Can I Weld Cast Iron With a Mig?

Specifically regarding welding the wastegate flapper on a turbo. I'm trying to put a budget together and need to know if I should expect to be paying for someone else to do some welding.

I know that ideally I'd preheat cast, then use nickel rod and all of that, but I'm not equipped for that.

Thanks, Bryan

I've never done it, but we had a good thread on that very topic.

http://grassrootsmotorsports.com/forum/grm/can-you-weld-cast-iron/43155/page1/

The last time the GRM hive mind discussed it, it sounded like the best results would be:

1) drill out the ends of the crack so it won't continue
2) bevel the edges of the crack for good penetration
3) pre-heat well
4) weld with nickle rod
5) post heat
6) cool SLOWLY to prevent cracks from forming.

the base material is brittle, so the pre and post heating are supposed to be very important. If you're not willing to follow all the steps, it probably won't turn out well.

It sounds like you just answered your own question.

I know GOOD welders that only get 50/50 results welding cast iron, doing everything right.

'Tis as I thought then.

These guys sell a wire for welding cast. http://www.crownalloys.com/products.php

You will need to preheat it or it will probably crack when it cools off. I usually use my turkey cooker burner. I haven't tried the cast wire, I use my rod machine.

Yikes that's not what I wanted to hear

What turbo/engine out of curiosity

Toyota Supra CT26 fated to make my Miata a fast, ghetto, ricey E36 M3box instead of just a slow, girly E36 M3box.

(Edited for accuracy)

Out of curiosity, is that the same turbo that was on an MR2?

You just trying to weld the thing shut, or is it broken?

Apexcarver wrote: Out of curiosity, is that the same turbo that was on an MR2?

Nominally, yes. The Supra version is single inlet and larger, though.

I just want to run an external wastegate.

If turbo housings are indeed cast iron and not cast steel then they have a low carbon content for what they are. I have welded on them using 309 stainless filler and they welded like steel. Not at all the way that cast iron welds (which you should use a nickel filler rod for)

I welded my wastegate flapper shut with a MIG.

ditchdigger wrote: If turbo housings are indeed cast iron and not cast steel then they have a low carbon content for what they are. I have welded on them using 309 stainless filler and they welded like steel. Not at all the way that cast iron welds (which you should use a nickel filler rod for) I welded my wastegate flapper shut with a MIG.

So... mig and stainless wire? Turbos are new territory for me. I've only messed with them briefly on other people's cars. I understand how the system works, what I need, and how to bolt it together, but, in regards to welding a wastegate flapper, I'm lost in the wilderness.

Educate me. I'm tired of sifting through conflicting information.

If all else fails, cant you just rig up a big honkin' spring to just hold that flapper shut?

I've welded up cracked Turbo T/A iron manifolds with my mig and standard mig wire.

I stop drill the ends of the crack and V out the crack until it's nearly through.

Next, I preheat on a non-food BBQ that I have kicking around.

Fill the groove with weld while still on the bbq.

Bury in a bucket of playsand overnight for a slow cool.

It may not be the most correct way but I've had good results with it.

This doesn't work on cast that has gotten so hot that the metal appears scaly and crystalised. It does work on cracks.

I'd bet a turbo housing is better cast iron than whatever GM made manifolds out of, you'll probably have good luck.

BTW, you can weld cast steel and nodular iron much easier than true cast iron.

Good luck.

Shawn

P.S. if you're not setup for pre/post heat, go to the local goodwill and buy a used camp stove or tabletop bbq for your preheat and a bag of clay kitty litter or playsand for cooldown.

Go to the Miller Welding forum or Practical Machinist forum and search. There's loads of info.

Essentially, bead blast the part absolutely clean, v-grove the area to be welded, pre-heat in a oven. Clean gas BBQ grills have been used IIRC. Weld w/ special nickel bearing rod or filler +TIG. Post slow cool. A common method is to light a charcoal grill, toss the part on the coals and leave it to burn down and cool off naturally.

Trans_Maro wrote: I've welded up cracked Turbo T/A iron manifolds with my mig and standard mig wire. I stop drill the ends of the crack and V out the crack until it's nearly through. Next, I preheat on a non-food BBQ that I have kicking around. Fill the groove with weld while still on the bbq. Bury in a bucket of playsand overnight for a slow cool. It may not be the most correct way but I've had good results with it. This doesn't work on cast that has gotten so hot that the metal appears scaly and crystalised. It does work on cracks. I'd bet a turbo housing is better cast iron than whatever GM made manifolds out of, you'll probably have good luck. BTW, you can weld cast steel and nodular iron much easier than true cast iron. Good luck. Shawn P.S. if you're not setup for pre/post heat, go to the local goodwill and buy a used camp stove or tabletop bbq for your preheat and a bag of clay kitty litter or playsand for cooldown.

This doesn't sound like a bad way to go on a cheap turbo. If I can't get it tig welded for some beer I'll have a go at with my mig.

my .02 is that welding wastegate flappers is pointless since you can just secure them shut in reversible ways that dont involve welding.

But, having said that, i fully intend to try welding cast iron with mig.

I have, in an emergency, welded cast iron with my mig. Not perfect, but with high heat setting I got it to work ok. Much prefer nickel rod with my arc welder and proper prep/heating as described above.