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Emmit

Welding rebar to stock

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Posted (edited)

Hi everyone,

Lately I've been welding a bit of rebar to whatever I'm trying to forge. My problem is that usually by the third or fourth heat the weld snaps and I'm left with a partially hammered piece of steel, a separate piece of rebar and a strong feeling of contempt. 

I feel like I'm doing everything to create a strong weld. By metals are clean, hot to the touch and beveled to add surface to the weld. Any suggestions?

Thanks in advance

Edited by Emmit

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Try doing it at a low red heat, then forge the weld at a high orange, then normalize it a couple of times.  It'll still fall off, but it may last a couple more heats. High carbon steel and hardenable steels like Rebar don't like arc welding, it creates a brittle heat-affected zone.  Forging and normalizing can help with that.  What are you welding with?  Stick, MIG, TIG?

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I'm welding with a MIG. I'll definitely try with the method you listed. I didn't even think about forging in the weld. Or normalizing.

 

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Without knowing your level of experience my advice might be useless....

I had the same issue to a much greater extent when I just started because of how I was holding the work piece and the stresses put on the weld while it's getting hit.

If the steel is flush with the anvil goes towards moving metal, if you're holding it slightly off there's a shock when you strike that bends and eventually breaks at the weld.

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the steps that described will definitely help on the metallurgy side especially given the wide range of carbon the rebar could have. many time weld failures are also due to weld geometry. if the rebar is cut flat and you are only fillet welding around it to the bar the stresses of hammering at high heat will always brake the weld. to gain longer life a full penetration weld will help. 

grind the rebar to almost a point at about a 45 deg angle and fill all that in with weld, then continue to build up the weld so it looks like the fillets you had before. a full pen groove weld with buttressing fillet.

with that you do not have the incipient crack of the flat part of the rebar and no stress risers.

 

good luck

 

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weld your billets with a press and the weld on the handle will hold a ton better :rolleyes:

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43 minutes ago, Joe Fonzi said:

the steps that described will definitely help on the metallurgy side especially given the wide range of carbon the rebar could have. many time weld failures are also due to weld geometry. if the rebar is cut flat and you are only fillet welding around it to the bar the stresses of hammering at high heat will always brake the weld. to gain longer life a full penetration weld will help. 

grind the rebar to almost a point at about a 45 deg angle and fill all that in with weld, then continue to build up the weld so it looks like the fillets you had before. a full pen groove weld with buttressing fillet.

with that you do not have the incipient crack of the flat part of the rebar and no stress risers.

 

good luck

 

I had the same problems as well, but then I did this method and the rebar holds much better. 

These days, I usually only weld enough on just to get tongs on the stock.  It seems to me that the tongs dissipate some of the shock from the hammer. 

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I've been told a lot of wire-feeds don't penetrate very far, this could be an issue. You might have more luck with an old stick welder and 7018 or 14 rod. I usually have to cut the rod off after I've done with the billet. I usually use 7014- yeah, I know 7018 is better but 7014 can stay out all year in my unheated shop and still spark.

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Or you might just get some mild round bar and use that; rebar has lots of remitted stuff like nuts and bolts that are higher carbon as mentioned above. It can be done but....

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I'll 2nd on the use of mild steel round bar - I've been welding that to a billet for San Mai, 45° the round bar to have close to 100% penetration and I've not had any problems with rod breaking off.  I stick weld only, and have used 6013, 7018, etc.  Mostly whatever rod I've got handy. 

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using a known steel that is weldable is better than taking a chance on rebar but i like the deformations in rebar makes it nice to hold on to and as long as it was "annealed" (we got red then cooled...i know i know close enough) you will really not have an issue in the HAZ (heat effected zone) of the rebar its usually not that high in carbon or that complex an alloy. it really is the geometry.

as for rod penetration use 6010, 6011 or 6013 they are not as fussy with needing clean steel as 7018 and have deeper penetration than 70series rods.

if you are using MIG then you are completely reliant on the geometry and cleanliness of the weld and material.

that was a topic in my welding party i had on Saturday where most of my junior structural engineers got to experience what they are designing and asking fabricators to do. last one i demonstrated forge welding but we never get to spec that out, bummer.

good luck.

Joe

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Another option is 8th wall 1" square tubing. That's what I use. Easier to get good penetration, more weld surface, better heat dispersion while forging. 3/4" square works good too, but holds heat longer. Saying this I realize this stuff isnt throw away material to most. If you got it though, it's what I'd recommend. 

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On 6/8/2019 at 11:34 AM, Al Massey said:

I've been told a lot of wire-feeds don't penetrate very far, this could be an issue.

They penetrate just fine, if you apply enough heat for the size of the stock you are welding. Trouble is, a lot of folks try and weld thick stock with an undersized welder.

On 6/8/2019 at 12:23 PM, SteveShimanek said:

Or you might just get some mild round bar and use that;

I use a round mild steel round rod inside a 1" square tube with lots of 1/4" holes drilled in the square tube. It dissipates the heat faster from the handle.

On 6/11/2019 at 6:37 PM, Zeb Camper said:

Another option is 8th wall 1" square tubing.

These ideas are on the mark Use homogenous mild steel for your handle, not rebar. Rebar really doesn't like to weld very well as compared to homogenous mild steel. When you consider how little difference there is in pricing, the mild steel is well worth the extra 50-70 cents per foot.

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