I have welded a lot of rebar doing embeds. As long as the rebar says W400 on it, its weldable, otherwise it will give you problems. Hard to say with out seeing the welds. Normally cracking or braking welds means either the weld was improper or the material is hard and needs preheat.

Also are your welds shallow and hot? Sometimes shallow welds crack easily. Post pics if you can.

 

Yes the welds would be considered heavy spot welds. I am just making a grid and one weld per joint. I will try to grab a pic of one. I already rewelded them with 7018 on the opposite side.

 

I believe I read on here last year that rebar is not the best to try and weld, might want to do a site search for rebar and see what comes up.

 

I know rebar is crap metal. And remembering from the past, it is always frowned upon for using it, just like bed frame. But for this purpose, it works. But I can do a search anyway.

 

rebar isnt crap metal. in a structure it withstands considerable loads. It is not mild steel, and as mentioned, most grades of rebar are not weldable. The rebar I weld onto bent plate to tie into the slab is not the same grade as what the rodbusters put in their dowels. I should learn the specifics; but the stuff I touch is always bundled and marked "weldable".

 

Was it weldable rebar? Check for stamped number on the end of the rebar. Will be stamped C60.
Rebar has a very high carbon content and is very susceptible to cracking.
Needs to be preheated to 250º then welded with E8018.

For the details to match Weldable type rebar and filler metals see page 17 in the AWS/ANSI D1.4
Yes you can weld rebar with SMAW, GMAW, or FCAW.
There are 3 group classifications of Weldable rebar.
Grade 40,grade 50, and grade 60.
REBAR Grade 40- Filler E7016,E7018,E7028 SMAW. FCAW is E7XT-X (See A5.20)
REBAR Grade 50- Filler E 8015-X,E8018-X,E 8016-X SMAW. FCAW is -XE8XTX
REBAR Grade 60- Filler E9015-X,E9016-X,E9018-X SMAW. FCAW is 9XTX-X

I did not list GMAW filler because you probably will be working outdoors.

Got to have a temp crayon for that preheat.

BTW...Hobart FABSHEILD 21B is a trade name, but is actually E71-T11.
Makes it easy for everyone on the forum to give the AWS number.

So to answer the question directly....We do not know what the rebar type was.
Your Filler metal would have covered C60 in groups 2 and group 3 (ASTM A706) and (ASTM A615,616,and 617), but you did not preheat and so all bets are off.

 

Only meant crap in the instance that most rebar is difficult to weld and after some thought I remember that I tried doing that last year in school with stick and not liking the results at all. As for its intended purpose for structural reinforcement in cement structures theres no doubt that it is worth its weight in gold.

 

Pictures would help , i do welding on poured wall foundations and havent had problems. We overlap 3" and make a 2" weld at each end , it is run thru a curbing machine with two runs of rebar in each wall. Weld with Miller Passport .035 fluxcore , normally burn it a little on the Hot side.

 

Turning up the amps using flux core wire can work against you. You will get deeper penetration, but will be mixing more of the high carbon base metal with the fill metal. The resulting weld profile will probably be more concave, and the lighter slag will result in a faxter quench rate. Like Donald said, when you take short cuts and deviate from engineered procedures, all bets are off. A lot of welders who are very qualified will argue that it can or can't be done based on their personal experiences, but the fact that you working under less than ideal conditions also worked against you.

 

This might be one of those instances where "ignorance is bliss". No one ever told me that rebar wasn't weldable, so I've been happily welding it for over 40 years with both stick and mig. I make my own fireplace gratings out of it too. Maybe I've always been lucky in getting "weldable" rebar?

 

Been there too. I welded it for years, untill I was on a site where someone used it for ladder rungs and one snapped off under a man's weight. I have never used it for critical applications since, no matter what grade it is.

 

If you really want to know how to weld rebar and see drawings of connections and so forth get the AWS publication. AWS/ANSI D1.4-98
Now it is called D1.4/D1.4M:2011 STRUCTURAL WELDING CODE - REINFORCING STEEL
It is back order now it says. (popular booklet)

 

I will try to get a number off of the rebar mon. I got it pre cut into 9" and 13" pieces in two drums. I will also take a pic of the finished product. I am going to guess it is the cheapest rebar available.

 

I have done a fair amount of splicing rebar in precast concrete panels. Used a combination of joint details 13-19, and 13-28, always used Lincoln's NS-3M.

 

I have 6 sets of wps and pull test certs for welding rebar all with E71T-8-H16 class flux core wires

 

Like I said, this is not critical. Any bad weldor could do this job.

Here is the marking on the rebar.

Here is one completed. They refer to them as "chicken ladders". Four welds....DONE!

Here is the empty jig I whipped up really quick.

Here is the jig loaded up to weld four at a time.

 

"Chicken ladder jig" :laugh: That'll have folks scracting their heads wondering WTF.

So those things must be disposable then? Just what is it they get used for? Besides chicken ladders that is.

 

You know, I have used rebar for years on the farm. We actually made a scaling drum out of 3/8 Rb to take scales off of fish. Ive also used it for rungs on ladders that went some 15 feet high ( top of a food pellet hopper). Now that I think of it, Ive welded probably a ton of the stuff....table legs.....tool hangers...cable hangers...weed draggers...My gosh, all the weed draggers. I have always used 6011 1/8th to weld it. Glad no one ever got hurt??!!

JD

 

It s about to repair a ferro cement boat.
have a look to the pics

http://www.flickr.com/photos/awab/?uploaded=65&magic_cookie=80ff8cfc3399170d0695045387cd4dae

The front is damaged. To repair I need to build a new armature. Should I weld the new rebar to the old one.
I just bought the boat and have no experience with welding.
What is doing the heat to the old cement.

need your guys advice in the matter
thanks
peter