Ed Huntress wrote:

It is an ART to repair a casting that won't crack again! A big part of
that is in the pre-heat and cool-down phases of the weld. I've had
mostly good luck but a bit of bad luck. A lot depends on the metal and
the phase of Venus.

Indeed it is an art. When the welding equipment companies, or other
researchers, do a metallographic analysis of cast iron welds, the
results will leave you wondering how it ever works at all. The weld
and heat-affected zone typically is like a layer cake of weirdness.

Anyone who can get good results *consistently* is worth his pay.

BTW, the guy who allegedly was the highest-paid c.i. welder in the
world, an Italian who did nothing else, was hired and shipped in many
years ago by Bill Harrah to weld a crack in the block of his priceless
Bugatti Royale. He did it with O/A and c.i. rod. It worked, even
though it doubtless had oil in the (then) 60-year-old cast iron.

I don't know how he did the pre-heat or stress relief.


Yeah the haz in a cast weld gets interesting. Areas of carbon migration,
grain structure changes and lot's more.

Gas works real good for thin wall iron. You have to watch your flame
real close and only fill enough to ensure a good bond. Then watch it
real close for contraction while it cools. Add enough filler and you get
a good bond and repair, go under and it will crack again due to the
tension stress at the site. If you go over it will probably crack in a
different area due to the stress the extra material adds as it act's
like a wedge.



--
Steve W.