How to fix this crack

[IslandTractor]

If you have a powerful enough Mig welder, by all means use it. I just love Lincoln's L-56 Mig wire. If you are going to use a stick welder, use 7018!

Now that is just unfair! Almost none of us have welders capable of spray transfer and if we did I bet we could also make beautiful well penetrated welds. I got to use a Miller 350 in a welding class and it made gorgeous welds. Sometimes equipment is the difference.

 

[Egon]

If you have a powerful enough Mig welder, by all means use it. I just love Lincoln's L-56 Mig wire. If you are going to use a stick welder, use 7018!

Just plain good looking welds. Don't see too many that nice.

 

[Mark @ Everlast]

So I am going to go with ArlyA fish plate design. Still working on steel thickness, probably a 3/8 piece I have will be the answer.

Still more questions though.

Would you Mig this or Stick this?

Is Co2 / Argon heavier than air or lighter than air? Wondering about the purge I am planning.

Finally, I assume that the fish plate should be a bit (1/4" or so) smaller than the piece I am welding on to. Meaning, I do not want to make the weld from the side but from the top.

Either would do an acceptable job. I'd probably grab stick and do it. Spend the extra money for a 10 lb can of fresh 7018's, probably Lincoln excalibur. It should be in a sealed steel can. While you are doing the repair, keep them in a make shift hot box, a cooler with a light bulb or something to keep the warm and dry. (Hot to the touch will make them weld like butter).

I would use something as thick as the metal thickness, or thicker. I don' think it would hurt if you went with a 3/8" plate, or a 5/16" plate. I'm thinking that tubing is probably 1/4" wall thickness???

Both CO2 and Ar are heavier than air, so it would only need to run a little while to push the O2 out. But I'd think that the main idea is to keep the oil from flashing. IF you have a Oxy-fuel, or even a good propane torch, I'd heat the metal to burn the oil out of the cracks and area of the weld first. It will help to prevent gassing off of the oil and subsequent (Possible) porosity in the weld area. It'd open up the cracks too so you could see how far the extended too if it is a concern.


You want to weld the plate across the top and I'd even weld a complimentary one on the bottom. Slide the plate over so that the inside rolled (radiused) edged of the tubing meets the edge of the "gusset". And while we are calling it a fish plate, it in my mind is really more of a gusset if it is reinforcing the tubing in a corner joint. Fill the weld (multi-pass more than likely) to the outside edge of the tubing and an equal amount high on the plate.

Like I said earlier, you probably want to weld the underside of the plate as well, or at least a few long tacks, an inch or so in length, spaced equally apart.

 

[Shield Arc]

Now that is just unfair! Almost none of us have welders capable of spray transfer and if we did I bet we could also make beautiful well penetrated welds. I got to use a Miller 350 in a welding class and it made gorgeous welds. Sometimes equipment is the difference.

Just plain good looking welds. Don't see too many that nice.

Thanks guys!
Now you realize, I've only been welding a few months now.

 

[Mark @ Everlast]

Thanks guys!
Now you realize, I've only been welding a few months now.

That's what happens when you start suffering from Old Timer's...decades turn into months. lol. Just had to you know.

 

[Shield Arc]

lol. Just had to you know.

_____________________

 

[ThomasH]

When you weld do not drain the tank fill it to the very top. Fumes are explosive not liquid gas so by not allowing the fumes a place to accumulate by filling the tank full, it is safer than a partially empty tank

No way I would do that, it's asking for a fire, probably ala blowtorch as the oil heats and sprays out the hole. The safe way to do it is to drain the tank, wash it out with some solvent, followed by soapy water, and then put as much water as you can in the tank.

 

[Jesse masterson]

Actually a better way is to not fill it with water. There could be trapped fume pockets in corners, fill it with a inert type of gas, most common approach is to connect hose from exhaust, (most common being car). Or argon from a mig welder, or CO2.or both

 

[Egon]

Car exhaust can also be explosive.

Industry may have one using soap, water, heat and follow up with a procedure using inert gas and also checking for explosive gasses with a meter, not a torch.

There may also be cases of a plug and standoff or monitored continuous purge. It's all situation directed.

 

[RedNeckGeek]

Lots of good thoughts here, but whatever you end up doing, you've got to grind out ALL of the crack. If you don't, it'll act as an initiation point for new cracks in your repair weld. That's probably what happened to the first repair. Unfortunately, grinding will tend smear metal over the crack and hide it. When you think you're done, use progressively finer grits of sand paper on a backing disk to polish out the crack area in an attempt to remove the smearing. Then use a liquid penetrant test to verify that the crack is gone. LP test kits aren't cheap, so if you're not willing to do it right, find someone that will or you'll be doing it again. A mag particle test would show the crack even if metal was smeared over it, but the equipment to do that is even more expensive than for the LP test.

If grinding the crack all the way out means going all the way through into the tank, you'll have to drain the tank, and I'd recommend some sort of inert gas purge while making the weld. As mentioned, auto exhaust can be explosive if it contains unburned fuel. And since grinding also makes sparks, it would be a good idea to clean and purge the tank before you broke through.

From the looks of the cracks, they're starting at the inside of the corner. I'd guess that the two legs forming that angle are twisting together and apart as the machine rides over rough ground, and that flexing is focused on the corner. I don't think a fish plate on the side is going to help, but triangular gussets top and bottom will distribute the loads over more area. See MossRoad's post #9. What ever else you do, try to end up with a smooth radius on the weld surface on the inside of that corner. Build it up and grind it smooth if you have to, and avoid undercut at the toes of the fillet as well.

I wouldn't have any hesitation using multiple passes with my Lincoln PowerMIG 180 welder on this. Probably end up running it wide open, but I've done way thicker stuff than this. Just make sure you push the wire toward the front of the pool so it impinges on base metal at the front of the weld pool. Lay down a stringer bead to start, then weave as the groove/fillet gets wider. Wouldn't hurt to hit it with a needle gun between passes to try to build some compressive stresses in along the way, but that might just be wishful thinking.