I welded an exhaust pipe from a Harley Davidson. I don't have the whole scoop on what it's called, but got some pictures of it. I was told it was from a 2011 model harley of some sort.

I can tell you that I didn't do much cleaning to the part (customer said it would not be visible, but covered up by something), and despite that, it welded very nicely and very clean. I think it was nickel plated (the plating which I did not remove.)

You can see how I got things clamped down so they didn't tip or move when I laid light pressure from my welding arms against the parts:
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I tried jigging it up with these giant magnetic balls the customer brought in to try for that specific purpose. I was surprised how strong they were. They worked kind of well. They had a little tendency to "wedge" the pieces apart though. They would have been great if I wanted to have the pieces held away from each other at a specific gap. They were kind of cool though, I've never seen "bucky balls" that big before. They were really hard to remove without practically prying them away from the metal part they were stuck to!
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Here are the first tack welds, after I got probably three of them on there. I took some time to get the parts aligned nice and close, because it pays off of stuff like this where you don't want to input a lot of heat adding an overly wide weld bead.
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I used a I think #7 or so (maybe #8) stubby gas lens, pure argon, 1/16" tungsten on this. Probably about 15 cfh or maybe some more.

The end result:
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I knew it was plated before I welded it, but I wasn't sure what kind of plating it was. I was ready for it to go all smutty on me (colored "soot" appearance around the weld area from things vaporizing), but it didn't do that at all. The plating must have not been a low melting temp metal like I was expecting (such as cadmium or zinc.) So I think it was nickel plating. I did not look quite like chrome, so I don't know what else it would be besides nickel.

I welded it with 309 stainess rod. I did use a flap disc to trim the mating surfaces so they were interfaced tightly with each other before welding, which helps get a neater result I think.