spring wire for sea water 1

[Ibreakstuffdigitally]

Hello

I'm speccing a piece of spring wire for service in sea water. The spring isn't going to see particularly high stress, but it will be in and out of the water, sometimes submerged for days, sometimes on deck for days.

My first choice would be a cold worked 304 or 316 stainless, but I understand that these materials can come to grief under these conditions, specifically, stress corrosion cracking.

We've used duplex stainless and nitronics before with good success in very different aplications, but I don't think these are particularly common as cold worked spring wires.

What common spring wire could I expect to give good service under these conditions? Do I have a range of price options? (It might make sense to go for an expensive material for a prototype, just to take material concerns out of the equation, and work on lowering material costs later.)

Thanks in advance for any help

 

[EdStainless]

It really depends on the risk of failure.
If failure is unacceptable then you will need to use a Ni alloy such as 625 or C-276.
A 6%Mo stainless (AL-6XN or 254SMO) will probably work.
The most common duplex, 2205, will resist cracking, but pitting corrosion will catch up over time.

I shouldn't forget other options such as Ti or BeCu. Both should work fine in seawater.

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Rust never sleeps
Neither should your protection

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

 

[Ibreakstuffdigitally]

Thanks for the suggestion. I think for the first run, we really can't be worried about corrosion at all, We have enough other unknowns in this setup.

Are there any special processing concerns for these materials? 2205 we have experience with, AL-6XN and 254SMO are aliens to us.

Are any of these particularly common as spring wire?

 

[swall]

You could also use titanium.

 

[EdStainless]

What size of wire? what strength?

No, no real processing differences from 304 wire. Make sure that they are clean before you stress relive.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

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

 

[CoryPad]

2205 is available as spring wire from Interwire:

http://www.interwiregroup.com/iwp_pr_sandvik.html

Regards,

Cory

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

 

[Matlsguy]

Ibreakstuffdigitally,

Your challenge is weighing fatigue requirements vs. corrosion resistence. I need more information about the spring loading (load vs time data) before I recommend a material. As a rule of thumb as the fatigue resistence goes up the chemical corrosion resistence goes down. Since stress corrosion cracking is both mechanical and chemical it doesn't follow this pattern, but still is a concern. Question, is coating the spring with a primer an option ? That could increase the life of your part. Is cathodically protecting the spring with a zinc plating an option ?

Regards,

Matlsguy

 

[Ibreakstuffdigitally]

Hello and thanks for the responses

The stress levels will be in the order of 165 ksi at maximum deflection in the current design, although I can probably bring that down some if it's critical to do so

Actual number of life cycles will be relatively low, although life expectency (doing nothing) in the marine environment will be many years.

The wire will be about 90 thou diameter.