January 25th, 1940
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- When researching armour for 25-50 mm plates, the Ilyich Research Laboratory made the correct decision to explore highly hardened steel while preserving the necessary degree of ductility. Despite existing opinions that thick tank armour (40-75 mm) must have lower hardness (3.4-3.6 mm), the Research Laboratory developed hard armour (2.9-3.1 mm), finding a successful combination of alloying components, which gave the armour satisfactory ductility.
- The commission remarks that work on MZ-2 armour was done very thoroughly. Experience with HZ steel made from byproducts of ship armour manufacturing proposed by engineer D.I. Chizhikov in 1937 was applied, work on determining the optimal combination of elements (C, Ni, Si) for various armour thicknesses was performed, although the analysis should be confirmed for 30 and 35 mm thick armour.
The process of smelting steel from byproducts of ship armour with minimal addition of nickel was developed. Work to establish the thermal hardening process was performed. Sufficient proving grounds trials were performed to present the type of steel to the commission.
However, the commission remarks on the insufficient amount of laboratory work performed on the materials, especially microscopic analysis and fracture tests, with correlations established between armour quality and fracture test results. - Let it be noted that, at the point of delivery of MZ-2 armour, it had already been used in the production of A-34 hull components, and has proven itself completely. Another positive note is that not one, but six plates were presented for delivery, which allows for more confident conclusions.
- Based on the results of trials, the commission concludes that MZ-2 steel demonstrates high resistance to shells and bullets when used in thicknesses of 40, 45, 50, and 25 mm against shells up to 45 mm in caliber inclusive, which is superior to tank armour of FD-4654, 4674, and 7634 types, as well as high quality HNM plates used by the AU to test shells.
In addition to high resistance (PSP and PTP [rear plate intactness and complete penetration]) against blunt tipped 45 mm shells, both at normal and at angles, 40, 45, and 50 mm plates also showed good resistance against sharp tipped 2-01991 45 mm shells, which approached the resistance of surface hardened plates against this type of shell.
Due to a lack of data against 37 mm ammunition, the commission could not perform a detailed comparison against other types of armour. MZ-2 plates also reliably destroy incoming shells. 40 mm thick plates and up do not allow a shell to penetrate with its HE chamber intact. - These excellent characteristics are achieved due to high hardness and satisfactory ductility demonstrated by 40, 45, and 50 mm thick plates against 37 and 45 mm shells. These characteristics (hardness and ductility) are the defining characteristics of MZ-2 steel. A simple heat treatment method ensures that production will be kept up to standards.
- From a cost standpoint, MZ-2 steel is very interesting, as it allows the production of tank armour, sufficiently hardened by additions of nickel and molybdenum, with minimal additions of nickel and use of ship armour byproducts. Existing types of tank armour, FD-4654, 7934, and even MIZ require a large amount of additional nickel and molybdenum.
The commission considers it necessary to task the Ilich Research Laboratory with the following work:
- Smelt MZ-2 steel with nickel and molybdenum from byproducts in such a way that additional nickel is not required.
- Explore other ways of smelting MZ-2 steel that are more cost effective than the duplex process.
- Confirm the chemical composition of nickel and carbon, especially to determine the feasibility of producing the armour without additional nickel.
- Explore the effect of chrome, silicon, and molybdenum on the characteristics of steel.
- Explore the optimal production process for MZ-2 steel.
The commission decrees that:
- Conditional on satisfactory results against 76 mm shells, the Chief of the Red Army ABTU and the Chief of the 7th Directorate of the People's Commissariat of Shipbuilding should accept MZ-2 into production for 40, 45, and 50 mm plates for A-34 tanks.
- MZ-2 steel is recommended for use in the production of 25 mm thick armour plates.
- The Ilyich laboratory should continue work on 30 and 35 mm thick plates, which demonstrated poor ductility during trials.
- Task the Ilyich laboratory with exploring the use of MZ-2 steel in the production of 55-75 mm thick plates. The 7th Directorate must provide the laboratory with a shooting range for a 76 mm gun for this work.
- Accelerate the completion of work to determine the suitability of MZ-2 steel for production of plates thinner than 25 mm.
- Establish the following tactical characteristics of MZ-2 armour:
- Thickness45 mm sample 013045 mm 2-0199137 mm blueprint 388212.7 mm DK0 degrees30 degrees0 degrees30 degrees0 degrees30 degrees0 degreesPTPPSPPTPPSPPTPPSPPTPPSPPTPPSPPTPPSPPTPPSP50745Higher than max velocity680712691>740743760----45725755Higher than max680-663>685680710740760--40669690740765665690-750630685675725--25450530500560----550650500650730-
- Advise the A-34 manufacturer to increase the thickness of the rear armour from 35 to 40 mm. At a cost of a small increase to mass (100 kg), it will drastically increase the performance of the vehicle.
- Accept the attached technical requirements draft. Propose and task the Ilyich laboratory with development of an MZ-2 plate fracture scale.
- Accept the attached instructions for production of MZ-2 steel by the Ilyich laboratory. Instruct the laboratory to develop a process to smelt steel using 50% of HNM steel byproducts."