I need to weld a stainless steel catalytic convertor back onto a cast
iron (forged steel maybe?) flange. The weld was very weak out of the
factory and its a known trouble spot on vw passats.
I have no problem with the welding itself but I am unsure of what filler
rod to use. My weak knowledge of metallurgy leads me to believ if I use
any old stainless rod on its own (the flange is much more massive than
the ss tube of the cat) I will not only end up with a weld that corrodes
quickly as I will lose chromium (not such a big deal really) but that
carbon from the flange will mix with the stainless and cause a brittle
weld that may well fail.
I understand it may be possible to put a layer of nickel down on the
flange first and then use the stainless rod to weld the tube to the
flange over the nickel layer. Is this as obvious as grinding some flange
away and welding a layer of nickel on so as to allow enough room for the
tueb to be inserted?
How thick should this layer be?

I know it might be the wrong group for this but I know theres some
pretty keen minds in here and I am doing it myself!

BTW probably will gas weld it as the preheating inherent should help, I
doubt there anything that can be damaged by the heat, I've had the turbo
almost incandescent in the past!
--
Mark Roberts

"mark" wrote in message
...
I need to weld a stainless steel catalytic convertor back onto a cast iron
(forged steel maybe?) flange. The weld was very weak out of the factory and
its a known trouble spot on vw passats.
I have no problem with the welding itself but I am unsure of what filler
rod to use. My weak knowledge of metallurgy leads me to believ if I use
any old stainless rod on its own (the flange is much more massive than the
ss tube of the cat) I will not only end up with a weld that corrodes
quickly as I will lose chromium (not such a big deal really) but that
carbon from the flange will mix with the stainless and cause a brittle
weld that may well fail.
I understand it may be possible to put a layer of nickel down on the
flange first and then use the stainless rod to weld the tube to the flange
over the nickel layer. Is this as obvious as grinding some flange away and
welding a layer of nickel on so as to allow enough room for the tueb to be
inserted?
How thick should this layer be?

I know it might be the wrong group for this but I know theres some pretty
keen minds in here and I am doing it myself!

BTW probably will gas weld it as the preheating inherent should help, I
doubt there anything that can be damaged by the heat, I've had the turbo
almost incandescent in the past!

I suggest you post this to uk.rec.models.engineering. People who struggle to
drain a hot water cylinder without help aren't likely to be your best source
of advice.
--
The internet. It's not a big truck.
It's a series of tubes.
Dave Baker

In message , Dave Baker
writes

I suggest you post this to uk.rec.models.engineering. People who struggle to
drain a hot water cylinder without help aren't likely to be your best source
of advice.

Bah!

I was hoping you might have been amongst the few who could have helped
though!



--
Mark Roberts

In message , mark
writes
I need to weld a stainless steel catalytic convertor back onto a cast
iron (forged steel maybe?) flange. The weld was very weak out of the
factory and its a known trouble spot on vw passats.

Can't help with the technology but you might consider involving the
professionals.

I was struggling with exhaust problems on an all terrain fork lift and
ended up with a very modestly priced stainless flexi link fitted to the
manifold by a small firm in St. Albans. They used inert gas but the rest
is beyond my knowledge.

Similar operations must exist elsewhere but you could try them for
advice. Top Gear Performance Ltd. 01727 850537

regards

--
Tim Lamb

Dave Baker wrote:

I suggest you post this to uk.rec.models.engineering. People who
struggle to drain a hot water cylinder without help aren't likely to
be your best source of advice.

:-)

That's just sarky.

Si