Tough cast iron welding job

[Qweaver]

I've welded a lot of cast iron and usually successfully.  But I have one to do that I think will fail.  It is a cider mill round crusher that has a crack the length of the cylinder and the spokes for one end are broken out.  The crack is in an area that is only 3/16" thick and I can not increase that thickness because it has to mate to the other crusher.  I'm going to put a 1/8"x 1"  piece on the inside of the crack, grind the crack out to about 1/8" and back step braze it. I will still have to grind the excess brass so that it does not foul on the other crusher.  I have my doubts!  The replaced spokes will help...but I have my doubts.  This is going to be a time consuming repair and I hate to charge for something that will not work.  Drilling and screwing to the backing strip may be a better option.  New parts for this old press are not available.

Suggestion?
Quinton

[Raider Bill]

I'd suggest pictures.

[Dan_Shade]

Sounds like a good opportunity to learn how to do sand casting    

Good luck

[Gary_C]

Some of the most difficult welding of cast is done by the people that fix engine heads and blocks and what they tell about the process is they mostly remelt the cast, reflow it together, and machine the repaired spot back to standard. While that may not be possible on your repairs of cast, the one thing they do that is most necessary is to put the item in an oven and heat it very hot and let it cool slowly.

So if you need a good tough repair of a cast item, put it in an oven, heat the entire piece as hot as you can get it, do your repair, then back into the oven to equalize the temperature and then cool slowly. That is the best way to equalize stresses in the weld.

If it's too big for an oven, take a torch and preheat as much of the entire part, do your welding and then back to the torch and reheat everything before letting it cool slowly.

I have never had much luck with brazing cast items. For me the best repairs were made with nickel rods and a stick welder. Just don't expect to drill a nickel rod repair spot, grinder only.

[Kbeitz]

I weld cast all the time... I use  Ni-cad cold weld rods.
Just a little dab and then use a needle scaler to peen and clean the weld.
Let it cool. Walk away and do something else. Come back and put another dab.
No need to pre heat. Just this year alone I have used around 75 lbs on 1/8  Ni-cad rods.
They cost around 3-4 $$$ each but they do the job.

What I can't weld is pig iron... I end up with more cracks than when I started
no matter what I do...

[sandsawmill14]

if i remember right preheat to 800-900* is about the best with over 1400* being were it gets critical far as cracking  also welding in short welds helps keep the temp down  i agree with gary about the old school nickel rods thats what i use most of the time but you can get by with the low hydrogen rods in a pinch and they have some kinda cast alloy rods that work pretty good  but i cant get it to flow like the nickel :-\ and i hate change >:( so much i dont change socks but once a week ;D :D :D so i stick with the nickel

[Ox]

I also do cast iron like Kbeitz said.  The least headaches as long as you're not in any hurry.  If you're in a hurry, lots of heat is in order.

If you don't have a needle scaler the pointy end of a welder's chipping hammer will work.  Just need to whack the metal around some (a lot) to rearrange the molecules a little.  Makes for strength. - Sincerely, an old timer

[scsmith42]

Quinton, when the retired Welding Instructor has his doubts, it seems to me like it's time to pursue plan B!  :D

Have you considered having a new piece cast?  I know that there are some Foundry's around that will do custom casting. 

http://www.tomahawkfoundry.com/

Cattail Foundry in PA.  their phone is 717-768-7323 Emanual King, Gordonville, PA

John Crippens Foundry makes castings 923-581-2693

Scott

[Ox]

YES!  New cast part!  The answer to your problems.  It may not be the most affordable, but this also depends on who's paying the bills...

The word affordable means many different things to many different people.  I can't afford a multi million dollar yacht but somebody else surely can, and it's affordable to them at that!  :D

[Larry]

I think your on the right track to think brazing.  That's about all I will do on cast iron just because its a high strength reliable repair.  It usually takes me a lot longer making a braze compared to nickel, but I think the extra time is well worth it.

I've got a bunch of gears that I've welded new teeth on, some in high stress applications running without problems.  One of my more time consuming repairs that sounds similar to your repair, is welding about 20 pieces on a Big Green Egg cast iron grill grate that was dropped.  Pay back was a delicious rack of ribs.

[Qweaver]

My crossbow is out of service so...Back to the cast iron repair tomorrow.  UGH 

[Sixacresand]

My Granddad used to buy, restore and sell wood stoves and heaters,  He would repair cracks or breaks in cast iron by grinding a vee in the crack and electric welding with nickel rods.  I don't know about the strength of the weld, but it always looked good.