Blogoguru

T-34 – Mice VS Cats – Part 10

2015-11-21

In case if you missed it, here is the previous part.

I believe  it’s a right time to talk armour toughness and what it could possibly mean from chemical point of view

Armour toughness is a balance of strength and ductility. Diamond is hard but brittle. Aluminum is ductile but not hard. The ideal aromour would be titanium having both strength and ductility. But at time of WW2 humankind had no means to work with  titanium on industrial level… well even today nobody makes tanks from titanium… it will be too pricey).

Military engineering is alway making a choices between the bad and very bad. American engineers were happy with soft alloys. Soft alloy will not crack but easier to penetrate. German engineers tried to find right mix for hard alloy and that was very typical for their engineers. Hard alloy is more difficult to penetrate, but it will crack more easily. Soviet engineers had just a rough idea what I’m taking about.

Before looking at the table you need to have at least a basic understanding of chemical components of armoured steel.

  • Carbon – Greatly improving alloy strength but reducing ductility. Also it makes steel more difficult to weld, not impossible but just more difficult. If Carbon content is more than 2% it is called cast iron.
  • Manganese – improving ductility without reducing alloy strength.
  • Silicon – improving alloy strength without reducing ductility.
  • Chromium – improving alloy strength without reducing ductility.
  • Nickel – improving ductility without reducing alloy strength.
  • Sulfur – Is not alloying agent but impurity and is a something we trying to avoid in any case. The more Sulfur content the less quality steel.
  • Phosphorus – Is not alloying agent but impurity and is a something we trying to avoid in any case. The more Sulfur content the less quality steel.
  • Vanadium – improving ductility without reducing alloy strength.
  • Molybdenum – improving alloy strength without reducing ductility.
Tank type mm  Chemical composition in %
 C Mn Si Cr Ni S P V Mo Al Cu
K.C.A 0,35 0,35 0.07 2,0 3,9 0,020 0,025
KC n/A 1 0,25-0,43 0,7-1,23 0,05 2,2 1,1-3,1 0.035 0.035 0,2-0,65
KC n/A 2 0,30 0,30 0,35 2,0 3,5-3,8 0,040 0.035 0,2-0,4
Ww 0,25 0,25 0,23 2,0 3,08 0,035 0,035 0,03 0,22 0,1
Wh 0,37 0,30 0,25 1,89 4,01 nd nd nd nd
Wsh 0,32 0,24 nd 1.95 2.75 0,025 0,025 Tr 0,5 Tr
PzKpfw I 10-15 0,42 0,55 1,75 1,04 3,48 0,007 0,02 0,8 0,25 - -
PzKpfw IV 50 0,36 0,39 0,21 1,32 3,06 0,006 0,031 nnd* nnd* - -
20 0,36 0,36 0,29 2,55 0,16 0,014 0,028 nnd* nnd* - -
 PzKpfw V  0,5 0,67 0,32 2,13  nil 0,032 0,015 0,14 Tr  0,01 0,1
T-34/76 45 0,27 1,5 1,6 1 1,5 0,025 0,03  nil 0,25
20 0,29 1,6 1,6 0,3 0,5 0,03 0,35  nil 0,25
KV-1* 2П* 0.27 1,1 1,6 0,3 0,5 0,03 0,35 nil 0,25
T-34/85 71Л 75-90 0,27 1,1 1,6 1,5 2,4 0,03 0,35  nil 0,25
IS-2* 71Л* 0,29 1,3 1,5 0,3 1 0,03 0,35  nil 0,35
Matilda 60-80 0,37 0,65 0,24 0,9 3 0,017 0,028  nil 0,4
Matilda II 25-70 0,24 0,5 0,2 0,7 3 0,02 0,035  nil 0,45
  • Tr – traces, nd – no data, nnd* – no exact numeric data, but chemical analysis confirms “significant” amount.
  • Sorry, but data regarding Krupp steel types is not accurate. It comes from rumors and undocumented sources, but still better than nothing.
  • Data regarding Soviets tanks are just technical requirements existing only on paper. Actual numbers may greatly vary. Sulfur content is the prime example: as documented it should not exceed 0,30% but in reality it was going up to 0,050 or even more%.
  • Data regarding German tanks and Matilda are the actual numbers. Data is taken either in Soviet or American labs in the process of reverse engineering.

Krupp Ww (Wotan weich). Homogeneous armour steel – soft. Used to build the Bismarck. Produced 1925 -1945.

Krupp Wh (Wotan hart). Homogeneous armour steel  – Hard. Used to build the Bismarck. Produced 1925 -1945

Krupp Wsh (Wotan Starrheit) – Extra-hard

Krupp cemented armour (K.C.A). Produced from circa 1905 – 1930. K.C.A became pretty much worldwide standard and was used as a standard in US Navy till 1930. From US Navy went over to Special Treatment Steel (STS), also known as Protective Deck Plate. Originally developed by Carnegie Steel. STS was expensive, more expensive than  Krupp’s post-World War I “Wotan weich” armor. As another interesting fact STS did not use molybdenum :) also it was used till 1960.

KC n/A (Krupp cementite, new type). Face-hardened armour steel. I marked it as type 1 since it was used 1920-1930. Used to build the Bismarck

KC n/A (Krupp cementite, new type). Face-hardened armour steel. I marked it as type 2. Used to build the Bismarck.

 

  • Have a look at the table and tell me who had more not needed impurities like Phosphorus Sulfur. In reality Soviets allowed Phosphorus content up to 0,045% and could not cope even with that level.
  • Speaking about lack of Molybdenum and replacing it with Vanadium. Vanadium and Molybdenum are adding absolutely opposite armour properties. German armour was well known to be hard alloy. By taking off Molybdenum and adding Vanadium will improve ductility while taking off over strength. All I can say it was a right move, because it makes no sense adding even more strength to the German armour of that time.
  • Krupp armor was well known for high carbon content even before WW2, giving more than enough strength. Another reason to withdraw Molybdenum.
  • From chemical point of view the only thing went wrong with Germans (PzKpfw V) was increased Sulfur content. It could be caused by increase of production or new technological process and they had no time to make it perfect. Frankly speaking even increased Sulfur content in German armor was still times less than in Soviet armor. Besides you can see increased Sulfur content even in British armour. Again it could be caused with increase of production numbers.
  • For now let’s move to the most interesting and most expensive component. Nil of Nickel. Yes it could be prime example of starving Germany, but it could be something else too. So here is surprise). In 1940 – 1941 Amrecan tanks had the same Nickel content as British tanks. Depending on model anywhere between 3-5%. From 1942 M4A2 and M4A3 had reduced Nickel content. Matilda II had steady 3% while M4A2 and M4A3 Nickel content was reduced up to 1,05-1,10%. Isn’t it insane to imagine to imagine that Americans were more short of Nickel than British? :) But this is what soviet engineers though, while themselves due to price and shortages used even less Nickel. But for me it looks American armour went close to PzKpfw IV armour composition. During Korean war Soviets managed to capture M26 and to their surprise Nickel simply disappeared, but content of Manganese and Molybdenum increased. Manganese content on M3 was 0,3%, on M4A3 it went up to 0,89-0,97%.  Molybdenum from 0.11% on M3, 0,21-0,60% on M4A3, 0,60% – 0,80% on M26. Soviet engineers called it identical to German armour in 1944:). So “starving” Germany did they same thing as non starving post WW2 America by replacing Nickel with less costly  Vanadium and Manganese. No Soviets or British had idea about Vanadium use. ) Also it was quite surprise to Americans when they seen it firs time. But from now it is obvious both Germans and Americans were going into the same direction even from very different start positions.

 If you still have an interest here is the next part