Method for Heating Cast Iron for Welding

[zzvyb6]

I have an old farm windmill to repair which has been damaged when they toppled it. There is a large piece broken out of the cast iron crankcase. It is a "clean" break (meaning just one very large piece is broken out. No small or lost pieces. Unfortunately, this piece has one of the standoffs on it used to hinge the tailbone (so there is some load on it even when its just sitting still.

I'm interested in welding it back together. I've done cast iron repair before with AC and nickel rod (some cast gears used on farm machinery that were in quite a few small pieces). For those jobs, I just clamped the gear pieces together and hit it with the nickel: no preheating, just some grinding to removed rusted metal and to create a groove in the parent metal to receive the nickel.

I saw an add on Craigslist for a gas fired oven specially used to preheat cast iron for welding and it occurred to me that I could use my barbeque grill to do the same job. Its a 4 burner unit, seldon used, and smells a lot like ribeye. What do you think of this idea? What temperature would be recommended to achieve with the cast iron before welding it? I'd do the same pre-treatments as with the gears: grind edges and use nickel. I suppose my other option could be to use my gas wrench with a rose bud to preheat it.

Any thoughts or advice? I've thought of a mechanical fix as well. I could use bolted angle iron pieces to tie it together and use the weldment just to seal the oil filled crankcase. I'd just don't want to make it brittle and disintegrate. Metal quality on these old parts is very good. It may even be cast steel.

 

[CalG]

Pre heat means about 500 degrees.

I repaired a broken exhaust manifold on a J-D crawler. It was a little three cylinder job.

Jigged the parts on to a length of angle iron. put the works in the BBQ with the break upper most and shut the cover. Waited about 1/2 an hour.

Brazed the pieces right there in the grill.

That was about 15 years ago......it's still going from what I see.

I don't weld iron .... brass is so strong. I hear they make bronze out of it ;-]

 

[cowski]

this is the way i would weld it .cast steel 1/8 7018.cast iron certanium 689 .i would v it out ,then weld about an inch peen it then let it cool .repeat til finished.

 

[Reyer Farms]

It is all about the heat. I have used fires, special ovens, cooking ovens ( gotta have a good wife), cutting torch and time. I do prefer to braze cast instead of welding. Have fun!

 

[CNC Dan]

one thing i would add is to practice first. get an old cast iron frying pan and break it, then try welding it.

 

[yomax4]

Grill is a great pre heat tool. Also can get a Weed burner or big bertha to do the job. I doubt that it's cast steel but you need to find out. There is a grind test you can do and you look at the sparks to see if it's cast iron or not. Oppinions vary on the repair. I would heat it, Tack it and do small stich welds until completed. Work opposite ends and work toward the middle. Peen after each weld. The key here is not getting in a hurry. You can use a multitude of Nickel rods. If it's cast steel, You can use Stoody Versalloy or Super Missle Weld (312 Stainless ). If it were mine I would use a Spray Powder Torch set up but use what you have. Any of the above will work ok.

 

[Egon]

Brazed the pieces right there in the grill.


Sounds like good advice. Take your time heating and cooling.

Make sure the better half doesn't put some sauce on it!:laughing:

 

[zzvyb6]

Brazed the pieces right there in the grill.

I watched some videos on YouTube about welding and brazing cast iron. The 1" stiches followed by peening is recommened by the Lincoln Electric demo. I had a Red Bull moment after watching as he stated that the reason for the preheating was to control the contraction as the weld cools. If they all cool together, there is less chance of cracking. Originally I was thinking that the preheating was necessary for some kind of chemical reaction to take place but it's really just a controlled thermal change. In fact, they recommend using the grill during welding so that you can gradually cool down the item by reducing the flame over the course of a few hours when you are finished.

 

[oldtractors]

Brazing it would probably be a better and stronger repair than welding. A BBQ grill works great to preheat. A kid's sandbox works great to slow the cooldown.

 

[tthopskin@yahoo.ca]

if this is any good to you but i would do the same as all the other guys ..one said watch the sparks off a grinder ...need a little more then that . i know that is how you tell your metals but dont know what yet too look for .......anyways a licensed welder told me once to weld real cast take your torch get the soot black all over the piece you need to heat when the soot is on there heat till the soot burns off the heat to bur the soot is the same heat thats needed for welding ...never done it yet never had to but some day maybe