From: gherbert@gw.retro.com
Mike Miller wrote:
>> Welding is not rocket science.
>
>Well, if you're using high-strength alloys with little tolerance
>toward welding, it can be as complicated as rocket science.
>
>Alloy segregation, grain size, heat affected zones, fusion, lack of
>fusion, slag inclusion, the effects of multiple weld passes, the
>problems with work piece orientation...welding is COMPLICATED,
>especially when dealing with high strength alloys fit for large
>pressure-fed rockets. It's so complicated that it's not yet possible
>to automate the welding of large submarine hulls, which use more
>forgiving alloys than the alloys considered for pressure-fed big dumb
>boosters.
As a slight rebuttal to this, though...
It is possible to braze a lot of the Al alloys with much
less complications. See "Alumiweld".
It's becoming possible to friction-stir weld a lot of things,
definitely including essentially all Aluminum alloys, and at
least some of the high strength steel ones, with a lot less
complications as well. Delta-IV common booster core main tank
wall segments are FSW'ed; it was initially used as an emergency
recovery test when manual welding wrecked one tankset, and it
worked so well that they abandoned the manual welding.
FSW has been done on equivalently high strength steels as
the HY-series used for sub hulls, but I don't know of any
serious program to try FSW on subs themselves. Among other
problems, the sub hull plates are a lot thicker than what
I have seen successfully reported as being FSWed.
A propellant tank, however, would be somewhat thinner.
Thicknesses up to 75mm of Al have been reported as being
successfully FSWed right now.
-george william herbert
gherbert@retro.com
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