FOLLOWUP TO USE OF 316 2

[hoopsnow]

Thanks for the helpful responses, this was my first request for help on the internet and it has been an great experience! The consensus appears to be that both 316 and 316L should not be used in the salt water towing application and that they would corrode due to stress corrosion cracking caused by the combination of a chloride environment and the tensile stress the chains would be under. One factor I didn't include is that the metal has to be non-magnetic.

I searched for candidates that meet the requirements and came up with several. The following metals meet the chains' requirements: Duplex steel 2205 (s31803), super-austenitic steels (904L or AL-6XN), Inconel 625, Monel K-500, titanium (6A14V). Price is an important factor and all the above metals easily fulfill the chains' requirements. 904L is significantly more expensive than the duplex steel because nickel and molybdenum are expensive components. Monel K-500 appears to be the most attractive because one of its typical applications is in the fabrication of chains. Since the metals easily meet the chains' requirements, price is the most important factor although I'd prefer to use Monel K-500 if its price is relatively low. Do you all have any further suggestions regarding the selection and particularly the relative costs.

Thanks once again for all the help.

 

[GregLocock]

We used titanium in the production version of our towed marine device.

Although it is pretty expensive, some of that cost is recouped by recycling the swarf, and the ease with which it can be machined by a competent machine shop, and the fact that it is relatively easy to get barstock made to a specific diameter. The attraction to us was the excellent corrosion properties and the high strength/density ratio.

In the end the machining cost was about 4 times the material cost, so there is a good chance that a cheaper material would have resulted in a more expensive component.




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rolledalloy]

Be aware that duplex stainless steels are magnetic unlike the other materials that you mention. Also the Monel 400 grade has a curie temperature very close to room temperature as a result change in climate can change it from magnetic to non magnetic or vice versa. Not sure if this is also the case with the Monel K-500 but you could check at Special Metals website.

The other alloys you mention 904L, AL-6XN, and 625 are non magnetic.

 

[rd400guy]

Monel K-500 is non-magnetic to -150°F.

http://www.specialmetals.com/products/monelalloyk500.htm

 

[DAVIDSTECKER]

I did not read your other posting, but have you looked into the high tech ropes such as Plasma or Am-Steel Blue.
Many of my customers have been using these types of ropes to replace the facing wires on their tug (push) boats, and others have replaced their mooring calbes with these lines also.
They have very low stretch and they float they are so light.
I have incorperated them into oil tanker emergency towing systems, replacing chain and steel cable. The tow line and messenger lines together only weigh about 950 lb.

 

[EdStainless]

AL-6XN and K-500 would both work. Can you actaully design to take avantage of the high strengths of these materials? They are more than twice as strong as 316.
If you can't reduce the amount of metal, then you won't be able to afford it. They are both very steep.
In raw material forms 6XN is about $9/lb. Given that K-500 is 65% Ni 35% Cu I don't see it being any less.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm