Welding Cast Iron

One thing I have to respectfully disagree with Mike on, and that's using a neutral flame. I was taught to use a slightly oxidizing flame when brazing steel and CI and a stronger oxidizing flame when gas welding brasses and bronze alloys. Not that you can't do an adequate braze job with a neutral flame, but the temp is higher with an oxidizing flame and you want to leave as little carbon contamination when welding the brass family.

Note though, the strong oxidizing flame temp is too high for welding steel. Your puddle will boil, the carbon in the base material will combine with the oxygen and become brittle and subject to cracks.

There are many write-ups online about it. I'm going from what school taught a couple of years ago ;), and listening to a lot of old grumps, one of them being my grandad.
 
Tony Wells said:
One thing I have to respectfully disagree with Mike on, and that's using a neutral flame. I was taught to use a slightly oxidizing flame when brazing steel and CI and a stronger oxidizing flame when gas welding brasses and bronze alloys. Not that you can't do an adequate braze job with a neutral flame, but the temp is higher with an oxidizing flame and you want to leave as little carbon contamination when welding the brass family.

Note though, the strong oxidizing flame temp is too high for welding steel. Your puddle will boil, the carbon in the base material will combine with the oxygen and become brittle and subject to cracks.

There are many write-ups online about it. I'm going from what school taught a couple of years ago ;), and listening to a lot of old grumps, one of them being my grandad.
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I was taught many years ago the same. Use to silver braze tool blanks for Acme Gridleys before tool form grinding.
 
Ironken said:
I run CI like Firestopper said, with a twist.......Not saying this is any better but, I use Aluminum Bronze and AC to TIG braze CI with good results. AL or SI Bronze isn't all that expensive either.
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I have si bronze and have used it with tig and DC but you are saying to use the SI Bronze with AC correct?
 
I hav not used SI bronze with good results on AC but, I have used AL bronze on AC with decent results. Cast Iron and me have a tumultous relationship. Sometimes we get along great, other times we hate each other.
 
Pre heat the part and have a "nest" of fiberglass insulation ready to put it in when it's hot and ready to weld. Weld it right in the nest of insulation. You can use 625 rod for cast . It is mostly a nickel rod , nickel doesn't shrink much like most iron/steel based rods. But the whole part will still contract when it cools, and that is the problem. If you have a torch on and ready, you can use it to prevent fast cooling of the part...Slowly less and less heat, then cover it with more insulation or figerglass matte plus insulation to continue cooling. If it is a "static" kind of part that doesn't see alot of stress, torque, vibration or cyclic physical or heat stresses, it is more likely to hold . Brazing it may be a better choice. I'm trying to envision the part you have...seems like it's some kind of hand cranking thing ...if that is the case, it may not see high torques and heat cycles. A buddy brought me a walk behind dirt backfill tamper. There is a cam inside it that bolts to the inside base, the engine turns this cast iron cam block which wobbles inside, pounding the base and tamps the backfill down . One of it's corner bolt tabs broke half off ...something like this was NOT a good candidate for welding. It would see thousands of high torque vibrating stresses . Yes you can weld cast iron and some are very good at it, but it's not like steel where the weld area is usually stronger than the parent material. Cast aluminum is much easier to weld than cast iron . I would suggest searching Jody Colliers youtube channel , weldingtipsandtricks
...He will give you the low down on welding cast iron ...and just about anything else too !
I think you've got a good chance with a low stress kind of part you've got there . Good luck ! Post some pics !
~Steve
 
One-match fire said:
Over the past several years, I have been fortunate to be able to break some cast iron parts for things I was moving from where they were to my shop where they are now.
I was told that the only good way to weld these parts back together was TiG. Does anyone have anything GOOD to say about this? I would really like to get these parts repaired.

Two of the parts involve a large hand-spinner for collecting honey. The spinner fell while in transit and broke not only the handle but the plate gear that actually drives the spinner. I have kept these parts in hopes that I would eventually become "less afraid" to try to weld them back together. The handle isn't that critical but the gear wheel seem to need some accuracy.

Does anyone have any suggestions? Recently, I sent away for some EZ Weld TiG wire from a guy on Lopez Island in Washington State. I saw these used on a video on YouTube by "Mr. TiG" and he gave them a very good review. I'd like to use them and would be interested in knowing if anyone else has any experience with them or was Mr. TiG just blowing welding smoke?

Thanx
Trim sends
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Hi - retired boilermaker here - this is critical, after grinding area to be welded, finish of with a file or burring tool, you must remove the last few thousands of an inch before welding. Also preheat, then weld with high nickel content rod just one inch at a time, then very quickly peen the weld with a light hammer. continue till finished. The problem with cast iron is that there are so many types its difficult to give advise, experimentation and experience is the key. last, if the casting is cracked and not broken, drill a 6mm hole at eack end of the crack to prevent further cracking as ou weld, also use the BACK STEP METHOD OF WELDING - hope tis is of some use.
 
Hi @deyve

deyve said:
this is critical, after grinding area to be welded, finish of with a file or burring tool, you must remove the last few thousands of an inch before welding.
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Can you expand on/explain this?
Is it about removing any contamination from the grinding disk itself?

Also, you don't mention post-heat or slow cooling. In your experience is it required?

Thanks!
-brino
 
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