your welder more than about 15 degrees of arc, you’ll direct heat away from the weld and could preheat the welding rod to the point of melting the rod before it gets to the joint being welded. If you’ve done everything right, you will have a weld that’s even, slightly convex and solidly fused to both sides of the joint. When done welding, break the arc but keep the shielding gas flowing over the weld for about 10 seconds until the weld cools.