[JJHess]

Hello All

Looking for a little guidance. I've been welding for about 10 years now, the last 5 years or so I weld on almost a daily basis. I never had any formal training, just bought a welding years back and started reading & practicing. My background is in residential construction, so not much welding there. Now I have a pile driving business and most of my welds are flat filet welds, when joining 2 pieces of pipe pile inside a coupler. Also some vertical welding when installing cross bracing.

I need to finally get certified, as I am seeing this requirement more and more, especially on commercial work. I'm planning on doing the 3G limited plate test. I've made a bunch of test coupons and built a bend tester for my press. I have the root pass down no problem as well as all the filling. The issue I'm having is with the cap. I can't seem to get rid of the undercut when I do the cap. I've ground the face flat and tried going over it again to fill the undercut but I end up with undercut on either side of that weld.

I running 110 amps for my root & fill. I've tried turning back to 105 for the cap but still have the undercut. I can't maintain an arc at less than 105.

[weldin mike 27]

The trick with capping any weld is to have to fill bugger all on the last layer. Less than 1mm depth between the top of the second last layer and the surface of the plate. That way, you can get a smooth action going without having to deposit too much metal. You may, in fact find that with a refinement in technique, you may need to up the amps in order to get a smooth arc and pool running, Please advise on what type of rods you are running.

Regards, Mick

[cj737]

...and mind your interpass temps! Capping straightaway on hot fill passes is a significant cause of cap undercut.

[JJHess]

Thanks for the input.

I was thinking about it a little more and I was running my cap when the plate was still pretty hot. I was running my fills about 10 minutes apart which seemed to work well so I could keep my amps lower and still get a hot bead. I will try again tomorrow and let the plate cool down to around 200 degrees before running the cap.

I'm running Radnor (Hobart?) 1/8" E7018 on a Lincoln 210MP. 110 amps on the root & fill passes seems to be ideal for this setup. I end up with a row of grapes if I turn the amperage up over 115.

[TheWeldingConnector]

Thanks for the input.

I was thinking about it a little more and I was running my cap when the plate was still pretty hot. I was running my fills about 10 minutes apart which seemed to work well so I could keep my amps lower and still get a hot bead. I will try again tomorrow and let the plate cool down to around 200 degrees before running the cap.

I'm running Radnor (Hobart?) 1/8" E7018 on a Lincoln 210MP. 110 amps on the root & fill passes seems to be ideal for this setup. I end up with a row of grapes if I turn the amperage up over 115.

Can you post a picture of the cap before you grind it down? Based on what I see you have your amps too low and are traveling too fast so the weld is not filling all the way out. Another thing that I noticed is that it does not seem like you are letting the metal burn into the sides of the plate. Remember that the existing weld is going to melt faster then the plate so it is important to make sure you hold the plate side slightly longer then the existing weld side. Also what type of rod angle do you have when running the cap? I have found that increasing rod angle helps counter the weld falling out when it is getting too hot.

[MinnesotaDave]

Definitely need to see the actual welds. I'd post root and fill pics too.

[JJHess]

Thanks

I don't have any other pics. I'm going to work on it again later this week so I'll get more pics then.

The root and fill all look good. No excessive undercut, nice even puddle, no voids. When I cut the backing strap off the toe looks fine. When I bend the root there are no cracks or voids that open up. It's just on the cap. I know it has to do with speed, heat, angle. I just can't figure out which one or which combination.

I'm holding a 90 rod angle, or slightly up hill. I set up a camera to record myself to see if I was running the rod downhill or something but I was at 90-95 degrees.

[HT2-4956]

Thanks

I don't have any other pics. I'm going to work on it again later this week so I'll get more pics then.

The root and fill all look good. No excessive undercut, nice even puddle, no voids. When I cut the backing strap off the toe looks fine. When I bend the root there are no cracks or voids that open up. It's just on the cap. I know it has to do with speed, heat, angle. I just can't figure out which one or which combination.

I'm holding a 90 rod angle, or slightly up hill. I set up a camera to record myself to see if I was running the rod downhill or something but I was at 90-95 degrees.

JJ,

A 3G limited thickness plate test with 1/8" 7018 takes a bit of skill and experience to pull off. With 1/8" rod I'd definitely be letting it cool all the way back to room temperature (or real close to that) before starting the cap. Besides not having your travel speed, amperage, rod angle and consistentcy of weave pattern (or some combination there of) dialed in just right are you sure you're not "long arcing" it a little to much at times?

Have you tried it with 3/32" rod? If I was wanting to do the best job I could vertical up with 7018 on 3/8" plate that'd be the rod size I'd opt to go with.

[Farmwelding]

...and mind your interpass temps! Capping straightaway on hot fill passes is a significant cause of cap undercut.

Biggest thing for me when I did it. I didn't get undercut because I watched but I got like a 1/4" reinforcement. Now I don't light up until it's under like 250 and I use a infrared thermometer. Worked out well for me. Just give them toes some loving and let it cool off.

[TheWeldingConnector]

Thanks

I don't have any other pics. I'm going to work on it again later this week so I'll get more pics then.

The root and fill all look good. No excessive undercut, nice even puddle, no voids. When I cut the backing strap off the toe looks fine. When I bend the root there are no cracks or voids that open up. It's just on the cap. I know it has to do with speed, heat, angle. I just can't figure out which one or which combination.

I'm holding a 90 rod angle, or slightly up hill. I set up a camera to record myself to see if I was running the rod downhill or something but I was at 90-95 degrees.

So how is the progress going? I am interested to see some more pictures.

[snoeproe]

From what I see left after grinding down your cap, you had plenty of undercut. That's a no no. You won't pass the visual inspection with that undercut on your cap. What code are you testing to? AWS D1.1?
What are you using for practice material? Thickness?

[JJHess]

Sorry for the lack of follow-up. I got busy on a couple jobs the last 2 weeks and fell behind.

snoeproe - I know I won't pass with the undercut. I was trying to figure out why I kept ending up with undercut on the cap. I think it was not letting the plate cool enough before the cap. AWS D1.1. I'm using A36, 3/8" plate, 22.5 bevel, 1/4" gap, 1/4" backing strap. Everything is cleaned to shiny before the root, wire wheel between passes. 110 amps for all passes. If I went to 120 amps I had a lot of dripping.

[weldin mike 27]

I honestly think it's trying to deposit too much on the capping run. It needs to full up by the you start. This is because you lose the surface tension of the sides of the prep. You need to keep the layer thin and the pool small to get it to stay in place

[Jarrod]

Go slower on the cap. Look behind your weld as well
in front. If your fill is below the plate youll have to wait longer for the weld metal to flow over the edge. youll see this if you look behind your weld when
welding. If you fill is flush with the plate then your travel speed will have to be faster.