not a test.....question

I need to weld rebar (#6) together; coupling them using welding instead of rebar clamps/tie's. What would you recomend using? I have a Hobart 120 with .030 wire; I hope
that will be good enough but I doubt it. If I have to use my buzz box, which stick should I use? 6011,6013 ; 70XX; I also have some Eutectic 680...that may well be overkill. But I have it already.
Thanks Mike
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Most rebar has too much carbon to weld. You can get weldable rebar, but it is a little costly. I have used a special coupler to connect rebar, but again, it is very costly. If you are covering in concrete, then just tie wire.
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Thanks All! I will talk to the engineer who designed the building (arched metal building) to see exactly which tie bars to use. I will not chance welding it. I have welded rebar to use as a trellis and it worked/welded just fine. I however do now want to take a chance of welding rebar that is not technically weldable and take a chance of having it structually unsound.
Thanks Mike

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wrote:

Hi Mike, I had learned to use 7024 because I was told that re-bar is similar to wrought iron.
Once I used some re-bar for a homemade screw jack and welded it on with 7018 with good results. - Regards Gordie
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Standard rebar runs .40% to .60% carbon, makes welding it chancy. If the stuff chills fast, it will get as brittle as glass. As in shattering in your hand when hit a short sample with a hammer. There are weldable grades of rebar, they are just considerably more expensive since they get their strength from alloys and not carbon.
One very scary application I've seen: a home built trailer with truss rods of rebar welded on each side. You never know when that rig will disassemble.
If you are just trying to hold the bars in place for concrete work, use the wire ties. If you must weld for concrete work, anything that will fuse will work. Buzz box with 6011 would be fine. If you want it for structural support DON'T weld it.
mike wrote:

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.

I am not disputing your statement but are you sure that re-bar is 0.4 - 0.6% carbon? That is, roughly, 1040 - 1060 steel.
I ask because all of the re-bar I have seen here in Asia is low enough in carbon that it won't heat treat and is used just about every where someone wants a piece of 6mm/10mm/whatever mm rod for anything, usually a welded brace.
I also spent more then 20 years building various structures for international oil companies here and while concrete mixes were almost always specified and slump tests taken each batch I never saw a spec for re-bar quoted. If U.S. re-bar is 0.4 - 0.6% carbon and Asian re-bar is 0.1 - 0.2% or less I would have expected that project specs would have spelled out the type of re-bar required, if different from local bar.
Bruce in Bangkok (brucepaigeatgmaildotcom)
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If it's not specifically marked as weldable, don't. Wire ties work, and don't cause embrittlement. Spool of tie wires and a spinny-hook to twist them with don't cost much, and get the job done faster than welding, too.
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At one time, the rule of thumb to have 100 percent strenght, was to use a '40 times the diameter' lap, tied parallel in at least 3 places. #6 bar is 6/8" or 3/4", so 30 inches of overlap should have you in the ball park for both tension and compression. Nothing is cheaper or stronger, if space allows. Be advised, I don't know if the rule has changed. . . . . . .
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Pre heat and weld with 7018
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I agree, pre heat, weld with 7018, and then cover immediately with sand and allow to cool slow....

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6011 is good. Good penetration, and the spatter won't matter.

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Thanks for everybodys imput. I called the building manufacturer and asked about connecting the #6 rebar by welding and they said that I should just tie wire them together, he didn't recomend welding as plain rebar is not considered weldable. I asked about other connectors and he said I could certinly use them but the engineers accept tie wire as an acceptable meas of securing them so guess what.....tie wire is easy and cheap so that's the way that I will be going. Why make things harder and more expensive than they need to be?!.
Mike

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