Porosity can be a problem melting and casting aluminum alloys that are
not formulated for casting. 6061 is one of them but I melt a lot of it
for non structural castings. What I do to reduce the porosity is what
the melt closely so not to over heat it. An overheating will draw
hydrogen from the gases and surrounding air. Minimize stirring as much
as possible. And degas just before you skim and pour. You can use
degassing powders or inert gas for degassing the melt. Argon, CO2
welding gas and dry nitrogen works good. The dry nitrogen is the best if
you have it on hand. I use CO2 as I have it on hand for my mig welder.
Another thing you can do to make melted aluminum easier to machine and
to improve the finish is to temper it. Proper tempering is not easy to
do in a home shop. I do a crude tempering by shaking out the casting as
soon as I dare and quench it in cold water to cool it rapidly.
On 12/10/2013 10:37 PM, wattcody@... wrote:
> Hello all,
> I have been casting bar stock from 6061 aluminum cutoff pieces I have.
> When I machine the bar stock on the lathe, it never gets the nice shiny
> finish like real bar stock does. It is rather porous. Is there something
> I can do to get it to be more uniform and give a better finish when
> machined? Maybe degass or something?
> Thanks in advance!
Camrose, Alberta, Canada.