Struggling to weld cast iron

[edd]

Lads,
I am trying to fix a casting on a drill that is (I assume) cast iron.
I have read the tutorials, used a small bit of pre heat, nickle rods, clean as possible etc.
I am trying to build up where a section has been broken off, rather than repairing a crack.

My problem is that when I strike the arc, and manage to get a small bit of metal deposited, it pops off when I remove the rod. Sometimes its pops off as soon as i remove the arc, other times a second after. Each time it pops off it takes a bit of the casting with it.

Does anyone know where i am going wrong here?

Thanks for your help.

Ed

 

[Bsmith]

Never knew of that happening, you sure the rods are for cast iron? Not hard facing rods or something like that?

 

[BrokenBiker]

sounds like you are using a rod that isn't suited to welding cast iron.

when I have used stick to weld a cast iron manifold I used a 312 stainless rod, didn't preheat but run the rod a bit hot and then used a blowtorch to slow the cooling as much as I could, kept monitoring it and using the torch to keep the heat in it for longer. worked well with no cracking and the weld metal didn't fall off either

are you sure it is cast iron and not something else. if you try to weld aluminium with a steel rod the same thing will happen

 

[edd]

I just bought 6 rods from the local welding supplies, it is possible I was given the wrong ones.

I will head back with them then.

BB, I am thinking it is cast iron, it's too heavy to be aluminium.
Is cast iron magnetic? because this piece isn't.

Cheers

 

[rich r]

In general cast iron is magnetic (though there are some types that are only weakly magnetic). I suspect what you have is an alloy of some sort, not pure cast iron. Maybe a nickel/iron alloy?

 

[Robotstar5]

Try a grinder on it, should get sparks - dull red for cast?

 

[BrokenBiker]

if its not magnetic then it probably isn't cast iron. we have cast steel in work that isn't magnetic but that gets welded with normal mig wire so that wouldn't be the issue you are having.

as above sounds like an alloy and unless you find out what is in it getting the correct rod might be difficult

 

[J.B. Welding]

Its worth seeing if a mig run will stick to it-Its a bit naughty but I often try with the mig first-if it sticks it sticks! (I'm a pretty tight git) It could be cast steel which can be welded pretty well with a mig, in my opinion.

 

[edd]

Ok, I'll give it a shot with the mig tonight and see.
Otherwise I will come at the repair from a different angle and make a bolt on piece.

Thanks all.

 

[500e]

Got a picture ? what sort of drill ? is it old & saturated in oil ?

 

[edd]

It's a Herbert c type, and I guess it has seen it's fair share of oil and grease in the 45 years it's been around.

The lug that holds the selector is broken, the shaft falls out of position if changing direction.

You can just make it out on the far right of the pic.

 

[wyn]

I'd be tempted to knock up some sort of seperate lug/bearing/guide and bolt it onto the casing somewhere up front.

 

[BrokenBiker]

we use the same drill on o e of the drill/tap stations in work, iirc the wed had trouble doing a weld repair to ours too

 

[edd]

Wyn,
That's the intention, if the mig doesn't stick tonight.

Brokenbiker,
That's interesting, makes you wonder what they were putting in the mix to cast these things.

Ed.

 

[Rig Pig]

Looking at the bits where the paint has worn off I would guess its an aluminium or pot metal casting.

 

[BrokenBiker]

Wyn,
That's the intention, if the mig doesn't stick tonight.

Brokenbiker,
That's interesting, makes you wonder what they were putting in the mix to cast these things.

Ed.

whatever they could get that gave them a good profit. im sure one of the lads in work has one of these in his shed that is waiting for a recon.

 

[edd]

Well whatever it is it doesn't want to be welded!

I will bolt a little bracket to the side, that will do nicely.

Thanks for your help all.
Ed

 

[Laurie Tedcastle]

Herbert's had 3 foundrys - 2 for grey cast iron and the 3rd with induction furnaces producing white iron (mainly for pulverising machine parts). The grey iron was very good quality - certainly easily weldable. That looks like a bought in part to me.

Laurie

 

[sardine]

I weld the crapiest cast iron on restoring solid fuel stoves, with pure nickel electrodes, I think it all comes down to doing it as slowly and gently as possible, loads of preheat, and long cooling off times buried in sand etc. And taking into account what the part will be subjected too after repair, basically its going to be very weak.

My secret methods must remain top secret !

 

[julianf]

The part is not magnetic, and this is the photo -

If its got iron in it, its an alloy of something, but its grey, without a hint of rust... Looks just like aged cast aluminium to me -

I dont think its got any ferrous in it! : )


edit:

i dont mean pure aluminium - one of the harder, brittler alloys, which would possibly account for the weight