shaft material choice: stainless 1

[abeschneider]

I need to specify a shaft material for the following application:
* submerged in freshwater
* Max torque 320 N-m(~3000 in-lbf)
* Continuous duty
* Will have plain bearings mounted on it (probably the bearings will actually reference against special shaft sleeves, not on the shaft itself)
* Will have roller-chain sprockets with keys mounted on it

I'm thinking a 416 Stainless Steel, Condition T (ASTM A582), hardened to ~30 Rockwell C; Tensile Strength: 758 MPa; Yield Strength 586 MPa. Material data can be found here:

http://www.azom.com/details.asp?ArticleID=971

Is there a better choice, that would supply similar properties at a better price, and be easy to machine?

Thanks...

 

[FACS]

I think you should stay with 300 series stainless if you are going to be getting it wet.

400 series is rust resistant, meaning it will corrode under conditions.

Charlie

http://www.facsco.com

 

[eromlignod]

300 series stainless steels are not hardenable.

416 will harden up to 43 Rc. It's not a corrosion resistant as 300 series or Nitronic 60, but it's probably OK for a fresh water application. Another possiblity is 410, which is a little cheaper, but it's not as machinable.

Don
Kansas City

 

[CorBlimeyLimey]

Type 303 is supposed to have better machinability & reduced galling than others in the 300 series.


Helpful SW websites FAQ559-520
How to get answers to your SW questions FAQ559-1091

 

[abeschneider]

In reading up on 400-series, it seems like the stuff has good corrosion resistance in fresh water. If it will rust, what is the timeframe in which this will expectedly happen?

I think I'd like to go with a 400-series for the hardenability; is the difference in machineability really large between 410 and 416? What about price?

17-4PH would be a nice choice but isn't it comparatively more expensive?

 

[abeschneider]

Perhaps 431 Stainless Steel is a good choice - a decent balance of corrosion resistance along with good hardenability (up to 42 Rockwell C / Brinell 388). Here's what Azom.com has to say about 431 corrosion:

"Corrosion Resistance

Excellent resistance to a wide variety of corrosive media. Reasonable resistance to salt water in cold southern waters but less resistant than Grade 316 in tropical waters. Overall the corrosion resistance of 431 is approximately the same as or slightly below that of grade 304.

Performance is best with a smooth surface finish, in the hardened and tempered condition."

Question is: how available is 431, and at what cost?

 

[JJPellin]

We commonly use 416 SS for shafting that is submerged in water. This is common in well water, oily water sewer sump, cooling tower water and similar services. We do not tend to see corrosion problems. We have shafts in these services running for 10 to 20 years. The material is readily available and relatively inexpensive. We just specify centerless ground, heat treated, shaft quality and have had very good luck.

 

[abeschneider]

JJPellin -

If you don't mind, a couple questions:

What level hardness do you specify? Do you source the metal in condition "P"? And what surface finish do you specify?

Thanks.

 

[eromlignod]

410 is about 25% cheaper than 416 (actually it's even cheaper than plain 303) It's a bitch to machine when it's soft, but it's not half bad to machine it after its hardened, believe it or not.

Someone mentioned 431, which I believe is supposed to have better corrosion resistance, but I think it's pretty exotic. My suppliers don't even carry it. I think it's also difficult to machine and particularly to grind, which you'll probably want to do. I think if you're not in salt water, you should be all right with the 416.

Don
Kansas City

 

[JJPellin]

For pump shafting, I don't even specify the hardness. I am not at work so I can't look up the supplier's catalog. But all we specify is 416 SS, centerless ground, heat treated, shaft quality. This give us a good shaft finish suitable for installation in vertical pumps with no additional machining or refinishing needed. At work in a few days, I will try to look up the detailed spec's for surface finish and hardness. I am not familiar with condition "P". My point may be, that the off-the-shelf 416 SS shafting works very well in submerged applications in machines up to 800 or even 1000 HP. We have not had to resort to higher cost, longer delivery, more exotic materials.

 

[abeschneider]

JJPellin - Does the centerless grind add a great deal to the price?

And what does "Shaft Quality" mean?

Sorry for the dumb questions; thanks for your insights.

 

[JJPellin]

Unfortunately, I don't know the answers to your questions. We only order this material as I have specified, so I don't know the cost difference. If it helps I can give an example. I stock 2-15/16" diameter, 416 SS Heat Treated, Centerless Ground, Pump Shaft Quality material in 20 foot lengths and they cost me $68US per foot. The term Pump Shaft Quality probably refers to a specification for straightness, but I don't know what that specification is. Normally, for lengths greater than 5 feet or so, we end up having to do some straightening ourselves before we install the shaft.

 

[metengr]

The 416 stainless steel material, supplied quench and tempered (heat treatment condition) to about 25-27 HRc should provide adequate strength and toughness for this application. We have numerous pump shafts that have been specified with this material and heat treatment condition. The 410 stainless steel is also acceptable with a similar heat treatment condition, but has a lower machining rating in comparison to 416 ss.

 

[rob768]

For shafting material in boats and ship, the complete 400 series is a good choice, with varying corrosion resistance depending on Chromium and Molydenum contents. Corrosion resistance isn't that bad, but be careful with conditions the provoke crevice corrosion (such as crevices, but also deposits or dirt due to stagnant flow)

 

[grizshop]

Hi I would go with type 440 it has a rc60 it has high strength corrosion resistance and good abrasion resistance hope that helps.

http://www.grizzlysprockets.com

 

[abeschneider]

I would like to just mention that I appreciate all the advice you have all given so far. I am still in the process of designing the machine and am weighing all of this input.

It's a wonderful resource to be able to learn from all of your collective experience. Thanks.

 

[NickE]

440 is not as corrosion resistant and I'd make a bet it costs way more than 416.

 

[unclesyd]

I would consider using the PH alloys, Aquamet, Aquatech and Aqualloy, along with the newest SS shafting material Temet 25. You can purchase this material already finished, ground and straightened and usually shipped in nice package. I've used these materials to replace many vertical pumps shafts that were originally Bronze, Monel, 410SS and 416SS.

These people have all the better wet shaft materials available.

http://www.gpcprop.com/inboard_shaft_machining.htm

http://www.wbmetals.com/shafting.asp#top

Here is a another representative for Aquamnt by Crucible.

http://www.aquamet.com/sizesdiameters/

 

[desertfox]

Hi abeschneider

I would consider using Stainless Steel 316L for your shafting.

regards

desertfox

 

[rob768]

The 400 series work well in fresh or salt water. We come across them in lost of boats and yachts. No general corrosion but be very careful in regions where oxygen starvation can occur, since crevice corrosion may pose a very serious problem (same for 316 series for that matter). We have seen serious pitting and fatigue induced fracture from this pitting in bearings (especially rubber bearings), seals, or, in the case of idle installations, under deposits. In some cases forced water refreshing had to be applied in order to solve such problems.