Hardenable stainless?

[timeline1968]

I have a product that currently uses CRS for a 3" roller in a press-type application. This roller is ground undersized, carburized to Rc 58-62 and chromed to prevent rusting.

It seems to me that this is overkill for this particular application since the press is only used to create impressions of fish scales between two plastic slides.

The diameter of these rollers is really meaningless (doesn't need to be held to the +/- .0005" called out on the original print) and I really can't see where it needs to be Rc 58-62 either. Maybe something in the Rc 40 range would suffice since it's only plastic against the rollers, never any metal or even the fish scales themselves.

So, my question is, what kind of steel (with processing) or stainless (that's hardenable? I'm thinking 17-4 PH?) should I use that will be rust resistant, semi hard and less costly for this application?

Any ideas or information would be greatly appreciated.

 

[rharr]

It could be the chrome is for a better release with the plastic. And the hardness was intended to provide a more durable surface that will stand up to repeated cleaning.
What are the finish requirements? A highly polished finish will last longer on the hardened and chromed surface.

 

[unclesyd]

!7/4 PH SS would be good one try if a lower hardness is acceptable.
You can get 40-46 Rc with a heat treatment of 4 hrs @ 925F. Use a good temperature controlled oven for the heat treatment.

If you later determine that you need something harder, materials like 440C will get you at or above your existing materials hardness range. The only problem is that it needs a different heat treatment.

 

[timeline1968]

There are no finish callouts on this print. If I were to add a finish callout it would be in the range of maybe 8 or 4 micro inches.

 

[EdStainless]

My hunch is that surface finish is critical. If there are any filler in the plastic this could be driving the hardness requirement. Any of the PH grades would be a good place to start, 17-4, 17-7 are the most common.
You do need to think about the level of corrosion resistance. Make sure that you don't end up with the same problem.

= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[tripleZ]

440C will give you the hardness. I manufacture food grinder plates out of 440C and hit 53-57 HRc in a heat treated/tempered state.

Cost is likely what will be prohibitive though. CRS is cheap, and chrome platers are abundant (at least in my next of the woods). SS isn't exactly the cheapest commodity out there now, which is why I'm guessing you're using the combo that you are.

 

[GTMule]

I think you'll find the cost of any 3" 17-4 Stainless is going to way outweigh any process savings. I'd figure on 8-10X the material cost, Precip hardening the 17-4 might cost the same or a little more than carburizing the CRS. Machining is going to be WAY more, and all you'll save on is losing the chrome plate.

I'd say you'd see some savings by opening up the .0005" diameter tolerance. You might could also look at some different options for obtaining the surf hardness and anti-corrosion props.