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In Reply to: Re: perhaps a bit off topic... grades of ss posted by mqracing on August 7, 2006 at 21:21:56:
the specificaiton of materials for watches, but based rather on the properties of the materials as indicated in other industrial applications, e.g. petrochemical and refinery, a type 316 alloy would not be my choice for a hard material that should retain edge sharpness and be resistant to chloride corrosion. I personally have seen badly chloride corroded 316 material expose in an offshore environment. 316 is more resistant than 304, but making it hard enough for clean machining and edge retention against spalling (say for fitting and removing the sealing cap-back) works against its corrosion resistance.Quoted Pitting Resistant Equivalent (PRE) data are typical for material in the solution annealed, softest, state. The hardened materials are not in that state and are not be expected to retain that PRE. For corrosive refinery applications, there are specifications for SSt hardness, and the softest state is typically required. If the material is cold worked i.e. work hardened, or if residual stress can exist, say from welding, the component is required to be solution annealed for acceptance.
If the ideal is permanence, for a watch case, a hardend alpha-beta or beta titanium alloy would seem a better choice than austenitic SSt. Given the actual low frequency the watches will be exposed in the seawater environment, it does not seem likely the material would be challenged in any case. It would be edifying if the maker were to publish the results of standardized corrosion tests using the assembled watch. For real world day to day use, a PH 17-4 SST or similar would be a less exotic but fully functional choice too.
And my opinion about nickel alergy would be that a ferritic stainless is preferrable since it (typically) has no nickel content. The 300 series SSt typically have significant nickel content. This is the reason I do not use SSt cookware, such is always austenitic SSt and likely leaches nickel at elelvated temperatures exposed to wet solutions.
"Submarine Steel", sounds like hype or a reference to a different material. I have seen a few statements about metallurgy in commercial literature that appear inconsistent with principal. The knife maker Haenkles [sp?] once advertised that their knife metal was ice tempered. I wrote a letter about that, and I have not seen them making that assertion lately.
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- Without knowing anything specific about - NewbieBaby 09:30:54 08/08/06 (0)
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