Cap Welding Techniques

Pipe Welding Techniques For The Cap

The cap was also done with a 3/32 E7018 electrode using 3 stringers beads to put in the cap. The technique to putting a half decent cap in is to spread out the weld. That is a very tight side to side motion, basically a tight weave. This is something I did not do in the beginning and disagreed with the welding instructor who conducted this test. Since taking this welding certification I have focused my efforts on spreading out the weld when using an E7018 electrode. I should have listened to someone who has made a career of welding X-Ray quality welds is very difficult conditions. Since I took this test and passed it at the bare minimum I have come close to a almost next to perfect cap. The last 6G weld test I took was for Fluor and I was allowed to take pictures. They are posted at the end of this page.

Some basic guidelines for welding the cap are as follows:

  • Keep your electrode angle pointed to the center of the pipe at all times with very few exceptions.
  • Keep your arc length as short as possible.
  • If possible, drag your electrode slightly no matter what the position is. Most people will disagree with this but it works for me because it keeps the slag behind the puddle.
  • Only move forward and side to side with the electrode otherwise the weld will become rough.
  • When the pipe gets to hot let it cool down or put on a vice grip to lean on.
  • Make sure you fuse the bevels edge.
  • Overlap stringer beads from at least 25% to a maximum of 50%. The goal is for the weld to have a single profile when finished.

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The Cap Weld In The 6G Position

Before putting in the cap I cleaned the hot pass with a wire wheel and hit it with a grinder. I did not have to use a grinder, but if I can, I will. It’s just safer if you are allowed. A light grinding of the surface will expose any trapped slag or porosity.

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The cap was done from the bottom to top. There is not much to the cap except make sure you fuse the edges of the bevel and keep spreading out the weld. The pictures below are of the first stringer bead I put in. The weld is a little rough because I would sometimes pause or move the electrode slightly back into the weld crater. This is solved by only moving forward and side to side.

These pictures below are of the second stringer bead. The weld got a little smoother because I was spreading the weld better. On the forth picture you can see where my electrode got stuck on the top of the pipe. I had to grind that spot before restarting there. If your electrode starts sticking try not to long arc it. If you do you will end up with porosity in the weld. The best way to keep the electrode from sticking is to keep the rod moving.

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The last stringer bead was done once the pipe cooled down enough for me to lean on it. On the last stringer bead I made sure I spread the weld over the edge of the bevel and into the second stringer. Those are the pictures below.

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