Best technique for vertical cover pass on 7018 rods?

by D. Lucido
(Pittsburg, CA)

I will be taking test doing a butt weld with back plate. I have to do a few root passes with 6010 and then cover with 7018. All passes with be vertical and my plates that I do the butt weld with are 3/4in thick. I will gauge the thickness of my gap with an 1/8 in rod. Then start my test. I just need the best vertical technique or pattern on 7018 so it looks good when I am done.

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May 18, 2015
Open butt or V bevel with a back up bar?
by: Steve

You didn't mention if it's an open butt or V bevel with a back up bar.

Open butt: The bevels should be prepared with a landing ( 1/16 to 3/32 depending on personal preference) at the bottom to help carry the heat. A 1/8th gap is pretty wide for an open butt. Here again, 1/16th to 3/32 with a slightly tighter gap for an uphill root pass with 6010. You can fill a wider gap uphill, but there is potential for undercut on the backside.

V Bevel with a back up bar: The bevels should be prepared with a feather edge. A 1/8 gap is a little narrow, although it would work ok with a first pass of 6010. It is possible to "float" the filler over the bottom edges, so you want to make sure you tie in both bottom edges of the bevels.

Filling and capping: Take your time, don't get in a hurry. 3/4 is pretty thick and if you just keep running bead after bead the base metal will heat up to the point that the filler metal will become too fluid and difficult to control. Once the bevel is filled just below flush, take a break. Mess with your hood, have a cup of coffee, visit with the inspector, anything to let the metal cool a little to help prevent undercut on the cap. Generally they will tell the welder if they want the cap beaded or if it can be weaved. Typically a bevel on 3/4 inch thick metal would be capped using multiple beads.

Steve Bleile.

May 11, 2015
7018 vertical test
by: Anonymous

Pretty hard to learn on your own unless you are lucky enough to be a natural. I had plenty of problems myself and I was taking a trades course. Best thing you can do is find someone good at it and have them give you some tips and demonstrations in real time.

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