[Jnez1987]

Hello, I was looking for some suggestions. I consider myself a good welder and can tackle most processes with little to no trouble. I am a welding instructor at a very large technical school in Oklahoma and I have a company looking to hire many of my students upon passing a 3G GMAW downhill root and FCAW uphill fill and cap weld test on 3/4" mild steel plate. The problem I am running into is, on the root pass my students and I all seem to get a concave root pass on the back side.

I have tried just about everything I can think of to rectify this issue. We have tried root openings from 1/16"-3/16", lands from straight to 1/8", pretty well every weld parameter for short circuit transfer mode with .035" wire, different travel speeds, different travel angles, arc control or inductance settings both directions, and anything else I could think of.

We are running Lincoln .035" ER70S-6 hard wire and using C25 gas.

Any suggestions to obtain a flush to slightly convex weld would be much appreciated. I have no trouble getting the desired results running uphill, unfortunately that is not what the company is looking for.

Thank You,
Justin

[weldin mike 27]

Hey,

Welcome to our forum.
I wonder if you problem could be remedied by having an unequal land on the plates, and pointing the wire towards the thicker land. This may create a fillet type situation on the root and create surface tension to hold the metal from sucking back.

Maybe?

Mick

[Braehill]

Maybe try A98/C2 gas. Just a thought.
Len

[Otto Nobedder]

Len and Mick,

Those are good thoughts. However, as this weld is for a particular potential employer, It's going to have to be learned the way is going to be done at the employer. Since they've gone so far as to specify root progression, I'd expect a WPS to exist for the weld, which likely specifies the gas, gap/land ranges permitted, etc., and on the employer's test, the coupons may be prepared in advance, so the land can't be tinkered with.

From my limited experience with MIG open root, I found my best results running fairly cold for a quick chill of the puddle, and a sharp drag angle to use arc force to "hold" the puddle behind the arc long enough to chill.

Got to go to work... I'll check back on this topic later.

Steve S

[rhfish]

i find it odd that they want a hard wire root pass and flux core fill and cap,i agree with otto on the pointing up,and with quick little movements from side to side with a cooler setting.

[Jnez1987]

Hello, I was looking for some suggestions. I consider myself a good welder and can tackle most processes with little to no trouble. I am a welding instructor at a very large technical school in Oklahoma and I have a company looking to hire many of my students upon passing a 3G GMAW downhill root and FCAW uphill fill and cap weld test on 3/4" mild steel plate. The problem I am running into is, on the root pass my students and I all seem to get a concave root pass on the back side.

I have tried just about everything I can think of to rectify this issue. We have tried root openings from 1/16"-3/16", lands from straight to 1/8", pretty well every weld parameter for short circuit transfer mode with .035" wire, different travel speeds, different travel angles, arc control or inductance settings both directions, and anything else I could think of.

We are running Lincoln .035" ER70S-6 hard wire and using C25 gas.

Any suggestions to obtain a flush to slightly convex weld would be much appreciated. I have no trouble getting the desired results running uphill, unfortunately that is not what the company is looking for.

Thank You,
Justin

Thanks for the assistance guys. I have the WPS and the range is basically short circuit transfer mode 17-20 V and up to 260 IPM. Gap is up to 3/16" no minimum, and land is optional. Its a pretty broad WPS. Its for a vessel shop and they do the hard wire roots to bridge the often large gaps created when fitting together a 3" thick 13' diameter can. Most of the time it can be back welded with sub arc or FCAW but that is not an option on the nozzles which use the same WPS. I have had the best luck with a cooler weld, higher arc control, very steep drag travel angle and about a 5/32" gap. From time to time it looks like what I want, but its very inconsistent (any minor change messes it up) . I will take all of the mentioned items into consideration. I know that I'm changing my work angle from side to side and not just pointing at one side, as well as very tight tolerances on my gap and land and well as making sure I have no high and low on my groove, that's why it seems weird that its not working. I do appreciate the time and I will try some of the new ideas and try and potentially post some pictures.

Thanks,
Justin

[Jnez1987]

Hello, I was looking for some suggestions. I consider myself a good welder and can tackle most processes with little to no trouble. I am a welding instructor at a very large technical school in Oklahoma and I have a company looking to hire many of my students upon passing a 3G GMAW downhill root and FCAW uphill fill and cap weld test on 3/4" mild steel plate. The problem I am running into is, on the root pass my students and I all seem to get a concave root pass on the back side.

I have tried just about everything I can think of to rectify this issue. We have tried root openings from 1/16"-3/16", lands from straight to 1/8", pretty well every weld parameter for short circuit transfer mode with .035" wire, different travel speeds, different travel angles, arc control or inductance settings both directions, and anything else I could think of.

We are running Lincoln .035" ER70S-6 hard wire and using C25 gas.

Any suggestions to obtain a flush to slightly convex weld would be much appreciated. I have no trouble getting the desired results running uphill, unfortunately that is not what the company is looking for.

Thank You,
Justin

Thanks for the assistance guys. I have the WPS and the range is basically short circuit transfer mode 17-20 V and up to 260 IPM. Gap is up to 3/16" no minimum, and land is optional. Its a pretty broad WPS. Its for a vessel shop and they do the hard wire roots to bridge the often large gaps created when fitting together a 3" thick 13' diameter can. Most of the time it can be back welded with sub arc or FCAW but that is not an option on the nozzles which use the same WPS. I have had the best luck with a cooler weld, higher arc control, very steep drag travel angle and about a 5/32" gap. From time to time it looks like what I want, but its very inconsistent (any minor change messes it up) . I will take all of the mentioned items into consideration. I know that I'm changing my work angle from side to side and not just pointing at one side, as well as very tight tolerances on my gap and land and well as making sure I have no high and low on my groove, that's why it seems weird that its not working. I do appreciate the time and I will try some of the new ideas and try and potentially post some pictures.

Thanks,
Justin

[Jnez1987]

Hello, I was looking for some suggestions. I consider myself a good welder and can tackle most processes with little to no trouble. I am a welding instructor at a very large technical school in Oklahoma and I have a company looking to hire many of my students upon passing a 3G GMAW downhill root and FCAW uphill fill and cap weld test on 3/4" mild steel plate. The problem I am running into is, on the root pass my students and I all seem to get a concave root pass on the back side.

I have tried just about everything I can think of to rectify this issue. We have tried root openings from 1/16"-3/16", lands from straight to 1/8", pretty well every weld parameter for short circuit transfer mode with .035" wire, different travel speeds, different travel angles, arc control or inductance settings both directions, and anything else I could think of.

We are running Lincoln .035" ER70S-6 hard wire and using C25 gas.

Any suggestions to obtain a flush to slightly convex weld would be much appreciated. I have no trouble getting the desired results running uphill, unfortunately that is not what the company is looking for.

Thank You,
Justin

Thanks for the assistance guys. I have the WPS and the range is basically short circuit transfer mode 17-20 V and up to 260 IPM. Gap is up to 3/16" no minimum, and land is optional. Its a pretty broad WPS. Its for a vessel shop and they do the hard wire roots to bridge the often large gaps created when fitting together a 3" thick 13' diameter can. Most of the time it can be back welded with sub arc or FCAW but that is not an option on the nozzles which use the same WPS. I have had the best luck with a cooler weld, higher arc control, very steep drag travel angle and about a 5/32" gap. From time to time it looks like what I want, but its very inconsistent (any minor change messes it up) . I will take all of the mentioned items into consideration. I know that I'm changing my work angle from side to side and not just pointing at one side, as well as very tight tolerances on my gap and land and well as making sure I have no high and low on my groove, that's why it seems weird that its not working. I do appreciate the time and I will try some of the new ideas and try and potentially post some pictures.

Thanks,
Justin

Mick,

In response to your message, I am getting surface tension. That seems to be the underlying problem, essential I'm unable to create or maintain a keyhole going downhill. Even with no land and a 3/16" gap. I barely weave it all, and I need to go try this now that its on my mind, but I wonder if it could be possible that I'm not weaving enough, or possibly even traveling too slow and creating the surface tension.

Thanks,
Justin

[noddybrian]

Never tried this as no procedure I've ever had called for downhill mig root - my migs don't display speed or volts so it's a bit tricky to replicate your WPS - but if I get a spare half hour I will give it a try - gut feeling is go with the upper limit on volts - close on wire - once the gap is bridged at the start aim dead center - no weave & go faster than you have been - it would seen you have to go against instinct - normally you'd be holding the sides but it would appear from your description the problem is not getting sufficient heat & material to form in the center.
It's no good blaming the WPS if that's what the job calls for - but whatever gaps they need to fill it surely would be more controllable doing it up - & if a welding instructor finds it difficult how are the students meant to master it?

[Otto Nobedder]

I'm with Brian on the "no weave", and forgot to mention it in my hurry to leave for work. The wire should be hitting the puddle dead-center in the gap, dead-center of the land (or on the knife-edge). The effect is similar to the "bury-rod" technique for 6010 down root, though a sharp drag angle is required. Given the volts/IPM range stated in the WPS, I'd take a different tack from Brian, and opt for the lower half of the voltage range, and aim for a "soft" arc with the wire speed, at least while sorting it out.

When I had to do this, it was a 6g, same parameters, same FCAW fill and cap. Boiler and boiler tube work. Right when I had it figured out, I got a better offer with money up front for travel. What ya gonna do?

Steve S

[weldin mike 27]

Hey,

I could only offer my rough assumptions to this problems because it is out of my work scope. I time that I used to do an open root "seal" weld was when, as you stated, filling an irregular gap, before the progressive runs were welding in another postition. The joint was 10mm to 10mm in a single bevel fillet weld,(where i got the Idea for the unequal land) I used to run very hot, same as flat, drag like lightning to make sure I burned in, The backs side was irrelevant because it was fully welded both side. Inspecting the root was purely for my own gratification.

One idea that comes to mind now, is that when our fab boys tack up our structures, there are inside corners that have a big gap, so the v down them so a robot can weld them without screwing the pooch. The blast them in and it leads to a concave run that sometimes cracks. So now that I think about it, the cooler setting would help, or maybe an increase in wire speed.

Mick

[9weld6]

What you'll want to do is begin with a 5/32" gap with a 1/32" to 1/16" land. I don't prefer a knife edge because it seams to cause porosity if you don't move fast enough and the puddle likes to constantly chew it away. Running colder lets you really take your time and have full control over manipulating the puddle so I would start around 18volts and 160 wire speed. Run a drag angle at about 60 degrees to the plate. This angle lets you aim good back up into the puddle pushing it back threw the root opening. The best nozzle to use is the small tapered ones so that you can rest the nozzle in bevel and what you'll do is pretty much walk the nozzle down the bevel like you would if you were tig welding. This helps you maintain the same stickout and keep a consistant weave and running the low voltage and wire speed lets you really focus and make sure everything goes as you want without being rushed. I run all my root passes on everything like this same settings too from 2" schedule 40 pipe up to 30" 2" thick vessels. Hope this helps you guys out. Also do not run a keyhole keep the wire in the middle to leading edge of the puddle this will help with pushing the bead threw the opening and when you weave side to side keep it to a minimum with the wire staying in your gap going from land to land. I prefer tacking with a 3?16" spacer and after tacks cool it will be a perfect 5/32 gap. Another thing i do when I'm welding vessel heads is leave the bevel knife edge at a 5/32" gap and then run an 1/8" grinding disk threw the gap this makes the gap perfectly even and puts a perfect land on both bevels at the same time.

[Braehill]

9weld6,

Can I ask what shielding gas you use. I'm trying to figure what different effects the shielding gas plays.

Len