Micro- Yes, aware that cast (SOME cast) can be welded. Brazing has some advantages, at other times welding is in order. Problem with welding on cast is getting good penetration - the heat required puts strains on the cast that can cause other areas of the casting to crack and fail. In class, we had a block from a 30's or 40's engine that was so high in carbon, had to use Mig to weld it .... one bead at a time. Had to cool between each bead. Any more than that, the damage just increased, rather than being decreased. Normal arc or brazing was simply out of the question - way too sensitive. Think we used nitrogen for the flux gas, intead of argon - better thermal cond. coef./thermal heat - ie. more cooling power.
Brazing has some advantages on 'high stress' cast - the brass has more give to it. As in woodwork - a really strongly glued seam can actually become a point of failure, due to no give. Dissimilar metals when welding (eg. coef. of expansion, flexibility, etc) all cause problems with cast. It is such an unyielding metal. So ... both techniques, pros and cons - that's where really experienced welders earn their keep.
It really is hard (almost impossible) to find a welding rod for cast that matches the base metal, and the higher temps of welding (usually,the mig method above is an exception) over brazing can cause problems. With brazing, one can heat a much larger area gradually, which reduces the very localized/focused heat load problems of arc - and get a successful repair/joining. Just don't try that with oxy welding of aluminum - you'll just get a big puddle and no joy at all. *lol*
Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good ...
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