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-   -   Can I weld a truck frame with a MIG welder? (http://www.diychatroom.com/f46/can-i-weld-truck-frame-mig-welder-96076/)

jpearson311 02-21-2011 10:10 AM

Can I weld a truck frame with a MIG welder?
 
Hi all. I just bought a 1986 3/4 ton GMC High Sierra 4X4 and there is a small split on the outside face of the right rear frame rail. I figured out a way to weld holes the other day and would like to try it with a MIG welder. Can you tell me what kind of steel the frame is made out of (I'm thinking carbon steel) and whether or not I can fix it with a MIG welder? Thanks!

Jesse

ukrkoz 02-21-2011 07:47 PM

not sure about your truck, but on 18 wheelers, i have seen quite a few times a bright yellow sticker:

FRAME IS MADE OUT OF HEAT TREATED ALLOY

DO NOT WELD!!

so, yeah, folks weld them left and right anyway.

i can tell most of the alloys by spark. you can prolly look it up on google..

Bigplanz 02-21-2011 08:05 PM

Theoretically, yes you could weld it. Practically, not really a good idea. The weld will reduce the strength of the frame, possibly by as much as 80%. Better to through bolt a metal brace, IMO, if you can, but if a frame is bad, it generally can't be economically correctly repaired.

Post a picture if you can.

ukrkoz 02-21-2011 08:17 PM

1. any heat treated alloy is annealed thereafter, or it will crack; too hard; taking welder to it overhardens alloys, as they harden at room temperature.
2. any long objects will warp, if a local high heat is applied. that;s why they normally do this in jigs, under longitudinal stretch, to prevent warp.

i second Big on this. drill and brace. basically, shackle it. or even better off, rid of it. donate and write off on taxes. one way or the other you mend it, it will only get weaker.

Bigplanz 02-21-2011 08:42 PM

Oh yeah, you need a high torque, low RPM drill and a really expensive drill bit to get through a frame rail. :)

Weld a cosmetic patch, grind it down and sand it, paint it and sell it. j/k :whistling2:

nap 02-21-2011 10:24 PM

I really must disagree with the rest of the posters, in general. There is generally no problem with welding a frame but the twist is, it does require somebody that knows what they are doing and understands how to repair it and why you repair it as you do. As well, you need to figure out why it cracked and consider that when considering a repair. If the metal is degraded (it is 25 years old after all), the frame may have rusted enough to make it unrepairable.

The comparison to a semi tractors frame is not a proper comparison. A semi uses different metal and it is much different in the loads placed on it. It is high tensile strength metal that is quite prone to damage by improper heating. You truck is very different and not subject to the same stresses.

Now, you do not just go willy nilly welding a crack and think it is repaired though. Depending where the crack is and the condition of the abutting metal, you generally need to apply a fish plate. This is something that unless you are the pro at the welding shop that repairs frames, you take it to the pro at the welding shop that repairs frames. It is a very serious matter and shouldn't be taken on by a novice.

So, if you want to keep the truck, find a weld shop that does frame repairs and let them inspect the thing to determine if it really is repairable.

Bondo 02-22-2011 07:20 AM

Ayuh,... I agree with Nap,...
But, to clearify,...
You'll need a mig with 200amps of power....
A little 100/ 140amp machine Ain't gonna do it...

jpearson311 02-22-2011 09:07 AM

Quote:

Originally Posted by nap (Post 595436)
I really must disagree with the rest of the posters, in general. There is generally no problem with welding a frame but the twist is, it does require somebody that knows what they are doing and understands how to repair it and why you repair it as you do. As well, you need to figure out why it cracked and consider that when considering a repair. If the metal is degraded (it is 25 years old after all), the frame may have rusted enough to make it unrepairable.

The comparison to a semi tractors frame is not a proper comparison. A semi uses different metal and it is much different in the loads placed on it. It is high tensile strength metal that is quite prone to damage by improper heating. You truck is very different and not subject to the same stresses.

Now, you do not just go willy nilly welding a crack and think it is repaired though. Depending where the crack is and the condition of the abutting metal, you generally need to apply a fish plate. This is something that unless you are the pro at the welding shop that repairs frames, you take it to the pro at the welding shop that repairs frames. It is a very serious matter and shouldn't be taken on by a novice.

So, if you want to keep the truck, find a weld shop that does frame repairs and let them inspect the thing to determine if it really is repairable.

Ok. I'll post a picture later on when I get home. It's on the right rear frame rail just in front of the rear bumper brace for that side. Can frames be welded without a fish plate? I'd like the repair job to look like it was never cracked in the first place. Nice and smooth. Thanks!

Jesse

tpolk 02-22-2011 09:20 AM

thought it was called a flitch plate?

jpearson311 02-22-2011 09:22 AM

Quote:

Originally Posted by tpolk (Post 595632)
thought it was called a flitch plate?

I don't know what it's called. I was just going off of what Nap said.

nap 02-22-2011 11:41 AM

Quote:

(fĭsh'plāt')
n.
A metal or wooden plate bolted to the sides of two abutting rails or beams, used especially in the laying of railroad track.


Read more: http://www.answers.com/topic/fishplate#ixzz1Ei6g31c7
Quote:

A flitch beam (or flitched beam) is a compound beam used in the construction of houses, decks, and other primarily wood-frame structures. Typically, the flitch beam is made up of a steel plate sandwiched between two wood beams, the three layers being held together with bolts. In that common form it is sometimes referenced as a steel flitch beam. Further alternating layers of wood and steel can be used to produce an even stronger beam. The metal plate(s) within the beam are known as flitch plates.
Ultimately, it doesn't matter what you call it as long as people understand what you mean. From my experience, a fish plate is simply plate which is used as a reinforcing member in a limited area such as a joint or a crack repair. A flitch plate or beam would be a complete construction of a multi-layered beam. The plate I suppose would be the steel plate in the center of the two wood members.

ukrkoz 02-22-2011 09:46 PM

unfortunately, i have to agree with nap.

there's a good reason it cracked where it cracked. probably, there was a good reason someone sold it either.

yes, tank armor plates are welded together, and they withstand huge stresses. so, all the best and god speed.

Bondo 02-23-2011 08:14 AM

Quote:

I'd like the repair job to look like it was never cracked in the first place. Nice and smooth.
Ayuh,... I really doubt That's gonna happen...

jpearson311 02-23-2011 09:32 AM

Quote:

Originally Posted by Bondo (Post 596349)
Ayuh,... I really doubt That's gonna happen...

That's what I didn't want to hear. :(

nap 02-23-2011 11:23 AM

I can make it look like it was never cracked but the problem is; it will not be an adequate repair. If your thought is to do this in an attempt to hide the problem and sell the vehicle: don't do it. It could cause you to not only be liable for the deception when it came time to look at rescinding the contract, it could also put you in a position of liability should that crack and subsequent repair fail and be the cause of an accident. God forbid a person would be injured. If that were to happen, there could be criminal as well as civil penalties involved.

I can't imagine an 86 vehicle looking all that sweet anyway so why a invisible repair is so important makes the intent a bit suspicious.


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