As with all things - there is a lot of myth, mis-information and fallacy
about heat treating. Since I do this for a living I might as well join the
fray.
6061 and 6063 are hardenable, heat treatable alloys. They are heated to
approximately 96F, then cooled rapidly using water, water sprays, poly
alkalyene glycols and oil (very rare), they are then aged to obtain final
properties (the -T tempers). The properties of a part vary widely depending
on the temper.
The first digit after the T indicates the sequence of operations. T 6
indicates solution heat treatment, quenched and artificially peak aged.
T8 indicates solution heat treat, quenched, cold worked (typically
stretched) and artificially aged.
The second digit indicates variation in basic heat treatment.
Both alloys are readily formable in the O condition. As a general rule you
need 1.5T to form in the O (annealed condition) - with larger allowances as
the part is formed in various heat treated conditions. The exception is the
AQ condition - where parts can be readily formed, then aged to the final
heat treated condition. This is different from steel where the parts are
hard and brittle when quenched.
Because of alloying content - in the T6 condition, the 6061 will have better
properties than 6063.
Both are quenched in water. The difference is the alloy content and the
process sequence. The T8 parts are typically drawn over a mandrel to
stretch them prior to final aged.
In the T8 condition, it is likely that the 6063-T832 will have similar
properties to 6061-T6.
If you have any other questions regarding heat treatment - and the proper
way to do it, please contact me via this thread or off-line
D. Scott MacKenzie, PhD Met Eng, FASM
Aka KB0FHP
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Roger (K8RI)
Sent: Tuesday, March 24, 2009 6:49 PM
To: TexasRF@aol.com
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] 6061 vs 6063
TexasRF@aol.com wrote:
> Most antenna manufacturers are using 6063-T832 alloy tubing. The T832
> is very important and I have seen no one refer to this in these tubing
> discussions.
>
> The yield strength of 6061-T6 and 6063-T832 is the same; typically
> 38,000 to 40,000 psi. I have tested both types of tubing by hanging
> weights on the end of six ft pieces until a permanent change in
> straightness occurred. Both types showed a slight bend with the same
> weight on them.
>
> Plain 6063, like you would find in a hardware store has a typical
> yield strength of about 27,000 psi, demonstrating the importance of
> the T (for temper) numbers.
>
> 6061-T6 is manufactured with an oil quenching process (what ever that
> is)
I'd like to enlarge on that a bit if I may and I'm no expert.
Quenching is the rapid, but controlled cooling of a material in some medium.
That medium may vary from water to oil, to even liquid Nitrogen. The
cooling medium used controls the rate at which the metal is cooled and thus
the hardness. The faster it's cooled the harder the result. The effects
also vary. In the case of quenching a piece of steel, which which I'm quite
familiar, water will result in a very hard and *brittle* piece. Quenching
the same piece in oil will slow the cooling process substantially. It will
also add carbon into the surface *layer*, not just on the surface. In this
case you end up with a very hard surface with an underlying support layer
that is very tough. Under that, depending on the size of the piece will be a
core of the native material. That surface layer has the carbon diffused down
into it which also adds to the hardness and durability essentially turning
that layer into a hardened high carbon steel.
The Quenching of Aluminum is similar, but I have no experience with it so
lack the details .
> and usually has a dull to ugly dark finish. 6063-T832 is manufactured
> with a completely different process that reduces manufacturing costs
> and leaves the material with a shiny bright finish.
>
> As far as bending and welding characteristics, I have not studied that
> and leave it to others to complete the story.
>
As a rough comparison, the springy Aluminum alloys are much like a steel
spring. They can be bent, but exceeding the minimum bend radius (which can
be quite large) will end up fracturing the material just like bending a flat
coiled spring too far will cause it to break or shatter at the bend.
With the advent of TIG welding, the ability to weld Aluminum has become far
easier. Oxyacetylene welding of Aluminum can be done, but takes practice
(One that I never managed to master). Even then it's easy to get a
"granular" weld which is not all that uncommon on Aluminum tower cross
braces. The reason "Torch welding" is so difficult with Aluminum
is the ability of Aluminum to transfer heat. TIG welding creates a lot
of heat concentrated in a small area from an electric arc. The welding rod
is fed into this arc with the two making the weld relatively easy to
control.
The differences I've seen are with welding steel the weld is usually the
strongest point where in Aluminum it is the softest and usually the weakest
point. Although due more to technique, or the lack there of, you'll see
Aluminum welds break at the edge which is "usually" due to lack of
penetration and is much like a cold solder joint.
That's welding and quenching Aluminum...more or less.
> 73,
> Gerald Williamson, K5GW, General Manager Texas Towers (we do have
> 6063-T832 tubing)
>
>
>
> In a message dated 3/24/2009 4:03:31 P.M. Central Daylight Time,
> K8RI-on-TowerTalk@tm.net writes:
>
>
>
> jim Jarvis wrote:
> > Dave,
> >
> > I haven't looked in a materials handbook to see the spec, so I'm
> only
> > repeating what Bethlehem Aluminum and Wikipedia said. But I
> think you
> > misread my comment.
> >
> > 6061 will spring.... it can be bent and NOT take a set. Up to
> the
> > point of breaking.
> >
> 6061 is much harder than 6063. It's what we use for aircraft skin,
> cowls, wheel pants... etc. so 6061 can be bent, it can be shaped
> into
> rather complex shapes using an English Wheel, as well as panishing to
> stretch or shrink the material. OTOH not all 6061 is created
> equal. It
> comes in a wide variety of hardness. I think that may be where at
> least
> some of the confusion over 6061 comes from. As was mentioned
> earlier in
> this thread, 6061-T6 can be bent and formed into complex shapes.
>
> There are several sites on the web devoted to metal working.
> http://www.metalmeet.com/ and http://www.metalshapers.org/ are two I
> know of.
> > 6063, on the other hand, can be bent into a curved shape and
> stay there.
> >
> >
> 6061 can be bent, be it tube or sheet, but it takes more care (and
> work)
> to do so than with 6063.
> > If you use a bending brake to bend 6061, it's likely to fracture
> or
> > surface distort,
> >
> 6061 can be bent to 90 degrees using a brake, BUT there are
> limitations.The radius of the bend needs to be at least 1.5 times the
> thickness and it depends on the hardness of the particular sheet.
> > rk it as well as you can 6063.
> >
> > One argument in favor of 6063 may be that being less brittle, it
> may
> > withstand
> > vibration better, over time.
> >
>
> I think you will find the softer alloys will work harden quicker than
> those that are springy.
>
> 73
>
> Roger (K8RI)
> > Perhaps I'm wrong. Check with the Alcoa Aluminum spec sheets,
> which
> > can be
> > linked to from Wikipedia.
> >
> > Jim
> >
> >
> >
> >
> > On Mar 24, 2009, at 1:37 PM, Dave Johnson wrote:
> >
> >
> >> Sorry Jim but who ever told you this is full of it. 6061-T6 is a
> >> alloy that is designed to be bent a long way and not take a set.
> >> It will not crack or orange peel.
> >>
> >> Dave - K4SSU
> >>
> >>
> >>
> >> ----- Original Message ----- From: "jim Jarvis"
> >> <jimjarvis@optonline.net>
> >> To: <towertalk@contesting.com>
> >> Sent: Tuesday, March 24, 2009 10:40 AM
> >> Subject: Re: [TowerTalk] 6061 vs 6063
> >>
> >>
> >>
> >>> I verified with the Al tube vendor the 6061/6063 question.
> >>>
> >>> They're both the same price.
> >>>
> >>> 6061 is stronger. but if you need to put a bend in the material,
> >>> 6063 is what you want.
> >>> 6061 will crack or orange peel if you try to bend it. 6063
> will
> >>> not.
> >>>
> >>> N2EA
> >>>
> >>>
> >>> _______________________________________________
> >>>
> >>>
> >>>
> >>> _______________________________________________
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> >>> TowerTalk@contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/towertalk
> >>>
> >
> > _______________________________________________
> >
> >
> >
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> >
> >
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