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Posted by chris case on Saturday, July 05, 2008 at 09:55:07 :
In Reply to: EMPHASIS ADDED posted by Gordon Maney on Friday, July 04, 2008 at 19:16:15 :
An acetylene torch will naturally preheat. Modern brazing rod alloys (bronze, actually) are actually stronger than steel, but soft enough to work well with the iron as it cools.
Peening has to be done perfectly, but at random? Too much peen, and the expanding filler forces the iron apart, causing cracking. Too little peen, and the filler shrinks, pulling away from the iron, causing cracks. How are you going to tell just enough? Plus you will need to pre-heat with a torch anyhow... might as well just braze it.
If you think brazing is deficient due to it's color, you might look into silver brazing. It would look like nickel rod when done...
That all being said, the latest technique for welding cast is to preheat, then metal spray the filler, and post-heat. But who has the $50k to set up to do a back yard repair?
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