17-4Ph and contact with food

[BobUXL]

I am working with a customer that wishes to change a shaft in food processing equipment to 17-4. But according to NSF guidelines, the material needs have chrome limits above 16%. Within these guidelines and the material properties he wishes to have (there is impact concerns), 440 A, B or C are his only choices (He also wants a readily available material). But there will be problems with corrosion. Part of the shaft will have some contact with a food slury.

Does anybody have any information or links to articles that talk about 17-4 in the food industry? I need to obtain information on the use of this grades in the food industry to try to get this grade qualified.

Thanks,

Bob

 

[metengr]

Here is a detailed specification sheet on 17-4PH that mentions use in the food processing industry and comparison of corrosion resistance to 304L ss in certain environments;

http://www.stainless-steel-plate.com/17-4PH-spec.html

What is the food slury and temperature?

 

[BobUXL]

The application is a shaft in a blender (part of the shaft will be exposed). The food slury could be just about anything and temperature could be up maybe 120F. I saw the same web page, but just having a product brochure say it's used for food will not be enough to convince a government agency. What I need is some technical documentation or publication with the material in actual use.

Thanks for the response.

Bob

 

[metengr]

BobUXL;
Just curious. What is the reason the customer wants to change shaft material (fatigue failures?)

What was the original shaft material?

If you are dealing with an agency like the National Sanitation Foundation that certifies products, you probably will have to have 3rd party testing to qualify this material especially with the 16% minimum chromium requirement.

Have you considered a duplex stainless steel alloy (2205) in lieu of 17-4 PH?

 

[BobUXL]

The material is Custom 450 and the reason he wants to change is because of the lack of availability. They want a material that is readily available. We thought about a duplex, but they need high strength and impact resistance. Duplex alloys just will not have the strength needed for the shaft. They have tried austenitics, but the shaft twisted.

Bob

 

[NickE]

Doesnt 17-4 have nominal Cr content of 17%?
We've been using lots of 17-7 and I havent seen a cert yet with Cr<16%, I would guess that 17-4 would be similar.

nick

 

[TVP]

NickE,

The Cr content of 17-4 is 15-17.5.

 

[NickE]

TVP- Ahhh.. Shoulda looked it up before posting.

BobUXL how about using 17-7 the strength should be high enough, the cost would be higher, and the Cr range is 16.0-18.0

nick

 

[mcguire]

Any reasonable producing mill would accept an order for 17-4PH with Cr restricted to 16.0% minimum. I believe the actual minimum is 15.5%. A typical standard deviation on chromium content is 0.10%. So the mill must aim at 15.8% anyway.
One can always use 301 in the cold worked condition. This is really cheap compared to 17-4PH or 450 or 2205. For a shaft this can be done with cold finished bar.

 

[TVP]

mcguire,

Table 1 from ASTM A 693 gives the minimum Cr content as 15.00%. This is a sheet spec, and I didn't bother to look up the bar spec.

BobUXL,

mcguire's suggestion of Type 301 seems like a favorable option. I would just add that Type 302 is more prevalent in North America for round products, whereas Type 301 is more common in flat products.

 

[mcguire]

TVP
I'll yield since I don't have a current set of specs. I don't think that alters requesting 16.0% minimum, however.
301, 302, 303, or 304 would work equally well. Even 316, if there were a benefit from higher corrosion resistance, would work.
Cold-worked austenitics are a very under-utilized alloy system.

 

[CoryPad]

mcguire,

I agree with you and TVP that a cold-worked austenitic stainless steel could be suitable. I would like to comment on your under-utilization comment: who does the cold working? Can I get the bar in the length and diameter I need, and with the requisite delivery time from a mill? Do I work with a "converter" who can provide smaller quantities with specialized requirements? Who are good converters?

Regards,

Cory

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

 

[mcguire]

Cory
I am much more experienced in flat rolled than in bar products...it's a whole different set of suppliers. I would think a converter would be a better bet than a mill, but I can't recommend anyone specifically.
In carbon steel it's always done by converters in cold finished bar. Any cold finished bar producer could do stainless as well as carbon steel.
Try calling Ulbrich, Allegheny, Cartech or Ugine. At the latter a guy named BobDrab at 800-523-3321 might be able to help.

 

[CoryPad]

[blue]mcguire[/blue],

Thanks for the reply. Now that you mention them, Ulbrich is a really good choice.

Regards,

Cory

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

 

[metman]

mcguire,
What percentage reduction is typical and for example what are the UTS and YS for 302 worked this amount.

Jesus is THE life,
Leonard

 

[BobUXL]

Hello Everyone,

All the suggestions and comments were good and very valid. However, not many of these suggestions are in anyone's standard inventory. With an austenitic, you have to order a cold worked material which no one really stocks, especially these days. 17-7 is the same. Not really mych call so there is very little inventory if any around. And for a 630 with a special Cr level, it can be done, but it is not standard. Plus, the customer is not using enough for a heat lot quanity of material.

The customer is already complaining about an alloy that is hard to get. And I am trying to establish whether a standard 630 has been used for food where is was OK'd by NSF.

Any links or documentation on this would be very helpful. I would like to get my ducks in a row to try, if necessary, to get the alloy approved.

Thanks,

Bob

 

[rnd2]

You may have a precedent with chef's knives.

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Fantes Pro Line Kitchen Knives... Cr Mo V15 Carbon content: 0.5% Chromium content: 15% Rockwell ... Fante's Pro Set of 4 Steak Knives, 5" serrated ... paring knife, 6" utility knife, 8" chef knife, Gift ...
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Swissmar Imports... Wenger developed a specific range of knives for the butcher and chef, known as SWIBO ... High grade alloy steel: Carbon content 0.2%-0.7%, Chromium content 13%-15 ...

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- 13k - Cached - Similar pages

 

[mcguire]

BobUXL
Why don't you get a distributor to stock your preferred item for you? They will simply go back to the mill and lean on them to make the item a standard. There's no reason a mill wouldn't logically make their 17-4 to a 16.0% minimum.
Or the size 301 you need. This would help everyone keep their customer.
Using a commonly available item has its disadvantage if anyone can obtain it. Wouldn't you want this customer dependent on you?