View Full Version : Ductile iron to mild steel

08-17-2005, 06:48 PM
Is there a rod that will weld the two with an AC welder?

I don't need alot of strength for this.


08-17-2005, 08:00 PM
On ductile cast iron (aka nodular iron or spheroidal-graphite cast iron) Nickel-base electrodes are widely accepted. Here's a link I often post

With correct preheat & control of interpass temp (plus furious peening of the weldment) ductile CI usually welds well to mild steel. Ductile CI behaves much like mild steel, as it has the lowest shrinkage of any of the CI's.

Ductile iron .7% shrinkage
Gray iron 1.0%
Malleable iron 1.0%
Austenitic iron 1.3-1.5%
White iron 2.0%

Specialty rods are available for "cold welding" cast iron. They are nice for special applications, but pricey & the process is SLOW!

08-17-2005, 08:06 PM
I don't need alot of strength for this.
Do you have extra pieces that you can do some tests on? Is there a good welding shop nearby with a large selection of electrodes to choose from?

In order, I would use these:

ANY stainless electrode
ANY steel electrode

Preheat the part, maybe on top of the BBQ. (How big are the parts you are welding?) Then, weld them and leave them and immediately peen the part with a chipping hammer, or, better yet, a needle gun. How long is the bead you need to make? This will tell us how much heat you are going to put into the weldment to determine if a cold or hot process would work better for you. Since you have just an AC welder, I'm assuming other resources are limited as well.

08-17-2005, 08:47 PM
Thanks ya'll ..

What I want to do is cut a C clamp in half and weld it to 11ga tube, so I can use the screw end to tighten against the tube but it will not have much pressure. I have used nickel rods before but only to fill holes in cast iron sprockets. Didn't know if it had to be an AC rod .. does it?

It's been so long ago since I've done this kind of thing I forgot about having to pre-heat. The BBQ is a good idea!

The only rod I have is a 7018AC - it's no problem to get another but would that work for what I'm doing?

Thanks again,

08-17-2005, 08:59 PM
I think I'd go ahead and weld one up with that 7018AC and test it out.

08-17-2005, 09:15 PM
Would you pre-heat?

And as far as strength, what would be a guess as to break it off? Would hitting it with a hammer be able too, ya think?

08-17-2005, 09:34 PM
Would you pre-heat?

And as far as strength, what would be a guess as to break it off? Would hitting it with a hammer be able too, ya think?
Yeah, preheat sure wouldn't hurt. C-clamps can be all sorts of types, but if you're thinking ductile or something similar, go ahead and preheat. It NEVER hurts, as a general rule.

Sure, a big enough hammer will break anything, BUT you'll probably be fine just putting it in the application you're going to use it for and then tightening it way more than you normally would and seeing if it holds. If so, then it will work for your application. Is anything critical being supported by these homemade clamps? Anybody or anything valuable going to be underneath them, just in case?

08-17-2005, 10:18 PM
No nothing that would cause injury.

I guess I should have just came out and explained my little project at the start ..

I'm wanting to fab a trimmer rack for my trailer. Today while in Lowes looking and thinking I found some C clamps with a button that will release the threaded rod so it'll slide back and forth. Kobalt brand believe it was. it's perfect for a quick release. All it'll take is to cut it as I said, drill a hole in the threaded rod for a lock and weld it to the sq. tube. And I'll likely glue an inner tube for protection aganist the metal, or go back to Lowes and wander around some more and find something.

That's why the hammer question. Would someone be able to wack it and get the trimmer. Should I grind some taper on the clamp and make a couple passes?

If it works and becomes the next big thing remember, you read it here first! lol

thanks for your help MAC,

08-17-2005, 10:41 PM
If it works and becomes the next big thing remember, you read it here first! lol

Well you'll be breaking new ground. :) Let us know how it works.

One problem is, even when it has 'ductile' stamped right on it, you still don't know which one of the many tweaks on ductile it might be. Nothing is simple anymore and cast isn't just cast with all the new methods and tecnologies. Ductile can be anywhere from high nickel anti-corrosive to high impact to plain old crap.

I've often thought of welding on C clamps but after looking at broken ones voted against it. Some of them won't even provide a decent work clamp connection when clamping to them, so who knows. ;)

08-17-2005, 11:42 PM
Veeing out the weld area is usually good practice. I welded 1" square solid stock to cast iron last night (Chinese, so probably contained old machinery parts, old car parts, old???) Preheated to 500*F, used the TIG with Nickel 99 filler 3/32". Nice thing about TIG is you can watch the cast iron melt and watch the mild steel melt - when both have a pool just poke in a bit of filler.

Weldment length about 3". First pass looked nice but cracked as soon as the arc was off. Reheated with the TIG torch, went slower to put more heat into the parts, peened like the ****ens, cracked again. Repeat. Cracked a little. Repeat - perfectomundo!!!

I'd much sooner weld aluminum overhead or vertical than cast iron. CI is so hard to predict. But it is weldable (usually) with patience.

08-18-2005, 09:54 AM
Most of the 'ductile' C-clamps I have needed to weld welded fine with 7018, though not all.

If you want some insurance, get some stainless threaded pins, and pin the joint before welding. To do this on square tube, you might bevel the clamp end a bit, drill several holes into the bevel and tap them. Thread in the pins, cut off so they stick out just enough to touch the square tube, maybe supporting the flat of the bevel on the clamp 1/32 or so off the square tube, than weld using the previously described technique. The pins have a mechanical grab to the clamp material, and weld quite well, providing reinforcemnet for the joint. Takes a couple minutes to prep, makes for a much surer joint.

You can use stainless screw of any weldable grade (308, 316), as well.

08-19-2005, 11:48 AM
Hey all - about finished the trimmer rack and here's a pic (maybe). Only thing I have to do is drill a hole for the lock. I used a 7018AC without heating and it worked OK. Good enough for this anyway. Thanks for all the help!

08-20-2005, 12:19 AM
Good Idea and it looks good too.

I've got one C clamp with the quick release button that is held on with a micro-dot sized screw. The screw vibrates loose. Time for some lock-tite I guess.