Monday, 29 August 2016

Improved T-34-85 Armour

"To: comrade I.V. Stalin

In order to increase the robustness of T-34-85 turrets, factory #183 developed a new turret design with thicker front and sides (90 and 75 mm vs 52 mm).

The weight of the new turret is equal to 4800-4900 kg, as opposed to 4500 kg weight of the turret with 52 mm thick sides produced at factory #112. As a result, the mass of the T-34-85 tank with thickened armour is 32.3-32.4 tons as opposed to 32.0 tons for a T-34-85 tank with 52 mm thick turret armour.
The mass of the tank with thickened turret armour (32.3-32.4 tons) is within the tactical-technical characteristics approved by the State Committee of Defense on December 15th, 1943, for T-34-85 tanks (32.0-32.5 tons).

We deem it necessary for factories #183, #112, and #174 to begin producing T-34-85 tanks with the new turret with thickened walls.

The new turret with thickened walls requires the use of 71-L type steel with a higher nickel content than the currently used 8S steel.

The attached decree draft contains a schedule for gradually changing production to T-34-85 tanks with a thickened turret and transfer of 100 tons of nickel to the NKTP in the 2nd quarter from state reserves.

We ask you for your decision.

L. Beria
V. Malyshev
Ya. Fedorenko"


"State Committee of Defense Decree #5690s
April 20th, 1944
Moscow, Kremlin

On improvement of T-34-85 turret armour

In order to improve the robustness of T-34-85 turret armour, the State Committee of Defense decrees that:
  1. The People's Commissariat of Tank Production (comrade Malyshev) must produce T-34-85 tanks with front and side turret armour thickened to 90-75 mm.
    1. At factory #183: beginning on April 1st, 1944
    2. At factory #112: beginning on July 1st, 1944
    3. At factory #174: beginning on October 1st, 1944
  2. Order the Main Directorate of State Material Reserves (comrade Danchenko) to free up and release to the NKTP 100 tons of nickel by April 25th, 1944.
    Central Planning will reimburse the Main Directorate of State Material Reserves the requested amount of nickel in the 3rd quarter of 1944.
Chair of the State Committee of Defense, I. Stalin"

10 comments:

  1. Is there any way to obtain those steels compositions?

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  2. Interesting. I didn´t knew the T34/85 had 52mm cast turrets originally.

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  3. How can factory 183 produce that modified turrets on the 1 st april when decree was made on 20 th april ? Mistake or sadism ?

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    1. Orrr just testing the Malyshevs response speed ?!

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    2. #183 developed the design, right? May just have been a retroactive confirmation or formalisation of a preliminary pilot batch or some similar bureaucratic bullshit.

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    3. Most likely a retroactive confirmation. It wouldn't be the first time.

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  4. http://i.imgur.com/a1rtQbQ.jpg

    Canadian spec sheet on the T-34-85 which basically has those 52mm sides.

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    Replies
    1. Thank You. It never occured to me before that the T34/85 when introduced had only 52mm turret armor and that the 90/75/52 frequently quoted for it actually represent already an upgrade in turret armor.

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  5. Very interesting Peter.

    Regarding the steel composition, manganese and chromium were increased to the upper limit of the tolerance. Carbon and silicon were reduced. This raised the viscosity and resistance of the towers, as early samples were rather fragile. The data come from Svirin, but he seems to refer to an early and later type of 71L. No mention to 8S steel.

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  6. Brittle tempering ranges were not well understood in this period. Chromium and Manganese may increase the sensitivity of steel to hardening and widen the possible temperature range but it also greatly enhances the britellness gap if treated to a specific range during tempering.
    To understand this problem, a Charpy V notch sample at various temperatures was required in addition to mettallographic studies to explore the shift of the brittle to fibrous crack temperature range. Was this done by ww2 soviet steel manufacturers?

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