Magnetic Corrosion Resistant Alloy Selection 2

[mighoser]

Looking for an upgrade to PH stainless which is more corrosion resistant (down hole conditions), stronger, and easily weldable (autogenously). Basically, I'd like a magnetic version of MP35N. Ideas??? I've looked at some of the duplex alloys and strength and weldability are of concern.

 

[CoryPad]

I think Ferrium S53 might meet your needs:

http://www.questek.com/ferrium-s53.html

 

[EdStainless]

Good luck, there is no such animal.
In order to get good strength and control phases at higher alloy content you end up going to an austenitic matrix.
And then they are non-magnetic.
Calling any age hardening alloy weldable is a stretch, you have to assume that you will re-anneal and age after welding. Or that you will weld with an austenitic filler and live with much softer welds.

How much more corrosion resistance do you need?
How magnetic do you need it?

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Plymouth Tube

 

[MagBen]

what kinds of magnetic properties are you looking for? Magnetic stainless alloys are normally ferritic with moderate mech strengths. For a decent magnetics, you would go for an Fe-based alloy, for a high mech strength while magnetic, you would go with a martensitic PH grade. Carpenter CUSTOM 450 TOURALLY 200 may be a choice.

 

[EdStainless]

I presume that he needs more corrosion resistance than 15-7PH.
However if he has only been using 17-4 then 15-7 might be an option.
C450 has rather unimpressive corrosion resistance.
C465 is better, but not quite weldable.

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Plymouth Tube

 

[MagBen]

Ed, nice to see you know carpenter's alloys. It is true C465 is better in terms of tensile strength. however, C450 is better in corrosion resistance and weldability. Among C450, C455, C465, C475, the smaller the number afer "C", the better corrosion, and better weldablity, but the worse the mechnical.
15-7PH is semi-martensitic, the austenitic would degrade the magnetics.

 

[EdStainless]

But 15-7 is the highest PRE you will find in a magnetic PH alloy.
Unless someone is still making AM350, it would be a little better.
Yes, C450 may be the easiest to work with and the best corrosion resistance. C465 is a pain unless you are dealing with very light sections.

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Plymouth Tube

 

[tbuelna]

When you say the material must be "weldable", what does that mean? Does the material need to be weldable using fusion welding processes like TIG or laser? Or is it possible to use solid state processes like friction or inertia welding? Solid state welding processes will result in a much higher quality weld joint than using a fusion weld process.

 

[MagBen]

Solid state welding can work basically for any alloys, including dissimiliar metals. but there are limitations: inertia has geometrical requirements (tight concentricity), the biggest problem for friction is the pin tooling, especially for these PH alloys. Friction stir is mainly used for Al, Cu alloys.

 

[tbuelna]

The OP asked about an autogenous welding process, which would include fusion welding processes like TIG, EB and laser, as well as solid state joining processes like inertia, friction and stir welding or diffusion bonding. As noted, inertia welding is limited to axisymmetric joints with limited cross section. Friction welds can be produced using linear or rotating processes.

The advantage of solid state joining processes is that the material at the weld interface is only heated to a plastic state, and does not undergo the phase change from solid-liquid-solid that a fusion weld involves. So the microstructure of a solid state weld is much closer to that of the basis material than that existing in a fusion weld.

 

[EdStainless]

But with any age hardening alloy you must expect to re-anneal and age after welding, buy any method, if you want the optimal properties.

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Plymouth Tube

 

[racookpe1978]

But won't that very re-annealing process step "un-magnetize" the metal because the time and heat are changing the crystal structure? If so, and I have to confess I don't know this metal very well, does he have to re-magnetize the final assembly if he wants it to hold a magnetic field of any given value and direction? Or does he anneal the assembly within a magnetic field of the proper configuration as it cools?

Or does he merely need the final assembly to be able to be picked up by an external magnetic field?

 

[EdStainless]

I presume that he wants a material that is ferromagnetic.
With the iron based age hardening materials they become more magnetic as you age them.
Some (such as 17-7PH) are non-magnetic when annealed and very magnetic when aged.
Others are at least weakly magnetic when aged and the very magnetic when aged as well.

After the anneal you would age the material to the desired strength level.

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Plymouth Tube

 

[mighoser]

Thank you all for replying. The material will be welded autogenously weld using TIG or laser. I realize that the heat effected zone is going to lose some strength but this is acceptable since we've fielded 17-4PH H1025 product for decades. The application is down hole oil well operations were some customers used magnetic properties to "fish" tools out. Customers who don't require magnetic properties get MP35N in the NACE approved condition. This alloy is light years ahead of 17-4PH for corrosion resistance and a good bump in strength. My objective is to find a magnetic equivalent. I'd even consider an equal strength equivalent but with corrosion resistance of MP35N. Pardon my generalities.

 

[EdStainless]

There is no ferromagnetic alloy with corrosion that begins to approach MP35N.
You can't get that high of Cr without going to an austenitic structure.
Of course calling MP35N weldable is a stretch of that term. When you autogenous weld aged hardened alloys you get the worst of both worlds. A brittle weld and a very low strength HAZ, but if it works I won't argue.

Either go with a high strength steel and give up corrosion resistance (Ferrium M54), or stay with what you have.
So why do you need more strength? Tensile loading? It can't be because of exterior pressure, because strength does not help with crush resistance.


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Plymouth Tube

 

[mighoser]

I don't need more strength. I'd settle for a 17-4PH strength alloy with MP35N corrosion. From a regulatory perspective, making an alloy change to equal or higher strength is appealing. I hear your point regarding bucking failure modes. With MP35N cobalt content we do gain some in stiffness so that helps. I was looking as duplex alloys but the yields are less than 100 KSI. I think 130-150 KSI min would be acceptable and 180 KSI would be preferred.