I’ve been trying to manufacture 24kt and 23.75kt gold leaf (Au, Zn
or Au, Ag) for some time now. We already manufacture silver (0.999)
leaf without any problems. The problem that we are facing, as you
will see below, is for gold and its alloys.
Basically the process is:
Continuous Cast metal in 50mm Wide * 3 - 5 mm thick strips
Roll metal down to 10 - 20 microns (4-hi rolling mill)
Hammer metal to 0.2 - 0.4 microns thick (singnificantly thinner
than a human hair)
Now…here’s the problem…it seems that after rolling AND annealing
the gold still seems to be hard and has very minimal expansion in
the hammering process.
I have a very good feeling that we are not annealing correctly. Our
annealing process is:
Till the gold is above 0.50 mm we anneal at 250 degrees C for 30
minutes, and than air cool it every time the reduction is around
75%. After the metal goes below 0.50 mm we anneal at 600 degrees C
for 3 - 5 minutes and air cool it for every 75% reduction.
We had tried to water quench the metal, as a cooling process after
annealing, but that caused significant pin holes in the final
product. ( we are using basic tap water)
I would really appreciate if anyone with any knowledge on this
subject can help me out.
Looking forward to your input.
I realize that this product might be a new subject for many of you
but please don’t hold back your opinions. We are very willing to try
any ideas you may have.
Thanks in advance for your help.