Hardest Stainless Steel Gades

[tangled]

I'm trying to find the hardest and strongest possible stainless steel, I have been recomended 17-4ph 900, what are the alternatives?

I also need to find the hardest and strongest non-mag stainless steel, I belive we are using nitronic?

The steel is needed to make tips for probes we push in the ground, the non-mag version houses a magnetometer.


Thanks.

 

[TVP]

Hardest and strongest are not the same thing. 17-4 PH is an excellent choice for strength, but 440C will have the highest hardness. 440c is a martensitic stainless steel (magnetic) that is used for bearing applications, so it has high surface hardness, but low ductility and fracture toughness. Very high strength under compression, but limited tensile strength. EdStainless or mcguire will probably have some recommendations for non-magnetic grades.

 

[mcguire]

Non-magnetic and strong is a short list. Use A-286. You can get 1300 MPa yield, 1400 MPa tensile. It's the only precipitation hardened austenitic, essentially an iron-base superalloy.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[arunmrao]

Can you try Kolsterising on 316 grade stainless steel. This will give all the benefits of a non magnetic material with a very wear resistant surface and corrosion resistance being intact. Hope it helps.

 

[tangled]

Thanks that's all very helpful.

440c is interesting, one supplier is quoting an elongation factor of 2% min, is this the same as fracture toughness? I worry these quality's will make 440c unsuitable due to side loads experienced when pushing through glacial till.

A-286 looks to be ideal, thanks.

 

[EdStainless]

What shape is your probe? is it a tube?
You can get cold drawn austenitic stainless (21-6-9) that is fully non-magnetic at strengths in the range of 175ksi.

You would get similar numbers for A286, maybe a bit higher if you cold worked and aged (without an anneal in between).

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Plymouth Tube

 

[mfgenggear]

Arunmrao

Interesting stuff Kolsterising.
is it similar to carbo-nitriding?
are you working with it now.

having a hard surface with a tough core would do the trick?

mfgenggear

 

[arunmrao]

It is a patented process and is proved very successful. You may contact my friend Mr Mario Ciampini from Bodycote Thermal,who can help you with more inputs. Honestly I do not know the process,but only know the benefits.

Mail id is mario.ciampini@bodycote.com

 

[EdStainless]

If you are forcing these into the ground then you need strength, not harness. A hard surface on a softer substrate will not work for you.

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Plymouth Tube

 

[arunmrao]

I assumed that this may not be repetetive,once inserted stays put,and thus made the suggestion,else my first choice would have been 440.

 

[TemperedMartensite]

A few ideas -

ATI S240 in the H950 will give you a hardness of 48-50HRc and a YS of about 230ksi. The advantage it has over 440C is that it is a high-strength PH grade (similar to 17-4ph)so it maintains toughness (10% elongation).

http://www.alleghenytechnologies.com/allvac/pages/PDF/tech/SS-240 S240.pdf

Non-magnetic...

718 to the AMS 5663 specification will give you the highest stregnth - but you are paying the price of nickel.

Another idea is an alloy such as Datalloy 2 ESR. It is a high-strength austenitic stainless steel. It comes with a minimum yield strength of 140ksi. The nice thing is that it is Mn stabalized, so it helps with the cost.

http://www.alleghenytechnologies.com/allvac/pages/PDF/tech/SS-844.pdf

 

[mfgenggear]

Edstainless

why not have a precipitation harden steel core harden
for strength then case harden the surface for wear.


Mfgenggear

 

[EdStainless]

I just didn't see the need for very expensive non-magnetic age hardening grades. We can reach the same strength cold working lower alloys.

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Plymouth Tube

 

[mcguire]

Ed is correct if you're lucky enough to have a geometry which permits cold working. Data 2 sounds clever. ATI has kept its existence a secret pretty well.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[MagnetDave]

Are you married to stainless steel?

I ask, because the magnetic properties of the steel change drastically with strain state, and it can be hard to get consist product magnetically, especially when your desired permeability is 1.

If you need it to be nonmagnetic, you should really consider a nonferrous alloy - inconel, titanium, aluminum, or bronze. I would likely recommend a very strong aluminum, like a well-tempered 7475, since aluminums tend to be cheaper and easier to work with that the others named above.

 

[tangled]

Ed - The probes are repeatedly inserted into the ground, hence the need for a harder material. The nitronic non-mag tips can wear very quickly, I believe the nitronic has a hardness of 95HRb.

ATI S240 looks an improvement on 17/4ph, Custom 465 seems to have very similar characteristics too.

Datalloy also looks good.

Magnetdave - This is interesting, I remember being told of an older magnetometer system we previously used that had bronze tips, I had wondered why they chose that material.

I have tried loading a nitronic tip in a 200kN press, and simpply tested the material with a magnet, I think I may have to load the entire probe and look for a change in o/p.

 

[EdStainless]

If you can tolerate the tip being magnetic then by all means go for making the tip from 440C.
If the tip and body need to be non-magnetic, and it is a fairly small part, then there are a few other alloys that come to mind.
I would seriously consider a tip cast in Tantung. This a non-magnetic and rather hard.

As for your shell, if you having wear issues some as-cold-drawn (not annealed) Nitronic (any of them) will be quite suitable.

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Plymouth Tube

 

[TemperedMartensite]

Tangled,

Yeah, S240 is similar to 465 - except it does not need a deep freeze during processing. I have seen prints that have them both as options.

I know of Datalloy 2 ESR as a drill collar material. However, drill collars are relatively large diameter so if you if you are looking for small diameter stuff you may out of luck.