Dumb Welding Question

Years ago an associate brought a bicycle over to my house and asked if I could weld the set post part of the frame where there was a crack. I
brushed it and washed it down with acetone and took a shot at it with my little flux core welder. It didn't touch it. No matter what I tried it looked like it had been some weld spatter on it, but I got no penetration at all. It wasn't thick tube. I hit it with as much heat as the little welder would put out. It wasn't a duty cycle issue. That welder would always give me about an inch of good weld on anything I'ld used it on before. Now I admit really knew nothing about welding back then (18-19 years ago) and I don't know much more now, but it baffled me. I am asking purely for speculative reasons now. That person and their broken bicycle have long since moved on, but what do you think the reason was?
It looked like a cheap noname Chinese bicycle which back then probably meant soft high lead steel, but I suppose it could have been Chromally tube. If I recall it had mediocre looking welds at all the joins. I recall thinking my weld wouldn't look to horrible next to the factory welds. Well it wouldn't if I could have made any welds. LOL.
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wrote:

If it was a "Cheap Chinese" bike it probably had mild steel tubes which shouldn't given any problem welding them. At least I've not experienced any. But general bicycle tubing is pretty thin I wonder what sort of "small welder" that you have that let you use the maximum heat setting.
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cheers,

John B.
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Sounds like it wasn't a ferrous (steel) frame to me. Did you try seeing if a magnet stuck to it?
wrote:

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On Thursday, August 6, 2015 at 12:46:02 AM UTC-4, Wally wrote:

I am thinking it may have been an aluminium alloy frame. If you happen to have some scrap aluminium around , try running a bead on it and see if the results are similar to what you remember.
Dan
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I guess that is possible, but I would think I would have been more likely to vaporize aluminum.
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wrote:

I never tried to weld aluminum with a steel filler but I did once weld magnesium with an aluminum filler rod. It welded beautifully but the bead fell off as it cooled :-)
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John B.
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