The exhaust manifold which I think is cast iron on my Clio has a crack on one of the exhaust port branches. Could I weld this using the mig and with what type of wire ?. Its a SIP130T mig.
I am loathed to pay Renault £140 for a new one.
I welded a fourbranch from my Accord Coupe........lasted 2 wks then cracked next to new weld. Did it with Arc and cast rods... preheated..and kept heat on then faded. Some one said I shouldn`t have pre-heated as these special rods don`t need it. Ended up paying 300 quid at Honda Stealer........could have bought some nice tools with that..Grrr!.
Guy on another forum did his with Mig and mild steel wire and it was ok. Different car and material. It`s just your luck unless you are a Pro. Try it.. you got nothing to lose.
When repairing a crack in cast iron it may be worthwhile drilling a small hole at each end to prevent the crack spreading. Maybe brazing would be better, or you could stitch it if the metal is thick enough.
Problem with cast iron is it's very stiff. As the weld cools down the cast iron doesn't move much and the stress cracks either the weld or the cast iron. Pre-heating to red hot helps as the cast iron expands with the heat. Welding with normal MIG wire and letting the whole thing cool slowly in the furnace is supposed to be the trick but I've never tried that approach.
Other approach is to use a soft wire. Nickel rods for arc welding, or brazing wire for MIG. The wire being soft doesn't put a lot of stress on the cast iron as it cools. Drill holes at the ends of the crack definately!
The trouble getting one from scrappies is they are usually sold with the engine. Also this is a common fault on the 8valve Clio.
I just thought I've got to take it off anyway so I may as well try and weld it.
The trouble getting one from scrappies is they are usually sold with the engine. Also this is a common fault on the 8valve Clio.
I just thought I've got to take it off anyway so I may as well try and weld it.
Theres got to be Clios in breakers with goosed engines though, lets face it, a lot pass through the hands of boyracers who stick a fart can exhaust on and then rev them to destruction.
Yes you can weld cast iron with MIG but before we get into details do you know that a spool of wire will cost you around £1000 (yes, one spool one thousand pounds)
I guess that kills it.
Really, ive never seen them only the 15kg ones.
In that case you can either get it very hot (over 538 oC) or do it "cold". Use low juice and small runs, peen the runs and allow to cool to room temp before putting another run down. Like someone said earlier, drill both ends of cracks and grind out the crack to form a vee prep.
And there are some cast irons that are unweldable so no matter what you do they crack.
I feel it all depends very much on the quality/chemistry of the cast iron.
I know on one of my welding courses I got to weld up a broken cast iron vice body, with MMA not mig though
First the broken edges were ground well back and then built up with cadmium based rods. BE WARNED They are really, really nasty fumy things, as cadmium is insidious (sp?) i.e. once in the body it cannot be removed, so excellent ventilation, seperate air suppy is the only answer when using.
The effect was to alter the chemical composition of the two surfaces which can then be welded using ordinary rods E6013. Jigging it all up was a problem, and I never did find out if the body actually held together after the course, or headed on to the big scrap bin.