can i mig weld cast?

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trying to weld some cast iron bull heads to a bbq pit to use for doorstops but im not getting good penitration,can i weld cast with a mig,i have a millermatic dc 210 with 75-25 mix argon with steel wire any help,can you braze it??
Reply:Hey paintman,Cast iron is a bugger. Cast steel is easier to work with. With cast iron, you're best results will be brazing, silver-soldering, or possibly a silicon-braze MIG wire. Also, preheating would be necessary, and after welding, a very slow, controlled cooling would apply. It can be done with success, but the rules of welding cast iron are quite different. I'm sure others here will contribute their successes with cast iron.     DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:i welded a piece of steel to the back side and thought i had a good weld but after tugging real hard the entire weld broke off but it did bring some of the cast with the weld so i was wondering  if i was close or still a long ways off? thanks
Reply:Hey paintman,You're still along way off. Cast iron is more brittle than cast steel, and preheating to 300-450 deg. would allow the cast iron to better take the melting of the MIG wire. Still, you would not have a good joint. Your best results would be to clean the cast iron, preheat, braze or silver-solder with a good flux, and cool slowly in white sand.   DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:Cast iron needs a good preheat. I would say 500* min. This will also help slow the cooling rate. I would braze it. Then cool in sand or kitty litter. Also it's always a good idea to bevel the cast. This helps with penetration and gets down to cleaner material. --Gol'
Reply:if i was to bevel it,pre-heat it,cool it properly could i mig it,i havnt brazed since high school?
Reply:Yes i would say mig is fine since the welds are just for door stops and are not for a critical application. It's not like your repairing a cast engine block or something. It would also help to weld an inch then peen, weld another inch and peen. --Gol'
Reply:peen??
Reply:A sharp pointed chipping hammer or you could probably get by with a small sharp chisel and hammer or a ball peen hammer. Just tap on the weld for a minuet. This helps reduce the internal residual stresses in the cast.Last edited by Go1lum; 01-10-2008 at 01:11 AM. --Gol'
Reply:wow ...i really dont know crap about welding thanks ...so i could pre-heat with my torch??
Reply:Peening - Peening is done by repeated blows to the metal surface.  Commonly performed with a hammer, Hammer and blunted punch or with pnuematic tools.  Peening stretches the surface of the metal, thus reducing contraction stresses in the metal or weld.Welding cast iron can be difficult.  Alot depends on the quality of the casting itself, in particular the Nickel content of the casting, the higher the Ni content the easier it is to weld.Preheat is always required and a preheat and interpass temperature should be 700°F-900°F. At this temperature the metal will glow a faint red.Typically cast iron is SMAW or GMAW with nickel base filler metal.  If you are are joining cast iron and steel.  The procedure I follow is the lay side by side welds of 99% Nickel rod (I use SMAW to do this) one the surface of the cast is covered or "buttered" with the Nickel you can weld the steel to it with standard 70S-6 GMAW wire or with a standard steel SMAW rod.  If the repair is critical, I would use a minum of 2 layers of nickel rod prior to welding the steel to the part.  I also peen each weld prior to laying the next bead.  I have repaired several old machine tool casting this way where a part of the original casting was missing.  Replacing the missing portions with steel.   All the repairs run daily production at a gear shop, as a matter of fact I was just there today, measuring up for an other chip basket fab job for the owners.I you have a SMAW (stick) machine available for use, Nickel Mig wire will likely be $50/lb and usually only comes in 25# spools.  You can pick up 99%Nickel in one pound packages.If you can stick weld it you could always braze it.  Bronze rod with flux is good.  The high carbon content in the castings makes silver brazing very difficult.Good luckRon ShopFloorTalk Millermatic 350P, M-25, M-40 gunsDynasty 300DX, Coolmate 3, Crafter CS-310 TorchTrailblazer 302, 12RC, WC-2430A spoolgunSpectrum 2050Thermal Arc Plasma Welder PS-3000/WC-100B
Reply:There is also a rod called nomacast.  It is also cheaper.I would first mig and peen, however.  I use the sharp end of my chipping hammer.  I start peening as soon as I finish welding per weld.
Reply:if you have a gas grill it works real well for the pre and post heat ,weld right on the grate and peen then close the cover to let it cook ,then make another weld ,then repeat as often as needed. I've done this alot with obsolete exhaust manifolds use nickle rod 600* wax pencil and go for it.Life is tuff,so be sharp  lincoln sp 100  cutmaster101  miller bobcat  miller 250 mig  $thousands in snapon