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#1 ncb OFFLINE  

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Posted July 16, 2011 - 05:28 AM

Can i weld cast iron with gasless flux cored mig welder . I only have a tank of argon for aluminum . the welder is gas capable but i only have the flux cored wire . I would appreciate a little advice from a pro before i mess something up , thanks in advance .
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#2 KennyP OFFLINE  

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Posted July 16, 2011 - 05:58 AM

Very good question and I would like to hear an answer to this one.

#3 mjodrey OFFLINE  

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Posted July 16, 2011 - 06:57 AM

I find that migs don't weld cast iron very good,be they flux core or gas type.You can stick the pieces together,but they won't be very strong. I.M.O.

#4 Big John OFFLINE  

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Posted July 16, 2011 - 09:10 AM

Cast iron is hard to weld with any welder. They make special rods for cast iron . One is machinable, the other is not. It helps to preheat the piece too. Depending on the
piece U might be able to braze it. U need advice from Olcowhand.He knows more than I do about welding cast iron.
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#5 olcowhand OFFLINE  

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Posted July 16, 2011 - 09:32 AM

You need either nickel or stainless steel to weld cast iron. I use stick with nickel (Ni) rod. Must be extremely clean. Best also to preheat the part with a torch, then weld short beads, maybe 1/2" long, then reheat with torch, then more weld/heat until done. Cast tends to crack as it cools when you weld it, so a very slow cooling is what it needs. I will wrap the hot part in normal house insulation to help it cool slow. Better yet, is to quickly place the part in an oven at 400F, then drop the temp every 15 minutes by 50 degrees till it's down to like 175, then shut off oven & let it sit in there until cooled. Even a good strong weld can contain tiny cold cracks, so on engine blocks or anything holding fluids, I coat the weld area & past the weld area with JB Weld.
The only thing with brazing is if you decide or need to nickel weld later, it's almost impossible to remove all the braze, making stick welding almost impossible.
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#6 ncb OFFLINE  

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Posted July 16, 2011 - 01:04 PM

thanks for the quick info guys .So with that information i believe i will just clean well , use jb weld , retap new threads and be done with it . it just holds the trash screen on so it is relatively light stress . the screen stayed in place with the boss broken but i would not trust at 3600 rpm . any further problems i will replace the flywheel . probably cheaper and quicker just to locate used part . thanks again guys .

#7 olcowhand OFFLINE  

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Posted July 16, 2011 - 01:12 PM

Oh yes, go the easy route with a part like that. You could always drill further in, then tap & use a longer bolt. The extra weight of the longer bolt won't likely be enough to cause any imbalance either.
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#8 ncb OFFLINE  

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Posted July 16, 2011 - 01:19 PM

for olcowhand, i tried getting some video of the stiga running and turning,,,,,and failed miserably,time to dig up the kodak intruction manual , will post that when i do , BTW the honda engine in the roper was manufactured in 2010 , nearly brand new. all the rest of the engines run smooth, quiet and smoke free except the 6 horse robin which hasnt been checked yet.

#9 olcowhand OFFLINE  

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Posted July 16, 2011 - 01:23 PM

for olcowhand, i tried getting some video of the stiga running and turning,,,,,and failed miserably,time to dig up the kodak intruction manual , will post that when i do , BTW the honda engine in the roper was manufactured in 2010 , nearly brand new. all the rest of the engines run smooth, quiet and smoke free except the 6 horse robin which hasnt been checked yet.


We try our best to be patient, so we'll wait on the video, but only so long! :bigrofl:

#10 tinner OFFLINE  

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Posted July 16, 2011 - 05:09 PM

Haven't welded any cast iron since around 1980 and I agree with Daniel, keeping it from cooling too quickly is important. I also used Ni rods and they worked well.

#11 lrhredjb OFFLINE  

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Posted July 18, 2011 - 06:22 PM

Haven't welded any cast iron since around 1980 and I agree with Daniel, keeping it from cooling too quickly is important. I also used Ni rods and they worked well.

I remember reading somewhere about a guy who preheated an exhaust manifold in a BBQ grill, welded it with nickel rod and used the grill to slowly lower the temp over a period of time. Heck you could even throw some ribs on there too.:D
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#12 mjodrey OFFLINE  

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Posted July 18, 2011 - 06:27 PM

Yes,Ni Rods do work nicely.

#13 olcowhand OFFLINE  

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Posted July 18, 2011 - 07:02 PM

I remember reading somewhere about a guy who preheated an exhaust manifold in a BBQ grill, welded it with nickel rod and used the grill to slowly lower the temp over a period of time. Heck you could even throw some ribs on there too.:D


That would be a great way to do it! Never dawned on me to use a charcoal grill! It would keep it hot for hours, with a good slow cool-down!

#14 RustyTub OFFLINE  

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Posted July 19, 2011 - 11:45 AM

You need either nickel or stainless steel to weld cast iron. I use stick with nickel (Ni) rod. Must be extremely clean. Best also to preheat the part with a torch, then weld short beads, maybe 1/2" long, then reheat with torch, then more weld/heat until done. Cast tends to crack as it cools when you weld it, so a very slow cooling is what it needs. I will wrap the hot part in normal house insulation to help it cool slow. Better yet, is to quickly place the part in an oven at 400F, then drop the temp every 15 minutes by 50 degrees till it's down to like 175, then shut off oven & let it sit in there until cooled. Even a good strong weld can contain tiny cold cracks, so on engine blocks or anything holding fluids, I coat the weld area & past the weld area with JB Weld.
The only thing with brazing is if you decide or need to nickel weld later, it's almost impossible to remove all the braze, making stick welding almost impossible.


X2, Welding cast is a PITA it is possible but on smaller easier to find part it is usually best to just replace.

But in your case I would try JB weld, if it is just a screen being held in place.
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#15 caseguy OFFLINE  

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Posted July 19, 2011 - 02:54 PM

I agree with all that has been said. I might offer this piece of advice though. Even if you decide to replace the part, give welding the old one a try to get some practice and experience for the next time. As a side note, know that nickel welding rod is EXPENSIVE! a few years ago, I paid $45 per pound for the 99% Ni rod to repair the engine block on my Case SC.
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