Tiger II armor quality

Discussions on the vehicles used by the Axis forces. Hosted by Christian Ankerstjerne
ThatZenoGuy
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Re: Tiger II armor quality

#61

Post by ThatZenoGuy » 06 Sep 2021, 13:36

Peasant wrote:
06 Sep 2021, 11:13
critical mass wrote:
04 Sep 2021, 10:46
Acc. to M. Krogfuss´s article about ARTKOM and De Marre, the 122mm BR471´s original shell steel had low carbon content, thus reducing hardenability. In essence, the specifications called for uniform hardness (Rc45) from base to top (no difference whatsoever). Later shel steels with increased carbon allowed an increase in hardness.
I don't believe this to be correct. There doesn't seem to be any correlation between the year of manufacturing and the hardness profile of the shell. This 45mm shell was manufactured in 1942 but has a higher nose hardness than the 85mm one manufactured in 1949.
Also, to my knowledge, it wasn't exactly 45 Rc but 45 Rc minumum.
From this graph we can see that there would not be a drastic difference in hardness between shells made with 0,29% C and 0.32% C steel (worst case scenario) for a given quench level.

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Isn't it a little silly to compare two entirely different scaled shells? Typically its harder to properly heat treat thicker things than thinner things IIRC.

critical mass
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Re: Tiger II armor quality

#62

Post by critical mass » 07 Sep 2021, 11:30

Yes, section thickness is an important criterium, because larger section thicknesses take more time to cool internally, allowing more probability of temper brittleness, particularely if manganese and silicon is present in the analysis (which it was in soviet wartime shell steel).

But Rc55ísh is not possible with the 35Х3НМ and 35ХГС shell steel used in wartime 122mm, 100mm and 85mm shells. The standart ww2 shell steel had 0.29-0.35% C, whihch allows for 43 to slightly over 50 RC, depending on heat treatment and completeness of martensitic phase transformation (You don´t want complete martensitic structure because it is very brittle, You ideally aim for tempered martensitic with ca. 90-95% martensitic crystal present). The low carbon content does not provide enough hardenability. However, in combination with Chromium, Si and Mn a higher carbon level would facilitate temper brittleness, which is exactly what the US examaination of soviet shell steel found in larger sections.
The lower resulting hardness of the shell steel allowed for use of ordinary tools to cut fragmentation grooves into the shell body of soviet wartime AP-ammo. Whether or not You regard ths as an advantageous feature is ambigous but hardness 53Rc and up (i.e. so called "instrument steels" considered at one point as replacement for ordinary domestic shell steel would also have required extra strong tool steel (preferably with tungsten) to work in the grooves.

The Soviets also tested more advanced, higher carbon content (and Mn + Si-free) shell steels -with good results- towards wars end (i.e. 60X30 shell steel with 0.6% C in a test from late may 1945, which IIRC You posted before), which became standart post war and helped to raise the shell steel hardness from 50 to ~60 RC.


Peasant
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Re: Tiger II armor quality

#63

Post by Peasant » 17 Sep 2021, 23:07

critical mass wrote:
07 Sep 2021, 11:30
Yes, section thickness is an important criterium, because larger section thicknesses take more time to cool internally, allowing more probability of temper brittleness, particularely if manganese and silicon is present in the analysis (which it was in soviet wartime shell steel).

But Rc55ísh is not possible with the 35Х3НМ and 35ХГС shell steel used in wartime 122mm, 100mm and 85mm shells. The standart ww2 shell steel had 0.29-0.35% C, whihch allows for 43 to slightly over 50 RC, depending on heat treatment and completeness of martensitic phase transformation (You don´t want complete martensitic structure because it is very brittle, You ideally aim for tempered martensitic with ca. 90-95% martensitic crystal present). The low carbon content does not provide enough hardenability. However, in combination with Chromium, Si and Mn a higher carbon level would facilitate temper brittleness, which is exactly what the US examaination of soviet shell steel found in larger sections.
The lower resulting hardness of the shell steel allowed for use of ordinary tools to cut fragmentation grooves into the shell body of soviet wartime AP-ammo. Whether or not You regard ths as an advantageous feature is ambigous but hardness 53Rc and up (i.e. so called "instrument steels" considered at one point as replacement for ordinary domestic shell steel would also have required extra strong tool steel (preferably with tungsten) to work in the grooves.

The Soviets also tested more advanced, higher carbon content (and Mn + Si-free) shell steels -with good results- towards wars end (i.e. 60X30 shell steel with 0.6% C in a test from late may 1945, which IIRC You posted before), which became standart post war and helped to raise the shell steel hardness from 50 to ~60 RC.
Interesting info. Although I'm not sure about the bolded parts of Your comment. I was unable to find any mention of excessive brittleness of the soviet AP shells examined by the US specialists but in one instance, in a 85mm APHE shell and even in that case it was confined to the base of the shot, not the nose or center portions.
Also I believe that the last part is wrong. From what I've seen the physical and chemical properties of blunt tipped soviet shells remained the same even after the war. As you can see in the image I've posted earlier of the 85mm shell manufactured in 1949 yet still has low carbon content.
Also, this 100mm BR-412B shell wa manufactured in 1951 according to the label on the propellant case, but it still has 52 RC hardness max.
In fact the US specialists suggest that relatively low nose and body hardness of the soviet blunt tipped shells is instrumental in keeping them from suffering complete shatter upon impact (at least at low obliquity), so increasing it would probably not improve their performance much if at all.

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Perhaps the post-war soviet APCBC designs have greater carbon content and hardness, but I have seen no such info about them.

Peasant
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Re: Tiger II armor quality

#64

Post by Peasant » 10 Jan 2022, 21:03

I have long been wondering who is responsible for this idiotic decision. Should've know it was Hitler. When in doubt, blame Hitler. :D

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ThatZenoGuy
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Re: Tiger II armor quality

#65

Post by ThatZenoGuy » 11 Jan 2022, 02:50

Peasant wrote:
10 Jan 2022, 21:03
I have long been wondering who is responsible for this idiotic decision. Should've know it was Hitler. When in doubt, blame Hitler. :D

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To be fair the added thickness to armor made the King Tiger frontally proof against pretty much any WW2 munition outside of naval cannon or sabot.

Germany simply wasn't in the position to make heavy tanks in the first place though, breakthrough tanks are awesome to push forwards, but not if they're outnumbered 30 to 1.

Peasant
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Re: Tiger II armor quality

#66

Post by Peasant » 15 Jan 2022, 09:59

ThatZenoGuy wrote:
11 Jan 2022, 02:50
To be fair the added thickness to armor made the King Tiger frontally proof against pretty much any WW2 munition outside of naval cannon or sabot.

Germany simply wasn't in the position to make heavy tanks in the first place though, breakthrough tanks are awesome to push forwards, but not if they're outnumbered 30 to 1.
Somewhat counter intuitively, tanks take hits on the side armour from ATGs more often than from enemy tanks on the frontal armour. If they meet an enemy tank head-on, they would likely spot them and engage at considerable distance, where the penetration ability of guns is lower and the reduced armour would've sufficed to resist a hit even from 122mm guns and 17pdr subcaliber rounds. While the ATGs are much harder to spot for the tank crew and so they usually have the advantage of the first shot (and probably the second and the third one as well). I believe that increasing the turret side and upper hull side armour to 90-100mm to make this vehicle immune to 6pdr guns firing AP and soviet 45/76mm ATGs firing APCR would've benefited this tank more than those extra 50mm of frontal armour.

ThatZenoGuy
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Re: Tiger II armor quality

#67

Post by ThatZenoGuy » 15 Jan 2022, 11:12

Peasant wrote:
15 Jan 2022, 09:59
ThatZenoGuy wrote:
11 Jan 2022, 02:50
To be fair the added thickness to armor made the King Tiger frontally proof against pretty much any WW2 munition outside of naval cannon or sabot.

Germany simply wasn't in the position to make heavy tanks in the first place though, breakthrough tanks are awesome to push forwards, but not if they're outnumbered 30 to 1.
Somewhat counter intuitively, tanks take hits on the side armour from ATGs more often than from enemy tanks on the frontal armour. If they meet an enemy tank head-on, they would likely spot them and engage at considerable distance, where the penetration ability of guns is lower and the reduced armour would've sufficed to resist a hit even from 122mm guns and 17pdr subcaliber rounds. While the ATGs are much harder to spot for the tank crew and so they usually have the advantage of the first shot (and probably the second and the third one as well). I believe that increasing the turret side and upper hull side armour to 90-100mm to make this vehicle immune to 6pdr guns firing AP and soviet 45/76mm ATGs firing APCR would've benefited this tank more than those extra 50mm of frontal armour.
Oh the turret sides were way under-armored IMO. Agreed entirely with that.

German late-war tanks in general, excluding the Maus, had curiously low side armors, something the tiger quite excelled at for it's time.

Peasant
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Re: Tiger II armor quality

#68

Post by Peasant » 29 Aug 2023, 21:27

There is new stuff to discuss boys!
It seems that the scanned file of this test was missing quite a lot of pictures. Now they are slowly appearing on the web. I've managed to track down some.

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And here are the schematics to help us match the hits in these photos to what weapon at what distance left them.

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Peasant
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Re: Tiger II armor quality

#69

Post by Peasant » 17 Oct 2023, 11:17

Found where this photo came from:

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Link: https://apps.dtic.mil/sti/tr/pdf/AD0155208.pdf

Peasant
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Re: Tiger II armor quality

#70

Post by Peasant » 24 Oct 2023, 20:57

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Note that the 1953 US MIL-A-12560 standard for RHA called for a V-Notch Charpy impact toughness at -40°F for a 6in plate of at least 28ft*lb. Much lower values of this specimen have probably made it much more susceptible to an attack from a HESH round (among other things).

Unlike other flaws of RHA like laminations or non-metallic inclusions, armour with low impact toughness will show a reduced ballistic resistance only against high caliber shells like the soviet 122mm and 152mm. Against small(-ish) caliber with high penetration, like 17pdr APDS or even full caliber 17pdr and US 90mm AP shells, it would've likely performed as well as one with adequate level of impact toughness.

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