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Metals in Submarines

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Lachlan Bowman

on 10 September 2014

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Transcript of Metals in Submarines

Metals in Submarines
To make a submarine effective in its environment, what metals are required?
When building a submarine, a lot of research must go into discovering which metal is going to be the best one for the job.

Using a base metal may not fill the full criteria that is required for the submarine to function effieciently in its environment, which is for the most part deep underwater.

By analysing the properties and suitabilities of different alloys, we can find out which metals would be suitable for working as the outer casing of a submarine.
What is an Alloy?
Properties required?
An alloy is essentially, a mix between two or more metals that have bonded chemically & physically to give the alloy specific properties not found in the base metals alone.
The metal most commonly used in submarines are forms of steel, an alloy made of mostly iron with carbon within it as well.
Steel has many useful properties such as a high density giving it strength, malluablity and an ability to be shaped. There are several properties that are required and not covered by steel alone, can an alternative alloy be used that covers all criteria.
Hillerts, 2012
A metal that is to be used in builiding a submarine would require certain properties and attributes to deal with some of the problems that are encountered.
Some of the problems that need to be addressed are:
The ability to withstand high amounts of underwater pressure when the submarine travels at low depths.
The ability of the metal to be made into thick sheets that can be curved and shaped into a hull that will stay stable.
The ability to withstand corrosion and avoidance of oxidizing reactions such as rust.
Light weight enough that it can be fast and effective when traveling underwater.
Non-magnetic for stealth and avoiding having a magnetic signature that can be tracked.
Underwater Pressure
When experiencing high amounts of pressure caused by the oustide water pushing inwards, the shape and density are important in making sure the submarine doesn't fold in on itself.
A metal alloy that would be able to withstand underwater pressure deep below the surface would need to be:
Strong with a high density that cant be broken easily when faced with pressure. Not brittle.
Able to be molded and shaped into a rounded, hemisphere shape to avoid being crushed.
Able to be flexible enough so that it can expand and retract slightly when faced with varying depths and water pressures.
A metal alloy needs to be able to withstand pressure to a certain, maximum point and then be able to yield or elongate enough that the metal doesn't break.
Currently, different navies use different metals to regulate and withstand underwater pressure. Examples today include titanium as it is strong and hard, a flexible steel alloy that bends to accommodate different pressures and other steel alloys with higher pressure ratings.
The right balance and ratios of metals in an alloy are important to making sure the metal has the right properties for the job.
The steel alloy will have to be able to withstand the outside pressure to its maximum ability and then be flexible so the metal doesn't just snap and break. By choosing a base, hard metal that can withstand high amounts of pressure like titanium or iron and then adding in a certain amount of other metals to make it flexible, an effective solution will be made.
Metals that can increase the elasticity in an alloy include:
Some metals that can increase hardness in an alloy include:

Corrosion Avoidance
Corrosion is a natural chemical reaction that occurs when the manufactured metal reacts or oxidises with the oxygen in the air or water surrounding it, returning it to its natural state eventually. Iron oxide or rust as it is more commonly known as, is a perfect example of corrossion.
The metal that makes up the hull of the submarine needs to be non corossive or it can lead to weakeness in the metal which can lead to leaks, holes and collapses under pressure.
Metals that don't corrode in sea water include:
Durimet Monel
Hasteloy B
Hasteloy C
Cobalt base alloy 6
Davis, U. (2012). Corrosion. Available: http://chemwiki.ucdavis.edu/Analytical_Chemistry/Electrochemistry/Case_Studies/Corrosion. Last accessed 27th Aug 2014.

Bell, T. (2014). Malleability. Available: http://metals.about.com/od/metallurgy/a/Malleability.htm. Last accessed 27th Aug 2014.

Tone, E. (2010). Metals and Corrosion Resistance. Available: http://www.engineeringtoolbox.com/metal-corrosion-resistance-d_491.html. Last accessed 27th Aug 2014.

Dr.Hillert, M. (2012). What are alloys?. Available: http://www.eurometaux.org/MetalsToday/MetalsFAQs/Whatarealloys.aspx. Last accessed 26th Aug 2014.

Jones, E. (2006). Test Depth and High Yield. Available: http://www.submarineresearch.com/bull31.html. Last accessed 8th Sep 2014.

Clark, J. (2012). Metallic Structures. Available: http://www.chemguide.co.uk/atoms/structures/metals.html. Last accessed 8th Sep 2014.

Calder, V. (2012). Non-Magnetic Metals. Available: http://www.newton.dep.anl.gov/askasci/phy05/phy05054.htm. Last accessed 9th Sep 2014.

Pike, J. (2013). Titanium Submarines. Available: http://www.globalsecurity.org/military/world/russia/pl-ti.htm. Last accessed 9th Sep 2014.

Gray, T. (2013). Chromium. Available: http://www.periodictable.com/index.html. Last accessed 8th Sep 2014.

http:// www.youtube.com/watch?v=hfmD1RyUWgY
(Davis, 2012)
Malleability, lightweight and sturdy
The thickness and strength of the hull is important in finding the right alloy and a balance between lightweight but sturdy must be achieved.
Malleaability also plays a part in this as it can regulate the thickness of the metal and allow it to be rolled into plates or sheets.
(Tone, 2010)
The thinner the metal hull, generally the smaller the submarine. Submarines made for speed will instead of using a more lightweight material, use the same material rolled into thinner plates.
Speed submarines use steel, around 1 and half inches thick whereas larger and more modern submarines hulls are 2-3 inches thick to allow them to dive deeper.
The malleability of a metal is to what extent the metal can be formed, shaped or flattened into a sheet. The external hull of a submarine needs to be a specific curvature to allow for the pressure outside it. The malleability of a metal is often measured by how much compressive strength it maintains or how much pressure can be withstood without breaking.
Metals that have a high malleability rate include:
(Bell, 2014)
Submarines are mostly used in warfare and therefore stealth and the avoidance of detection can be an important problem to be addressed when choosing a metal.
If a metal was giving off a strong magnetic signal then it may show up on enemies radars and detection systems. For this reason the metal that is used for the hull is not going to be effective if it has a magnetic signal attatched to it.
Metals that are non-magnetic include:
So which metal is the best for the job?
To incorporate all the necessary properties into one metal, an alloy must be formed using the right proportions of different metals.
The properties required were:
Atomic Structure of Alloys
Pure metals have atoms that are arranged in evenly spaced rows and columns. The electrons of each individual atom are delocalised and are 'shared' between the other atoms in the metal, moving around randomly.
Alloys have atoms from other metals that have been melted in with the base metal. This mix of other atoms changes the properties of the metal. Depending on which metals are added can affect the flow of atoms (conductivity), restrict or give access to movement and shaping, ultimately making the metal harder or softer (density and malleability). The atoms can still be arranged in these rows and columns but the size of the additives atoms can affect how the electrons react when forces are applied to the metal now.
(Jones 2006)
(Jones 2006)
(Clarke, 2012)
(Clarke, 2012)
(Calder, 2012)
(PBS Learning Media)
By comparing these metals and their properties I have been able to find an alloy that matches this criteria.
The base metal would be Titanium, as it is hard and strong, capable of withstanding pressure, able to be shaped properly and it is non-corrosive. To give the metal more yield and make it softer slightly, I would add Chromium or Carbon to the alloy, this could also make it more malleable. Trying to achieve a sense of non magnetism in the hull would be difficult as these metals can be magnetic to a certain degree but by adding some non-magnetic metals such as Lead or Zinc it could try and block some excess magnetism .
(Gray, 2013)
(Toose, 2012)
Toose, M. (2012). Understanding Air and its Relationship to 5 key areas in Scuba Diving. Available: http://divewithmia.com/understanding-air-and-its-relationship-to-5-key-areas-in-scuba-diving. Last accessed 10th Sep 2014.
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