Dupont Corp once had a plant in NW Wisconsin that was making NH3NO3
the last time I toured it (summer of 1960).  A few years later I was
working in a neighboring town and we were often alerted to what
sounded like distant-thunder.  I found out that Dupont was forming
metal in an old gravel-pit in the neighboring National Forest.


Among other things, Dupont was using the power of explosives to
manufacture the nickel-copper laminates used to make the (then new)
silverless American coins.  My understanding is that they used some
type of molds and backing materials, sandwiched the entire bundle
between layers of explosives, bound the entire bundle together with
a welded network of concrete re-bar, and touched the entire thing
of.


I once helped some friends pour a new concrete floor for their barn.
All the re-bar in the slab was severely-stretched, but the price was
right, having been obtained free-for-the taking in the National
forest.

I suspect that similar technology could be used to hydroform most
anything, using the pressure of an expanding gas instead of water or
oil.

I've seen shotguns that have had their barrels hydroformed simply
because the end of the muzzle was plugged with a glob of mud.

R Berglund



Re. the use of explosives. In the 60's I worked for ICI at one of
their large chemical sites and as they also made explosives and
ammunition (a different site) they provided explosives that we used
to repair leaks in tubular heat exchangers.

They also supplied others with similar explosives to make fancy
design hub caps as it was cheaper than pressing or forging. One
company used the explosive method to put the final curves in
aluminium boats where the reinforced patten was made with air escape
holes. The rough shaped hull was put in the mould and filled with
water and the explosive set off making the hull come out with the
precise curves they wanted.

They could do several boats a day.  I would think using water would
work much better than a gas to form the metal parts as the shock wave
is transmitted better in liquid than in the air and does not need to
be sealed in. Colin Dale



The tube should be preformed a bit to fit inside a mold.  The liquid is
injected inside the tube while pressure is also applied axially on the
ends of the tube causing the metal to flow into the section of the tube
that is being expanded by the pressure inside the tube.

https://www.youtube.com/watch?v=XicB7I-gDEw

 Mark LaPierre

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