Speaking of, what'd you end up deciding on for welding rod and process?
I may as well take you through my learning process, I'm sure some will appreciate the tech.
I've yet to take material science, so what I've learned thus far came from hours of research both online and talking to those who weld for a profession. I found that there are many types of cast, and assume the knuckle/wedge to be gray cast. After determining that, I researched different rod/processes. I found most online resources suggested using a rod with high nickel content, yet the question of whether to preheat/postheat was kind of up in the air.
I called a welding shop in Farmington (as suggested on a local forum) and explained my situation. He seemed like your average backyard rod burner and suggested preheating to 200*F and use a general purpose rod - burn it, knock off the slag, peen it, and let it cool slowly. In his experience he never joined mild steel to cast, just repaired cracked/broken cast parts.
After that I stopped by Pekin Weldors'. This guy suggested preheating to 400*F or so and using a high nickel rod - peen, slow cool, etc. They didn't sell any rod so he sent me to Paxair on 8th st. and told me to explain my situation to them. He thought they may have a better idea of what rod to use.
I go to Pax, and the guy wasn't positive which rod to use. He suggested a rod consisting of many different alloys but found that he didn't have any in stock and couldn't get any (great). He referred me to the company that provides them with their welding supplies. Said to explain my situation, they'll explain the process/which rod etc, then we'll see what we can do about getting that rod to Pax for me to buy (Wholesaler sold to distributors only).
I called their provider (Messer Welding) and talked with a tech. He confirmed that the material was likely gray iron and explained 2 processes. One was to preheat to 400*F, burn,peen,slow cool,etc. The tricky part about this process is it needs to stay AT 400*F the whole time. He said you don't want it to rise to 500* or drop to 300*. Without a furnace I don't see how this is possible. The other process he explained was "cold welding" it. He said start at or a little above room temp, no hotter than 100*F. Weld .5-1", knock off slag, peen, and allow to slow cool back to room temp. Come back and do another .5-1", allow to cool, etc. till the job is done. Takes a long time but said its extremely effective. If multiple passes are required, make a root pass first, followed by the overlapping 'filler' passes. He also suggested 99% nickel rod.
After talking to him I researched the cold welding process and found that this is one of the processes lincoln electric suggests on their site. I talked to a guy who welded cast for Cat and he said they did it all cold, due to their parts being far too large to preheat uniformly.
After all my research I decided to buy the 1/8" Ni-99 rod (they had it at Pax) due to the high ductility of the nickel. It cost $78 per lb
. On the package, it again described the cold welding process. Amperage suggestion per the box is 65-115amps.
I plan to go down, fire up that huge salamander we have, and heat up the axle to 70-80* (I have a digital infared temp guage from my r/c days). Weld an inch or so, peen, and again set in front of heater to allow it to cool slowly. I'll continue this process until its finished.
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