Re: THe NAC Lots-O-Post Thread
For welding tubes (or anything else) to a cast iron diff am i better off with ENI55 rod or ENI99 rod? Also, in a 3/32 or 1/8 diameter?
I'd like to qualify what I'm going to say with the fact that I've never personally done it, but I have done a bit of reading and discussion on the topic.
ENI55 creates a harder (read: stronger & stiffer weld) while ENI99 is easier to weld but is softer. The trade off to using ENI55 is that it's much more likely to crack the casting around it (because it's so much stiffer). ENI99 is generally considered easier to weld with.
The diameter of the stick is dependent on much current you're going to be running through it. If tube is 1/4"+ thick I'd go with the 3/32 rod. 1/8"-1/4" and I'd do 1/8" rod. Billy, are you talking about truss tubing or the axle tubes? For axle tubes I'd get 3/32 and run the highest amperage that the package allows.
The other important thing to remember when welding cast iron is that it can either be done as a hot operation or a cold operation, but never both (ie, don't switch your plan of attack halfway through). If you preheat, use post heat and insulate it with sand or a welding blanket during cooling. If you choose to go the cold route, 1" length of weld at a time and let everything cool back down. It's pretty tedious and slow going from what I understand, which is why most go with the option of preheating.
Depending on what it is, I'd be inclined to use ENI99 and just tie it into a part that's not cast with a gusset or two with regular mig.
Also, FWIW, Ross has had decent success welding cast iron with MIG and preheat. He uses post heat when he's not being lazy, too.
