Spalling in the T-34

[Jeff Duquette]

The soviet scientists and engineers of the time were as advanced or more as any western counterpart in regards metallurgic studies, so in relation with steel composition, I don’t believe there was any theoretical shortcoming of their part…

A shortcoming to exist had to be in the manufacturing process in likes of the ones I talked in the 1st paragraph or some others also pointed in this topic. Even this manufacturing defects most likely had nothing to do with lack of knowledge but instead had their origin in the war itself… (Unlike the UK and USA, USSR had a very destructive war in his home soil as we all know).

I tend to agree. I think Soviet tank and armament designers\engineers were fairly shrewd.

Problems associated with Soviet movement of, and retooling of heavy industry during 1941-1942 go along way toward explaining degradation of Russian steel during this period. A large percentage of Soviet pre-war steel production was in the Don basin. This area was lost to the Germans in 1941 and didn’t fall back into Soviet possession until late 1943.

Russian rolled steel production dropped from 13,000,000 metric tons in 1940 to a mere 5,400,000 metric tons in 1942. Iron Ore production went from 29,800,000 tons in 1940 to only 9,700,000 tons in 1942. It seems logical that the quality of steel being produced also suffered during this period.

Yet non-ferrous metal production (aside form zinc and manganese) remained relatively constant during this same period. Nickel production dropping by only 15% between 1940 and 1942. By 1943 both non-ferrous metal production, iron ore production and steel production are again on the rise. In my opinion the quality of Soviet steel probably increased as the war continued.

[Jeff Duquette]

I found the following to be rather interesting:

Guderian on the T34:

“As has already been mentioned, during November 1941 prominent designers, industrialists and armament administration officers arrived at my Panzer Army for familiarization with the Russian T –34 tank, which exceeds the capabilities of our own combat vehicles. Immediately they wanted to outline, on the basis of previously obtained combat experience, the best approach that would allows us to attain technical superiority over Russians. The proposals of combat officers to produce a tank very similar to the T –34 for the purpose of relieving the extremely unfavorable position of German armored troops within the shortest period time met with no support from the designers. This was not an aversion on their part to imitation, but rather the designers relayed the impossibility of issuing with the required rapidity critical components of an imitation T –34; especially the aluminum diesel motor. Furthermore, our alloy steel, whose quality was reduced by the absence of the necessary raw materials, was also inferior to alloy steel of Russians.”

Guderian H. Erinnerungen eines Soldaten. _ Heidelberg, 1951

See paragraph two

http://militera.lib.ru/memo/german/guderian/08.html

I would be curious if anyone can verify my translation of the above passage. Or better yet whether someone has access to Guderian H. “The Recollections of a Soldier” and can translate the original German.

[Keke]

I would be curious if anyone can verify my translation of the above passage. Or better yet whether someone has access to Guderian H. “The Recollections of a Soldier” and can translate the original German.

There´s another book which I have read, but don´t own (we have quite good libraries here in Finland, y´know). Can´t remember the passage.

German nickel steel production was a rather rare commodity during the war.

Jeff, I forgot to mention this earlier. 75% of the nickel ore German war production needed came from Petsamo (Finland) during the years 41-44. I have understood that only after Finland turned against its former ally (15.9.-44), German war production began to suffer from low nickel supply.

[Skipper]

> had just come off of the production line (from

> the Stalingrad factory IIRC

Stalingrad factory just before it was shut down has produced some very fancy T-34s. Like, with friction bearings, no turret motor and so on - they were just trying to use whatever they had in stock to make "sort of like" tanks. On the basic principle "something is better than nothing". So, if it was one of those T-34s, then no wonder.

[flamingknives]

Tempering, as I understand it from my engineering degree, involves heating the steel to a temperature below the phase change temp. and then quenching it (cool it quickly [to avoid confusion]). Alternatively, I think that the rate of cooling affects the end result. The difference is in the size of crystals formed, but AFAIK, doesn't involve a phase change.

Tempering can produce a wide range of hardness/toughness balences (hardess being more or less inversely proportional to toughness)

Martensite, IIRC, is extremely hard (harder than glass) and is a result of hardening.( heat above phase change temp. and cool quickly.

Face hardening is where only the very outer layer of steel is hardened. This can be either by heating - quenching, or by applying carbon to the heated surface, making a high carbon steel on the exposed surface.

I hope this helps, and that it's right. It's been a couple of years since I did the metallurgy course, and I don't have the time to root around for the notes.

[Tanaka]

Originally posted by flamingknives:

Tempering, as I understand it from my engineering degree, involves heating the steel to a temperature below the phase change temp. and then quenching it (cool it quickly [to avoid confusion])...

I remember my teacher’s alert regarding conflicting names between English and Latin origin literatures... The funny part is that I think the “tempering” English word comes from the Latin one (Romans), so the different technical meaning must have some funny history behind it.

For instances, in Portuguese (a Latin origin language) we type “tempera”, meaning a fast (or not so fast) cooling from the “austenite” domain with intention of forming “martensite” or “bainite”… (This is equal at least for French, Italian and Spanish)

The direct translation into English is “tempering”; wish for the English speakers is a thermal treatment made normally after “quenching” and under the faze transformation temperature (A1).

So the correct translation shouldn’t be “tempering” but “hardening” or “quenching”… I think “quenching” is more appropriate for the “martensite” formation, as for non Fe alloys there are martensite forming treatments that nothing have to do with hardening.

Martensite, IIRC, is extremely hard (harder than glass) and is a result of hardening.( heat above phase change temp. and cool quickly.

Martensite is hard in Fe alloys, due to his capacity to retain Carbon in its crystal structure… For instance non Fe alloys, martensite is softer then the austenite faze… (Austenite is a high temperature faze and it very important regarding the final structure of the material)

...This can be either by heating - quenching, or by applying carbon to the heated surface, making a high carbon steel on the exposed surface.

The C flows into the steel by diffusion… This process was used for many centuries in Japan on its famous Samurai swords… (I also think the Persian used it).

I hope this helps, and that it's right. It's been a couple of years since I did the metallurgy course, and I don't have the time to root around for the notes.

Yes, thanks, it clarified the things… I did a metallurgy “chair” a year ago and I’m now doing a thermal and mechanical treatment “chair”… This together with a composites materials one are my favorites

In a more general way, its funny how the 2nd ww armor used the “all or nothing theory”… an hard steel armor vs. a full of kinetic energy AP projectile… bigger/harder the steel armor the better…hehehe

The only energy dispersion method used was the “slope” introduced by some designers, even then as we all know not all sides of the war went by sloping the armor, wish is quite funny as the principle behind sloping is one of the XVIII classical mechanics.

(I think maybe the problem for some tank designer not going after the slope was the difficulty of manufacturing the edges needed for the “sloped” armor…as we know stress-cumulating points).

When the micro-soldering (heat) penetrating type projectiles come along, the tank designers answered with pre detonation plates…

Its also of some interest to see in nowadays TV (for reasons I totally dislike) how the Israeli army rehabilitated their M60 with pre-detonations blocks (useful anti-rpg)…

What fun I and others would take out of an armor analysis of a nowadays LAV or a MBT…

Now if any of you gentlemen’s out there wants to give to “my” university one of these vehicles, obviously only for didactical and learning proposes, is more then welcome

I herd submarines are even funnier…if a submarine comes along… ok forget it

Just to finish this already long post, Jeff Duquette…

Yes it would be interesting to find the original text and get someone who could read it… As we all know Russian translation about Russian armor are as impartial as English translation about American/English armor (hehehe…don’t flame me!)

[flamingknives]

From what I see of modern Soviet/CIS MBTs, most of them mount pre-detonation blocks, also known as reactive armour. There's even a french company making add on reactive armour for the BMP 3.

You coundn't pay me enough to be an infantryman supporting something like that.

Looking at Tanaka's comments, I'd say that hardening would be the correct term. Quenching is used to describe part of the process.

[rexford]

The IS-2 development article on the Russian Battlefield site has info on how brittle IS-2 armor initially was. Tests with 76.2mm ammo at 500 to 600 meters resulted in IS-2 armor penetrations at all angles, and while only a few rounds went completely through, most created lethal fragments inside the turret.

So serious armor problems continued throughout the war even if they were not continuous.

If Russia used their skilled steelworkers to fill out the army, it is possible those left behind to make the tanks may have less skill and make more mistakes.

T34 is high hardness armor, which will fragment more on the inside than a Sherman. One of the interviews with Russian vets discusses how glancing hits on T34 were more dangerous than against Shermans.

Stalin supposedly made a statement that poor quality tanks were okay cause the life of a tank was short anyway (and most kills came on side armor hits, where armor quality has little impact on survival).

There is another story, put forth by John Waters some time ago (I believer), where IS-3 tanks were running over a cross country course during tests and the weld line on the glacis front broke open. Quality can be elusive.

[rexford]

U.S. metallurgical analysis of IS-2 armor found in Berlin ruins discovered that hits on turret would probably crack the turret ring, disabling the tank. There were problems with the armor production.

T34 and KV-I armor analyzed by Allies had problems.

On other hand, Allies put out how many 56 degree glacis Shermans with armor that was famous for the types of flaws and brittleness it could contain. Russian Battlefield has analysis of T34 and KV-I where 76.2mm round penetrates Sherman front at 1100 meters and American engineers say nasty things about Sherman armor.

Armor goes bad for many reasons.

[Jeff Duquette]

Just so I am absolutely clear on this Lorrin, you are saying Soviet wartime armor was flawed…throughout the war.