Hi all,
I have a new problem that has popped up with my mokume and I’m
wondering if anyone out there with more experience might have some
advice for me.
So, I started making copper and silver mokume about a year ago and,
after the first billet being an utter failure, I’ve had good
success… until now. My past, successful billets were 12-14 layers
alternating copper and sterling 1" square sheets, 22-24 guage.
They’ve turned out great – not a single crack in the forging
process. Now I’m trying to make it 16 layers, alternating copper (24
guage) and sterling (26 guage) 1" square sheets with a thick sterling
piece on the bottom (12 guage). I’ve tried this twice and it has
twice failed in the forging process – massive billet failure with
multple tiny lines forming between layers with the first 2-3 forgings
and those develop into cracks before the billet reaches 7.5mm (starts
just over 9.0 mm). Here are the details I can think of:
-
sand down each piece with 400 grit paper
-
wash meticulously with perfumeless soap and then distilled water
then spray with distilled water until no beading takes place, then
dry with a blower… -
place between 3/4" steel torque plates with four 1/2" bolts. Torque
each bolt to 90 foot lbs. -
place in steel tool wrap bag with activated carbon, fire at 1360
for 10 hours. -
remove billet from torque plates, linish down on all sides until
no visible spaces/cracks, then linish off an additional.25 cm from
all sides. -
set kiln to anneal billet at 1100 F for 2 minutes (kiln gets up to
about 1140 though, then stays around 1100). -
reduce by .05-.01 mm by cold forging, then anneal and repeat over
and over until it fits in my 5.5 mm rolling mill.
I think I’ve done everything exactly the same for the billets that
succeeded and for those that failed, except a couple things I can
think of that might have been different:
-
used less soap in initail washinge
-
copper may have been in worse shapee I see pits when looking
through a 10X loop, but sheets are totally clean to the naked eye. -
annealing at a different temeraturee I didn’t log the annealing
temp on the successful trials! -
I think I used to torque to 80 foot lbs instead of 90?
Any ideas as to what I once did correctly, but now am clearly doing
wrong?
Thanks!
Benjamin