Another welding question

Without pictures this might be tough to describe but I will do my best and post pictures when I can (busy week).
The backhoe on my 202 Massey Workbull attaches to the loader frame on the bottom by a beam slung under and bolted to the front end loader frame. The top link comes down at an angle and attaches to a point just behind where the loader frame goes up to accept the front end loader arms.
Right behind the top link attachment point a stress crack has developed, well re-developed, someone had fixed it before. I took the backhoe off last weekend, removed all the necessary brackets so I could get to it and ground down the old weld and re-welded it. After using the loader and backhoe a few hours this week I noticed it's cracked again. Now the loader frame is what holds the hydraulic fluid and I saw some seeping out yesterday so I have to fix it.
I started with 6013 for an initial pass with better penetration and then ran 4 passes of 1/8" 7018. It looked good, I ground a bit off to look for porosity and the weld was nice and solid. I am wondering if the problem is the weld is flawed, if I should use a different rod or if I need to add some bracing. This is a pretty high stress connection so I am thinking about adding some sort of brace.

I'm just re-reading this and thinking I will have to add some pictures.

Pictures are always nice.
I think you may have a design problem. Or your metal is just over worked, (case hardened) and needs to be replaced.

Your problem is all you did was welded the crack. When metal cracks it really has small cracks all around the crack you see so you weld up the one you can see but miss all the others so some where down the line it cracks right next to the first crack. What you need to do is V out the crack then weld it back up than put what is called a fish plate over it. A fish plate is another piece of metal that covers the area by at least 2 inches out from the crack all the way around and if you want a real good one you cut it so it is not square but has a sort of diamond shape at the ends

Here is a good picture of a fish plate. :wink:

yep I'm guessing you agree with what I told him

Another problem you have, besides what old mentioned, is that you said the frame holds the oil and is leaking through the crack. I don't care how much you V the crack, heat the area aroud the crack, or whatever you do, you are never going to get all the oil out of the metal in the area where the crack is without doing things to the machine that simply aren't feasible to do. As a result of that any weld you put back into the crack is going to draw oil from the metal and that results in a weld that is both hard and brittle and very prone to recracking. I run into this type of situation when I have to build up holes that have had lubricants in them in order to get them ready to line bore. Often the oil leaching into the weld will leave spots that are so hard even carbide doesn't want to cut it. Oh well, it's just one of the things that makes my job fun...

Anyway, given that you still need to weld up the initial crack but this time vee it out, then drill a small hole at each end to insure it doesn't run further when it recracks. Next weld it up and grind the weld back flat. Lastly do as old suggested and plate the area with a plate around the same thickness or slightly greater than the base metal, and large enough that it catches v1rg1n metal at least a couple of inches on every side of the crack. This won't necessarly keep the old crack from reforming but the holes you drilled and filled with weld should keep it from getting any longer, and the plate will keep the oil in. Good luck.

(quoted from post at 12:45:53 05/19/11) yep I'm guessing you agree with what I told him

Click to expand...

Yes sir, so far all good suggestions.

I hope you meant to say 6010 (or 6011) for your initial pass, not 6013. 6013's penetration is slightly worse than bubble gum.

And that's why I keep coming back here, good advice all around!
I had wondered about weak metal, hadn't considered it being brittle but that does make sense.
I will use what was suggested here..........and make sure I have some 6010 for the initial pass.
Looks like Saturday is gonna rain so that will be a good day to tackle it. I'll try to remember to take pictures as I go.

Puddles that first picture you posted, the top plate added there looks pretty much like the area I am working with. What is that from?

That is an excavator boom.

Why do you weld out past the points on the plate?

To confuse the heat line, and prevent stress risers.

Ok, so I picked up some 1/8" E6011 rod today which I will use for the initial pass. Turns out I was using 6013 the first time.......that might explain a few things. Also picked up some fresh 7018 (1/8" as well). I owe the neighbor some from last weekends work and I'm sure I'll burn up the rest!
I will do as recommended, hopefully start on it tomorrow...........wife want some fence posts etc. done first though, gonna turn the hay burners into grass burners for awhile.......so the tractor will have to "bleed" a little more before she's fixed.