Alternative to 316L SS

[Cpt Mark]

A while back somebody posted about a newer version of SS than 316L. Lighter, stronger, more corrosion resistance and of course a bit pricier. I thought I'd made a note on it somewhere but no luck finding it. If anyone has an idea of what I'm asking about, please let me know.

Thanks,

Mark

[dlj]

Originally Posted by Cpt Mark

A while back somebody posted about a newer version of SS than 316L. Lighter, stronger, more corrosion resistance and of course a bit pricier. I thought I'd made a note on it somewhere but no luck finding it. If anyone has an idea of what I'm asking about, please let me know.

Thanks,

Mark

In what context did you see the original post?

The "lighter" part I don't think you'll get in a stainless steel, but for both stronger and more corrosion resistant I could give you suggestions. But you'd have to give me more to go on... Most of the "marine" conversations currently are talking about titanium alloys, specificallly Ti6Al4V. That alloy fits the - lighter, stronger and more corrosion resistant - description you've posted. It's a significantly more expensive alloy. There are also some ferritic alloys that are gaining popularity that are stronger than 316L and arguably with some improvements in corrosion resistance, they aren't lighter. There are also precipitation hardening stainless steels. Lots of choices...

What do you want to use it for?

dj

[s/v Jedi]

Originally Posted by Cpt Mark

A while back somebody posted about a newer version of SS than 316L. Lighter, stronger, more corrosion resistance and of course a bit pricier. I thought I'd made a note on it somewhere but no luck finding it. If anyone has an idea of what I'm asking about, please let me know.

Thanks,

Mark

I think it is Nitronic that you’re after… think of it as 316L but twice as strong, so you could save weight for equal strength.
https://en.wikipedia.org/wiki/Nitronic

[dlj]

Originally Posted by s/v Jedi

I think it is Nitronic that you’re after… think of it as 316L but twice as strong, so you could save weight for equal strength.
https://en.wikipedia.org/wiki/Nitronic

I hadn't thought about reducing cross section to get equal strength for a part. I was thinking density. Using that logic any of the higher strength stainless steels would fit.

Rod rigging is typically made from Nitronic 50, definitely stronger and more corrosoin resistant that 316L. There's also Nitronic 60, haven't seen that one used in the marine world so much, but also the same applies. Those are both austenitic stainless steels like 316L...

Nice one!

dj

[jordanbigel]

What about Aquamet 22 - I was going to say that it is another name for Nitronic 50, but after a little googling before I spoke, I found this illuminating article - the bottom line seems to be that Nitronic 50 has better corrosion resistance, but less strength than Aquamet, which (according to this article) is why it is used for shafts instead of Nitronic.

Although the chemical composition of Nitronic 50 and “the alloy commonly used in propeller shafts,” Aquamet 22, is essentially the same, there is a significant difference in the thermal processing of these two products. Aquamet 22, the boat shaft (propeller shaft) alloy, receives no thermal processing following the conversion from billet to bar stock. Nitronic 50, on the other hand, is solution-annealed at some temperature between 1,850° F and 2,200° F, after rolling, to place the material in a condition of ultimate corrosion resistance. So, even though the two productsAquamet 22 and Nitronic 50have the same chemical composition, they have significantly different thermal processing. The combination of chemical composition and thermal processing is necessary to give Nitronic 50 its superior corrosion-resistance properties.


https://oceannavigator.com/reader-ti...lt-definition/

[Jim Cate]

Perhaps you are thinking of the duplex stainless alloys, 2205 being a commonly used one. Roughly twice as strong as 316 and much more resistant to crevice corrosion... and not terribly expensive either. Our chainplates, prop shaft and rudder stock are 2205 and are holding up very well at 31 years of age. There are also super duplex alloys, even stronger, but I have no experience with them.

There is no significant difference in density between any of the ss alloys.

Jim

[Cpt Mark]

This site is amazing. Ask a question and voila... in most cases you get an answer or a ton of answers.

Jim Cate had the one I was looking for. Not sure it's a possibility for my application so I'm going to ask another question of you all.

I have a catamaran, IPY, Packet cat 35. The mainsheet is attached to a dead head? Single point aft and low, no traveller. The mainsheet angle due to length of boom hits me in the back of the head while sitting at the helm. Very annoying. I also want to put up a hardtop bimini for a few reasons. 1. Solar panels. 2. Sun/weather shade. 3. Be able to easily service the boom/mainsail. (as it is now I have to be very precariously balanced on the helm) 4. move the mainsheet controls to above my head.

I had an engineer spec 2" x 3/16" wall SS 316L as being a strong enough pole to take the loads (live load 1100 lbs) . The aft edge of the hardtop bimini will attach back here.

This bimini will also become the hard dodger as well.

If I can use another metal/product that is strong enough and is lighter that is a very good thing. I'm also curious if aluminum I-beam could work. Bimini is roughly 10'x10'. Planning on 2 large 72 cell rigid solar panels, 1 on each side. These will be mounted in open space, ie. nothing below them to lessen weight and provide lots of airflow.

Thanks for any ideas. I'll look at nironic as well.

[dlj]

Have you got a sketch of the design with dimensions? I'm having a hard time envisioning what the piece you want to swap out is exactly doing, where it sits, what it's loads might be, and it's length. The 2" X 3/16" - is that round tubular stock?

dj

[Benz]

Look at all the aluminum T-tops and tuna towers out there--very few of them are SS, and that's because Alu is light, strong, and easy to engineer for those sorts of applications. Have your engineer spec. aluminum, remembering that the integral structure for the bimini can be designed to spread the load.

[s/v Jedi]

For Nitronic: many boats have Lewmar self tailing winches. The self tailer shiny piece of metal is Nitronic 50 (from memory but pretty sure). Never stains, perfect alloy for boats.

But in this case I agree that aluminum sounds like a better choice

[dlj]

Just as a FYI - there are several concerns that are not being talked about that come into play here where a "specialty" alloy may be desired compared with a "comodity" alloy.

1) the availability of a wide varieties of shapes. Comodity alloys, like 316L, come in all sorts of sizes and shapes including tubular cross-sections. The specialty alloys are available only in limited stock sizes. So if your design requires a shape that is not available, you'd have to have a larger stock size modified to meet your size requirements. This is a very expensive step to perform.

2) Joining to the specialty alloy - how are you going to attach other parts to this member? If done through mechanical fastening, not too bad, but what if you want to weld another part to this piece? You either have to now use the same material at that weld or you'll have a dissimilar metal weld where you are joining the specialty to comody (likely) alloy - does your welder know how to do this? These can be some of the most complex weld problems you can face...

3) At some time in the future you may wish to repair this piece, change the piece, add to the structure etc. - Are you going to continue to use this specialty alloy? What if you are in some remote part of the world? Sailboats do tend to move around...

Just some food for thought...

dj

[EWOL Props]

Totally agree ! Duplex and Super-Duplex are great !
Also to be considered that higher strength allows for reduced dimensions (so lower weight) while keeping the same resistance or increase resistance at same dimensions and weight.

Originally Posted by Jim Cate

Perhaps you are thinking of the duplex stainless alloys, 2205 being a commonly used one. Roughly twice as strong as 316 and much more resistant to crevice corrosion... and not terribly expensive either. Our chainplates, prop shaft and rudder stock are 2205 and are holding up very well at 31 years of age. There are also super duplex alloys, even stronger, but I have no experience with them.

There is no significant difference in density between any of the ss alloys.

Jim

[PUDDLE JUMPER II]

Sent you a PM to discuss the particulars working with 2205SS if you have a moment sir? Thanks...

Thomas

[coopec43]

Mark
Is this what you are looking for? (I can't see where "nitronic" or 2205 is mentioned though?)

A new class of lightweight, stainless steels with ultra-high ...

by J Moon · 2020 · Cited by 18 — Here, we report a leap forward toward this aim through the development of a new family of low-density stainless steels with ultra-high strength

https://www.nature.com › scientific reports › articles

https://www.mpie.de/4401449/lightwei...-high_strength