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Silver brazing cast iron

bhigdog

Stainless
Joined
Jul 20, 2005
Location
Eastern PA
I have a maybe 5 pound cast iron casting that has an "ear" broken off. New casting. Clean break. Will silver braze "suck" into the joint and join the parts. Very low stress part. I guess the question is will silver braze adhere to cast iron. A few ways to skin this cat but silver braze would be fastest/easiest. Thanks.........Bob
 

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Yes silver solder will work. As far as being the quickest and easiest way, I have repaired a lot of cast iron using nickle rods and any buzz box. They aren't cheap but 1/2 pound or so will last you a long time if you only weld cast iron occasionally. You don't need to really clean it all that well because the repair is on the surface and you are not relying on wicking.
 
Yow. Lots of info there, and some contradictory opinions. I've posted a pix to the initial post. Plan is to clean the area around the break of paint, smallish chamfer on edges to feed the braze. I'm thinking rather than clamping the "ear" I'll let gravity hold it in position and that should leave clearance for wicking action.
Thoughts?......Bob
 
Just nickel rod weld it...needs a preheat.
But not all rods are equal some just weld better than others, i used to like liquid arc rods they are about $3 AUD a rod though, may be more now as its been a while.

If you go one step further you can weld it with the oxy torch ( job needs to be very hot) and a cast rod with flux. This method can warp the job as stresses in it are relieved.
Its the best for getting a good matching weld and is strong but has its downsides.
Its just takes a lot of skill to do it and warping issue make it unsuitable for all jobs.
you cannot tell its been welded with this way if you do it properly its a very good match.

Nickel weld is easily seen as its different to the parent metal.

Since your asking just go the nickel route as it is easier for you, when your skill improves try the oxy method if you wish on a different job later.
 
I’ve repaired a lot of broken cast parts in my day. I like to use brass rods with a white colored flux on it. Takes a lot of heat from an oxy & act torch. Seems to do a good job. It holds very well. I’ve had a few of my repairs break but they seem to break in a different spot. I used to have a ‘69 Ford truck with a broken exhaust manifold. I bolted the manifold down to the welding table, V’d it out real good and brazed it up. Lasted for about ten years till I sold the truck.


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I'd not rely on or even expect 'wicking'. In my experience the only way to get a good repair short of welding is to vee it out and fill with brass/bronze, silicon-bronze, etc.

edit: It looks like you maybe could easily drill from the bottom and counterbore for a socket-head cap screw. Leaving the broken surface as is will provide a hairline joint with good mechanical locking. Only one screw needed but you'd have to hold the pieces in perfect alignment while drilling/tapping.
 
Where I worked ,welded a lot of cast iron for maintenance......started out using nickle bronze braze rod /white& pink flux......end of the day was I just MIG welding the cast iron .....break shown is a base of a submersible pump ,and does take a bit of stress and impact.........There is a very good spray metal method of welding manifolds,resists the usual problems caused by heat.
 
Spray yes, i have that gear.
Obviously you need to buy it and it has a cost...its only nickel powder anyway.
It has its uses and applications.

Mig welding cast...well it goes very hard the weld that is. rough fix not that good.
 
I'd not rely on or even expect 'wicking'. In my experience the only way to get a good repair short of welding is to vee it out and fill with brass/bronze, silicon-bronze, etc.

edit: It looks like you maybe could easily drill from the bottom and counterbore for a socket-head cap screw. Leaving the broken surface as is will provide a hairline joint with good mechanical locking. Only one screw needed but you'd have to hold the pieces in perfect alignment while drilling/tapping.

The casting is the base of a submersible pump as mentioned below. Zoeller E-188 to be exact. I don't think the broken leg will be under too much stress. There may be some starting torgue but it has 4 legs and sets on an aluminum plate so it should slide easily.
I also was thinking of drilling for a cap screw from the top into the leg. Impeller and tool clearance may be a problem. I was also thinking of making a scab and just bolting the parts together. Looks are unimportant since it will never be seen but an ugly fix goes against my grain. If I go the silver braze route I'm thinking of a slot the length of the break big enough to accept a length of brazing wire. That might help with wicking by letting it flow both into and out of the break.
Grainger lists the pump for $1,404 plus freight. I got this one new in the box for $500 as damaged goods. I'm keeping it as a spare for the one I have in service now so no hurry.
Rainy Sunday tomorrow so a good day to study the problem in the shop.
Thanks all for the advice...........Bob
 
If I go the braze route I was thinking of placing a plate across all four legs. That should hold the top and the grain should lock the bottom in. I'm afraid clamping will prevent the braze running into the break.............
 
I would use silver solder in paste form and brush it on to both breaks, but what I would fear is all of the carbon coming to the surface during the heating process. If you pre-bake it out, you might get a good joint.

OTOH, why not face off the break on the base, drill and tap a 1/2-13 blind hole, then screw in a bolt with a jam nut and a lock washer/loctite. Level the bolt with the other legs and tighten the jam nut.

Or, check to see what a replacement base costs. I looked and saw a replacement for under $40, but it was for a different Zoeller.
 
I would use silver solder in paste form and brush it on to both breaks, but what I would fear is all of the carbon coming to the surface during the heating process. If you pre-bake it out, you might get a good joint.

OTOH, why not face off the break on the base, drill and tap a 1/2-13 blind hole, then screw in a bolt with a jam nut and a lock washer/loctite. Level the bolt with the other legs and tighten the jam nut.

Or, check to see what a replacement base costs. I looked and saw a replacement for under $40, but it was for a different Zoeller.

Excellent ideas. The bolt and jam nut will likely be my fall back solution. If I use that plan I'll likely lock the bolt in with a cross drilled roll pin.
Zoeller lists the casting in it's parts list but being retired and loving a good project I'd rather fix than replace..Thanks........Bob
 
I've done stuff like this before. One was a handle on vintage lathe tailstock screw, one end of the handle fractured off when I dropped it on the floor. Clean break, but the exterior had a lot of nice patina. So I fluxed up the break (fit back together nicely, like this part will) and clamped up gently. Used an O/A torch and handy and harmon EZ flow silver solder.

Did not appear to wet the joint at all - but when I unclamped it and cleaned the flux off, that thing was basically brand new, and was NOT coming apart.

For a large part like this, I would suggest generous preheat before applying the torch.
 
I once brazed a cast iron car exhaust manifold. One of them had the portion on the bottom break off where the exhaust pipe bolted to it. I beveled the joint on both sides then preheated to nearly red hot. I used the white flux covered brass rod with blue flux added. It took the brass nicely and once finished I covered in in a thick burlap cloth and let it cool overnight. It was for a friend.
As far as I know, it held.

If I had to do it again, I'd use this stuff - Muggy Weld.

Stick Welding Cast Iron with Muggy Weld 72 and 77 Rods - Muggy Weld
 
I brazed a casting with a similar break (and an attempted mig weld?) where the guide roller for a bandsaw through bolted. I cleaned it in acetone, brazed it with only a slight filed edge break, and filed it down to shape and redrilled the hole. I had absolutely no issues with the casting after that, and it was even under decent load keeping the band secured and twisted.

I didn't snap it apart to check how far the braze wet in, but it was strong enough. Seems a whole lot easier than grinding out and welding the crack.
 
First ,make sure your filler and flux will wet the iron casting.....any braze is going to need preheat to near red hot of the big part.....I would use nickle bronze ,start with the scaling powder ,then use the pink flux.....when hot enough the braze will flash all over where the flux is melted............Now for a quickie maintenance weld ,five minute allowance.....grind a bevel and MIG weld .
 
Typicly
Nobody tells about the failures they had with CI
I had plenty
Nickle cracking Nickel not wetting the CI Just bubbles Distortion with a OA torch
Never knew what CI it was So tried different methods

Peter
 








 
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