Anybody here have a metallurgical background?

[Kilroy]

I picked up a German 8.8cm APC projectile with a missing base fuse as part of a complete shell buy, and I've seen the diagrams of these things, and how they are supposed to work. The hardened steel cap below the windscreen has me wondering as one who has worked with alloys of steel all my life and what additives to the steel produce what effective property in a finished steel product. Carbon we all know, but it's mild for hardened steel standards. Adding a little Chrome will do something, Vanadium does something else, Molybdenum does something else too and tungsten and cobalt all impart various performance qualities to a finished steel.

What's got me interested is the metallurgical analysis of not the tungsten carbide type core Germany produced a number of rounds for, but the cheaper and more readily available hardened steel caps that were fitted under the ballistic cap of many projectiles as a substitute for the preferred tungsten cored type.
I read about them, but there was a whole lot of science that had to go into those hardened steel penetrators, and I was just wondering if anybody had ever come across any serious specs on the alloy formula for these types of caps.

Here's some pictures of the thing in question.

Thanks,
Walt

 

[pzgr40/42]

Hey Walt,

The cap behind the windshield on the PzGr 39 rounds actually is not hardened steel, it's mild steel.
The nose of the projectile main body is hardened. The cap behid the windshield serves the puurpose of spreading the force of impact over all of the nose of the projectiles main body, which, iff concentrated on the sheer tip, might cause the main body to shatter before penetration is achieved.

I've read, that as a side effect the cap seems to act as a "guide" for the main body at awkward angles of impact, but I'm not sure how much of that is true or myth.

regards,

Menno.

 

[2pounder]

A great deal of research went on by the winning sides of the loosers metalurgy, I worked for Rolls Royce aero engines in in their library inhereted from De Havilland were various books on aircraft parts analysis. I'm sure RL carried out similar work on hardened steels. from memory penetrators are only relatively hard to be able to be tough enough to stand the shock. Brasseys Ammunition bookgoes into some detail on this.

 

[Kilroy]

Yes, that is another consideration, toughness of a steel vs hardness. The two are not mutually exclusive, but the harder a steel is made, the less of it's toughness may show up in impact studies but the toughness will definitely remain a component of the metals ability to withstand various stresses.

I've worked extensively with cobalt/chrome alloy orthopedic implants for knees and hips ( about 50% cobalt, 40% chrome, 10% other ), and toughness can really be an SOB to deal with yet the hardness can remain almost mild at Rockwell "C" 45 or so.

But try and make something like that shatter!

This is what is interesting about the whole physics of armor penetration. I have read a few articles on the tungsten carbide type the Germans had to curtail production of due to scarcity of that metal, and interestingly, one article said the analysis was not merely tungsten carbide but also an alloy add mixture of some cobalt, for what I have my suspicions, but it might react entirely different in the crystal structure of tungsten carbide than a steel alloy.

Walt

 

[Kilroy]

Hi Menno,

Hmmm....I was under the impression that the cap behind the windshield was the hardened portion. Live and learn.

It would make sense to have a softer "pad" form a sort of setting or grip on the surface, giving the penetrator a sturdy foundation on which to
spend it's kinetic energy.

Thanks for the info

Walt

 

[HAZORD]

Kilroy,

There are a number of books and references that deal with the defeat of armor. Even the older Tungsten penetrators used a softer alloy cap in front of the carbide penetrator. There is a sectioned U.S. 105mm APDS projectile shown here: http://www.bocn.co.uk/vbforum/threads/76540-M728-105-mm-apds-t?highlight=M392

The sub-projectile is a combination of specific purpose metals. The outer skin is magnesium to make a flash on impact to let the tank commander know if he hit where he wanted, and to add incendiary effect. The Tungsten alloy penetrator that is turned to a sharp point, the cap on the penetrator to lessen the shock, and to act like like an adhesive to keep the tungsten from bouncing off, sticking it long enough for it to start a hole through the armor, and the steel body to carry the tracer and hold everything together.

One interesting note as it relates to U.S. AP-Capped steel penetrator ammo, is that the 37mm and 40mm projectiles were the only ones that had caps but never had explosive fill. The 57mm, 75mm, 76mm, 3inch, 90mm, 155mm Army, and 3, 4, 5, 6, 8, 10, 12, 14, and 16 inch Navy projectiles that had caps, were all designed with explosive burster cavities to be filled with Explosive D. Some times they weren't issued with a burster and only had a base plug and tracer instead of base fuze, but the Army calibers were all supplied with rounds that were AP-T solid shot for armor piercing. Even the 120mm Marine Corps tank was issued with Solid shot projectiles.

 

[Kilroy]

Hi Hazord,

As I read, I find these intermediary impact "pads" of a softer material than the intended penetrator go back at least to the dawn of black powder propelled assemblies the French began to experiment with because they could see the penetrator bounce off the hull, or wall in those days, and this had to be remedied. The penetrator might have a medial component of leather or lead, or perhaps a device made of both lashed together, and this would , under the force of velocity, provide a surface specifically formed to the surface to be pierced, and make it difficult for the penetrator to go anywhere but ''in" where it was fired.

Another penetrator , a more exotic one than tungsten carbide is DU.

DU I have not read much on. Recent articles warn of breathing in the oxidized dusts that would accumulate in a tank or APC destroyed by DU where the very hard and apparently also incendiary metal of a DU projectile could just fall to the floor of the vehicle, where they could be disturbed and made airborne again, presenting what one specialist doctor has warned is the real danger of DU residual metal in a post combat setting.

DU is never made completely free of it's radioactive isotope U-235, as separation of the isotope from normal Uranium metal is never complete, leaving maybe 1/3 of the original amount still in the metal referred to as DU.

I will see what I can find on it.

I know in the U.S. only one factory is permitted to machine DU, and this is located in Tennessee.

 

[HAZORD]

Stabaloy (depleted uranium) has been discussed at length here on BOCN. You might do some searching through the posts. I have a hell of a time getting the search engine to find what I'm looking for.

If you go out to Advanced Search, and key in depleted uranium to search in the posts, a number of listings will come up.