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Huh, that’s weird, usually Bainite is undesired for armor or structural components due to excessive brittleness: 

 

http://navweaps.com/index_nathan/metalprpsept2009.php#Bainite 
 

pearlite being just as tough but less brittle (on average) and martensite also being less brittle, and even tougher. Unless they want the contents of the container to fall out after the first hit, like ERA or something similar, this doesn’t look like an advancement. 

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pavise-product-image-dt.jpg

armored-steel-DSEi.jpg

This is what also called pizza bainite, super bainite,  etc

It is (nothing more, nothing less) than replicating the bainitic matrix of ADI (Austempered Ductile Iron) in a steel.

 

There are attempts to sell this as armour, for instance PAIVSE 600

https://www.tatasteeleurope.com/en/news/news/2013/2013_lightweight_armour_steel_trade

It is very suitable for making in a perforated state,  it can be supplied "soft" then punched/machined/rolled,  and then austenised and controlled (slow) cooling for final hardness/strength.

 

the main problem with this grade of steel, is that it requires a high carbon content (and high silicon) to drive the grain refining process to make it both tough and strong,  unfortunately, that also makes not suitable for welding.

Both PAIVSE 600 and it's Polish equivalent seem to have attempted to replicated superbainite, while keeping carbon low enough to be close to/within some other grade of steel, its still not suitable for welding, but its easier to source than purely optimized super bainite, although it not as good ballisticly as higher carbon versions.

 

This style of steel was kinda accidental discovered by Francisca Caballero in Cambridge UK around the year 2000, by 2006 https://www.phase-trans.msm.cam.ac.uk/2006/ICASS.pdf

 

 

https://link.springer.com/article/10.1007/s11665-013-0557-4/tables/2

 

 

 

 

 

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ID44999_600.jpg

http://msmsjec.blogspot.com/2016/08/super-bainite-high-hardness-steel.html

Commercial Super Bainite Steel is low alloy –4.7% (Si Mn Cr Mo) –0.8% C -with no Al, Co, Ti, Ni.

Proof Stress at 0.2% (0.2PS -Rp0.2) is -1673 MPa

Ultimate Tensile Strength (UTS) (RMm) is -2098 MPa

Elongation (El) is 11% Reduction of Area (RA) is5%

Charpy Notch Impact number 5 Joule -based on a 10mm x 10mm specimen at room temperature

Vickers Hardness (HV30) of 690HV30 Brinell (10 mm Ball, 3000 kg load) of 574HBW Rockwell C (20 degree cone 150 kg) of HRC 57

Available in a fixed width of 1250mm up to 5.5m length  and two gauges 6.3mm & 8.5mm.

 

Made as a Pearlite -easy to process

Ballistic mass efficiency of 2.5 in a perforated steel armour system

 

increasing the Carbon, and or adding Al,Co are the main ways to improve this steel.  The key takeaway is that this is a lower cost/ lower performance version

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This technique could've been applied to silicon spring steel circa WWII if people had known about it, also it is very suitable for casting,  it would've allowed for superior cheap cast turrets fro Soviet or Israeli tanks, but that era is over.

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After getting some time to read through the article provided by @Militarysta (thank you), I can sorta see how they can pull it off: Manganese and Silicon are both great for making strong steel, manganese increasing the harden-ability of low carbon steels, and silicon also increasing the harden-ability, and having the added benefit of maintaining the harness after tempering. 
 

http://navweaps.com/index_nathan/metalprpsept2009.php#Manganese 

 

http://navweaps.com/index_nathan/metalprpsept2009.php#Silicon 
 

The retention of the bainite is still a mystery to me, as tempering and annealing (as discussed in the article) would transform the bainite with the remaining austenite into a more stable structure (again, pearlite), though maybe the large amount of silicon present (1.56-1.61% by mass) is interfering? 
 

I’m curious too see how this armor develops, if they can make the plates thicker, or if they can keep the quality control while making these plates on a full industrial level. 

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1 hour ago, Lord_James said:

After getting some time to read through the article provided by @Militarysta (thank you), I can sorta see how they can pull it off: Manganese and Silicon are both great for making strong steel, manganese increasing the harden-ability of low carbon steels, and silicon also increasing the harden-ability

No, that is not how it works in this case.  by far the greatest source of the strength is the fineness of the structure, which is depended upon carbon to drive it, silicon to stabilize it, and soak time at a suitable temperature to let it occur.

 

This stuff really is the steel matrix from Austempered Ductile Iron, but soaked at around 200 to 300 Celcius, thus the name pizza because it cooks really well at 200 celcius.

 

(and usefully, a 200Celcius cooked bainite retains its strength to temperature like 500 Celcius,  which is different to how QT steels work)

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Militarysta has shown only one part of the subject. Here's the second, more material part.

 

https://www.docdroid.net/eErYUPU/jmm-2-marcisz.pdf?fbclid=IwAR14GTxI9wUzmz4mHTv_jq4aNHNmHPUI7ipN0Za9faXAxH5clGpWlxZYxuU

 

There's a third part too but that would only disguise the origin of this steel. I can only say that this Polish grade steel is a reverse-engineered version of some well known nanostructural armor steel.

 

The thickest steel plates which was made by Poles were 10mm (0,4") thick and there will be two production lines in Poland. One in Labedy mechanical plant, second in civilian part of Huta Stalowa Wola which is the main Polish producer of military grade steel.

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Ito-Bessyo formula isn't good for steels with more than 0,16% C.

In this case better is the formula from International Institute of Welding

 

JuKxNvy.png

And according to this CEV is 1,31% which means this steel is not good for welding unless you heat it up to ~370 Celsius degrees.

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7 minutes ago, Kal said:

Just how much carbon is in the polish bainite?

 

Well

 

Quote

The examined material consisted of sections of nanostruc-tured bainitic steel (NBA) with the following composition Fe-0.58%C-1.9%Mn-1.8%Si-1.3%Cr-0.75%Mo (weight %)

 

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On 3/11/2020 at 12:20 AM, Zadlo said:

There's a third part too but that would only disguise the origin of this steel. I can only say that this Polish grade steel is a reverse-engineered version of some well known nanostructural armor steel.

 

The thickest steel plates which was made by Poles were 10mm (0,4") thick and there will be two production lines in Poland. One in Labedy mechanical plant, second in civilian part of Huta Stalowa Wola which is the main Polish producer of military grade steel.

 

Oh, my fault. That's domestic design with Western-style name. :lol: The steel is called NANOS-BA. And thickest steel plates made were 15mm thick. 

 

I'll send the main article where the modern Polish armor steels (also maraging and amorphous) are presented but first at all I need my PC back. 

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  • 4 months later...

I have learned enough about ferrous metallurgy to contribute to this discussion.



Sooooo...

Bainite itself isn't brittle.  Bainite itself is fairly tough, but less hard than the more typical tempered martensitic steels used for armor.  However, a funny thing can happen during the formation of bainite.

 

Bainite doesn't just form; it grows within and eventually replaces crystals of a phase called austenite, like so:

xRcMsaj.png

This is done during a special heat treating process called austempering.  Compared to other heat treatment processes, austempering is fairly slow, but it also produces low amounts of warpage and cracking in the steel, works well with simple and cheap low-alloy steels, and does not require any secondary processes like additional tempering after it is done.

 

What can happen during bainite formation is that the growth of those little lathe crystals segregates out impurities like sulfur and phosphorus, piling them up into dense bands that promote crack propagation.  There are ways to counteract this, but if the bainite/pearlite formation was an unintended side effect of an imperfect heat treatment in the first place, then they probably didn't do anything to counteract it.  Also, steel mills today are probably a bit better at removing the sulfur and phosphorus in the first place.

Small grain size is desirable regardless of the microstructure of the steel.  The Hall-Petch strengthening mechanism is of considerable interest because it is one of the few mechanisms that simultaneously improves the hardness and toughness of steel.

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