Cast iron welding
- Thread starter peterj
- Start date
trbomax
Well-known member
You can stick weld it w/stainless rod,but the best way is to use rod for cast iron. Its a good idea to preheat the piece w/ a torch (if its small) and then use the torch to keep heat in the piece so that it cools slowly,otherwise it will crack right next to where you just welded. If its a a biger piece, heat it up in the oven, and cool it off in the oven. I did a 427 side oiler block a few years ago,took it to the shop where my son works,took 4 hrs to heat it up and 6 to cool it off,but it never broke while I had it.
ironheadtom
Well-known member
An experienced welder can make it into a thing of beauty. I've seen it done with stick with a rod that I believe has a high nickel content. Also I believe it takes a lot of pre-heat, post heat, and a slow cool down process. I never learned how to weld it myself , so I braze it when it's not a super important job. Even when brazing, I pre-heat, post heat, and then bury the part in kitty litter so it can cool as slowly as possible.(Sometimes taking many hours)
ironheadtom
Well-known member
Trbomax, looks like we were typing at the same time.
GeorgiaHybrid
Well-known member
If you want to weld it, ni-rod (nickel) is the way to go.
ZRX61
Well-known member
Palco rods: 808 & 827 cast iron alloy machinable 
Sometimes you can have acceptable results just usuing mild steel wire in a Mig....
Sometimes you can have acceptable results just usuing mild steel wire in a Mig....
My method is
PRE Heat to 350
Tig Weld with Stainless Steel
Post heat at 300 till cool down never had a problem,
Nickel rods work good to but I always used what I had on hand, you would not belive how many guys around here forget to drain their boats when winter comes
PRE Heat to 350
Tig Weld with Stainless Steel
Post heat at 300 till cool down never had a problem,
Nickel rods work good to but I always used what I had on hand, you would not belive how many guys around here forget to drain their boats when winter comes
rsanter
Well-known member
if you pre and post heat and then slow cool you can mig weld it
what is it?
generally I preheat in a BBQ and then locally preheat the area to be welded with a torch.
weld and then take the torch back to the area welded.
after a bit you let it sit in the BBQ for some more post heating and then step the temp down to cool slowly
bob
what is it?
generally I preheat in a BBQ and then locally preheat the area to be welded with a torch.
weld and then take the torch back to the area welded.
after a bit you let it sit in the BBQ for some more post heating and then step the temp down to cool slowly
bob
tonydanzah
Well-known member
It also depends on the quality of the cast. I successfully migged a decent quality USA made vise. I didn't preheat just welded vary slow to get the heat up and used the vise for years with no problem. I tried the same technique with with an overseas made vise, the weld cracked the first time I went to use it.
38Chevy454
Well-known member
I am a metallurgical engineer. Here is why welding cast iron is so difficult.
Cast iron has approx 3-4% carbon (C). Regular mild steel is about 0.1-0.2% C. Iron (Fe) and C combine to make iron carbides at the right conditions. Iron can only have up to 0.8% C before it has to form a carbide or be free carbon in the iron matrix. Most cast iron is grey iron, because it appears grey on the fracture surface. The grey is because it has flakes of carbon (graphite) in the iron. Flakes do not make it stronger or help ductility. Nodular iron has round nodules of C in the matrix. Much more ductile.
Any cast iron when welded will form the carbides at the fusion line. Carbides are not ductile at all. When the weld metal shrinks - ALL welds shrink - it pulls on the base metal at the fusion line where you have carbides and you get fusion line cracking.
All the techniques: preheat, slow cool, high ductility filler, peening after welding, are all attempts to minimize cracking. They all help. Brazing is used for a lot of cast iron repairs for the exact reason it does not form carbides.
Cast iron has approx 3-4% carbon (C). Regular mild steel is about 0.1-0.2% C. Iron (Fe) and C combine to make iron carbides at the right conditions. Iron can only have up to 0.8% C before it has to form a carbide or be free carbon in the iron matrix. Most cast iron is grey iron, because it appears grey on the fracture surface. The grey is because it has flakes of carbon (graphite) in the iron. Flakes do not make it stronger or help ductility. Nodular iron has round nodules of C in the matrix. Much more ductile.
Any cast iron when welded will form the carbides at the fusion line. Carbides are not ductile at all. When the weld metal shrinks - ALL welds shrink - it pulls on the base metal at the fusion line where you have carbides and you get fusion line cracking.
All the techniques: preheat, slow cool, high ductility filler, peening after welding, are all attempts to minimize cracking. They all help. Brazing is used for a lot of cast iron repairs for the exact reason it does not form carbides.
porschedude996TT
Well-known member
I have welded the bolt hole ears that protrude from the casting on a small block chevy head years ago and machined them on a mill. One other time I welded cast iron with no sucess, it was on a pool heater manifold. As soon as I hit the stick large pockets appeared. I ended up pre-heating the manifold and brazing with brass. Never tried to TIG weld cast iron, now that I have a TIG I may give it a try.
I recall an article about using a bed of match light charcoal to pre-heat.
Good luck with your welding project, and I hope it doesn't become carbon arc light.
I recall an article about using a bed of match light charcoal to pre-heat.
Good luck with your welding project, and I hope it doesn't become carbon arc light.
dr_clyde
Well-known member
well, to be honest, the high carbon content of cast iron makes it impossible to get a truly metallurgically sound weld. However, you can braze it very well. You can get a weld that will hold rather well with stainless, but the best way is to preheat with a torch, then tig braze it with silicon bronze rod, then postheat it. If you hear a tinking sound, your weld is breaking and you have a problem with either your preheat or post heat, depending on when you hear the sound. from the sound of things, you've already heard all this.
If it's worth the $$ take it to some one that welds cast iron all day. The best IMHO methoud to repair cast parts ( heads, blocks etc..) is to gas weld them with a torch. I took my last head ( cummins 6bta) to a guy that did nothing but weld cast iron engine parts all day for over 20 years. He heated the parts in a furnace until it glowed almost yellow hot, then removed it and placed it on a table with gas burners keeping it warm. He then welded it up using a triangle shaped cast iron "rod". After welding it went back into another furnace to cool slowly ( ramped down) over night. After it was done all the machined surfaces needed to be re-machined as the metal moves around, but you couldn't tell where the repairs were even done....
William.....
William.....
bayou985
Well-known member
If cast iron is not too porous Tig weld with 320L wire...If You find porosity at toe of weld.grind and weld over toe again...Hammer Peen and cover for slow cool...Clean,Cleanand Clean again the secret too all Tig Welding
rsanter
Well-known member
if you really need to save something there are places that do 'metal deposition'
they will grind out the weld and then so an electrical powdered metal deposition to build the area back up.
it makes it about as close to new in strenth and looks as you will ever get
bob
they will grind out the weld and then so an electrical powdered metal deposition to build the area back up.
it makes it about as close to new in strenth and looks as you will ever get
bob
enginenut
Member
Peter, Lots of good welding information at ; WWW.shopfloortalk.com take a look at welding and metalworking forum.