Was: Melting gold
As cast grain structure is very large. The slower it cools the
larger the grains. So forging followed by annealing produces a
small equiaxed grain structure that is best for rolling. Also due
to the way alloys solidify the chemistry varies within the grain so
the annealing helps to homogenize the distribution of the elements
in the alloy.
Wouldn't you achieve the same thing by a sufficient amount of
rolling? I don't mean just one or two passes.
Hammering is inconsistently, and randomly, impacting the the metal
that reduces the metal at the point of impact. Rolling is (usually)
consistently reducing the metal in a uniform manner.
The reason I'm thinking this, is that I used to work in the
aluminium industry, and was fortunate enough to have metallurgists
conveniently located so that I could ask questions. Ingots would come
out of the furnace and be rolled, or extruded, and of course due to
the mechanical forces involved the aluminium alloys were work
hardened. There was no hammering prior to rolling. BTW it was very
cool to watch machines of that size in action :-)
I'm open to changing my opinion, it's just have to work out all the
questions that come up due to my personal experiences. I'm not being
rude it's just they way my brain works.
If forging an ingot is desirable to do before rolling, what's to
stop me getting a handful of large ball bearings, and a leather bag.
Putting the ingot into the bag, and manipulating the bag with my feet
whilst I do something else with my hands. I'm thinking it would
achieve the same results as the preliminary cold forge before
rolling. It would also make the ingot nice and shiny. This technique
isn't something I've cooked up in the last five minutes, it's a very
old technique that has been around for about 12 Centuries (although
the ball bearings are my addition, the technique is the same).
Initially I thought that using a tumbler would be the same process,
but it isn't.
Regards Charles A.