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PostPosted: Tue Jul 14, 2009 10:14 am 
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Matt,
Do you know what grade of aluminum is used in production for the various tubular items such as tiller arms, tiller crossbar? Is a 6000 series used (6061T) or a 5000 series? I have been told by metal suppliers the 5000 series holds up better in a marine environment, and that anodizing more than anything protects the aluminum from corrosion.

If there's another grade used for the heavier extrusions... mast, crossbeams. That is also helpful.
Thanks!

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PostPosted: Tue Jul 14, 2009 10:22 am 
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I believe all of the extrusions are 6061 with a T6 hardness. Choice of aluminum is also related to bend requirements. This is for production bending process and the actual bending while under sailing loads, so maybe why this grade was choosen?

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PostPosted: Wed Jul 15, 2009 8:57 am 
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Some aluminums are not maliable(sp?) and cannot be welded. 6061 is weldable and is used in many high end bicycles and aircraft. 6075 is not weldable if I remember correctly.

What are you looking to make Bowman? Spinpole?


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PostPosted: Wed Jul 15, 2009 3:20 pm 
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ncmbm wrote:
Some aluminums are not maliable(sp?) and cannot be welded. 6061 is weldable and is used in many high end bicycles and aircraft. 6075 is not weldable if I remember correctly.

What are you looking to make Bowman? Spinpole?


However, for 6061 T6 aluminum, welding negates the T6 heat treatment in the heat effected zone, which weakens the aluminum by as much as 30%. The process of restoring the temper must be applied to the entire piece:
Quote:
T6 Heat Treatment is a specific heat treatment process which may be applied to aluminum / copper / silicon alloys, such as hypereutectic, to increase the strength of the alloy by as much as 30%. In the case of T6 heat treatment, the process occurs in two phases.

The First Phase of T6 heat treatment is called the Quench Phase. In this phase the alloy is heated to 920 degrees Fahrenheit for 9 hours causing the copper in the alloy to become dissolved in the aluminum and forming what is called a "Single Phase Alloy". If allowed to air cool naturally, the copper will tend to reconstitute, or reform itself within the alloy. However, when the heated alloy is cooled rapidly by water quenching the reformation of the copper is retarded and the aluminum, supersaturated with copper, is locked into the "Single Phase Alloy" state.

Precipitation
In the Second Phase of the T6 heat treatment process, called the Aging Phase, the alloy is heated to 350 degrees Fahrenheit for 10 hours and then allowed to air cool. During this phase the copper combines with the aluminum in a process called "precipitation hardening" to form a copper aluminum crystal, CuAl2. It is the formation of these copper aluminum crystals which gives the alloy its strength.

The key to maximizing alloy strength comes from controlling the size of the copper / aluminum crystals. Maximum strength is attained when the size of the crystals, or precipitated particles, is kept very small forcing them to conform to the structure of the aluminum.

The end result is an aluminum alloy, or hypereutectic piston, that is up to 30% stronger.


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PostPosted: Wed Jul 15, 2009 6:09 pm 
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Is all that also true for Magnum wing frames?


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PostPosted: Wed Jul 15, 2009 7:48 pm 
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Technically, yes. There are some applications where annealing and heat treating are not critical but it is always recommended. The molecules must be properly aligned for maximum strength and heat treating allows the metals to relax and align, if I remember the laymans interpretation.
If magnum wings were re-welded they should be heat treated as well to regain proper strength. If a brace were welded on to a small area then maybe not.


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PostPosted: Sun Jul 19, 2009 4:10 am 
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been out of town for several days...
yes, Mike. a spin pole. When discussing it with a metal supplier, he mentioned 5000 series was better suited for a marine environment. But I got to thinking the HC would not use the more costlly aluminum if not necessary for their applications. Plus the anodizing is what really makes the barrier to corrosion.

Thanks Matt for the info.

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