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What was the reason that US had the inferior still quality for all WW2 participants except Japanese?

Perhaps to many readers' surprise, the United States was not able to manufacture the best type of battleship armor, known as "face-hardened" (Class A in American terminology) in adequate quantities. That which it could produce was seriously inferior to, for example British and Italian armor. I am going to try to avoid a string of statistics in a Daily Content article (for those go to innumerable Internet sites) but will consider one very common comparison between Iowa and Vanguard (King George V has a virtually identical armor system, but is a smaller ship).

Put exceedingly simply, the American belt is just over 12 inches, the British just under 15 inches. However, if we take into account the relative quality of the steel, the British belt "increases" to over 17 inches. Incidentally, Italian and probably French face-hardened steel was also superior, while the Japanese is marginally inferior. Also the sad shortage of American face-hardened steel meant that only the upper half of the belt could use this type of armor.

http://www.avalanchepress.com/overrated3.php?mode=print

ORIGINAL: Dili

What was the reason that US had the inferior still quality for all WW2 participants except Japanese?

Perhaps to many readers' surprise, the United States was not able to manufacture the best type of battleship armor, known as "face-hardened" (Class A in American terminology) in adequate quantities. That which it could produce was seriously inferior to, for example British and Italian armor. I am going to try to avoid a string of statistics in a Daily Content article (for those go to innumerable Internet sites) but will consider one very common comparison between Iowa and Vanguard (King George V has a virtually identical armor system, but is a smaller ship).

Put exceedingly simply, the American belt is just over 12 inches, the British just under 15 inches. However, if we take into account the relative quality of the steel, the British belt "increases" to over 17 inches. Incidentally, Italian and probably French face-hardened steel was also superior, while the Japanese is marginally inferior. Also the sad shortage of American face-hardened steel meant that only the upper half of the belt could use this type of armor.

http://www.avalanchepress.com/overrated3.php?mode=print

Ask Nathan Okun.

That isn't a particularly helpful essay. The Americans had metal of exceptional quality, but they prepared their face-hardened armor in an unusual way that resulted in inferior performance against large-caliber shells. As you can guess, face-hardened armor has one surface that is especially hardened while the back layer remains more ductile. In most navies, the face layer was about 30% of the total plate thickness. The Americans ran into problems, and this is a good example of how an institution can be led astray by tunnel vision. Knowing that penetration can be greatly reduced by breaking the shell, the Americans established a criterion for their armor to be able to break shells. The better criterion would be more generally to resist penetration. What went wrong for the Americans was the development of modern shells that were highly resistant to breakage. The response was to thicken the face layer to about 50% of the plate thickness, and this had unusual results. Against large shells, performance declined; against the largest shells (46cm), Japanese face-hardened armor actually gives a better performance than Class A. But against shells of around 8in or less, the thick face gives an advantage. These scaling effects were unknown at the time except to the Italians who consequently had very good face-hardened armor for their battleships and their cruisers. So Class A was "inferior" only in the specific application of defeating large-caliber shells.
The use of Class B in the Iowa/SoDak lower belt had nothing to do with a "sad shortage."

As if the USA had suffered a shortage of anything in WW2 (ramp up time excluded of course). Class A has no place in anything resembling a TDS, because it's too brittle, that's all.

btw, i had thought that rejecting BB shells was the main purpose of a main belt. must have been a case of 'foresight' (luck? since the only time a treaty BB got hit by main battery fire was Guadalcanal, iirc, by 14" WW1 vintage guns.

South Dakota hit by Kirishima IIRC

There was a problem with Class A armor procurement, but I don't know exactly what it was. The decision to use Class B in the SoDak and Iowa classes seems to have arisen from this. Permission was also granted to switch Iowa's conning tower to Class B.

Thanks Tiornu, so this will mean that the hardened part unable to break the biggest projectiles will crack(is this the result that will happen?) and since the ductile part was reduced in thickness the overall performance was reduced?

That discovery by Italians was when? Did Zaras already had that knowledge in their armor? Or was only Littorios and last Condotieris including the Garibaldi(she had a very unusual Armor from the drawing/diagram i have seen).

I think we had this discussion before in the UV forum
http://combinedfleet.com/okun_biz.htm
“On the other extreme, for cruiser-level armor 7 inches (179 mm) or less in thickness, the extreme face thickness of WWII U.S. Class 'A' armor caused the scaling effects to work in reverse to make that armor superior to its thinner-faced foreign contemporaries. U.S. cruisers thus had the best protection of any warships of their size. The thick face was an attempt to allow the armor to break the very superior U.S. armor-piercing projectiles that were developed at the same time. These projectiles were the best in the world at resisting damage, though they were sometimes slightly inferior in penetration ability if they and their foreign contemporary could both penetrate the same plate intact. Eventually the armor manufacturers had to give up trying to damage the best U.S. projectiles, but by then they had gone "over the top" in overall resistance and had made the thick-faced armor inferior to many foreign contemporaries in its thickest grades due to scaling, which had a major detrimental impact an WWII U.S. battleship armor resistance when not compensated for by other methods. The U.S. armor designers had some idea of this problem, as can be seen by certain modifications that they made, such as using Class 'B' homogeneous armor in the thickest plates on the faces of WWII battleship main gun turrets, something that was not done by any other navy, while retaining face-hardened armor on WWII U.S. cruiser turret faces up through 8 inches (203 mm) thick. “[/i]
Also this will bring the whole U.S. "Class 'B'" armor or "Special Treatment Steel (STS) discussion back to light..  which, summarized is that the STS decks would decap an AP projectile before it hit the main armor, thus dramatically Lessing its penetrating ability

yeah i was gonna say that this is a good page but hornblower beat me to it.
http://www.combinedfleet.com/baddest.htm

Apparently, American metallurgical inferiority did not extend to aluminum [;)]

Or this stuff [;)]

ORIGINAL: Cap Mandrake

Or this stuff [;)]

Uranium?

or this stuff [;)]

One needs much thicker gloves.

Plutonium?

ORIGINAL: Cap Mandrake

Apparently, American metallurgical inferiority did not extend to aluminum [;)]

is that the same as aluminium?

Since the colonials insist on misspelling aluminium, why don't they spell it uranum and plutonum?

ORIGINAL: Terminus

Since the colonials insist on misspelling aluminium, why don't they spell it uranum and plutonum?

Get your own Periodic table. [:'(]


Aluminum
Uranium
Plutonium

(in picture order)

ORIGINAL: Cap Mandrake

ORIGINAL: Terminus

Since the colonials insist on misspelling aluminium, why don't they spell it uranum and plutonum?

Get your own Periodic table. [:'(]


Aluminum
Uranium
Plutonium

(in picture order)

I have... Have you got a proper spellchecker?[:'(]

Just goes to show how complicated it becomes when attempting to compare armor types across the years, considering the different defense systems and strategies each navy wished to deploy.

I believe the Zaras enjoyed the benefits of scaling, and they may have been the only Italian cruisers with face-hardened armor. I don't know about the Abruzzis.
I cannot confirm some of Nathan's comments regarding faceplates. The order to switch to Class B faceplates also included an order for the plates to be thickened, as though compensating for the lesser resistance of thick Class B in low-obliquity impacts.
Th de-capping of a shell by the bomb deck is not much of a plus. First, trajectories through the upper hull side will hit the armor deck without ever contacting the bomb deck. This is why the outboard deck is thicker than the inboard section. Whatever good the bomb deck does by slowing and decapping the shell is negated by the downward deflection of the shell and the thinner armor it meets on the protective deck. The General Board understood that thickening the upper deck decreased the shell resistance of the armor deck (compared to adding that thickness instead to the armor deck itself).
Last time I checked into it, "aluminum" was a "better" anglicization than "aluminium." But what about the "z" in "anglicization"?