French 1940 armor quality ?

Discussions on all aspects of France during the Inter-War era and Second World War.
User avatar
David Lehmann
Posts: 2863
Joined: 01 Apr 2002 10:50
Location: France

French 1940 armor quality ?

Post by David Lehmann » 06 Oct 2003 12:02


I would like to know about the quality of the armor on Fraench tanks in 1940. On the internet I only found general explanations on naval armor : (* see quote) but nothing about tank armor.

- type of steel, iron etc. (composition)

- welded (soudé) or bolted (riveté) (the FCM36 has a welded armor and the B1Bis a bolted one for example)

- rolled (laminé) armor or cast (moulé) armor ? ... the Somua S35 was the world's first tank having cast armor.

- I am looking for info like the "Brinnel Hardness Number" (BNH) and "Tensile Strength" for the French armor types.

Could someone share information about these points ?


* quote :
1) France introduced Molybdenum in 1912 to improve the manufacturing process for naval armor by increasing the hardenability and toughness of the steel and by making the metal tougher when in its high-temperature solid austenite form. This indicates to me that French World War I-era armor was the equal to the best foreign armor, at least in standard manufacturing processes, steel quality, and so forth.

2) French naval designers decided during the 1930's that steeply-falling armor-piercing aircraft bombs would be more of a threat than more shallow impacts by medium-to-long-range naval gun projectiles and they therefore had face-hardened armor used for all plates over 4" (10.2cm) on turret and conning tower roofs where layered protection (spaced decks) was not possible. To my knowledge, no other nation did this. Ironically, while this idea turned out to be absolutely true in almost every case in World War II, the one case where a French main turret roof--a 5.91" (15cm) roof plate on the battle-cruiser DUNKERQUE--was hit was not by an aircraft bomb, but by a 15" (38.1cm) 1938-pound hard-capped armor-piercing projectile at about 70-75o obliquity fired by the HMS HOOD at close range. The projectile broke in half and the nose ricocheted off, but the projectile lower body did not ricochet and the plate ended up with a large, projectile-shaped hole in it (it actually seems to be an outline of the British projectile on its side pushed into the plate!), throwing a large amount of plate material into the turret at high velocity, followed by the lower portion of the projectile, which then exploded (probably a less-than-full-strength explosion, but what difference did it make?) inside the turret, knocking out the right half of the split 4-gun mount (each turret was divided by heavy internal armored bulkheads into two adjacent 2-gun turrets on one mount, a unique French design). If the armor had been homogeneous, the projectile would have ricocheted off in one piece and probably no armor would have been ejected from the plate hit.

3) French World War II-era armor test results (I have a couple) give their face-hardened armor a perfect fit (my formulae give the exact (!!) complete penetration velocities found in the tests) for an armor of the best World War II-era plate quality using the 35% face of original German KC armor (i.e., Krupp World War II KC n/A with a Krupp World War I-era KC a/A face depth).

. . . . 4) In 1938-39 an experimental 5.91" (15cm) KC-type plate was manufactured that was standard except that it had been "baked" in the cementing oven for an entire year (!!). After the fall of France in 1940, the Germans took this plate back to Krupp where it was found to give unusual (I bet!) ballistic performance. Does anyone know more about this plate?



User avatar
Juha Tompuri
Forum Staff
Posts: 11550
Joined: 11 Sep 2002 20:02
Location: Mylsä

Post by Juha Tompuri » 06 Oct 2003 23:01


Not an answer :( , but related to your question: ... highlight=

Regards, Juha

Posts: 922
Joined: 20 Aug 2003 20:16
Location: NAmerica

Re: French 1940 armor quality ?

Post by Tiornu » 09 Oct 2003 06:27

Nathan Okun holds the opinion that France was metallurgically competitive in WWI, and he knows no reason to suppose any subsequent regression on their part.

Return to “France 1919-1945”