Posted: Wed Mar 20, 2013 8:22 am Post subject: A No-PreHeat Cast Iron Welding Technique
So, this is the latest of my Cast Iron welding videos... I repaired a crack in a transmission housing without any kind of a preheat, or a post-heat...
Basically, Cast Iron cracks when it's heated and/or cooled rapidly, hence the reason why its usually pre-heated and allowed to cool slowly, but theres a chance that you can get around this by just not getting it very hot...
I used a Nickel-99 electrode to make welds under 1" in length, which I then peened and allowed to cool completely, so that I could run my fingers directly over the weld, at which point I ran another short weld using the "back-stepping" technique, and repeated...
This is a technique that can be used with any of the main electric arc welding processes... I've seen it done with TIG using stainless filler, and I've heard of people having success with it running MIG , again with stainless filler...
Its just a little technique that I heard of, and had to try, I made a video about it and just thought i'd share... Doesnt seem like a bad way to weld a cracked engine block or something along those lines...
Well, hope you guys like the video... Have a great week, everyone!!
Posted: Wed Mar 20, 2013 10:17 am Post subject: Re: A No-PreHeat Cast Iron Welding Technique
Its more than just hitting it, you have to hit it hard enough to keep deforming the weld metal. Its spreads the weld and relieves the stress as the casting cools and shrinks trying to pull away from the weld area.
The weld material is very soft compared to the brittle casting but the weld zone to the cast isn't strong enough to pull it wider on its own, you're just beating it flat and wide to keep that weld zone from pulling apart.
Posted: Wed Mar 20, 2013 11:43 am Post subject: Re: A No-PreHeat Cast Iron Welding Technique
Interesting video with some very good basic techniques and ideas.
Not trying to be critical but I have just a couple observations that are certainly subject to scrutiny by others.
On that first pass, since the outside temp was about 20 degrees and the part was really cold, I think preheating the part to a nice very warm to the touch might have helped with that. On the subsequent passes it was already that temperature and seemed to weld better.
Also, since the test part was not truly cracked it might not weld the same as if it had been. The back side of a cracked part will still have a either a small crack or a least a stress line if was welded it all the way through. Also, welding on the outside of a rounded piece is a little easier to do, since as the cast expands it can spread apart a tiny bit over the radius of the round part. If that were to be done in the middle of the side of a motor block, say a freeze crack to a frost plug, the large flat area on either side of the crack has no where to go and is much more difficult to weld. I realize that's the whole point of the video, keeping the heat out, but those motor blocks are tough to do, at least for me! I might add that an old timer told me recently, on a jod like that to weld across the crack one short weld at a time. I've not had the occasion to try that yet but he said he does it all the time and it works the best. (Hope I don't have tobr> Oh, and that nickle rod... good stuff, but they're pricey little fellas aren't they!?? LOL
I'm sure others will add to this that know a lot more than me for the education of all.
Posted: Wed Mar 20, 2013 11:48 am Post subject: Re: A No-PreHeat Cast Iron Welding Technique
On things like engine blocks and heads you will always get hair line cracks that antifreeze will seep through. I used to take some things to a welder by me that would weld it then lay a patch of solder over it. These held well.
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