Metallurgy experts?

Olliejunkie · Apr 13, 2018

I cut the fenders off my trailer and made some brackets there will make them removeable. I'm getting ready to weld them on but have some repairs to do first. Previous owner did some welding on it before me and it's cracking out by the welds. I need to fix that and do not want to cause it to do the same. Can anyone tell what caused it and how to prevent it?

Mike Groom · Apr 13, 2018

I would think the cracking is due to vibration of the fenders,better support would help some but the material itself could be of a harder steel,(more carbon)and
you may be stuck with it.

Bob M · Apr 13, 2018

As Mike says the cracked welds are from vibration.

Solution is to provide better support (bracing, etc) to minimize flexing at the welds.

jon f mn · Apr 13, 2018

Get a pic from further back. That crack
that runs lengthwise looks lik e it's from
twisting the tube. I need to see more of
the structure and the entire trailer to
give a better opinion.

jon f mn · Apr 13, 2018

I don't think it's vibration. I think someone has been really torqueing on those chain hooks.

carvel minne farmer · Apr 13, 2018

(quoted from post at 15:14:41 04/13/18) I don't think it's vibration. I think someone has been really torqueing on those chain hooks.

ditto what jon said, it looks like it's broken out on each side of the tie down, from tightening a boomer down way to tight.

Janicholson · Apr 13, 2018

Wire brush everything to bare metal. grind off all weld bead above the surface. v each crack through the thickness. Put a
straight edge on it to assure it is straight. Weld E7018 with amps to get penetration. again grind to flush. Use 3/8 plate to
"fishplate" the side for at least 18 inches either way of the hold down hook. Use 3/8 thick strap on the top of the existing frame
and weld it in place. Fillet weld the strap to the fishplate. If there are cracks on the inside, do the same there. pound the
living devil out of the welds with a chipping hammer. Wire brush and coat with epoxy paint. Jim

Olliejunkie · Apr 13, 2018

I will try to get better pics but I got I started grinding on it and patched it up a bit. The tubing is pretty thin walled.

jon f mn · Apr 13, 2018

I would say it's 3/16" wall, pretty
standard for trailers.

Olliejunkie · Apr 13, 2018

First pic is the side I posted pics of first. I started to put my new fender mounts on. I need to get some bigger C clamps and some 7018.
Second pic is the other side. The cracks are right where the ends of the fenders mounted so maybe it was from vibration and someone had attempted to patch it. Also had an ugly patch over a spot behind the rear of the fender where it looks like something heavy hit it. I never use the D rings.

jon f mn · Apr 13, 2018

You don't need 7018, that is all mild steel
so any rod you have or mig will work.

Olliejunkie · Apr 13, 2018

I have been using 6013. I thought 7018 would be better for the vertical welds?
My first attempt vertical weld with 6013 didn't go well.

ErnieD · Apr 13, 2018

My opinion. Trailer had overload or unit load front and back. Flexed fore and aft of axle/fulcrum. Heat affected zones from welding the fenders crystallized the metal promoting the area to cracking. Derate trailer or sister in more metal to re-enforce the frame to absorb the bending moment at the axles.

jon f mn · Apr 13, 2018

It might if you have a DC welder. Usually
you're best bet is to use what you are used
to. For that tube you should be using 3/32
rod or m maybe even 1/16 if you can get it.
The most common welding problem is using
wrong size rod for the job.

buickanddeere · Apr 13, 2018

(quoted from post at 20:53:37 04/13/18) My opinion. Trailer had overload or unit load front and back. Flexed fore and aft of axle/fulcrum. Heat affected zones from welding the fenders crystallized the metal promoting the area to cracking. Derate trailer or sister in more metal to re-enforce the frame to absorb the bending moment at the axles.

Should that frame be tempered to remove the stress risers ?
Could be getting into more work than what the trailer is worth ?

Olliejunkie · Apr 13, 2018

I agree that heat at fenders may have made the metal brittle. Wondering if there is a way to treat it to reverse affect?
It's a tilt trailer and pivots right in front of the rear axle. It could've been overloaded and definitely had something dropped on it before I got it.
Think maybe I better go back to 6011 for my vertical weld. I never have had any official training and do not well enough to get good at it. Thank you all for your input.

jon f mn · Apr 13, 2018

You folks are way over thinking this. This
is only mild steel tube. Weld it, and plate
with 3/16 and thats good. The hard part
will be getting it back in place where it
belongs.

jon f mn · Apr 13, 2018

There isn't anything you can do about the
haz area around a weld in this case. That
is why you have to plan for it and
fabricate accordingly. Get the tube back in
shape, weld it, grind it and plate the side
with a piece of 3/16 plate. You can also
plate the top. The plates should be 3-6" on
each side of the weld, just a bit narrower
than the flat of the tube, and the ends
should be cut angled, radiused, or left unwelded and offset from each other so the ends don't line up.

RBnWA · Apr 13, 2018

Hey Olliejunkie bring trailer and steel to Raymond. I ll fix it. RB

Olliejunkie · Apr 13, 2018

Thanks for the offer. Would be a fun trip but I need to fix it before I head up the freeway.
Doubt I will be plating unless my vertical welds get better.

jon f mn · Apr 14, 2018

Post a pic of them. When you do a vertical
weld, you do a small weave with a pause on
each side. Do a count, Right one two, left
one two and so on.

Olliejunkie · Apr 14, 2018

Thanks Jon. I watched some videos. Probably need to practice first. One problem is I can't get comfortable that low. When I was patching the rectangular tube I kept burning holes. It is very thin.

jon f mn · Apr 14, 2018

If you're burning through you are too hot
and likely need smaller rod.

Olliejunkie · Apr 14, 2018

Been running 3/32. Went to town to get more and accidentally grabbed 5/32. Guess I'm going back or calling it a day.

fdt860 · Apr 14, 2018

If you are not that good with vertical welds, you can put the trailer on the side of you have a way to lift it.

Texasmark1 · Apr 15, 2018

I didn't read the other responses. I had similar problems on brush hog type rotary mowers top decks splitting.....flat 9-11 ga. steel plate.
What worked for me was to use a scab plate over the crack of twice the thickness or so and wide enough to extend half an inch or so on
either side to cover the cracked area so that the weld joint was the scab edges to the deck plate; not trying to weld the plate edges back
together......which is what I did initially and it just broke at the weld edge like your picture. Vibration is the culprit....was for me.

Olliejunkie · Apr 15, 2018

I finally found some rod and laid down a few beads that are acceptable in my book but not good enough for pics. Then I got rained out. Looks like rain for quite awhile. Maybe I can get some done between showers. New brakes should be here Tuesday I hope. That will be good. I can get that part done if I find the ambition.

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