I’ve recently started experimenting with Titanium, and have a couple
questions. First, I’d like to achieve the finish that is often seen
on titanium products, the sand blasted, dark finish. I tried sand
blasting, but that doesn’t produce the darker look. I’ve seen this
finish on watches and golf clubs, and it seems to be the most common
Titanium finish. Is it an oxidation…?
Any reccomendations for someone in Arizona who can cast Ti?
Last Question: I’ve heard a bit about the various alloys, but how
are they stronger? For instance, are Ti 6AL 4V and Ti 6AL 2V 2Sn
more scratch resistant, or do they give greater pressure in a
tension set (all else being equal)?
Thanks for your help!
David Tomich
NAU student
Hello dave, The finer the sandblasting grid is the darker the look.
also if you oil the surface after blasting the surface will look
darker than a decrease surface.
here a copy of my explanation of tension rings and the effect with
different material alloys.
Hello Shaun, Ti6AL-4V is the most sold alloy of titanium. (55% of
the market) . 35% is titanium pure is several grades. and the rest
others special alloys… So every titanium industrial supplier should
be able to supply you this alloy. However if you want to use this
alloy you need to deform it above 450 degrees Celsius to wind rings.
The problem is now that you have damaged the structure and if you
want a strength back you need to quench an precipitate harden this
alloy. Precipitation hardening is the same as age hardening, you need
to give the alloy elements the movement (heat) and time to creep
towards the crystal edges. they will form wedges and increase so the
strength. The best way is now to heat again up to 700 degr. C. and
quench in water. Make fine crystals again) Now age harden at this
same temperature for 2-4 hours. at 500 degr C. What you get now is an
alloy with a tensile strength of 1000N/mm2 This is the double of
unalloyed titanium.
But why the fuzz.
The stiffness (flexibility) of the titanium is determing the force
necessary to bend for an x distance. Read this twice to understand.
This stiffness factor is called E-modules.
E-mod for :
grade 1 = 102000N/mm2
grade2-3 = 104000N/mm2
TiAl16-V4 = 115000N/mm2
So by using an alloyed titanium, the force to remove a stone out of
a tension ring is only 10-13% higher. The tensile strength is only
saying how high you can pull on this material before is breaks., but
the elongation still goes along the E-modules line.
My advise is to stick with the unalloyed stuff. it is also easier to
deform, and we don’t need the high tensile strength. we are not
building airplanes.
Martin Niemeijer