Spalling in the T-34

[Runyan99]

Just dropping some knowledge on you all. I do not know if this is commonly known, so I thought I would post.

The following is taken from "Fighting for the Soviet Motherland" by Dmitriy Loza, Nebraska Press.

From the beginning of the Great Patriotic War, the Soviet government was faced with the enourmous problem of evacuating countless indistrial enterprises from the country's western regions to its eastern regions. The relocated defense plants, as the chairman of the Council of Ministers [J.V. Stalin] reported,"began production at their new sites some seven or eight months later. This [lapse in production] has led to a weakening of our defense capability and has placed the Soviet Union in mortal dnager."

The Red Army's failures during the initial period of the war allowed the enemy to capture a number of mineral-rich regions of Ukraine and Belorussia. As a result of the Soviets' having lost control of these regions, a complicated situation developed in the plants that manufactured the armor for their tanks. Because these factories had recieved insufficient quantities of some of the smelted metals required to ensure the necessary toughness of armor, the armor plate they produced turned out to be somewhat brittle in its composition - and, of course, there were negative consequences on the battlefield.

...

The T-34s assembled with this defective armor arrived as equipment for units of 45th Brigade, 4th Tank Corps, in June 1942. They were brand-new tanks, just of the assembly line, still bearing factory paint.

The brittle-armored tanks of the brigade fought their first battle in the defense of Voronezh the month following their delivery. It was a fierce engagement with the enemy. Almost immediately the unit commander had begun to recieve radio messages with strange contents. Despite the failure of enemy shells to penetrate the T-34 tanks' armor, crew members were being wounded inside their turrets, primarily in the exposed areas of the body- the hands and arms, the face, and, in the case of some commander-gunners, the eyes.

With the first lull in the battle, the Soviet troops began to investigate these mysterious wounds. It soon became clear to them that the steep slope angle of the t-34 turret's exterior surfaces was allowing enemy solid-shot rounds generally to ricochet when they struck that area. But when such a round did indeed hit the turret's outer wall, pieces of the tank's armor itself flew off the inner wall at extremely high velocities- a rate that seemed to vary according to the kinetic energy of round at the monemt of impact. In general, if the enemy round struck on the left side of the tank, the commander-gunner- whose crew position closest to the left inner wall of the turret- was being injured by the fragmenting armor of the vehicle wall. If the round hit on the right side, the armor spalling was striking the loader, whose crew position was on that side. The size of the fragments ranged from microscopic to several millimeters in diameter.

...

This serious deficiency in the combat worthiness of the T-34 was finally eliminated in early 1943. It was the tankers of the older generation- soldiers and officers who had gone through training before the Great Patriotic War and come into the active army in the first months of that conflict- who experienced the situation firsthand.

The author (who was himself a tanker, and a Hero of the Soviet Union) goes on to state that the Sherman M4A2 tanks which his 233d Tank Brigade, 5th Mechanized Corps recieved in late 1943 never suffered from spalling.

[Jeff Duquette]

Runyan99:

I have read of this T34 spalling phenomena within other sources. It is always good to read independent verification of such information. Thanks for posting the above.

Regards

Jeff Duquette

[illo]

Yes, thanks for posting.

[zukkov]

did the kv series have any spalling problems? a friend of mine who's pretty knowledgeable about ww2 history mentioned a long time ago that they did. but i have not read of it anywhere. just wondering...

[Keke]

This serious deficiency in the combat worthiness of the T-34 was finally eliminated in early 1943. It was the tankers of the older generation- soldiers and officers who had gone through training before the Great Patriotic War and come into the active army in the first months of that conflict- who experienced the situation firsthand.

How convenient that all the spalling problems came to an end after Stalingrad...

It doesn´t seem to be a well known fact that throughout the war Russian armor plates lacked ingredients like molybden, vanadin and decent amounts of chrome to make them as strong as western armor.

[Jeff Duquette]

Keke Said: How convenient that all the spalling problems came to an end after Stalingrad...

It doesn´t seem to be a well known fact that throughout the war Russian armor plates lacked ingredients like molybden, vanadin and decent amounts of chrome to make them as strong as western armor.

Impurities within a specific heat, as well as hardening, tempering and rolling mill processes are as critical as alloying when considering impact spalling. Laminations can occur during rolling as impurities are squeezed and flattened within a plate. Results can be linier planes of weakness and susceptibility to impact spalling.

I am curious as to your comment regarding the convenience of spalling problems coming to an end during early 1943. Can you elaborate?

[ May 18, 2002, 05:04 PM: Message edited by: Jeff Duquette ]

[Tanaka]

Originally posted by Keke:

...Russian armor plates lacked ingredients like molybden, vanadin and decent amounts of chrome to make them as strong as western armor.

Could you elaborate a little bit more?

Lack of Cr?

Lack of V?

Lack of Mo?

thanks

[Keke]

I am curious as to your comment regarding the convenience of spalling problems coming to an end during early 1943. Can you elaborate?

I love Soviet historiography as much as communism.

And there are no rational reasons for improvement of Soviet armor quality in early -43.

[Keke]

Could you elaborate a little bit more?

Lack of Cr?

Lack of V?

Lack of Mo?

Cr half as much as in western armor.

No V.

No Mo.

[Denizen]

Here's a quote from http://www.battlefield.ru/library/archives/stat/stat7.html

(a translated document from the russian archives that offers insight on what the Americans testing a lended T-34 thought of its armor):

"A chemical analysis of the armor showed that on both tanks the armor plating has a shallow surface tempering, whereas the main mass of the armored plating is made of soft steel.

In this regard the Americans consider that by changing the technology used to temper the armored plating, it would be possible to significantly reduce its thickness while preserving its protective ability (the situation with American armor was even worse. Engineers in Aberdeen have criticized their armor on Shermans. Soviet engineers have agreed with them because during the comparative trials Soviet ZIS-3 gun could penetrate Sherman's galcis from 1100 metres - Valera). As a result the weight of the tank could be decreased by 8-10%, with all the resulting benefits (an increase in speed, reduction in ground pressure, etc.)"

[Jeff Duquette]

Armor steel in both the KV-1 and T34/76 contained both molybdenum and chromium. Vanadium is not present in significant amounts in any of the rather common RHA recipes listed below...western or eastern armor steel. Nickel alloy percentages in Soviet armor steel appeared to exceed common recipes of both the British and Americans. German nickel steel production was a rather rare commodity during the war.

Samples of T34/76 plate indicated the following alloying:

C - 0.23% to 0.28%

Mn – 1.2% to 1.27%

Si – 1.09% to 1.45%

Ni – 1.24% to 1.32%

Cr – 0.85% to 1.05%

Mo - 0.195% to 0.22%

V – only trace amounts

Samples of KV-1 plate indicated the following alloying:

C - 0.30% to 0.32%

Mn - 0.41% to 0.44%

Si - 0.32% to 0.34%

Ni - 2.91%

Cr - 1.47% to 2.34%

Mo - 0.25% to 0.27%

V – only trace amounts

Samples of German Plate from the MKIII:

C - 0.44% to 0.54%

Mn – 0.69% to 1.03%

Si – 0.21% to 0.64%

Ni – only trace amounts

Cr – 0.83% to 1.47%

Mo - 0.18% to 0.38%

V – only trace amounts

Samples of German Plate from the MKIVf2:

C - 0.39% to 0.42%

Mn – 0.42% to 1.03%

Si – 0.33% to 1.48%

Ni – only trace amounts

Cr – 1.26% to 2.66%

Mo - 0.03% to 0.25%

V – only trace amounts

United States 2.25” RHA plate, Carnegie Steel:

C - 0.28% to 0.35%

Mn – 1.21% to 1.28%

Si – 0.20% to 0.23%

Ni – 0.77% to 0.84%

Cr – 0.78% to 0.82%

Mo - 0.39% to 0.40%

V – nil

British 1” to 2.5” RHA Plates, Dominion Foundries and Steel ltd

C - 0.25% to 0.27%

Mn – 0.73% to 0.83%

Si – 0.28%

Ni – 0.83% to 0.84%

Cr – 0.79% to 0.93%

Mo - 0.44% to 0.47%

V – nil

[Keke]

Jeff, from what source did you get that detailed information?

[Paul Lakowski]

Originally posted by Jeff Duquette:

Armor steel in both the KV-1 and T34/76 contained both molybdenum and chromium. Vanadium is not present in significant amounts in any of the rather common RHA recipes listed below...western or eastern armor steel. Nickel alloy percentages in Soviet armor steel appeared to exceed common recipes of both the British and Americans. German nickel steel production was a rather rare commodity during the war.

Samples of T34/76 plate indicated the following alloying:

C - 0.23% to 0.28%

Mn – 1.2% to 1.27%

Si – 1.09% to 1.45%

Ni – 1.24% to 1.32%

Cr – 0.85% to 1.05%

Mo - 0.195% to 0.22%

V – only trace amounts

Samples of KV-1 plate indicated the following alloying:

C - 0.30% to 0.32%

Mn - 0.41% to 0.44%

Si - 0.32% to 0.34%

Ni - 2.91%

Cr - 1.47% to 2.34%

Mo - 0.25% to 0.27%

V – only trace amounts

Samples of German Plate from the MKIII:

C - 0.44% to 0.54%

Mn – 0.69% to 1.03%

Si – 0.21% to 0.64%

Ni – only trace amounts

Cr – 0.83% to 1.47%

Mo - 0.18% to 0.38%

V – only trace amounts

Samples of German Plate from the MKIVf2:

C - 0.39% to 0.42%

Mn – 0.42% to 1.03%

Si – 0.33% to 1.48%

Ni – only trace amounts

Cr – 1.26% to 2.66%

Mo - 0.03% to 0.25%

V – only trace amounts

If I remember right the quality of German armor that made it superior was the higher carbon content , while high silicon leads to more brittle armor [ as in the T-34]....but KV armor looks like its more in the german vane [higher carbon and lower Silicon]?

[ May 18, 2002, 09:22 PM: Message edited by: Paul Lakowski ]

[Jeff Duquette]

"Denizen brought us the often quoted bit from the Russian Battlefield web page regarding the Aberdeen T34/76:

A chemical analysis of the armor showed that on both tanks the armor plating has a shallow surface tempering, whereas the main mass of the armored plating is made of soft steel.”

The actual Aberdeen Proving Ground\Watertown Arsenal Reports bares little resemblance to the information presented on the RBF site. The T34/76 sent to Aberdeen by the Soviets in 1942 actually possessed armor that was excessively hard by US Standards. Not face hardened ala some German tank armor, but homogeneously hard throughout its plates. Hardness levels on samples taken from the T34/76 varied between BHN 429 to 495. Typical US practice entailed use of RHA armor for plate thickness between 1” to 2” with uniform hardness of between BHN 280 to 320.

What is really said in the report regarding the Aberdeen T34/76 is as follows:

“The subject armor [T34/76] is considerably harder than American Armor of comparable thickness. It is the practice of this country to reduce the hardness of armor with the increase in thickness to maintain good resistance to the shock resulting from impact of larger caliber projectiles. It has been demonstrated by ballistic tests that there is an optimum hardness for each thickness of armor for maximum ballistic properties, and that the optimum hardness is an inverse function of thickness under overmatching projectile conditions at normal incidence of fire. The maximum ballistic properties include not only resistance to penetration, but also resistance to spalling, shattering, or cracking under impact of both overmatching armor-piercing and deforming projectiles, the latter type producing a high order of shock impact.

American Armor does not generally fail structurally upon complete penetration; the projectile either pushes the material aside, or punches out a plug, leaving the armor still capable of affording protection against further ballistic attack. On the other hand, very hard armor has a tendency to fail structurally when impacted by projectiles of sufficient caliber and velocity to produce complete penetration; the armor breaking up or cracking so extensively as to effectively decrease it ability to resist further impacts. Hard armor would be expected to have higher ballistic limits against under matching projectiles than soft armor at all obliquities, and would possibly have superior resistance to penetration of overmatching projectiles at very high obliquity. In the case of hard armor under ballistic attack at high obliquities, it is believed that the high hardness would be instrumental in deflecting the projectile in such as to increase its obliquity, thereby enabling the armor to defeat the projectile.

In designing armor to afford maximum protection against armor-piercing high explosive projectiles intended to detonate after complete penetration of the armor, the consideration of resistance to penetration may, in some cases, be more important than resistance to shock. The subject Russian armor appears to have been designed for maximum resistance to penetration of undermatching A.P.H.E. projectiles at high obliquities. Armor up to 3 inches inthickness and having hardness in the range of 400 to 500 Brinell [bHN] would be expected to evidence extremely brittle behavior under normal and low obliquity impact of overmatching armor-piercing projectiles.”

[Jeff Duquette]

KeKe Said: Jeff, from what source did you get that detailed information?

There are numerous sources involved...all primary source information. Drop me an email if you like and I will provide you a full listing of references.

I suspect Paul Lakowski can verify most if not all of the alloying information posted above.

[Keke]

There are numerous sources involved...all primary source information. Drop me an email if you like and I will provide you a full listing of references.

I suspect Paul Lakowski can verify most if not all of the alloying information posted above.

Because I´m lazy, could you provide the list here?

Not all of them, if there´s too many.

I just want to be sure, that those samples of Soviet tanks are decent ones. Not like samples send over to US by Soviet officials.

[Keke]

My only source on this matter is Pekka Kantakoski´s book "Punaiset panssarit - Puna-armeijan panssarijoukot 1918-1945 (Red tanks - Red Army armoured forces 1918-1945)".

[Jeff Duquette]

War Office 185/171 Armour Plate;

Watertown Arsenal 710/691 Metallurgical Examination of 2-1/4” RHA Carnegie Steel Corporation;

WAL 640/91 Armor and Welding; Russian Medium Tank T-34 and Heavy Tank KV-1;

Aberdeen Proving Grounds 470.5/4492 Tests on Armor Plate, German Armor from a Pz.Kw. III;

Office of the Chief of Ordnance 400.112/4800 Metallurgical Examination, Model GF2, German Tank.

I am very interested in the alloying details for Soviet armor plate in Kantakoski's book. Can you provide specifics on Soviet armor alloying from it? It might explain some the spalling effects noted in Loza's book.

[Paul Lakowski]

Originally posted by Jeff Duquette:

"What is really said in the report regarding the Aberdeen T34/76 is as follows:

“The subject armor [T34/76] is considerably harder than American Armor of comparable thickness. .....It has been demonstrated by ballistic tests that there is an optimum hardness for each thickness of armor for maximum ballistic properties, and that the optimum hardness is an inverse function of thickness under overmatching projectile conditions at normal incidence of fire. The maximum ballistic properties include not only resistance to penetration, but also resistance to spalling, shattering, or cracking under impact of both overmatching armor-piercing and deforming projectiles, the latter type producing a high order of shock impact.

.”

Ok just to stir things up a bit, but that description could be applied to the Panthers inability to survive 100 & 122mm AP hits at those Kubinka test?Come to think of it , if US projectiles where low hardness [ compared to Germans] then that might also fit as "deforming projectiles".

[ May 19, 2002, 01:27 PM: Message edited by: Paul Lakowski ]

[Tanaka]

Originally posted by Denizen:

..."A chemical analysis of the armor showed that on both tanks the armor plating has a shallow surface tempering, whereas the main mass of the armored plating is made of soft steel.

This is an important source of true problems, steel temperability, and it shown by the difficulty, due to internal tensions, of uniformly tempering a big piece of steel (see Jominy works). Another true source of poor steel quality could be defects on the steel manufacturing process allowing problems as the high level of S or P or yet “bubbles” to show up in the final steel.

Now, as for the steel composition, you all point only for trace amounts of V in all 2nd ww steel armors, I’m a bit amazed that the grain size limiter proprieties of the thin vanadium carbonates were not explored by the time.

It is also commonly known Cr is a steel hardening element, but it is of no use if this Cr doesn’t have sufficient C to form the (FeCr)3C…

Saying these and also not wanting to annoy anymore any one with technical details, it is my believe that:

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).

[Keke]

I am very interested in the alloying details for Soviet armor plate in Kantakoski's book. Can you provide specifics on Soviet armor alloying from it? It might explain some the spalling effects noted in Loza's book.

Sorry, I cannot give you a detailed answer yet, because I don´t own the book. So I asked buddy of mine, who does, for a couple of quick examples of information it offers:

The armor igredients of T-34/85(!) (p177, in the order presented on this forum earlier):

C - 0.45%

Mn - 0.78%

Si – 0.67%

Ni – 0.00

Cr – 0.62%

Mo – 0.00%

V - 0.00%

The armor igredients of Stug40 (p177):

C - 0.46%

Mn - 0.59%

Si – 0.40%

Ni – 1.51%

Cr – 1.25%

Mo – 0.05%

V - 0.10%

I´ll give you more detailed reply as soon as I get hold of the book again.

[ May 19, 2002, 02:48 PM: Message edited by: Keke ]

[Jeff Duquette]

Paul Said: Just to stir things up a bit, but that description could be applied to the Panthers inability to survive 100 & 122mm AP hits at those Kubinka test?Come to think of it , if US projectiles where low hardness [ compared to Germans] then that might also fit as "deforming projectiles".

Not sure how this is stirring things up. Perhaps I don’t understand what it is you are trying to say. Panther armor hardness was not in the realm of the Russian T34/76 armor hardness. Hardness of Panther glacis plate was (as per BIOS “German Tank Armor”) more in the realm of 260 to 310 and was even softer by 1945. This is a hardness level more in tune with American and British practices (US 3" to 4" RHA being the realm of 250 to 300 BHN). German armor production also followed the American philosophy of increasing thickness of plate and decreasing hardness for optimum protection.

Its my beleif that the Soviet made a conscious design decision early on with the rather hard T-34/76’s armor. I don't buy into the accidental high hardness idea put forth by various folks. The T34/76's armor was designed to combat under-matching projectiles. This would have been consistent with their experience tank combat during the Spanish Civil War in which the majority Soviet tank casualties were the result of heavy caliber MGs firing AP ammunition, or small bore anti-tank guns of calibers 20mm to 37mm.

[Skipper]

Afaik, standard recipe for armor plate changed quite a bit during the 4 years of war. Besides, there were large deviations from standards due to availability of rare metals in a given place at a given time.

So, it's not at all surprising that one book says one thing, and another says something completely different.

[Michael Emrys]

Originally posted by Tanaka:

Another true source of poor steel quality could be defects on the steel manufacturing process allowing problems as the high level of S or P or yet “bubbles” to show up in the final steel.

This could very well be. I recall reading one German officer (Guderian?) writing of some T-34s he inspected that had just come off of the production line (from the Stalingrad factory IIRC). He claimed that he observed flaws in the armor castings that were big enough to put his fist into. He was rather shocked at this, and implied that it was not uncommon, but since there was a general tendency on the part of the Germans to regard all things Russian as substandard, he may have exaggerated that part. In any event, such flaws in the production process were not unknown.

Michael

[Tanaka]

C - 0.45%

Mn - 0.78%

Si – 0.67%

Ni – 0.00

Cr – 0.62%

Mo – 0.00%

V - 0.00%

Again, this composition numbers or any others, in the form they have been presented here, have no great value…

How did they get them? X-Ray diffraction?

From what part of the tank/armor are them?

From how deep are them? Surface of the armor? Crew compartment?

Even if at a certain place in the armor, the steel composition was exactly that, it might be the result of a poor homogenizing processes (austenitizing) and be far away form the rest of the armor composition.

In my view, there is much more importance in how the steel was tempered* (speed/austenizing temperature and time) and what thermal treatment it had after tempering*...

*-I can’t remember exactly, but I think there is a conflict in what is the meaning of tempering for Latin origin languages and Anglo-Saxon ones… By tempering I mean fast (or not so fast) cooling of a material (main goal is to obtain martensite).

“Quenching”?!? Is that the word you use ?

For instances, for the composition quoted above in order for a complete martensite composition, a quite fast tempering* would have to be done wish add up with the Cr composition, would lead to a very fissure prone steel.

----------------------------------------

Edited after seeing Michael emrys post...

Again, there is a technical word for what I mean by "bubbles", and again I don't know the English counterpart... "bubbles" is what I did when was a child with soup and water

[ May 19, 2002, 07:49 PM: Message edited by: Tanaka ]