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Posted by David Sherman [216.18.131.134] on Friday, September 25, 2009 at 12:17:50 :
In Reply to: Porous welds posted by David Sherman [24.32.202.83] on Thursday, September 24, 2009 at 22:52:20 :
This is about driving me nuts. I got the tub flipped upside down, ground two of the cracked welded-up holes down so they were nice and clean and I could see all the cracks. Did a neat, clean job of putting a thin layer of brazing all over it, being careful to not burn the zinc out. Used extra flux. When it cooled down, I found even bigger cracks in the brazing than there had been in the steel! Also, the cracks in the base steel had grown even further into the surrounding metal, which I don't think had even gotten red hot. I tried re-melting one of the brazed holes and then cooling it slowly by pulling the torch away from it gradually while keeping a neutral/reducing flame. Same thing -- big cracks in the brass. This steel must have some very serious contraction to it to pull the brazing apart like that.
At this point I'm convinced I'm dealing with some especially evil military grade steel, rather than the simple dumb reliable mild steel that you'd think an engine crate would be made out of. Any suggestions would sure be appreciated. I don't have a wire feed or other electric welder, and it's not worth spending the money to have it done in a professional shop. I've never had brazing fail like that. I've brazed lots of cast iron, which is usually more prone to cracks than mild steel.
At this point, I'm out of ideas, other than to just paint the inside of it and hope the paint seals the cracks. The way this stuff is, though, I wonder if the cracks will keep growing just from the heat of the fire under it.
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