Quote:
Originally Posted by Jim Cate
If the above were true why are airplanes, subject to flexing and vast numbers of cycles of stress, built of aluminium? They seem to last for decades.
Jim
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Simply because the aeronautic industry know how to select, manage and to source the materials properly (most of the time these materials are not at reach of common people out of the industry), on the opposite of a
single individual
buying common aluminium plate in a local
DIY....They are 2 differents worlds.
About SS qualities, only duly certified materials will have proper characteristics, as there are "real" 304 and 316, and they are ones form unknowm origin and quality.
In
Europe, certified metallic material have mill certificates according EN 10204, with different levels of severity, the higher the better.
Type 3.2 certificates (higher level of conformity certificate) ensure that your product has been tested under witnessing of an independant body (other than the manufacturer itself, for example a mandated laboratory) or yourself as customer, and has all the grade characteristics it should have according the manufacturing standard (for example ASTM A 240 for 304 and 316 for plate).
Anything you buy without such certificate can be any grade and any quality, including the worst one.
That is why industrial material management has nothing to do with common
DIY customers...
SS Welds issue is also well known and easily
solved by :
mechanical
cleaning first (brushing, with compatible to SS
brushes or grinding discs)
polishing 2nd
pickling and passivation at last.
To be repeated time to time when corrosion is appearing again...as it always do...
Any SS weld not treated like that will ruin all the
work by quickly developping corrosion and potential failure of the assembly in the long run.
A good example of bad practices can be seen on SS
exhaust manufacturer that leave the welds "as is" after welding, duly colored (so without any post welding surface treatment, neither mechanical, nor chimicial...), they'll last as long as a carbon
steel one, if not shorter.