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Japanese Tanks and FHA


Is there a clear explanation on this?

 

I keep seeing confusing articles saying that the Japanese tanks used normal armour, make no mention of it at all, or used FHA; then various sites contesting the effectiveness of it (i.e. can the Ha-Go FHA be penned by .50 cal). What I got myself from a bit of research is this:

  • Every Japanese tank, aside from the Chi-To and the Chi-Ri, used FHA exclusively.
  • FHA enables the armour to be rather thin in comparison to RHA but still be able to deflect shells that would normally go through it, such as rumors of 45 mm M1937 bouncing or being blocked by the armour of the Type 97 Chi-Ha at the Battle of Khalkhin Gol. However, at the same time it would deteriorate and shatter when put under repeated and concentrated fire like .30/.50 cals against the plates of the Ha-Go; it's also heavily weak towards shells that have a larger caliber than the armour itself.
  • The Brinnell hardness of Japanese FHA on their tanks was around 800 to 900.

 

Is this accurate?

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i think i saw the post war documents about this a while back

but in theory its not much different than normal RHA and it shatters shell in contact with it that arent as hard as the armor.

Kind of like how russian 76mm would shatter if it shot at the vorpanzer of Pz III M and L, makes it invulnerable against early MD-5 fuze at +500m if you angle it a bit.

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I have no idea if Japanese tanks used FHA or not, but I know a good bit about how armor works.

 

RHA (rolled homogeneous armor) works by deflecting or stopping projectiles. It is usually of relatively low Brinell hardness, which makes it somewhat flexible. It bends and stretches, helping it more easily deflect a projectile. 

 

FHA (face hardened armor) works by breaking projectiles. Unlike homogeneous armor, it has different hardness levels at different depths of the plate. The front face is incredibly hard (several times the Brinell hardness of most RHA), but that face usually only makes up ~30% of the plate's thickness. There is often a thin transition layer, and then the rest of the plate is fairly soft, much like RHA. The hard face is designed to break a projectile, allowing the softer backing layer to "catch" the pieces more easily.

 

These two kinds of armor work very differently. But FHA is a bit of a gamble to use. If the plate can break the projectile, it has similar resistance to a significantly thicker plate of RHA. But if the plate can't break the projectile, it is significantly weaker. It is also less effective at high angles due to a broken projectile being harder to deflect.

 

The USN actually used RHA for their battleship turret faces in the 1930s and 40s. This was due to the face hardened armor they were using being incapable of breaking the nearly indestructible AP shells the USN was using at the time. Thus, the RHA was more effective for a given thickness. Against other shells the FHA probably would've been better, but without any to test the USN couldn't really know that.

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1 hour ago, Samuel_Hyde said:

i think i saw the post war documents about this a while back

but in theory its not much different than normal RHA and it shatters shell in contact with it that arent as hard as the armor.

Kind of like how russian 76mm would shatter if it shot at the vorpanzer of Pz III M and L, makes it invulnerable against early MD-5 fuze at +500m if you angle it a bit.

http://ww2f.com/threads/japanese-tanks-and-armored-vehicles.72238/

I did find that saying pretty much all of the tanks, except for the Chi-To, used FHA; though he doesn't give any information beyond that. 

 

What originally got me asking this question is that I was compiling a list of the issues with Japanese GF (bugs with vehicles, etc; v1 version) and stumbled upon this old Steam discussion saying their armour should be FHA. I decided to try looking a bit deeper and well, the most useful piece of information led be back to War Thunder to this even older post talking about the quality of Japanese armour; most specifically the Chi-Ha's armour. The claim that the Japanese armour is FHA, or was at least very hardened on the Brinell scale when compared to other nations, which allowed them to take more punishment than you would expect the armour to take (i.e. the Chi-Ha's 16 mm of armour bouncing/blocking 37 mm/2-pounder/45 mm rounds according to reports from Malaysia and after-action reports of the Khalkhin Gol Battle), is echoed throughout discussions on it while at the same time it's denied by other people as myth. However, no one has really brought any sources up to support either side from what I have seen.

Edited by Wiggly_Armed_Man
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The most I've really seen was about the Type 1 and Type 2 armor and their use in penetration tests, ie how much can this shell penetrate the Type 1 armor vs the Type 2 armor. But I haven't seen any files/sources about their use in tanks, unfortunately. I did read somewhere that the Type 1 armor was apparently considered more or less equivalent to the standard RHA used by the US, though.

 

5UcVPnU.jpgrY3AiBa.jpg

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5 hours ago, Tasty95215 said:

The most I've really seen was about the Type 1 and Type 2 armor and their use in penetration tests, ie how much can this shell penetrate the Type 1 armor vs the Type 2 armor. But I haven't seen any files/sources about their use in tanks, unfortunately. I did read somewhere that the Type 1 armor was apparently considered more or less equivalent to the standard RHA used by the US, though.

 

-image snip-

Thanks for your input, though I don't know where to go with that.

 

Edit: Does Type 1 and Type 2 mean the year of introduction (1941 and 1942) or was that just the designation for the two pieces of armour?

Edited by Wiggly_Armed_Man
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On 23/11/2019 at 23:41, Wiggly_Armed_Man said:
  • Every Japanese tank, aside from the Chi-To and the Chi-Ri, used FHA exclusively.
  • FHA enables the armour to be rather thin in comparison to RHA but still be able to deflect shells that would normally go through it, such as rumors of 45 mm M1937 bouncing or being blocked by the armour of the Type 97 Chi-Ha at the Battle of Khalkhin Gol. However, at the same time it would deteriorate and shatter when put under repeated and concentrated fire like .30/.50 cals against the plates of the Ha-Go; it's also heavily weak towards shells that have a larger caliber than the armour itself.
  • The Brinnell hardness of Japanese FHA on their tanks was around 800 to 900.

 

Where did you take this values from?

 

800-900 BHN seem to be extremely high. The book 'World War II Japanese Tank Tactics' out of the Osprey Elite Series (No. 169) states, that some armor plates were lightly face-hardend, but most were not. Something else, what is  stated in book is some kind of added armor plates, taken from destroyed M3 LT's, but only for the company leader, as far as I remember. Something the Japanese WW2 tanks had, were armored plates for the springs of their suspensions, something that in game is only featured in the last few vehicles.

 

Towards your armament bugs (reddit post): You say, that every type 94 gun could use the type 1 shell. Are you sure this really had fitted? I'm not talking about the the projectile, but about the propellant charge. All pictures I had seen, those cartridges were already completely filled for the type 94 shell. Maybe they could pressure it a bit, but I think that this is the reason for the bored out Type 98 (or 100, not sure which is which) to use the type 94 anti-tank cartridge.

 

Shouldn't the Ha-Go variant in game (read that it's a relatively early one) and the Ro-Go using the 6.5 mm Type 91 MG, like the I-Go? The 12 cm short gun could also fire a time-fuzed he shell. As those are added to the game, it could also use them (beside only having 15° elevation, but maybe someone could make them work.

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4 hours ago, craenker said:

Where did you take this values from?

 

800-900 BHN seem to be extremely high. The book 'World War II Japanese Tank Tactics' out of the Osprey Elite Series (No. 169) states, that some armor plates were lightly face-hardend, but most were not. Something else, what is  stated in book is some kind of added armor plates, taken from destroyed M3 LT's, but only for the company leader, as far as I remember. Something the Japanese WW2 tanks had, were armored plates for the springs of their suspensions, something that in game is only featured in the last few vehicles.

 

Towards your armament bugs (reddit post): You say, that every type 94 gun could use the type 1 shell. Are you sure this really had fitted? I'm not talking about the the projectile, but about the propellant charge. All pictures I had seen, those cartridges were already completely filled for the type 94 shell. Maybe they could pressure it a bit, but I think that this is the reason for the bored out Type 98 (or 100, not sure which is which) to use the type 94 anti-tank cartridge.

 

Shouldn't the Ha-Go variant in game (read that it's a relatively early one) and the Ro-Go using the 6.5 mm Type 91 MG, like the I-Go? The 12 cm short gun could also fire a time-fuzed he shell. As those are added to the game, it could also use them (beside only having 15° elevation, but maybe someone could make them work.

The Brinnell Hardness values come from bad memory, I conflated 500-600 to that found on this discussion I already mentioned.

 

While the rest of your post is off-topic, i will answer them:

  • The Type 94 could use the Type 1 according to @Tasty95215 and both his post about the missing Japanese shells and his bug report on them.
  • The Ha-Go isn't an early variant, that was a separate producing run of about >100 vehicles that was quickly stopped primarily due to having horrible characteristics including a top speed of 40 km/h from its 110 hp engine and using Type 91 instead of Type 97 machine guns; additionally having a longer fender and other minor details. As far as I can tell the mid variant is what the Ha-Go in-game is and I haven't been told otherwise in either the v2 version or the earlier corrected chart for the ground forces.
  • I don't know if the Ro-Go should be using them.
  • The Chi-Ha Short Gun only has evidence of using the HE shell; the other shells (like the anti-submarine shell) it could use but didn't.
Edited by Wiggly_Armed_Man
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I summarized what I knew very roughly.

 

Class I Bulletproof Steel Plate (第I種防弾鋼板): Rolled Homogeneous Armor, 320 BHN, for general use

Class II Bulletproof Steel Plate (第II種防弾鋼板): Carburizing Face Hardened Armor, 550 HV (505 BHN), used with Type 95 Ha-Go, Type 97 Chi-Ha

Class III Bulletproof Steel Plate (第III種防弾鋼板): Face Hardened Armor, hardness is between Class I and Class II, used with Type 3 Chi-Nu

 

0Ys9fDj.jpg

 

Reference

Imperial Japanese Army Bulletproof Steel Plate Data

https://web.archive.org/web/20150117082251/http://sus3041.sakura.ne.jp/contents/arm_var/armor_data_japan.htm

 

Japanese Light Armor Article 1, USNTMJ-200F-0153-0230 Report O-36-1

https://web.archive.org/web/20141022175259/http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/USNTMJ Reports/USNTMJ-200F-0153-0230 Report O-36-1.pdf

 

Japanese comments about this article.

http://ftr.wot-news.com/2014/10/20/buff-my-tank-chi-to/#comment-211332

 

German Tank Armor Research. Written by Yasufumi Kunimoto

http://wau.private.coocan.jp/wwtef/misc/pam.pdf

Edited by *tester188
Type 3 Chi-Ri -> Type 3 Chi-Nu
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1 hour ago, *tester188 said:

-snip-

Class III Bulletproof Steel Plate (第III種防弾鋼板): Face Hardened Armor, hardness is between Class I and Class II, used with Type 3 Chi-Ri

.

-image snip-

Just to be clear, do you mean Type 3 Chi-Nu?

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So according to @*tester188's information, the following tanks should have FHA (which would only give them a 1.05x modifier because Gaijin is bad at modeling armour):

  • Type 95 Ha-Go and derivatives
    • Type 95 Ha-Go (1.0)
    • Type 95 Ha-Go Commander (1.0)
  • Type 97 Chi-Ha and derivatives
    • Type 97 Chi-Ha (1.3)
    • Type 97 Chi-Ha Kai (2.0)
    • Type 97 Chi-Ha Short Gun (1.7)
    • Type 1 Ho-Ni I (2.0)
    • Type 3 Ho-Ni III (2.3)
  • Type 3 Chi-Nu and derivatives
    • Type 3 Chi-Nu (3.3)
    • Type 3 Chi-Nu II (3.7)

I imagine the tanks developed between them would have FHA too (Ke-Ni, Ho-I, etc) but the documents, from what Google Translate would translate, and what @*tester188 said only specified the following.

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This is about Japanese Army aircraft armor, but it might be helpful. It seems to be equivalent to Class II bulletproof steel plate (Carburized FHA) for tanks.

 

Sample: Kawasaki Ki-48 Army Type 99 Twin-engined Light Bomber (Allied code name: "Lily")

qZsTi6u.jpg

  • Type of plate: Carburizing Face Hardened Armor
  • Thickness: 16.5 mm
  • Hardness:
    • Face 555-589 BHN
    • Back 302-341 BHN

zEeXycw.jpg

OPNAV-Z6-V No. T235, March 1945, technical air intelligence center report No. 35, firing test of armor from Lily and Oscar. Report No. 13-c(27), USSBS Index Section 6

http://dl.ndl.go.jp/info:ndljp/pid/4010109?itemId=info%3Andljp%2Fpid%2F4010109&__lang=en

 

Report by United States Strategic Bombing Survey:

kMxegN7.jpg

Japanese Air Weapons and Tactics(final report and original draft). Report No. 63, USSBS Index Section 2

http://dl.ndl.go.jp/info:ndljp/pid/8821500/39?itemId=info%3Andljp%2Fpid%2F8821500&contentNo=39&__lang=en

 

(Please support the suggestions of Ki-48! :D)

 

Edited by *tester188
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  • 3 months later...

US tests vs Chi-Ha armour 

 

https://www.lonesentry.com/articles/jp_type97_tank/index.html

 

The 37-mm antitank gun was fired at ranges of 100 and 350 yards. Only armor-piercing shells were used. At 100 yards, the 37-mm registered penetrations on all parts of the tank when fired at angles from normal to 45 degrees from normal. At 350 yards, penetration of the tank armor could be made only when the antitank gun was fired at normal angle. The diameter of penetration was approximately 1 1/2 inches.

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  • 7 months later...
On 28/11/2019 at 22:58, [email protected] said:

Class III Bulletproof Steel Plate (第III種防弾鋼板): Face Hardened Armor, hardness is between Class I and Class II, used with Type 3 Chi-Nu

Wikipedia references that the Chi-Ri also uses this, "The armor of the prototype vehicle is not the type 1 bulletproof steel plate or type 2 bulletproof steel plate used in conventional tanks, but the newly developed surface-hardened steel plate (type 3 bulletproof steel plate)"; though I do not know how accurate that is.

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