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High strength cast stainless for marine service
2

High strength cast stainless for marine service

High strength cast stainless for marine service

(OP)
We are currently designing a high strength structural bracket for service above the water line on the back of ocean going vessels (operating just about everywhere)

For various reasons it's desireable to use a modestly corrosion resistant alloy, and historically we've used 17-4 PH H1075 stainless for this type of service.

We're currently considering a cast solution instead of the welded/machined parts we normally use. The first material candidate is CB-7Cu-1, however we're interested in comparing it to other options, which may have different combinations of strength, castability, corrosion resistance and price.

Our local vendors have limited experience with marine conditions, and with the exception of a small number of austenitic and duplex grades, we have limited experience with stainless castings. Can anyone suggest a good reference text for high performance marine grade casting alloys, or alternatively suggest a few candidate alloys we might consider looking at?

Thanks for any suggestions!

RE: High strength cast stainless for marine service

You will need an alloy with better corrosion resistance than 17-4 in order to make up for some of the casting related issues.
A duplex SS makes a lot of sense for this application.
You should not need a 25% Cr grade, one of the Mo bearing 22-24% Cr alloys should do the trick.
Remember that the castings need to be annealed and pickled to optimize properties and corrosion resistance.

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Plymouth Tube

RE: High strength cast stainless for marine service

(OP)
Thanks for the info all.

Ed: I'm having some trouble finding a good reference for the corrosion issues in CB-7Cu-1, at least in the 1075 condition. Is this a stress corrosion issue I should be worried about, or something else?

RE: High strength cast stainless for marine service

Is there any risk of impact or shock loading?
The cast equivalent of 17-4 may have similar strength but it will have lower corrosion resistance and lower toughness.

The duplex grades won't be as strong, but the strength/corrosion balance will be better.

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Plymouth Tube

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