cast weld/fill

[wallace]

Hi all, the machine I'm working on at the moment has a cast cover with two damaged corners. I went to see my local fabricator who said it would be £30. I thought for that much I may as well have a go myself and maybe learn something. I thought brazing would be a good choice but I have no gear. I have a mig and a little stick welder that I got given (don't know if it works). I thought I would try the stick welder. Am I correct in thinking I need nickel rods?

 

[t8hants]

I don't get involved with cast, but if you are having a go yourself you will need to pre-heat the cover and after welding allow it to cool down again VERY slowly.
back in my general fabrication days its the sort of job we would try and avoid, but we were very low tech.
If your man will guarantee it that will take the holding screw pressure for £30 thats quite reasonable, and a lot less disappointing then watching your efforts ping off the moment there is any weight applied to the fixing screws.

We did use special rods for cast iron repairs I seem to recall, but they weren't cheap.

 

[flh801978]

I've done dozens of repairs on cast iron and never pre-heated and to date not had any failures
I use Castrod 3 rods which are a nickel rod and as above they are not cheap

Ian

 

[-Matt-]

Braver than I would be with not preheating !

I've always taken it up to a dull orange to medium orange with oxy torch, done the welding (remember to pein the welds to sort of 'tamp' the weld down), and then warmed the whole thing up again to a bright red/orange and just leave it to cool on its own.
The slower you can cool it the better. I have buried some things in sand or the coke dust of a forge before to stop it cooling too quick.

And nickel is what you need yes.

 

[novocaine]

At 30 quid id let him do it. Thats dirt cheap for cast welding.

If you must do it yourself then yes pre heat and wrap to cool. Nickle rods are a good idea but not a must. V grove the piece before hand to reduce the temperature you need to put in and run a stringer and a weave. Be ready for all sorts of crap to float to the surface and ruin your weld. I've done a few cast items and fecked a few up in practise when I've got a chunk of scrap to play with.

 

[heimlaga]

I have a rather good stick welder and I have become a pretty decent hobby welder. However I don't yet feel competent to tackle cast iron and especially not thin cast iron parts like you have there. I always leave those jobs to an aquintance who is good at it.

30 pounds sounds like a very reasonable price for a job like that. I think you should let them do it.

If you still want to do it you need a good DC type welder and some nickel rod and plenty of training before you start. Weld a centimetre at a time and peen the blob of weld with the slag hammer or a ball peen hammer while it is red hot. let everything cool properly then weld the next blob.
This type of cool welding is generally used for thin sections while bigger sections are easier to preheat and weld all at once and pack in rockwool for slow cooling.