[ZKR]

Hey guys, I`m totally new to welding. I purchased a 160 stick welder.

1. Now I have to weld construction rods together. The rods are in the ceiling surrounded by concrete, they were cut in the middle. I was instructed to open the concrete about 10-15 cm (4" - 6") on each side and weld a parallel bar, so that it connects the rods on both sides. I use 7018 2.5 mm.

My question is, how should I approach the weld, what`s the right technique, angle, stages...
I watched many youtube videos but need to know the right way for that job.

Seen here are 2 sample bars. Remember it will be in the ceiling.

http://i44.tinypic.com/250jfdj.jpg

2. The 2nd issue is to fill const. bars which were damaged by a disc grinder. I was told fill them with little jab strikes. How can I connect them to the ground without expanding the opening around them. Can I hold the ground clip with the glove (and pvc glove under it) while wlding ?


http://i43.tinypic.com/2mpl9hv.jpg

Thanks for any help on that

[weldin mike 27]

Hey, Not much help on your first question, but with your limited access grounding, get some bare copper cable and wrap it around as best you can, then attach your clamp to the cable.

Mick

[jwmacawful]

this doesen't answer your question but welding on re-bars is frowned in some circles.

[jwmacawful]

this doesen't answer your question but welding on re-bars is frowned on in some circles.

[Otto Nobedder]

Welding rebar with 7018 is like using superglue on paper... It's overkill. 6013 would be stronger than the rebar.

That said, expect to weld at 115A, uphand, with 15* "push".

Good luck.

Steve S

[rake]

this doesen't answer your question but welding on re-bars is frowned in some circles.

Which circles? I took a welder's job in a precast concrete plant and we welded miles of the stuff!

Don't over think this job. a couple inches of weld at each joint is more than enough to hold them together. Besides, once the concrete is hardened around them they'll all be locked together anyways. 7018 is overkill as Steve noted but it wouldn't be a bad thing either if that's the only wire on hand.

What's frowned upon is using re-bar as structural members.

Your second Question.

If there's more than one damaged area of the same rod you could try attaching your ground to an old heavy screwdriver and have a helper jamb it in one crack while you weld another. If the entire grid was welded together to begin with you could also try grounding to one of the exposed rebars. Oh, don't weld for long. concrete tends to have mini explosions and flying chips if you overheat it!

[jwmacawful]

this doesen't answer your question but welding on re-bars is frowned in some circles.

Which circles? I took a welder's job in a precast concrete plant and we welded miles of the stuff!

Don't over think this job. a couple inches of weld at each joint is more than enough to hold them together. Besides, once the concrete is hardened around them they'll all be locked together anyways. 7018 is overkill as Steve noted but it wouldn't be a bad thing either if that's the only wire on hand.

What's frowned upon is using re-bar as structural members.

Your second Question.

If there's more than one damaged area of the same rod you could try attaching your ground to an old heavy screwdriver and have a helper jamb it in one crack while you weld another. If the entire grid was welded together to begin with you could also try grounding to one of the exposed rebars. Oh, don't weld for long. concrete tends to have mini explosions and flying chips if you overheat it!

i got this info from an engineer at i.m. pei after an apprentice fell into the hole after putting his foot on a rebar that was welded to a beam and the 7018 weld cracked.

[jwmacawful]

speaking of welding re-bar....

[ZKR]

this doesen't answer your question but welding on re-bars is frowned in some circles.

Which circles? I took a welder's job in a precast concrete plant and we welded miles of the stuff!

Don't over think this job. a couple inches of weld at each joint is more than enough to hold them together. Besides, once the concrete is hardened around them they'll all be locked together anyways. 7018 is overkill as Steve noted but it wouldn't be a bad thing either if that's the only wire on hand.

What's frowned upon is using re-bar as structural members.

Your second Question.

If there's more than one damaged area of the same rod you could try attaching your ground to an old heavy screwdriver and have a helper jamb it in one crack while you weld another. If the entire grid was welded together to begin with you could also try grounding to one of the exposed rebars. Oh, don't weld for long. concrete tends to have mini explosions and flying chips if you overheat it!

Thanks, I actually had an enlightenment on that yesterday and got to the same idea with the other exposed parts, as the metals are probably connected all together in the ceiling.

Don`t if it`s overkill, I`d rather over than underkill. The elect`s limit is 75-100A I prefer the lowest possible, not to damage the existing bar. An engineer instructed me to weld it this way, didn`t mention 7018 however.

[ZKR]

The main issue I have now is to start those sun of a gun 7018. They just stick to the metal !
Maybe 75-80 is too cold for them, but I need low A so I won`t damage the bars.

And I don`t mean restarting, just starting, even when the inner metal is exposed, it`s just sticks.
How do I start them poperly?

[noddybrian]

Generally if your not used to welding & can't set amps by experience I would start with 3/4 of the rods maximum amps as otherwise your likely to have start / sticking issues - if the heat input for the material is too high go down a rod size or weld in short runs with the shortest possible arc length & allow it to cool a little between welds - I think 7018 overhead doing stop starts is going to be challenging & as there is no procedure & strength is not really the issue then using a decent quality 6013 will be way easier.

If the rebar is "high yield" as per you picture then normally it should not be welded ( UK rules anyhow ) - I don't know the exact composition of it - but it always appear to be very high carbon & weld usually peels off it leaving a very crystaline surface & has very little strength - when bars are fixed together into a cage or structure the steel fixers only tie it together with 16 gauge iron wire - the strength comes from the overlaps & shapes created once it's poured with concrete - I'm kinda curious as to your application.

On the earth issue if you have an autodark mask - hold the earth clamp with a short off cut of the bar in it with one hand - touch it to the bar your going to weld at its extremity - tack it & the clamp will stay put - quick tap with a hammer or bent it towards the tack when finished & it should fall off - given the very small diameter I would rather think it's actually mesh & will all be interconnected.

[Bill Beauregard]

Are you sure they are 5/16? 5/8" is pretty common, and a lot more tolerant of heat.

[Otto Nobedder]

If you're required to use 75-80A on 7018, they'd better be 3/32"rods. 1/8" will barely run at that current, if you're very experienced. With 1/8", you run the risk of chill cracking at the low heat as well.

If you're using 3/32", and 80 amps won't work, your machine may not be calibrated. (The amps indicated may not be "actual".) I'd prefer 85, but 80 should be quite doable.

Steve S