Depending on the specification: Condition N is normalized and ready to be heat
treated. CDSR is stress-relieved. More than likely the material is in a form
similar to hot rolled, and not normalized for uniform microstructure. It is
heated to some nominal temperature to relieve any stresses from the
manufacturing process. The final commercial grade is an unknow, but I would
suspect that it is simply as-received from the mill. It would be in a
microstructure similar to a hot rolled microstructure. However, all these
grades can be heat treated to fairly high strength and toughness - and would
yield (excuse the pun) excellent results. Another big difference between the
grades is the amount of testing done - the AMS grades require more testing, but
the alloy chemistry is essentially the same. There may also be some difference
in the inclusion content which would affect fatigue life and impact strength.
As a metallurgist, I would feel comfortable with using any of the grades,
especially if they were heat treated appropriately. The best is probably the
airframe grade, followed by the aircraft grade, and finally the commercial
grade. For the purpose of mast materials, the service is relatively low, with
failure usually being overload instead of fatigue. Any one of them would
work....
Hope that helps
Scott, KB0FHP
-------------- Original message --------------
From: "Ron Hylton" <ad7l@hevanet.com>
> Here in the Portland metro area, we have an excellent source of tubing from
> a company called Tube Service. They offer several grades of 4130 alloy
> Chrome-Moly tube, including:
>
> 4130 Airframe (Cond. N) Specs: Mil-T-6736, AMS 6360
> 4130 Aircraft (CDSR) Specs: AMS-6371
> 4130 Commercial Specs: ASTM A-519
>
> My question is, which grade is typically used for masts?
>
> 73,
> Ron AD7L
> Hillsboro, Oregon
>
>
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