5A,6A vs 6% Mo stainless in desalination process. 2

[snellen]

What are your thoughts gents about the pitting and crevice resistance of the cheaper 5A and 6A (CE3MN, CD3MWCuN) Duplex vs. the AL6XN, 254SMO (CN3MN,CK3MCuN).It is for pumps and valves in a desalination plant. So I asume seawater. The PRN or CPT in the literature is fairly similar especially if one tweak the Nitrogen in the duplex. Is the extra cost worth the seemingly small increase in performance (with 45$/lbs Mo....)?

Gerard

 

[EdStainless]

The superduplex alloys are often used in seawater service. Alloys such as J93380 (6A) and J93404 (5A)are used as well as cast 6% Mo alloys J93254, J94651 and J94653.
I don't know that they will cost any less. They are still made from premium melt stock, they must be annealed, and they are not easy to machine.
You can get by with a slightly lower PREN using a duplex. The calculation does not put the alloy families all on the same line. A superferritic with PREN of 35 will have the same G48 CCCT as a superduplex with 40 and a superaustenitic with 45. I am using PREN = (Cr+3.3Mo+16N)
If you go duplex make sure that you require A923 testing.

The last time that I looked Ni was ~$6.75 and Mo ~$35.
No joy for us. I can sell a lot more stainless when it is $4 and $6.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[StoneCold]

snellen
What about just using fiberglass pipe or HDPE?

StoneCold

 

[snellen]

With our AOD vessel the cost for the 6% Mo is around $3.50/lbs vs $2.25/lbs for the super duplexes. We heat treat in house but do not machine. I'll meet with the customer and find out if they have any mech. requirement that would indicate one over the other. StoneCold we are a foundry and are quoting pump and valve work.

Gerard

 

[EdStainless]

Make sure that you keep the Cr, Mo and N all at mid-range or higher. If you let them drop to the low end you could have some trouble.
Good rapid quench from anneal and you should be fine.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm