best grade of stainless steel for conveyor chain application 1

[Naz14]

The company I work for manufactures drop forged rivetless chain for overhead conveyor systems ie; X 348, X 458, and X 678 chain. This chain is comprised of (3) components: a male link, a pair of female links, and connecting pins, which are all drop forged out of Carbon and Alloy steel and then heat treated for improved wear ability and strength. Our customer base has been the automotive, metal working, and finishing plants around the world. We are now pursuing customers in the food processing industry and corrosion resistance has become a major requirement for our chain and accessory products. Our chain has to endure heavy linear loading, continuous operation, slight bending motions, substantial side loading, frequent impact issues, and direct metal on metal articulation with minimum lubrication. With that in mind, I am trying to decide on the correct grade of forgeable stainless steel to use to maximize corrosion resistance, maintain excellent high linear strength, have maximum fatigue resistance, and good wear ability. I am currently considering 17-4 martensitic precipitation/age-hardening stainless steel or conventionally quench and tempered 410 grade stainless steel. Since my background has been mostly mechanical and not material focused, I am looking for any ideas that may give me some direction in my quest for corrosion resistant, strong, and wearable chain. Any ideas or thought would be more than welcome. a sketch of the product I am referring to is in the attached

 

[EdStainless]

316 is the darling of the food process guys, not because of the food but because the chemicals that they use for cleaning and sterilizing.
But you need a lot more strength, and in stainless galling is a big concern.
That said, using different alloys at different hardness will help prevent galling, and some alloys resist it better than others.
You will likely have to use lower strength rating for the SS versions.
I would suggest that you look at using 17-4PH in the H1025 condition for the pins.
For links and plates an alloy like Nitronic 40 will offer good corrosion resistance and great wear resistance. This alloy only hardens by cold work, I have seen it used at 175ksi UTS and 150ksi yield with it still having usable ductility.

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P.E. Metallurgy, Plymouth Tube

 

[Naz14]

Thanks a bunch for this info. I was keeping away from the 300 series materials because of the galling and potential poor wear ability issues but had not found the "Nitronic 40". but it sounds like it may have some good potential. We totally understand that we will not be able to replicate the strength of the Carbon or Alloy material but because of the old adage, "a chain is only as strong as it's weakest link" some very careful thought is going to be required, Thanks again for the reply.

 

[Compositepro]

Have checked what your competition uses?

 

[Naz14]

I am in the process of doing that right now. A sample of my competitor's product is being sent to me and I will have it analyzed to determine the grade being used but with new technologies and improvements in materials, it certainly doesn't hurt to explore new possibilities. Thanks for the interest.

 

[WKTaylor]

I suspect that wear/fretting, chipping and spall debris are also serious factors to consider...

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[Naz14]

Hey Will,
You are absolutely correct. Since there are two mating pieces, one a convex radii and the other a concave radii, rubbing together under fairly heavy loads any chipping or spalling debris introduced between the two surfaces accelerates wear and critically reduces the life of the chain. With that said, there is also bending motions when traveling around horizontal and vertical bends that can create fatigue issues that challenge the overall integrity of the links and since a conveyor chain is a non-redundant means of conveyance in an production environment, a failure of one link or connecting pin can create catastrophic stoppage of production. Unfortunately, I've seen this type event in automotive assembly plants using various grades of Carbon and alloy steel chains and it ain't pretty, hence I am doing everything possible to find the best corrosion resistant material for leap into the food processing industry. Sorry for the wordy response and I thank you for your interest.

Best Regards, Paul Naz

 

[WKTaylor]

Naz14

Have You considered [aerospace specs cited, likely there are other industrial standards...

Titanium nitride coating
AMS2444 Coating, Titanium Nitride Physical Vapor Deposition
Ref AMS03-28 Part 3 Physical Vapor Deposition of Metals: Physical Vapor Deposition of Titanium Nitride for Surface Protection
Provides high pressure/temperature 'dry' lubricity and wear improvements.

CRES Bearing grades [Typ, aerospace]:
CORROSION RESISTANT NITROGEN (CREN) STEEL [AMS5898, AMS5925]
422 CRES [AMS5655]

CRES Heat treatment:
CREN STEEL PER AMS5898 AND AMS5925 THROUGH HARDEN TO 58 HRC MINIMUM.
CRES PER AMS5655 - CASE HARDEN TO 58 HRC MINIMUM AT A CASE DEPTH OF .030

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[tbuelna]

One of the high-strength Nitronic alloys would be a good choice for the pins to minimize galling. Something like Custom 455 strip might be good for forming the links.

 

[EdStainless]

Tbuelna, I would rather go the other way around, use Nitronic 40 for the plates and and 17-4PH for the pins.
There is no reason to get the pins much over 150ksi yield, since the plates will not be that strong and the galling resistance would be nice for whatever the chain is running on.
Though making the plates from PH SS and using cold drawn Nitronic bar might be much easier to manufacture since the products will be readily available.
I might consider 15-7PH since it has slightly better corrosion resistance (much better than the Custom alloys)

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P.E. Metallurgy, Plymouth Tube