A Brief History of Naval Armour - Successfully Forging Onwards

[Music] [Music] the history of armor for ships is something that comes in fits and starts throughout early history and across many cultures various experiments came and went with such vessels as the Korean turtle ships carrying a form of iron plate armor there's some American Civil War ships like the kii Asajj improvising armor from iron chains and indeed the wooden holes of HSL warships also being a form of armor as the thick wooden sides of these ships could resist small arms fire and depending on the size of ship and the thickness and species of wood used sometimes even resist the smaller cannonballs in certain cases however the start of the almost unbroken line of development that would bring about the armored battleships of the 20th century had its origins in the first half of the 19th during this period iron was beginning to be manufactured in the quantity and in theory the quality that was needed to use plates and beams of iron to supplement or replace wood in ship construction and there was some initial resistance on the ground that wood floats and iron rather obviously does not but after the demonstration of the first iron barges and the like those who were not entirely okay with things like the lore of displacement were mostly silenced and the first iron ships began to enter service in the civilian world iron held a lot of attractions although it was much denser than wood it was also stronger meaning that a heavily built wooden ship could actually be replicated in iron and weigh less at the same time there were also considerable space savings to be had an iron beam whose thickness was measured in inches could do the job of a wooden beam whose thickness was measured in feet large wooden Timbers were becoming scarce whereas iron could be manufactured at great in great lengths and securely bonded by riveted joints where an even greater length was needed an iron plate an inch thick could replace wooden sides that were feet thick and so overall internal volume became greater and with the lesser weight of the hull great heavier goods could be carried iron didn't wrought iron didn't flex as much as wood did and this promised longer-lasting and physically longer ships now this will sounded great and from a military perspective being stronger iron could resist more shot than any practical thickness of wood iron was not flammable which was very important given recent innovations in explosive shells heated shot and its successor the molten iron filled Martin shell and further tests appear to show that when you shot at it with something that was big enough to punch through it you ended up with a small cannon ball shaped hole that could be fairly easily patched and which resulted in few if any splinters as opposed to wooden ships where a 32 pound or heavier shot coming through was accompanied by a vast cloud of lethal oak splinters and a large ragged hole that was rather difficult to make good assuming that anybody in the nearby vicinity had survived to make the attempt us of course if it sounds too good to be true usually is and in this case there were a number of issues that were less appreciated at first and at least until after the first generation of iron warships had been laid down the mass of the iron in the ship's hull affected the magnetic compasses that were used for navigation of a copper plating that was used to keep marine growth away from ships hulls induced a galvanic battery reaction with the iron of the hull when the ship was emerged in immersed in salt water and this corroded both of them to nothing in fairly short order and having your ship literally dissolve itself away into nothing is a pretty good party trick but not really good for the long-term health of the crew lastly there came news from further tests as well as combat actions abroad that the iron was behaving in strange ways instead of behaving as it had done in tests iron plates were shattering leaving large holes and sending large chunks of razor-edged metal siding through the gun decks massive cracks were developing that ran across multiple decks and often ran the full length of a given plate rather rapidly iron warships were canceled and those that had already been built or were too far along in construction were turned in to survey ships troops tugboats and really practically anything that a Navy could need that wouldn't involve direct combat well what exactly had happened here the problem was one of several material properties of iron and steel which didn't really occur in wood at human livable temperatures if at all and one of these would be the dominant factor in almost all armor development thereafter and was particularly responsible for this particular issue that is the brittle ductile transition this is a bit of engineering material science so forgive me if I get a little bit technical on you but this is one of the fields I studied for our engineering degree and one that I was a relatively good at essentially iron has what you is called an impact energy that is the amount of energy you need to hit it with with a kinetic impact in order to break it the kinetic impact being something like say shooting at it with a cannon shot or an explosive shell however this energy varies as you can see on this lovely graph according to the temperature of the metal involved it's a rather steep gradient in most cases and below a certain point of temperature significantly less energy is needed to break the iron that is needed much above that point the nature of the failure is also key an impact that occurs to the left of this transitional line will cause a brittle failure which is essentially a shattering effect that you might more commonly associate with glass or something that's been dropped in liquid nitrogen which is actually the same brittle ductile transition effect just dropping the temperature of practically anything that you can handle below its own transition point above this you get ductile failure that's to the right of the line and this involves the material splitting and bending again to use an extreme example this is an effect a bit more like poking a hole in a sheet of cardboard with a pencil or stabbing into a plastics drinks bottle now the early tests of cannon against iron had seen the latter ductile behavior now reports were coming in of the brittle type of failure but the material being used on the ships was not that much removed from the material they've been used in the test so what was the problem well it was this change in temperature a sheet of iron set up on a grassy field on a summer's day would be considerably warmer than practically any metal sheet built into the side of a ship that was then placed in a cold ocean in some very warm environments such as the shallow coastal waters off china ships like the east india merchant vessel nemesis had still seemed ductile behavior but in the more common deep ocean environment that covered most of the planet and the north atlantic horns of most of the major navies at the time the brittle behavior was experienced which not only meant that iron ships would resist shot far less well than expected in the first place because of that lower impact energy but the damage caused would also be far greater there are also further complications that weird ships hulls cracking under the stress of oceanic operations instead of flexing as it was intended but that's a completely different story there was one other factor that was playing into all of this and that was the presence of trace elements or impurities in the iron as you can see these change the duration and location of the brittle to ductile transition point on the scale of temperature as well as making a difference to the overall resistance of the iron because of course the iron that was being forged was not pure elemental iron we leave that to doors who dig too greedily and too deep the presence of carbon manganese chromium molybdenum all sorts of other random little bits and pieces would all have their own effect and more on some of those later but it just so happened that the mix of trace elements in iron produced at the time placed the transition point squarely in the operational temp range of temperatures that warships would experience with the most of that transition occurring at somewhat of the higher end of things and this was the cause of the unexpected issues and the fact the iron was performing completely differently depending on how warm the environment was and so it was the the use of metal protection for shipping had dropped back a little bit until the Crimean War during this period the Industrial Revolution was taking place and iron was being produced in large amounts mean thicker plates and in slightly different mixtures with improvements to purity as well leading to changes in the overall resistance and the material behavior of iron plate and so during this Crimean conflict a floating batteries coated in iron plates were employed having been proposed a few years ago by a number of different inventors these proved to be highly proficient at keeping out shot and shell pointing the way forward and indicating that armoring of ships against incoming fire was both now possible and practical now before we usher in the age of armour a few more notes on iron and eventually steel production there were other factors that would go on to affect the material properties of the material the method of production mattered both in manufacture and in finish removing contact between the fuel and the iron with the development of puddling furnaces allow a much greater degree of control over the level of impurities whether you wanted them or whether you wanted to get rid of them and other techniques would follow during the development of armor as we'll see when it becomes more relevant but the main thing to take away at this point is those puddling furnaces since this removed iron and later steel production from the old-school method where you would end up with the raw ore in amongst the burning charcoal coal wood or whatever it was you were using which of course allowed all sorts of fun things that were in your fuel to find their way into your metal additional to this there were various methods of pinning shing you could hammer an ingot down into shape you could compress it between giant rollers and some people experimented with a few other ways and this would of course affect the overall strength and behavior of the metal and the limits on the capabilities of these industries would indeed affect much early armor development in various nations only the most advanced countries for instance had the industrial capacity and capability to manufacture good quality sheets of iron of significant thickness whereas others who could only make thinner plates or poor quality thick plates would have to settle for either lesser thick single thickness protection or laminate thinner sheets and use the sheer bulk that you could achieve in this method to compensate for the deficiencies in resistance that were inherent in laminated metal armor and finally you have how you finish treating the metal whilst this is less of a concern with basic iron as you introduce more trace elements and head towards steel how a metal is cooled how long it takes what temperature you brought up to in the first place and all sorts of other interesting factors become more more important but again we'll cover elements of that when it becomes more relevant essentially what all this leads to in very basic terms is the ability to create metal that can fall anywhere on this rather handy 2x2 grid you have a hard soft also known as strong weak on one axis and brittle ductile on the other a part of strong metal needs a lot of energy to actually break it and a soft weak one needs less and we've already covered for brittle and ductile mean in terms of the manner of failure most commonly metals tend towards either hard and brittle or would make it strong and brittle or soft and ductile or we conduct I'll and you either need to work with this or as we'll see you can start creating esoteric alloys and or production methods to try and get a better mix of behaviors and to give one final set of extreme examples before we get on with the history of armor an example of hard and brittle would be a rock or metal drilling bit which is incredibly hard razor-edged ANCA when it comes out the packaging at least and can eat through lesser metals and stone with relative ease but will also shatter into a million pieces if you happen to drop it six foot onto a concrete floor and can be snapped into if you lock it in a vise and tap it lightly on the side with a hammer conversely soft and ductile would be best represented by her hat perhaps an iron nail a reasonably strong person can bend an iron nail with their hands but unless you bend it back and forth so many times you end up work hardening it it's not actually gonna break work hardening is another factor with metals but it's not one we're going to just now and so after the false dawn of the iron ships the first true armored warships would appear at the close of the 1850s with the new technologies available and the increasing power and destructive ability of naval guns both Britain and France as the leading naval powers at the time we're considering the next step in warship evolution taking lessons from the floating batteries that they'd both used in the recent conflict they had a choice wrought iron which we've discussed mostly in the previous section or cast iron cast iron was cheaper and it had a much higher carbon content but it was brittle and I had a tendency to crack with fractures running the length of the plate features that given their past experience with the iron ship's naval designers weren't exactly keen on thus wrought iron would be the material for the ironclad warship ductile and malleable forms of cast iron were decades in the future the first ships to be so protected would be the French guar class and the British warrior class iron clads the former being wooden ships that were fitted with iron plate and the latter iron ships with armor plate over an iron hull however warrior's armor was given an 18 inch thick teak wood backing whilst gwah likewise retained a portion of the thick wooden hull of age of sail warships since the thicker plates used between four and a half and 4.7 inches depending on the ship and could resist almost any income shot or shell available at the time but to provide resistance against cracking of the plates and they're connecting bolts as well as to catch spalling from the back of the plates the wood was also necessary the wood backing also reduced the chances of penetration by distributing the force of the impact more widely across the plate then the metal plate alone would have done now both ships did have some issues glue was wooden hull flexed and strained at sea under the load imposed by the iron plating as well as its own natural mass and the screws that we used to fit the iron to the wood showed that they were a critical point of failure under fire or indeed under heavy load warriors iron hull was a much better platform to mount the armor to but its own plates were fitted together with tongue and groove joints the theory being to distribute impacts that occurred close to the edges of the plate accrue a jacent plates which was a good idea in principle but turned out to be substantially less effective in practice and the tongue and groove fitting made replacement and maintenance of the armed plates considerably more difficult than it otherwise needed to be material quality was also important Gulas plates were point two of an inch thicker than Warriors Burt gunnery tests by both parties showed that warriors plate was manufactured of superior material as it took less damage when resisting at the same shot now in this period the use of scrap iron was favored in the manufacture of armor plate for a number of reasons when mixed with new iron one of them being that as scrap iron had already been manufactured it had been purified to an extent at least once before which would lead to overall a more controllable output of the new material since even at this point in time the level of control that could be exerted over potentially fatal fatally compromising impurities was still somewhat limited these ships initial success spurred the development inevitably of bigger and better guns to penetrate the new protection which in turn demanded thicker and better armor to counter them in the UK this took the form of the Special Committee on iron which brought together engineers metallurgists and naval architects to work on better sources of raw material a better production methods and better forms of use for iron armor plate including some experiments with inclined armor ironically knowing in full detail the properties of the excellent armor they were developing they were also the best place to advise on how to defeat the said armor with their work also informing gun makers as to the size of their guns the speed of the projectiles and the form and material of shot and shell that would best defeat an enemy ships protection the two main processes for manufacture at this point were hammering and rolling the former method was essentially the same way that swords and other weapons had been hand forged in ancient times only on a much larger scale you'd heat up huge chunks of iron usually a mixture of reused scrap and newly made puddled iron and then a massive mechanical hammers would smash the material together again and again Forge welding it into a single mess and also shaping it to the dimensions and thickness that were needed this was believe it or not a relatively simple method to use and was employed in the making of hms warrior's armor plate as well as that for a number of other early iron clads rolling the plate was harder to do again you'd stack up your various bits of heated iron except now they were fed through giant rollers akin to a gargantuan mangle which squeeze the plates together and down into a thinner single plate this gave a melt more uniform quality of metal compared to the hammering process but whereas the older method of hammering that could be used numerous smaller if still hugely powerful machines the rolling process required a single massive and massively powerful machine which was itself fairly difficult to manufacture and required a huge factory however with Britain being the leading industrial power in less than half a decade managed to make the process significantly easier and much more common the need to build the industry that was required to build machine parts that we needed to build the rolling machines that could then produce the iron plate itself was one of the major bottlenecks for a number of other countries for some years to come and this is why it despite the extensive use of iron armor plate in various forms during the American Civil War which occurred obviously in the 1860s it doesn't feature too highly in the overall development of naval armor since America was one of those countries with this technological bottleneck and but therefore whilst many innovative ways of making armor plate to work such as using railway sleepers and chains as we mentioned earlier and came about during this conflict they were more methods of making do with what you've got rather than pushing the technological envelope however even at this stage five six years after the first armored warships had properly been deployed new methods were being considered and this led to a second if somewhat less disruptive false dawn as the Bessemer process and other related processes in the mid 1850s started to produce large quantities of Steel this was immediately studied as a possible alternate since the much stronger steel was seen to possibly serve to either improve protection or reduce weight as even by this point ships were on the drawing board with double the thickness of armor found aboard the warrior and this meant the arm was beginning to take up more and more of a ships displacement fortunately the system of testing before construction was now fully in place and so when the tests showed that the steel was far too brittle for practical use in ships armor it was put aside as an armored ship material at least for now and without any classes of steel armored warships being prematurely laid down however as time marched on there were physical limits to what you could do to strengthen iron whilst gun and shell technology just kept on going by the 1880s iron plates eighteen to twenty inches or e and thicker were being used to have even a hope of keeping out the latest high-velocity armour-piercing guns which had grown from the relatively short six and seven inch weapons of the early 1860s through to the somewhat longer barreled 12 13 16 and 1/2 and 17 inch guns that were using ever more powerful explosives to propel their shells through the air whereas warrior and her kin had been fully seagoing in order to reduce the target area of the ships so as to minimize the space that needed protection the last iron clads were gradually becoming squatter and less able to handle the open sea and trending more towards giant monitors purely because of the sheer weight of armor they had to carry understanding the relationship between the iron armor and its wooden backing attempts were now made to replicate this effect with steel and iron with the much harder steel in theory resisting or breaking up an incoming shell with the more ductile iron supporting and distributing the load behind it with the steel having so much more resistance per inch this outer face could then be made thinner and thus lighter than the sheer monolithic iron that would be needed otherwise however early attempts to replicate the wood iron combination by simply bolting a steel face on to an iron plate didn't work very well with in some places the steel actually being a detriment as fragments of shattered steel plate were forced back into the iron spreading it apart and making it easier for the shell to force its way through in a manner similar to World War 2 era armor-piercing shells with that they're armor-piercing caps additionally once they were broken shattered shards of armored steel would fall away exposing the now much thinner iron plate to relatively easy penetration by follow-up shots attempts were therefore made to see if making the steel a little bit softer might work which would in theory allow the replacement of the whole belt with a thinner belt of softer steel you didn't have quite the same increase in resistance that you would with a brittle steel but it would still be better than iron on its own and thus you could reduce the thickness somewhat in tests this seemed to be possible but in practice the steel was still far too vulnerable to breaking up under stress these various issues frustrating early French and Italian efforts to get ahead of the game with Britain at this point still the leading industrial power the solution would eventually come from the UK as in the late 1870s the great steelmaking city of Sheffield yielded up to engineers who managed to solve the problem independently a mr. Wilson of John Brown and company worked out a technique that involved placing a wrought iron plate in a casting box and then simply as it might sound pouring a molten steel on top of it whilst mr. Ellis of Cammell Laird took a pre-made steel plate then put it next to an iron plate with a small gap between and poured molten steel into the resulting gap in either case and this created a bonded plate that was made of steel on one side and iron on the other this plate could then be heated up and rolled out to a final thickness with the steel generally making up about a third of the plates overall thickness this gave the world the first successful compound armor as discussed this replicates the effect of backing iron with wood only with the much harder steel taking the place of iron and the iron taking the place of the wood the steel provided superior resistance but the welding effect created by the new manufacturing techniques prevented broken shards from falling off or spreading the iron in the back apart at whilst the iron provided additional resistance whilst preventing weak spots from being exposed by holding onto the steel the iron also spread the shockwave through the whole plate in the same way that the wood did for the iron and kept any broken steel elements together in one location which assisted in resisting follow up shots this overall gave armor an instant kinetic resistance bonus of about 20 to 30 percent depending on the technique the material quality being used and the relative thickness of the two plates that were being sandwiched together not only with this allows ships to continue to be protected against the advancing power of guns but a ship that had previously needed 24 inches of armor could now make do with only 18 inches and it also began to make armoring smaller ships such as cruisers against their own guns much more possible thus paving the way for the rise of the armored Cruiser compound armor however would prove to be the shortest-lived of the armor technologies as steel technology was still advancing at quite the rapid pace which helped compound armor still further obviously as it was made partially of steel but in the latter part of the 1880s those various trace elements we mentioned earlier on began to come into play as a various alloys were now being deliberately created a potent power obviously steel is in an on itself an alloy of iron chrome alloy steel gave shells a massive increase in punching power whilst nickel alloy steel now promised a steel that could stand up to incoming fire on its own without scattering to the four winds this was because nickel steel introduced the element shockingly nickel do the equation which improved the strength of the steel further but also critically improved the toughness which made it less prone to brittle failure which was the key finally failing of steel up to this point the French firms Schneider and Caruso were early innovators in this field whilst the strength increase over compound armor was less than compound armor had been over iron are only about 5% it was still something but as time went on and the 1890s began a major innovation was coming that would refine nickel steel into a substantially better armored material but this time the innovation would not come from Britain but from the United States of America courtesy of mr. Harvey whilst nickel steel had allowed homogeneous steel armor to be made practical it had lost something of the ultra-hard former Steel's resistance to impact but the Harvey process and now exploited the physics of steel to recreate the benefits of compound armor wholly within a single material now it had been known for centuries that the balance of trace elements in steel could be combined with heating the metal to a variety of temperatures to create different forms of steel with different crystal lattices on a molecular level even if the precise science behind this had obviously not been fully comprehended but then further varying how and at what rate the metal was cooled you could affect the crystal growth within the metal as it was brought back down to normal solid temperatures all this affected the material properties of the metal involved and can be illustrated by a phase change diagram such as this one which shows what temperatures created what forms of steel or iron at different levels of carbon or other trace material content and there's pages and pages of these things if you study engineering however unlike forging a sword or a breastplate massive blocks of steel need considerably longer to heat up and take a lot longer to cool down weave commensurately more effort needed if you're going to change this rate of heating or cooling for your benefit the sheer mass of steel also meant that under the Harvey process you could change the properties of some parts of armor plate without this spreading to the whole block if you didn't want it to the changing crystal formations are what are shown on the phase change diagram and it's the alignment and size of these which dictate much of the physical properties of the metal depending of course on trace element content which is why you end up with pages and pages and pages of slightly different phase change diagrams the overall effect that Harvey was going for was called cementing or face hardening under the Harvey process you'd start off with your sheet of nickel steel I you've gone through pretty much all of the process that you'd have gone through to make regular steel armor plate previously then you'd put your flat plate on a platform or other container and heap charcoal over the top of it then set fire to the whole thing and cook gently at about 1,200 degrees Celsius for just over a fortnight bringing smalls to work was apparently optional what this eventually did is to cause carbon from the charcoal to seep into the steel and kind of a reverse process to the puddle furnaces that were designed to remove fuel based impurities now you were using fuel to try and bring those impurities back in specifically the carbon part at least as the steel never actually went molten this higher carbon content was most present in the upper face of the plate and decreased relatively rapidly the further in that you went then with a pair of very large tongs you picked up your steel plate and dipped it in a pool of oil to quench it and then off into a water bath to finish the process off now those of you who've watched shows like forged in fire will know that sticking a very hot piece of metal into water can create a lot of stress and brittleness in the metal possibly even fractures and so the plate would be heated back up again to several hundred degrees and allowed to cool much more slowly this is a process called annealing which gets rid of most of the stress points and generally softens the steel back down again oversee assuming they didn't crack it as things progress this basic formula would be improved in a couple of ways firstly by forging the steel after the water bath which helps to distress it somewhat and secondly by replacing the water bath itself with water jets as it was found that dropping superheated metal into water would cause an awful lot of steam to form at the interface between the water and the steel this mimics the Leidenfrost effect which is when you drop a little droplet of water onto an exceptionally hot frying pan and it races around the frying pan on little cushion of steam and much as the droplet is insulated from the pan by a cushion of steam that it's generating the steel was kept in a water bath from the cooling water by the layer steam that it was generating this of course affected the rate of cooling and made it more difficult to control which factors into that whole phase change diagram we looked at earlier now this process would give you a steel plate with an integral hardened face and a tougher back this gave about a 20% greater level of resistance compared to two nickel steel on its own the Harvie process was rapidly adopted the world over as you could once again drop the thickness of armor for the same protection and thus save weight compared to the old iron plate Harvey steel offered at least 60% greater protection if you took the very best iron compared with the worst standard of manufacturing pass Harvey steel at its best Harvey steel offered double the protection of the average wartime plate that had been in use as little as 10 to 15 years ago it was also found that you could get similar results using the Harvey process if you used normal steel at least in terms of overall shell resistance but due to its tougher nature and thus more ductile back a nickel steel plates would take less widespread damaged if if penetrated once they'd undergone the Harvey process and so was still the superior choice the progress of armor resistance can be seen in that the lost iron protected British battleships the Trafalgar class had 20 inch thick belts whilst racing newer bigger and more powerful guns the follow-on Royal Sovereign Clause had a compound on the belt that nonetheless dropped to 18 inches but left the ship overall better protected then as Harvey Armour was introduced and built protection dropped down to between nine and twelve inches but we're still two generations away from armor in its final form at sea the next development would come from Germany where the Krupp steel works started off with the Harvey process but made a number of changes crop steel was made with chromium added to the normal nickel steel mixture and giving the new steel alloy a capacity for even greater hardness next instead of the bed of charcoal Jets of carbon rich superheated gas were blown into the face of the heat steel at great pressure and following which even more heat in the form of great burner Jets was applied this forced the cementing process ie the introduction of more carbon to the steel much deeper into the face of the steel before this level of heat could reach too far into the plate and about a third of the Steel's overall depth was what you'd want but this was much greater than obviously just the inch or two possible with the Harvey process the face would then be rapidly cooled with pressurized Jets of freezing cold water following which the back which had called more slowly in a bed of clay whilst the cemented front was being blasted by the ice water would also get a jet of cooling liquids this took advantage of the fact that the armor plate was so thick the these huge fluctuations in temperature on one side and took a fair bit of time to translate through to the other now if you kept up with the Mattel G so far you'd recognize this process would give the steel and absurdly hard outer face it was relatively deep as well as the tougher more ductile back to hold it all together and indeed the basic crop steal proved to be about 15 to 20 percent more effective than Harvey steel armor this would be further refined in the early 1900s with slight changes to the steel formula that now included not just ironed carbon nickel and chromium but also trace elements of manganese silicon phosphorus and sulfur this allowed the back of the armor to retain more toughness which reduced spalling and cracking and overall increase the effectiveness by about another 10 percent thus giving the armor that would be used on most chips in the dreadnought race approximately a 30 percent advantage in protection compared to Harvey armor thus despite the continually increasing power of guns armor belts remained relatively static in thickness during the late 1890s and early 1900s the royal navy's armored belts for instance hovering at around 9 inches thickness on their crop armored pre-dreadnought until the Lord Nelson class and then of course dreadnought herself German battleships likewise remainder between nine and ten inches of thickness and American and French vessels at around eleven inches of maximum a thickness as said in a period where gun performance was climbing quickly now at this point it's probably worth a quick summation of the total process of armor manufacture as it now stood remote and different as it was from the manufacture of what now seemed like relatively simple iron plate about twenty to thirty years previously this is taken from a u.s. Navy manual on the subject from the early 20th century step one of the charge of pig iron and or or pig iron and scrap still in use banknote is melted in a basic open hearth furnace and is then poured into an iron or sand mold the dimensions of an ingot are varied to suit conditions for instance an ingot for a three gun turret port plate is about 42 inches by 150 inches by 250 inches and weighs 425 thousand pounds whilst one for a belt plate is about 26 inches thick 132 inches tall and 200 inches wide and weighs about 200,000 pounds step 2 the ingot whilst still hot is stripped from the mold cleaned and prepared for forging step 3 the ingot is then reheated and forged under a hydraulic press to within about 15 percent of the final thickness the forging reduces the ingot to about one third of its previous thickness the segregation of impurities in the central upper portion is discarded by cutting this portion off step four the forging is annealed to produce a partially fibrous condition of the microstructure to prevent cracking in cooling and to eliminate the strains due to forging step 5 it is then super carburized the time required for this step varies with the size of the forging with large forgings taking anything from 10 to 14 days step 6 reheating reforging to nearly the final thickness and annealing an hour follow step 7 several heat treatments may follow to develop the proper physical properties in the metal fibers step 8 the forging is next machined to rough dimensions step 9 it's then reheated and formed to shape step 10 the front face is then heated above the critical temperature depending upon the depth of chill desired and hardened by oil or water spraying step 11 after low heating the curvature of the plate is rectified and step 12 the plate is machined to the finished dimensions that critical temperature of course being where the temperature climbs above the line on the phase change diagram that's necessary to get the desired form of the metal so this then would be the armor that with various combinations and minor variations would see service in pretty much all the various navies of World War one now post-war there was one final further stage of developments this is where the various major armor manufacturers began to go off in their own unique directions as the process of armor manufacturing became more and more secretive and we finally begin to see a divergence in armor capabilities that depends more on the country of origin and not so much on minor variations in manufacturing process and materials one last diversion into material science before we go on by this stage there are many factors to consider when it comes to evaluating the true properties of armor steel and its various resistive properties if enough people want I can go into those and metal crystal structures etc but that will be for another video now back to the world war ii period and the immediate now run-up to it in Germany and the UK further advances were made in the formula for the steel itself introducing even more exotic trace elements such as molybdenum into the mix and making subtle changes in the manufacturing process these advances occurred independently of each other but resulted in british and german face hardened armor steel having superior resistive qualities to the world war 1 standard that almost everyone had used previously now this is where sources disagree i've said before in some Drydocks some give this new formula a 5 to 8% resistive advantage others go as high as 25% better whilst most tend to suggest something in the low teens I personally usually settle at using around 12% in my estimates thus if a ship's armor is of the old type or the ship belongs to a nation that has not made any substantial improvements in their metallurgy since then the armor of say a Scharnhorst or a vanguard at 14 inches thick would be equivalent to almost 16 inches of the armor present on say a Queen Elizabeth Pennsylvania Keizer or fuso class vessel if we're using the 12% bigger in the USA there was a rather disastrous project in the mid nineteen tens that would have a ongoing impact on all US battleship and Cruiser armor thereafter ironically this problem arose out of another part of the same US company having a great success this was Midvale they'd come up with a new way of making stronger shells their so called unbreakable series of shells and indeed they proved quite effective and so they decided to develop a new armor to try and defeat and shatter them since one of the major advantages of Krupp style armor over Harvey Armour was the much deeper hardened face Midvale decided that an even deeper face would obviously be better and went all-in deploying a block of Steel that was 80% hardened face and 20% ductile backing the armor succeeded in shattering the unbreakable shells proving to be not quite unbreakable as everyone thought but further testing using 12 14 and 16 inch variants of the unbreakable shell revealed that in actual fact the resistance of the plate made up as it was a large d extremely hard brittle metal had in fact dropped to about equivalent to Harvey steel only the sheer mass of the plate had given the shattering result now this result was probably somewhat less surprising to you listeners having just heard me go on at length about the various problems inherent with having too much brittle material in your armor however whilst this rather absurd 80/20 ductile brittle ratio was walked back a bit constantly improving armor-piercing shells and a constant desire to shatter them meant that us class-a armor which was the US navy's designation for face hardened battleship and Cruiser armor plate would end up having a much deeper hardened face than anyone else in the 1930s and 1940s at a 50 to 55% hardened depth now this did result in absolutely phenomenal performance when it was used a cruiser grade thicknesses against Cruiser great guns with the lighter weight 6-inch and 8-inch projectiles smearing themselves all over it like flies over a windscreen but passed about 12 inch caliber shells the scaling effect that had been noticed with the more extreme our mother we talked about from the Midvale 1910s era testing began to reassert itself and this left class-a armor as of pretty decent material quality but somewhat less actual resistive value compared to similar thicknesses of other nations battleship plate going into world war ii as by now it was just as much the technique used to make the plate that made a difference as much as the material properties of the basic steel itself now as an interesting side note british armed we covered earlier had the opposite issue it had a thinner than average face backed by absurdly high tensile strength ductile steel which made the armor massively resistive against the largest battleship projectiles but at the same time left British cruisers slightly more vulnerable than most the Germans meanwhile varied their levels of trace elements in their armor depending on thickness with the overall quality of their plate being pretty good at the higher thicknesses hence the overall comparative values weird the British plate but dropping off to as bad as early 1900s Harvey or early Krupp steel levels in some cases when it came to Cruiser grade plate with a huge degree of variance now the Japanese modified their production process by making the hardest part of their face somewhat inside the outer layer of the armor with a much more gradual transition between hard and soft layers this resulted in a good quality armor at Cruiser grade thicknesses and but a relatively unremarkable level of resistance per inch at higher thicknesses and somewhat compensated for by the absurd thicknesses that were manufactured for parts of the Yamato class although this did have a few problems arising as the thickest plates that they manufactured turned out to be so massive that the cooling systems used their various Jets of water and oil couldn't actually cool the interior of the armor fast enough which left these very large plates vulnerable to snapping on impact even if the shell didn't actually make it through now the Italians had their own way of going about things which happily straddled the line they varied the thickness of their hardened face depending on how thick the armor they were making this gave their tourney plate a similar effectiveness to us class-a armor against cruiser great firepower as at this the overall thickness it had a very deep base hardened plate but this would transition to a thinner and more British level of face hardening at battleship grades of thickness thus exploiting those factors as well for good resistance at the upper end of thicknesses of plate as well as the better Cruiser performance now this has led some sources to classify Italian plate as the best overall World War 2 armored plate as it scores well at both ends of the scale unlike practically everybody else's but it's not the best a battleship specific plate due to its overall strength and especially that of its backing section being materially weaker than some other nations armour quality control however was pretty good which is some ironic given the state of the Italian shell and charge manufacturing thus by the world war two ERA and the final generation of shipboard armor if you wanted to protect a cruiser you'd be best off using either American or Italian followed up by Japanese plate roughly that order whereas if you wanted to protect a battleship you would want British German or Italian plate again roughly in that order there's also homogeneous Armour but that and that's armor plate without the face hardened layers but I think that can be for another time so there you have it a brief potted history of the development of naval armor from simple iron plates all the way up to the World War 2 era I say brief yes it's taken us about 50 minutes but on the other hand if you really want to get into it there are literally two to three inch thick books and multiple of them that discuss this subject so yes there are a few small details here and there that I've left out yes there are lots of variations Lester yes there's a huge body of testing that was involved in the manufacturing creation of these various plates and yes there were a lot of other interesting dead ends such as the use of rubber as a backing material instead of wood and so on and so forth but hopefully this has provided a relatively decent overview and please please feel free to engage in many technical and engineering discussions in the comments below or perhaps the more mundane conversations as I will enjoy both but I might be a little bit more tempted to engage on the really complex engineering side of things because after all that is why I was a trained for way back when anyway thank you very much for listening that's it for this video thanks for watching if you have a comment or suggestion for a ship to review let us know in the comments below don't forget to comment on the pinned post for drydock questions

Channel: Drachinifel

Views: 730,982

Rating: 4.9044409 out of 5

Keywords: wows, world of warships, battleship armour, Iron plate, Compound armour, Steel Armour, Harvey Armour, Krupp Armour, Creusot, Schneider, HMS Warrior, La Gloire, Terni, Class A, Vickers Cemented

Id: BoEFjl0buiM

Length: 50min 54sec (3054 seconds)

Published: Wed Nov 27 2019