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Bulk annealing of sterling silver tubing


#1

Hello all,

Does anyone have any recommendations for how I can bulk anneal
tubing? I have ~200 ft. of a custom size of tubing (about 4mm OD w/ a
thin wall) headed my way, most likely in an “as drawn” temper. I need
it dead soft for my application. The idea of getting out the torch
and annealing by hand is a bit daunting, especially since I will
receive it in random lengths up to 6 ft!

I was pondering a kiln approach along these lines:

-chop up tubing into ~1ft lengths

-get stainless steel “crucible” (maybe some restaurant supply thingy
like they use in cafeterias for storing silverware?)

-pack “crucible” with tubing

-lay plate on top to exclude air

-anneal for a good long time to make sure center of load reaches
temp

I’d appreciate any refinements, alternatives, or other ideas. For
example, is it silly to contemplate filling the void volume in the
pack crucible with powdered charcoal to help minimize oxidation?
Seems like it would be incredibly messy…maybe better to just accept
the oxidation and pickle later? Or maybe the whole “crucible” thing
is overkill, and I should just chop up the tubing, bundle it up with
some binding wire and bang it into the kiln for an hour.

Thanks!
Tom Colson


#2
Does anyone have any recommendations for how I can bulk anneal
tubing? 

Hello Tom,

Don’t know if this option is applicable to your situation or not but
if it is it could be a good solution.

My father and uncle used to make “replacement” parts for 1/10 scale
replica steam engines, 6 inch steel wheels, rocker arms, etc. Often
these parts required annealing before and after they’d been machined
so what they did is bought up a bunch (several dozen?) used furnace
bricks and custom built a temporary “kiln” to suit their particular
needs for a given job.

They’d just mark out the space they needed on the shop floor, lay
down a couple layers of the furnace bricks, stack up the parts to
anneal, and build up walls around it all with more bricks. No mortar,
just stacked bricks. I think they topped it off with a layer of heavy
gauge steel mesh with more bricks on top of that. The heat source was
a simple tiger torch (propane torch used to heat engines in winter,
lay tar roofing, etc). Sure it took a few hours to get up to
temperature but boy did it ever get up to temperature! I remember
looking in once and seeing a stack of these steel wheels glowing red.
Apparently they were still dull a day later and that was long after
the torch had been withdrawn. Their cooling times were measured in
days.

Once a given job was done they’d simply disassemble the temporary
kiln and stack the bricks in the corner of the shop. Sounds a bit
bush-league I know but I’ve always admired the directness --and
effectiveness I’m told-- of their approach.

Cheers,
Trevor F.


#3

Tom,

My suggestion is to do something along the lines you mentioned with
the restaurant stainless pot & charcoal. I use a similar method
for firing my mokume billets. I use granular charcoal that I get
from McMaster Carr (mcmaster.com) their stock # 3190K522 and some of
those standard stainless cans with lids. The work can spend hours at
high temperatures with little or no oxidation. It is somewhat messy
but it is the simplest and cheapest method for creating a controlled
reducing atmosphere in a studio kiln. A second method is to get heat
treaters foil (Mcmaster-Carr again part # 3254K72), this is a
stainless steel foil that is about .002" thick and fold it to make
bags to put the tubing in. These bags with the tubing inside are
then placed in the kiln and annealed, it heats up faster then the
pot with the charcoal so there is less potential for grain growth in
the sterling due to long times at annealing temp. The drawback are
that you need to make a new bag every time you do this and the foil
is not inexpensive and not all the oxygen in the bag is trapped by
the titainium in the foil so you have more oxidation than with the
charcoal method.

Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160


@James_Binnion
Member of the Better Business Bureau


#4

Trevor, In a times such as this with high end and costly solutions
such as, laser, cad/cam, etc. It is wonderful to read a brick
solution to a potentially expensive alternative.

I believe is is messages such as yours that are precious to us as a
community. They deserve to be mentioned here and archived under a
category such as Charles Lewton Brain has in his delightful book,
“Cheap Tricks.”

Here is to Simple Solutions, how many others out there have a few
good ones to share? Terrie


#5

Tom: Question: Why didn’t you order the tubing soft.? We make
tubing all the time and if a customer requests soft, we anneal after
drawing. Years ago we made a furnace similar to the one Trevor
describes. Brick layout was much the same; however we used a heavy
wire screen midpoint in the brick stack. This arrangement allowed an
area under it to lay a couple of torches, one at each end to create a
fire box area. We then took the tubing in bunches (10-15 lengths
4m/m tubes about 4’ long) inserting in the furnace to a mid point,
and continually turned them over until the desired color for
annealing temp was reached.and then moved them back to an area that
wasn’t annealed, repeating until reaching the end. Then put the
other end in furnace, overlapping the mid point and repeat the
process. Sounds complicated, but really isn’t.

You could do the same with just a torch set at a large soft flame to
cover a large area without the brick furnace arrangement. Just hold
the torch on the tubing, maybe 5 or 6 tubes and continue to rotate
the bunch of tubing gently plying the flame over the area. Light wall
tubing comes up to temp easily, light red color, about 1200 degrees
F. You must rotate or continuously move the tubes to eliminate
burning the tubing. Light wall tubing can be burned through very
easily. Once completed tubing will be oxidized black, but a simple
pickle will remedy that. The downside is the tubing will no longer be
straight if that is an issue.

Ron