Cast Iron Mig Welding

malcolm · Nov 15, 2005

I've bought a lathe. It was cheap as it fell off a fork lift and some of the castings have broken.

Here's a pic of the worst bit:

I gather from other forums that it is possible to weld cast iron using ordinary mild steel wire so long as the cast iron isn't stress bearing.

My problem is I'm missing the rest of this casting. My plan is to make a new section using mild steel and weld it on.

Has anyone else tried this sort of botch? Any ideas on a better solution, or advice on how to go about this sort of thing?

Hitch · Nov 15, 2005

I have tried miging cast iron before, cast to cast. Its bl00dy hideous!
Will probably suffice for that though Malc.
If its just a covering section how about fabricating a 3 sided cover out of 2/3mm and drill/taping it on with a few m5 csks?

malcolm · Nov 15, 2005

Not sure I'd fancy fabricating the whole lot - it's a gearbox and there are a whole load of nic ely aligned bearing mountings in there. I'm going to have to make one bearing mounting for the wheel lying to the bottom right of the photo - that's supposed to somewhere in the middle of the missing bit.

Why was the cast iron you welded so bad? Does the weld not stick to it? Or does it crack and do nasty things.

Hitch · Nov 15, 2005

I thought it was purely cosmetic, the cover plan i had wouldnt be much cop.
The cast seemed to spit and ended up with porostity, it also didnt withstand any presure put on it and subsequently cracked..... It was only a fence for a tablesaw.
Admitadly i didnt preheat it at all.
I think stick maybe you best bet Malc.
Anotherway, depending on the thickness of you casing, is to screw in a number of studs or bolts sideways, cut out the new section to fit then cut slots in the new piece to align with the studs, (a bit like flatpack furniture!)
Then weld the bolts in the slots, then weld the rest of the joint, that will eliminate the problem with cracking. I saw an old bloke do that then stick weld it up, looked spot on.
Have a lok at http://www.lincolnelectric.com/knowledge/articles/content/castironpreheat.asp

malcolm · Nov 16, 2005

Thanks for the advice. I'll hopefully be able to get the lathe into the workshop at the weekend and will give it a go. I've found some of the bits in the box of tooling - it'll be a big jigsaw puzzle. Using studs might be useful to hold it all in place as well.

There is also big flat cover that's cracked in half. I'll be able to experiment with that and if the worse comes to the worst I can make a new cover from mild steel and borrow a gas kit to braze the rest. I'll post back with progress.

There are some useful articles on that Lincoln Electric site.

malcolm · Nov 23, 2005

The loadall still hasn't turned up so the lathe hasn't moved, but I've been thinking about the job.

I'm quite keen to give cast welding a go just for the hell of it. It's really cold here so I'll stick the cast iron panel into our oil drum BBQ and heat it up.

I thought this would be a great opportunity to try out MIG brazing. I've ordered some silicone bronze wire from welduk so hopefully I'll be in for a weekend of experimenting.

^neo^ · Nov 24, 2005

Grind out a bit of a weld prep, heat it up a little and do it with a stick welder. The rods arent cheap, but im sure you could find a local welder who will sell you a couple rather than paying for a tin of them! It's easy enough to do and seems to weld better than mild steel!

malcolm · Nov 27, 2005

I tried studding on the door for the lathe tool compartment. I didn't pre-heat so there are cracks in the weld. I could have probably avoided the cracks by welding just on one side of the stud so it could have moved sideways when cooling, but the repair is still strong enough to take my weight so it'll be fine for what it is. I'll use body filler to fill in the rest of the gap.

For the gearbox I'm tempted to put it together using studs and then pre-heat and seam weld - for interest to see whether the heating prevents cracking as much as anything.

malcolm · Nov 29, 2005

I've got a little further on this. Turns out if you just weld one side of the stud to the cast iron the weld doesn't crack. I put the gearbox back together with studding and then brazed it.

The brazing seemed to work using a decent power setting and a forward motion for the torch with no side to side wiggling - I could even see the flux moving ahead of the braze.

Here's the finished job (the gears still fit!)

sclurgess · Nov 30, 2005

looks pretty damn good to me malcolm

carotman · Dec 1, 2005

Wow!

That's a great job!

malcolm · Dec 1, 2005

Thanks - it's probably not the strongest method of welding cast iron but I don't have any cracks so I feel it was a success. I've written up the full story on http://www.mig-welding.co.uk/cast-iron.htm (although I need to step back in there to correct the appalling grammar).

Hitch · Dec 1, 2005

Get some die penetrant on there Malc se if you really have any cracks!! :lol:

malcolm · Dec 1, 2005

That's a good idea- it would be fun to try. Where would you buy that sort of thing from?

Hitch · Dec 2, 2005

Any half decent industrial/welding supplier should do it, Rocol make a kit, but thats about £35.
The cheap ones are just as good!
Ask about a 'Dye penetrant testing kit' 3 parts in the kit, a cleaner, dye, and developer.

malcolm · Dec 5, 2005

I found a Rocal kit on the internet but that'll end up at £50 once they've added VAT and postage and VAT on the postage etc. I suspect trade suppliers would be easier - it's not the sort of thing that would have a lot of DIY interest.

I'll see if the BOC shop have any next time I go in for a bottle refill.

Hitch · Dec 5, 2005

Malc, have a look here, this is one of my local suppliers;
http://www.wellyweld.com/index.php?session=dcd469f1fab65ecbe0f3cd0e60b34037&sec=fset
(the 3,4,5th items)
Not sure if they do a postal delivery service though.

kernowcam · Dec 10, 2005

Hi GUys
Just a thought. My local works would probably cast you new parts from the old?? Price ??

Cast Iron Mig Welding

malcolm

& Clementine the Cat

Hitch

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malcolm

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^neo^

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malcolm

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