Military Review

Armor for "Joseph Stalin". The rise of Soviet heavy tank building

War is known to be the best engine of progress. Tank The industry of the Soviet Union made a dizzying qualitative breakthrough in just a few war years. The true crown of this was the tanks of the IS series.

IS-2 are heading to Red Square. Source:

Magnitogorsk recipes

In the previous part stories it was about cast high-hardness 70L armor used for the turrets of the IS tanks. The armor developers from TsNII-48 were far from the first experience in creating protection for heavy tanks.

Before the Kursk Bulge, which became a catalyst for the development of domestic heavy tank building, the main object of modernization was the KV tank. Initially, all work was aimed at reducing the proportion of scarce alloying additives in the composition of the armor. Even the name in TsNII-48 came up with an appropriate one - economically alloyed steel. The original armor of the FD-7954 brand, with which the KV tank entered the Great Patriotic War, according to technical requirements, contained up to 0,45% molybdenum, 2,7% nickel and chromium.

By the end of 1941, a group of researchers led by Andrei Sergeevich Zavyalov at the Armored Institute created a recipe for steel FD-6633 or 49C, in which molybdenum required no more than 0,3%, chromium - up to 2,3%, and nickel - up to 1,5 ,five%. Considering that about 1941 thousand copies of the KV series tanks from the second half of 1943 to 4 were collected, one can imagine the amount of real savings in alloying metals.

KV-1 at the British training ground in Bovington. Source:

The secret of success

The secret of the metallurgists' success lies in the study of the parameters of the formation of fibrous fracture of armor - the main parameter of projectile resistance. It turned out that it is possible to do without a significant proportion of alloying elements by simply changing the cooling rate of the armor during quenching. But this is simple in words - how many preliminary experiments and melts metallurgists had to do, only the now classified archives can tell.

In 1941, the first prototypes of 49C steel were obtained at the Magnitogorsk Metallurgical Combine, which were not inferior to the traditional "pre-war" armor. In particular, the shelling with a 76-mm cannon showed full compliance with the tactical requirements for the tank. And since 1942, only armor with the name 49C was used for the KV series. It is worth remembering that the consumption of chromium, molybdenum and nickel has significantly decreased.

The search for new formulations of armor for heavy equipment did not end there. In 1942 steel GD-63-3 was “welded”, completely devoid of scarce chromium and nickel. To some extent, nickel was replaced by manganese - its share increased more than three times (to 1,43%). Prototypes of the new armor were fired upon. And they turned out to be quite suitable for mass use in the design of the KV. But the Klim Voroshilov tanks with medium hardness armor were retiring. And the place of heavy vehicles was taken by “Joseph Stalin” vehicles with high hardness armor.

Rolled armor 51C

If the 70L armor for the IS-2 turret could be cast, then this trick did not work with the hull parts of the tank. Here, engineers faced two problems at once - the creation of high-hardness armor of great thickness and the need to weld it into a finished hull.

Everyone who is interested is probably already aware of the problems caused by welding of the T-34 armor - the high probability of cracking in the area of ​​welds. The IS-2 was no exception. And its body was originally supposed to be cooked from finally heat-treated parts.

Realizing what difficulties and dangers such a technological solution would bring in military operation, TsNII-48 specialists changed the tank production cycle. As a result, in 1943 at the Ural Heavy Engineering Plant and the Chelyabinsk Plant No. 200 of the IS-2 hull, it was decided to cook from armor plates that had passed after rolling only a high vacation. That is, in fact, the hull of a heavy tank was assembled from "raw" steel. This significantly reduced welding defects on the 51C high-hardness rolled armor.

The final heat treatment by heating before quenching was carried out already on the welded body of the tank, having previously strengthened it with internal struts. The body was kept in the oven for three hours. And then, on special devices, they were transferred to a water quenching tank and kept in it for 15 minutes. Moreover, the water temperature in the quench tank rose from 30 to 55 ° C. The surface temperature of the case after being removed from the water was 100–150 ° С. And that's not all.

After quenching, the body was immediately subjected to low tempering in a circulating furnace at a temperature of 280–320 ° С with holding after reaching this temperature for 10–12 hours. The low tempering of cast towers from 70L armor was carried out in a similar way. Interestingly, crack control in the experimental IS-2 hulls lasted for four months, when the first serial tanks left the factory gates.

Repair of the V-2 engine of the IS-2 tank in the field. Source:

Chemical composition

What was the 51C rolled armor that became the main one for the IS-2, ISU-122 and ISU-152? It is a deep hardening steel for large armor thicknesses with the following chemical composition (%):

C 0,18-0,24
Mn 0,70-1,0
Si 1,20-1,60
Cr 1,0-1,5
Ni 3,0-3,8
Mo 0,20–0,40
P ≤0,035
S ≤0,035.

In comparison with the cast armor 70L, the proportion of molybdenum and nickel in rolled steel 51C was higher, which guaranteed an increase in hardenability up to 200 mm. When the hulls of heavy tanks were fired at with 88-mm shells, it turned out that the armor of high hardness was much superior in durability to its medium-hard predecessors. The issue of placing rolled armor 51C was resolved immediately.

Smart welding

An important contribution to the success of the development of armor production of tanks of the IS series was made by automatic welding of steel under a layer of flux. Since it was impossible to transfer the entire process of manufacturing a tank armored hull to such welding at the beginning of 1944, the engineers focused on automating the most extended and mechanically loaded seams.

At the Chelyabinsk plant No. 200, in the process of assembling the hull of the heavy tank IS-2, only 25% of all welds could be automated. By the middle of 1944, Tankograd was able to automate 18% of all possible 25% of welds. The total length of the welded seams along the hull of the IS-2 heavy tank was 410 running meters, of which 80 running meters were carried out by the automated welding method.

This result led to significant savings in scarce resources and electricity. It was possible to free up to 50 skilled manual welders (their labor costs amounted to 15 man-hours) and save 400 kilowatt-hours of electricity. Decreased consumption of electrodes (about 48 kg, austenitic - 000 kg), oxygen (by 20 cubic meters).

The time spent on welding has also been significantly reduced. For example, welding the bottom and the turret box to the sides with a sixteen-meter seam took 9,5 man-hours in manual mode, and only 2. A seam similar in length connecting the bottom to the sides of the tank hull in automatic mode required 3 man-hours ( in manual immediately 11,4). At the same time, highly qualified welders could be replaced by low-skilled workers in automatic welding.

IS-2 before the Victory Parade and near the Reichstag. Source:

Ural SAGs

Researcher of the Soviet tank industry, candidate of historical sciences Zapariy Vasily Vladimirovich from the Institute of History and Archeology of the Ural Branch of the Russian Academy of Sciences in one of his works describes in great detail the automatic welding units used in the Urals for armored hull production.

The most widespread was an assault rifle of the "ACC" type with a Bushtedt head. There were eight such installations at Uralmash. The wire feed speed in this machine depended on the voltage in the arc. It required 5 units, including 3 kinematic electric motors and 1 motor-generator.

By the middle of 1943, the SA-2 automatic welding machine was designed for the needs of the IS-1000 heavy tanks. Or a welding machine with a capacity of up to 1000 A.

In order to master the production of armored hulls for the new Chelyabinsk heavy tank IS-3, the engineers of the plant in 1944 designed the apparatus "SG-2000". This machine was designed to work with low-carbon welding wires of increased diameter (6–8 mm) and found its application during the manufacture of the IS-3 tower. The installation had a dispenser for introducing a special composition (various ferroalloys) into the weld section for the purpose of deoxidizing (reducing) the metal in it. In total, on the principle of self-regulation of the welding arc at UZTM, by 1945, 9 automatic welding installations of three types were created: "SA-1000", "SG-2000", "SAG" ("Automatic welding head").

More beautiful than German armor

The result of the whole story with the armor of heavy IS tanks was the surprisingly prompt development of a steel recipe that surpassed German armor in its tactical properties. TsNII-48 received a hardenable 120-mm steel, the thickness of which, if necessary, could be increased to 200 mm.

This became the main foundation for the development of the post-war family of heavy Soviet tanks.
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  1. Antifreeze
    Antifreeze 26 November 2020 18: 05
    Today is straight "tank evening" smile
  2. The leader of the Redskins
    The leader of the Redskins 26 November 2020 18: 12
    Once again, I thank the author for an interesting article. I hope he will please us more than once with something like that.
  3. polpot
    polpot 26 November 2020 18: 22
    They were great people, eternal memory, thanks for the article.
  4. Recoil
    Recoil 26 November 2020 18: 57
    Thanks for the interesting material!
    Glory to the heroes!
  5. Potter
    Potter 26 November 2020 19: 10
    Thanks, very interesting. On VO, unfortunately, articles with good technical content are rare.
  6. Mountain shooter
    Mountain shooter 26 November 2020 19: 19
    How quickly they developed such complex things as armor steel! It wasn't cooked in test tubes. In open-hearth furnaces ... and each such melt is the same time, metal, additives, tests ... When did they even sleep in those years?
  7. paul3390
    paul3390 26 November 2020 19: 23
    It's strange - but the biggest one says that the Soviet Union did not do anything more complicated than galoshes ... recourse
    1. Uncle Vanya Susanin
      Uncle Vanya Susanin 26 November 2020 20: 29
      Strange - but the biggest one says that the Soviet Union did not do anything more complicated than galoshes ... recourse

      What is the largest ???
    2. Tochilka
      Tochilka 27 November 2020 11: 30
      They simply did not report to him. And the blizzard doesn't need to know it. The article is excellent. As a technologist, it is very interesting to me.
  8. Free wind
    Free wind 26 November 2020 19: 26
    Wow a 1000 amp welder. I used 300 mm surfacing electrodes with 6 amperes. And for 1000 you can probably dip the scrap in shit and cook. Well, although there were warmers.
  9. Krasnoyarsk
    Krasnoyarsk 26 November 2020 20: 25
    I read the article with interest and pleasure. Thanks to the author.
  10. lucul
    lucul 26 November 2020 20: 38
    Thoroughly. Article plus is unambiguous. And most importantly - a politically neutral article. )))
    I am glad that there were reserves, and if necessary, the armor could be increased from 120 mm to 200 mm.
  11. Aviator_
    Aviator_ 26 November 2020 20: 41
    There are many technical amateurish notes on VO, and Fedorov is one of the few authors who writes reasonably and easily about what he himself knows. Respect to the author! Will there be a sequel about post-war technology?
    1. Evgeny Fedorov
      27 November 2020 07: 17
      Thanks. Post-war armor is more difficult - the materials are not fully open. But I think you can find it.
      1. Aviator_
        Aviator_ 27 November 2020 08: 49
        I understand that the 70s and closer, of course, are under the stamp. But the 50s, when there was only homogeneous armor, maybe already declassified?
        1. Evgeny Fedorov
          27 November 2020 09: 51
          Partially yes. For example, you can collect information in the "Bulletin of armored vehicles"
          1. volodimer
            volodimer 28 November 2020 15: 41
            Eugene, we hope for you, the cycle is just great. good So a sequel is required! Thank you for your work. hi
  12. Undecim
    Undecim 26 November 2020 21: 01
    The secret of the metallurgists' success lies in the study of the parameters of the formation of fibrous fracture of armor - the main parameter of projectile resistance.
    The author writes excellent articles, but trying to cover the issue as informatively as possible, delves into the intricacies of technology and sometimes gets the opposite effect.
    Kink cannot be a projectile resistance parameter. A fracture is the fracture surface of a metal. Studying the fracture, it is possible to identify the quality of the metal and the reasons for its reduced properties (for example, improper heat treatment, accumulation of non-metallic inclusions). In some cases, on the basis of a break, you can make a correct conclusion about the nature and causes of the breakdown or accident. The science that deals with the description of the types and types of kinks is called fractography.
    Fibrous structure is a conventional name. At high magnifications (more than 30-50 times), a pit microrelief is revealed in the fibrous fracture. As the viscosity of the material increases, the depth of the pits increases.
    That is, by examining the resulting fibrous fracture, it is possible to determine such a characteristic of steel as impact toughness, which is an important indicator of projectile resistance.
  13. 911sx
    911sx 26 November 2020 21: 17
    Interesting article. Thanks. In my student years, at the department of steel, I asked the teachers questions about the chemical composition of armor. In the 80s, this was secret information and no one could really say about it, one could guess that the main alloying elements of the armor are nickel, chromium, manganese. Knowing that it was the Ural armor that was famous during the war years, they planted some (I don't remember) Ural field on my course project. It turned out that there was a serious content of vanadium in the ore. Even after blast-furnace processing, I had a decent content of vanadium in cast iron, and, accordingly, in steel. In steel it could be at the level of 0,1 -0,3%. I know that vanadium gives good hardenability on the surface ... Well, these are my guesses and speculations ...
  14. Momotomba
    Momotomba 26 November 2020 21: 55
    The article is great! I would not mind reading similar works about the manufacture of submarine hulls. Surely there were also enough problems and interesting solutions.
    1. Leha667
      Leha667 26 November 2020 23: 17
      The hulls of the 667bdr boats were made of AK29 steel.
      For me, as an operator, this knowledge was enough)
      1. Paragraph Epitafievich Y.
        Paragraph Epitafievich Y. 26 November 2020 23: 48
        Quote: Leha667
        The hulls of the 667bdr boats were made of AK29 steel.
        For me, as an operator, this knowledge was enough)

        Great answer!))
      2. Momotomba
        Momotomba 27 November 2020 09: 56
        It turns out interestingly that you, as an operator, are not interested in the process of making your own iron, inside which you dive, but you read about making tank armor ...
        1. Leha667
          Leha667 28 November 2020 00: 48
          At the school, metal science was taught well. I remember the Iron-carbon diagram even now)
          We were not taught the technology of making steels and alloys. And they did the right thing. We didn't go to the factory to work after college. During factory repairs, knowledge of steel production technology is also not needed.
          1. Momotomba
            Momotomba 28 November 2020 19: 05
            It is pleasant to talk with a person who remembers the solidus and liquidus lines and knows the differences between primary and secondary austenite hi
  15. Al_lexx
    Al_lexx 26 November 2020 22: 19
    Thanks. Pts interesting.
  16. storm
    storm 26 November 2020 23: 57
    Under the "lord of galoshes" for 20 years of rule, not a single serial armata was put into the army ...
    During Stalin's time, they were poisoned with mothballs ...
  17. svp67
    svp67 27 November 2020 05: 31
    If the 70L armor for the IS-2 turret could be cast, then this trick did not work with the hull parts of the tank.
    Even as it passed ... The original version with a "stepped nose" for the IS tanks, the nose was cast, after the "straightening" of the nose, this part was already done in two versions,
    and so it is, there are tanks with a cast bow ...

    so with the swish katanna

  18. BAI
    BAI 27 November 2020 09: 19
    Everything is good, but impersonal, as if everything was done by itself. Where are the people? Here is the engineer Danilevsky, the developer of the KV armor. An excellent specialist, but as always he was sent to prison. And in 1943 after Stalingrad, a satisfied Stalin asked at a meeting "What does the tank industry need"? And the deputy minister - director of the Chelyabinsk Kirov plant (this is the Kirov plant from Leningrad was transported) Zaltsman stands up and says: "The tank industry needs engineer Danilevsky." And Danilevsky was released. And in the armor of the ISs, Danilevsky's developments were also used, the armor was not created from scratch. And other people, no less interesting, participated.
    1. mat-vey
      mat-vey 28 November 2020 11: 50
      What's wrong?

      August 3, 1942 - sentenced to 15 years in camps (Nizhny Tagil) with disqualification (Article 58.7).
      From the essay by Y. Frumkin-Rybakov "Armor of Russia":
      In May 1942, Oleg Fedorovich Danilevsky was arrested by the NKVD and on August 3, 1942, he was sentenced by the Gorky city tribunal under Article 58-7 to imprisonment in a labor camp for 15 years with disqualification.
      He was charged with sabotage, on the grounds that he signed the deflection cards to smelt armor.
      In addition, he was remembered that he was the son of a tsarist general. Danilevsky's father, Danilevsky Fedor Stepanovich,
      received the rank of major general in the First World War, after the revolution he became a red military expert and died of typhoid in Baku in 1922.
      Iosif Aronovich Frumkin was the first to defend Danilevsky. He called to the Krasnoye Sormovo plant
      from Sverdlovsk Anastasia Mikhailovna Bodisko, a metallurgical engineer, employee of TsNII-48, the country's first armored institute, where Andrei Sergeevich Zavyalov was the director.
      Anastasia Mikhailovna Bodisko came from Sverdlovsk to Gorky without a pass, at her own peril and risk.
      Frumkin and Bodisko, at the call of the deputy commissar of the tank industry M.N. Popov, left for Moscow.
      Iosif Aronovich told me that in Moscow, at Popov's, he vouched for Oleg Fedorovich, writing in a Statement to the People's Commissar of the Tank Industry about Danilevsky's complete innocence and his readiness to share responsibility for the marriage, if his presence is documented. It was decided to write a statement addressed to the USSR prosecutor on the creation of an expert technical commission, which was supposed to understand the essence of the case.
      Anastasia Mikhailovna, in vain tried to transfer the Application to the Prosecutor's Office, there were huge queues, and she had to return to Sverdlovsk (she left Sverdlovsk, in wartime, without documents, because there was time to arrange a business trip to the Krasnoye Sormovo plant she did not have it), besides there were serious fears that the Statement would be lost in the office of the Prosecutor's Office.
      In this situation, Popov called the Heavy Industry People's Commissar.
      Nikolai Stepanovich Kazakov, People's Commissar of Heavy Industry of the USSR, former director of the Izhora plant, who personally knew
      Oleg Fedorovich called the USSR prosecutor and asked him to make sure that the Statement was not lost.
      By the decision of the Presidium of the Supreme Court of the USSR, an expert commission was created in order to supervise the validity of sentencing Danilevsky.
      Frumkin, as the head of the open-hearth shop, provided materials for the smelting of armor, which, allegedly, was of inadequate quality. He gave these materials to Anastasia Mikhailovna Bodisko.
      In addition to the fact that Anastasia Mikhailovna was a talented metallurgist, she loved Oleg Fedorovich. They were having an affair.
      Engineer Bodisko, based on materials provided by Joseph Aronovich Frumkin, collected documents for all heats, for which Danilevsky signed a deviation.
      She traced from which smelting the armor plate was rolled, which tanks and at which avoda were made of this armor. All this data she transferred to Moscow to the People's Commissariat of Tank Industry. Head of the 3rd Main Directorate of the People's Commissariat of Tank Industry Artemy Aleksandrovich Khabakpashev tracked down these tanks on the fronts of the Second World War and demanded material on how these tanks performed in battle. When all the materials were processed, it turned out that the front-line soldiers had no complaints about the quality of the armor for these vehicles. The properly executed documents were transferred to the Expert Commission, which was supposed to give a technical opinion on the merits of the accusation.
      All the time while Danilevsky was in the camp, Frumkin sent to the Danilevsky family: his wife Lyudmila Vasilievna Purtseladze, son Vladimir and stepdaughter Shura, on behalf of Oleg Fedorovich
      pay, and with the opportunity and products ...
      On March 25, 1943, the Presidium of the USSR Supreme Court issued Resolution No. 6 / m to discontinue the case against Oleg Fedorovich Danilevsky. Danilevsky was completely rehabilitated.
      June 3, 1943 - released and fully rehabilitated for lack of corpus delicti.
      The head of the 2nd department of the correctional labor colony “Tagilstroy”, when parting with Oleg Fedorovich, said: “Lucky you, this is the first time in my work”.
      Danilevsky was issued a certificate of release, travel documents to Sverdlovsk, he was sent to the NII-48, where he had a job and Anastasia Mikhailovna Bodisko, who became the common-law wife of Oleg Fedorovich.
  19. Aristarch
    Aristarch 27 November 2020 12: 41
    Thanks a lot for the article! My grandfather worked in a closed design bureau at ChTZ and until his retirement. He said that the IS-3 was the best tank at that time. And in general, his words, "we were ready to fulfill any task that was set before us."
  20. DrEng527
    DrEng527 27 November 2020 14: 20
    Thanks to the author! very interesting!
  21. Constanty
    Constanty 27 November 2020 15: 14
    KV-1 at the British training ground in Bovington

    The reports on the tests of the T-34 and KW-1 at the American proving ground in Aberdeen are fairly well known, but are there any reports from Bovington about Soviet tanks?
  22. Ros 56
    Ros 56 28 November 2020 09: 10
    The topic is interesting. But at the dawn of our youth we were called to MISIS, but we are young, proud, what the hell to us is ferrous metallurgy, give us only fighter aircraft. Now, in his declining years, laughter makes out, but still I do not regret anything. hi
  23. Alien From
    Alien From 28 November 2020 17: 52
    Thanks to the author, it's always interesting to read!)
  24. DemikSPb
    DemikSPb 1 December 2020 23: 59
    It's funny. Tempering (high, medium, low) is assumed to be a post-quench heat treatment operation. Before quenching is called annealing.
  25. Sars
    Sars 1 January 2021 10: 52
    The KV armor, judging by the ruts and holes from small-caliber shells, was not armor at all.
    Problems with welding and heat treatment of ISs, judging by the scattering of the IS-3 pike noses, then were not finally resolved.
    The muzzle of the IS-2 was made by injection molding. I didn't understand the author about the tower, how did its casting affect the strength? That there were no welds?
    Internal stresses in the welded seams are removed by high annealing of the body (650-720 degrees, cooling with the furnace).
    Tempering the entire body? I haven't studied this question, but I can't believe it. Why have a stuck bottom and stern.
    And most importantly, with this method, the Armor is hardened from the outside and inside. Which is fraught with damage to the crew from armor fragments.
  26. Sergey Sfiedu
    Sergey Sfiedu 30 January 2021 19: 48
    I don't remember where, but in some edition I read that the IS-2 armor was still fragile.
    LOCOMOTIVE VL60 LOCOMOTIVE VL82 23 February 2021 17: 41
    As for the heavy tanks IS-2 and TIGER, the IS-2 was much easier to operate, the TIGER, on the other hand, was a very heavy and clumsy tank, but the German designers must pay that the Red Army tanks that came under fire from TIGER tanks were of course restored were not subject, but the TIGER tanks were of little maintenance in the field, secondly, they ran on gasoline, which made the German TIGER tanks even more vulnerable, in the third, the location of the rollers was so unfortunate that in order to replace the faulty one