Welding Tips and Tricks

A company has contacted our school looking for welders and sent a copy of the WPS that they use to qualify welders and it calls for 7018 open root, fill and cap. This is the first open root 7018 procedure that I have encountered. Is this a common WPS that I somehow overlooked because I have been having my students do all open roots with 6010. Any help will be appreciated.

Kevin

We did a lot of low hydrogen open root when I was at the shipyard. Ours was 8018 & 11018
but they have very similar characteristics to 7018. Most of our structural work was open root,
fill, cap, back gouge, grind, MT, fill, cap. Then, depending on location it was either visual/MT,
visual/MT/UT or visual/MT/x-ray.

Thanks for the response. Were these welds always back gouged or were they sometimes left as open roots?

I think it depends a bit on location & who is approving the WPS - in the UK this is a very common practice whereas 6010 is almost unheard of - there is a small amount used on some pipe work done in the field - but even that is dying out - it's not common practice - so much now depends on who the insurance guys favor - until recently ASME coding was accepted - but now that we have to comply with Euro regulation none of the ASME qualification or WPS are valid.

I am going to update my job sheets to include some open root 7018's to cover as many bases as possible. When putting in a root pass with 7018, do you stick it in like a 6010. I plan to try a couple when I get to school Monday but I was just wondering what technique is best to use.

Most of the UA and AWS based WPS's do not call for open root 7018 so I have never taught it to my classes. I have a friend who runs a welding business and he had to back gouge several welds on a job a few years ago where the first pass penetrated all the way through when it was not supposed to and it cost him several man-hours to fix. So I guess depends on who is setting the standard.

I can only comment on the WPS we had to work with - this was for single sided access welds on pressure vessels / pipe - usually on boiler plate - the prep was knife edged 70 degree included angle V with a root gap spec I can't remember but we generally used 2.5mm ( set using welding rod stub for measurement ) this was for 1/2" plate in vertical & overhead which qualified for all position in plate thicknesses from1/4" up to 1" the only quirk was maintaining a keyhole consistently - the root was with 2.5mm rod running electrode negative - the fill passes also in 2.5mm with electrode positive - the cap / cover pass could be done in 2.5mm or 3.25mm according to welder preference - it was expected to maintain a slight but not excessive bead on the backside - it's too long ago to remember but there was a min / max allowance for that & the height & width of the cover pass.
This may not be a currently valid spec as it's all down to the insurance company that is covering the liability & what they approve - I originally did this with a 350amp Kempi power source but later did it with a 305 Ranger diesel - both were good but it was easier on the Ranger as we had the remote amp control for it - if you can get a remote for your welder it does make life easier - it's common practice here.

Thank you so much, that is the same WPS that I looked at except for the DCEN on the root pass. I will change my job sheets on Monday.

It's so long since I did this I can't remember where the reverse polarity on the root pass came from - it was meant to make it easier to maintain a consistent back bead without undercutting the back or the toes - I imagine with practice it can be done either polarity - the stability of the power source does make a big difference though - especially on the overhead - hope this helped & good luck with the new procedure.