Metal-cored wires provide a high deposition rate. Once they realize the ramifications of this high deposition, many welders try to pour as much metal into the joint as possible. This can lead to problems. One of the biggest problems welders encounter when they convert to metal-cored wires for multiple pass weld joints is that they tend to “ride” the puddle rather than staying on the leading edge of the puddle. This results in inadequate penetration, and in some cases, failed radiographs or UT inspections.

In a deep groove, after gouging, or when the joint root is very narrow, the first several passes must be conducted at a higher travel speed. After the joint is rooted in, and you get to the point where the joint opening is wider, the travel speeds can be reduced to increase the fill.

Another common mistake is made with the gun angle. While some welders prefer the “lagging” or pushing gun angle, in critical applications, it is best to pull or use a “leading” gun angle. The latter will generally yield better penetration.

When welding on tubes or pipes with the pipe in a 1G position and rotated, a good starting point is to angle the torch so that if you could extend the wire through the pipe it would intersect the center of the pipe. Your torch orientation will depend on the tube or pipe diameter. For small diameters and as you increase travel speed, move further from the top dead center opposite the direction of travel. If you are too close to top dead center, the weld bead will have a high “crown” or center, and the toes of the weld bead may be undercut. To make the weld flatter at a given travel speed, move further from top dead center. If you are too far down the pipe or the travel speed is too slow, the weld will exhibit poor transition of the weld toes into the parent metal and the center of the weld bead may appear lower than the sides.