Some questions regarding steel and polymer

[_Sarcasticat_]

Hello all (at least those who've decided to click on this thread, and I hope those that have actually have the ability to answer my questions...)

 

I've been getting a little into the very intricate art of ship design lately and and I was wondering about steel, the ubiquitous metal that holds - quite literally - our first and old-world civilizations. There is a lot to steel as I am learning and I couldn't find much on the different types of grades and, more specifically, how other elements help create a better or more specialized steel. Elements like Boron, Lead, Moly, Silicone, etc. How do those elements affect steel, or at least Carbon Steel (I know Carbon and Chromium Steels at least so there's that). Also, a nice, good chart of AISI steel grades for all the different steels would be much, MUCH appreciated.

 

 

That aside, I would like to know what the best grade and type of steel would be best for shipbuilding - or the steel used in framing and then steel plates (also, do welded ships actually have frames?).

 

Now, here's a question to boggle the mind: what of Polymer 2 (as in, the type of Polymer used in Glock pistols)? Would IT be a suitable material for shipbuilding, despite it's plastic nature? Some boats I know actually are, but what of a warship? Something like a Wickes or Fletcher?

 

These questions, answered, would be much appreciated. Thanks!

[Nhi_Vanye]

This is a stupendously complex subject that would take many texts and graduate courses in materials science to cover.  In simplest terms, the various elements that are added to iron to make different types of steels affect the way that the iron forms crystalline structures when it converts from a liquid to a solid.  The impurities (carbon, nickel, etc) cause the size, shape and orientation of the crystalline structures to change.  These changes affect the properties of the metal in a wide variety of ways, including its tensile strength, brittleness, hardness, ductility, elasticity, and even its chemical reactiveness (an example is chromium in modest proportions inhibits oxidation).  These properties can also be modified by the conditions under which the metal makes its transformation (temperature, pressure, etc.).

As for making warship hulls, that is also a supremely complex topic.  In theory, any material with a combination of sufficient tensile strength and sufficient elasticity could be used to make a ship hull.  In practice, economic realities have a huge impact on what materials actually get used.  Ship hulls undergo a lot of complex stresses, and need to not only be strong and flexible, but also cheap to make and easy to repair.  Various reinforced plastics are often used to make small hulls that can be formed in a single build because they can be cheaply made that way.  Unfortunately, mechanisms to join reinforced plastics to one another tend to be much weaker and more subject to working stress than "solid" pieces, so they are rarely used for really large hulls.  Steel, and frequently these days, aluminum alloys are common because they have high strength to weight properties, good elasticity (when properly manufactured), and are relatively easy to join together into very large structures that maintain the strength and elasticity of the base materials.  You can access some pretty good basic texts on marine architecture through iBooks.  They will discuss the basic uses of materials for various structural components of ships from both an engineering and an economic standpoint.  I don't know of any freely available texts like that although you might try a local university library.

Good luck in your search.

Oh, and yes, welded ships to indeed have frames.  The welding does add structural strength, but would not inhibit inelastic deformation enough without the hull being overly thick (and thus both heavy and expensive).

[MrDeaf]

https://en.wikipedia.org/wiki/Alloy_steel

[_Sarcasticat_]

16 hours ago, Nhi_Vanye said:

This is a stupendously complex subject that would take many texts and graduate courses in materials science to cover.  In simplest terms, the various elements that are added to iron to make different types of steels affect the way that the iron forms crystalline structures when it converts from a liquid to a solid.  The impurities (carbon, nickel, etc) cause the size, shape and orientation of the crystalline structures to change.  These changes affect the properties of the metal in a wide variety of ways, including its tensile strength, brittleness, hardness, ductility, elasticity, and even its chemical reactiveness (an example is chromium in modest proportions inhibits oxidation).  These properties can also be modified by the conditions under which the metal makes its transformation (temperature, pressure, etc.).

As for making warship hulls, that is also a supremely complex topic.  In theory, any material with a combination of sufficient tensile strength and sufficient elasticity could be used to make a ship hull.  In practice, economic realities have a huge impact on what materials actually get used.  Ship hulls undergo a lot of complex stresses, and need to not only be strong and flexible, but also cheap to make and easy to repair.  Various reinforced plastics are often used to make small hulls that can be formed in a single build because they can be cheaply made that way.  Unfortunately, mechanisms to join reinforced plastics to one another tend to be much weaker and more subject to working stress than "solid" pieces, so they are rarely used for really large hulls.  Steel, and frequently these days, aluminum alloys are common because they have high strength to weight properties, good elasticity (when properly manufactured), and are relatively easy to join together into very large structures that maintain the strength and elasticity of the base materials.  You can access some pretty good basic texts on marine architecture through iBooks.  They will discuss the basic uses of materials for various structural components of ships from both an engineering and an economic standpoint.  I don't know of any freely available texts like that although you might try a local university library.

Good luck in your search.

Oh, and yes, welded ships to indeed have frames.  The welding does add structural strength, but would not inhibit inelastic deformation enough without the hull being overly thick (and thus both heavy and expensive).

I understand the complexity but I'm looking for a dumbed-down version - if even really possible - to help me gather an understanding. If I remember correctly, there are HUNDREDS of SAE/AISI steel grade designations under very many different types of steel. What I'm looking for might include a variety of different steels to deal with stress of elasticity (perhaps in the frame) and then the strength and durability as well as protection from rust (on the side plating). I guess you could also say I'm looking for a structured list of the best steels in each category from best to worst, but is even that possible?

Thanks for answering that question on the plastics. I am 100% sure Polymer 2 would be a much better material than carbon steels but if the methods for holding them together are weak, then there's no real reason to use it. Forming a 100 meter x 11 meter x ~6 meter Destroyer entirely would, of course, today at least, be impossible. 

Hmm. These Aluminum alloys, I've read a little on them...Any good as hulls? I hear that they can match steel strength for a greatly reduced weight but can they even handle stressful applications light a boat? They do well as airplanes...

iBooks? Never heard of it but I'll look into it.

Also, regarding welded hulls, would you personally use one? In something small, of course. Deformation of the hull does not appeal to me, but what about Arleigh-Burke-class DDs? Are their hulls not welded? Then again, I'm not sure of their thickness.

 

13 hours ago, MrDeaf said:

https://en.wikipedia.org/wiki/Alloy_steel

Thanks.

[Nhi_Vanye]

I believe that the new LCS ships are made with welded aluminum hulls.  Many people feel that these hulls are not durable enough, and that the Navy should use steel alloys instead as they are better at resisting combat damage.  I believe that almost all modern navy ships are welded hulls.  The point is that the welded hulls are supported by a frame made of alloy steel that strengthens, stiffens, and distributes the loads over a greater area of the hull.  If you look at some of the analysis of the USS Cole damage, you can see an example of a welded hull DD with a backing frame.

[MrDeaf]

Aluminum, although highly corrosion resistant, can corrode when constantly exposed to salt water.

https://www.boatingmag.com/protecting-aluminum-boats-from-salt-water-corrosion#page-17

These days, the going materials for machines are carbon fiber, titanium and stainless steel.
Carbon fiber is easiest to work with, Titanium is expensive, while stainless steel is difficult to weld.

Although carbon fiber is easiest to work with, I don't think anyone has attempted to build a >1000t displacement ship out of it yet.
Basically, the issue is that carbon fiber has almost no give and if it gets rolled around in rough waves, there's no telling how well the ship will react to it.