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Advice sought - cast iron repair

Mcgyver

Diamond
Joined
Aug 5, 2005
Location
Toronto
This is drive housing on a light Brown Boggs set of rolls. The casting holds the opposing rolls together so is subject to the forces on the rolls, and some rock star busted it.

We are a fab shop so have good welders, but we make new equipment; not maintenance and repair and almost never need to weld cast iron. I'm sure they can do it, but what seems the key to success is the preheat, rod and cool down which they don't have the cast iron experience with. As its a bit out of our wheelhouse, I figured I'd get some good advice here. The part takes a lot of force and we want to get this machine back up quickly. I've thought about fabricating a replacement but that will take a lot more time.

casting is as per pics, material is about 1/2" thick

Can you advise what temp to preheat to and the cooling procedure? do I need an oven or is a blanket and maybe a bit of propane enough? V out the weld as usual? Nickel rod - anything specific for the big win?

What about Mig silicon bronze? I guess thats a brazing process? Where would you use that over welding? easier/harder? stronger/weaker?

thanks for any help you can give

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DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
Looks like it's been repaired a few times.

How about torch cut sides (with the slots) from 1"-1.5" thick and a simple outside cover/box of 1/2" plate ?

Might not even need to be curved/rounded.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
I would drill a 1/4 or 3/8 hole at the rounded side just past the crack ..for the crack to run into.
Then put a c clamp on the other side and braze it.

Could even put a small steel bridge strap Inside at the open end ..and then braze it.

looks like a design error and the nut at the top can stress the casting. I would try to design something that would support somehow to avoid that happening again.

If you don't have a good brazing guy then drill the into-hole and send it out to s brazing shop.
 

DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
Maybe make a whole series of bridges cut on the cnc plasma, to go over top, down the sides,
and some across the bottom too.
Start welding them in place on one side, drive wedges in under a temporary tab to drive
crack back together, finish weld re-enforcing ribs in place.
 

scsmith42

Aluminum
Joined
Jul 28, 2020
Location
New Hill, NC
MIG is not an good option; you won't get proper penetration. Your options, as I see, are

1. TIG brazing with silicon bronze filler
2. Nickel arc weld
3. TIG weld with nickel filler. In some instances, you can substitute some stainless filler for nickel.
4. O/A brazing.

Yes re v-ing it out. You might want to fabricate some external gussets from heavy steel to strengthen the casting after welding.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
I knew one guy who could arc weld cast iron. He did a few jobs for me welding cast, and welding aluminum.
He was the only journeyman blacksmith I have ever met. I would call him a master welder.

Bobby Doduh I'm not sure if that is the correct way to spell his last name.
Sometimes he would follow his weld with a piece of fire blanket, some he would sink into his bucket of ashes. He had a lot of tricks that I never saw another welder use. To bad that he did not write a book on welding.
 

Bondo

Hot Rolled
Joined
May 14, 2011
Location
Bridgeton NJ
If you arc weld it, you need to keep the welding material and base material as close as possible so they cool at the same rate. So try to find out how much nickel and such is inside the cast, if possible.

Preheat is generally always at 500* for cast iron, and I think cast steel.

Keeping inter pass temps in check is very important. Also if your going slow, keeping the welded section and the not welded section at preheat levels.

Look up different peening way as some work better then others for applications. What you do at the end is just as portant as what you do at the beginning.



If your brazing it, well hell, you can do about anything you want as cooling and post heat and peening is nothing like welding it. Still have to control pre, inter pass, and post heat.

Sent from my SM-G960U using Tapatalk
 

hvnlymachining

Aluminum
Joined
Jun 21, 2019
Location
St.Onge
For a first timer with cast, brazing is the easiest and most forgiving. We've also nickel welded things ranging from a cat d7 engine block to old stove parts with good success when paired with a LOT of patience and a good peening. Weld half inch of weld at a time, peen for a minute and a half to two. Plenty of videos can be found on this process. It's slow but holds well. Definitely vee the break before brazing or welding. Welding cast is not for the faint of heart, nor the man in a hurry.

Good luck!
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Nickle works but is fabuluosly expensive.....lots of preheat and braze .....however looks like its under massive load....nothing will be more than temporary.........Id be looking at weld fabricating a new part from steel .
 

Ries

Diamond
Joined
Mar 15, 2004
Location
Edison Washington USA
I have done a fair amount of tig brazing on cast with silicon bronze filler. And I would say this is not a great candidate for that, unless you have a good accurately controlled temp oven to pre and post heat this in. Silly bronze works best on thinner parts that dont soak up the heat so fast.
I have also done tig nickel repairs. Generally better, and stronger, than silly bronze. Again, easier on thin (up to maybe 3/16") material.
Above that, again, accurate pre and post heat.

The real pros use ovens, and then gas weld with cast iron filler- thats the best, used for things like irreplaceable heads for vintage cars.
But its an art, and requires experience.

First- I would search, hard, for a local cast iron repair shop. They still exist, but are rare and hard to find.
Second- really accurate pre and post heat.

The bigger problem I see is that it appears the rolls on this are around 4" or 5" in diameter.
That means this is a 12 gage or 14 gage roll, but for the last half century or so, people have rolled heavier stuff thru it, my guess.
If you fix it, and use it to its capacity, and no more, the fix may work.
But pushing it again will break it again.
 

Mcgyver

Diamond
Joined
Aug 5, 2005
Location
Toronto
Thanks for all the ideas.

Current plan is to look for someone specializing in it, if I can't get a sense of anyone is actually great at it we'll do it ourselves with nickle rods. V it, 500 degree preheat, short welds, peening in between, slow cool under blanket. Within reason, don't care that much about the cost; this is production machine used to make a certain part so need it working, and the cost even of used rolls is frightening.

That should get us up and running, but I'm also going to sketch the the key dimensions so if it snaps again we'll be able to more quickly fab something

I'd not seen that metal stitching before, neat idea. I'm reluctant to use it here as there would be a lot less cast iron in cross section that would have to break than the original casting.

thanks again...will take pics and let you know how it works out
 

M.B. Naegle

Titanium
Joined
Feb 7, 2011
Location
Conroe, TX USA
I'd be most curious as to WHY it broke. As noted above, it might be a design flaw, but I'd first look if there was something wrong with how the piece is being assembled, adjusted, used, etc. before I started trying to improve it. If this set of rolls is only designed for a certain class of work, and it's being pushed juuust slightly past that threshold by a rushed job, "improving" the casting so that it doesn't break again IMO is only going to mean that something ELSE is going to break or wear out next time that the rushed operator gets behind the wheel.
 








 
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