Metalurgy of German steel cartridge cases....from small to large.....

[Kilroy]

Hello All,
I have a long history in the machine tool trades, spending my last 20 years making CNC programs for Medical orthopedic prosthetic implants ( hips, knees,patellas,etc.) of innumerable types, as well as the surgical tools that are necessary to make the implants fit their purpose closely. As a result, I have been exposed over the years to a great lot of various metals, and the science of metals has become a fascination all it's own over time. So much so did it become an interest, a company metallurgist and i would have lunch sometimes and "talk metal". He was educated at Lehigh U. in Pennsylvania, the University Bethlehem Steel instituted to supply their steel mills with engineers for almost a century.

Because of this interest in metallurgy, one thing that I read of many years ago were the lengths the German industrial arm had to go to in finding a substitute for the usually ideal metal for making cartridge cases, brass. Just as crude oil is the best raw material from which to make gasoline and lubricating oils, Germany was forced there as well to find a substitute raw material from which to make a usable substitute for natural distilled gasoline and lube oils from crude. It took some very clever chemistry to turn coal into gasoline and oil substitutes, and some portions of the process I understand are still a mystery, lost to time and probably those chemists did not all survive the bombing their workplaces got walloped by. it was maybe the most fortunate shortage of supplies the Germans endured the shortage of.....they walked back to Germany in the middle of the Battle of the Bulge......scuttling dozens of brand new Tiger II and Tiger tanks reserved for Hitler's last Hurrah!! of the German military.

Copper was in a much shorter supply in Germany to begin with than iron. Iron ore in the form of magnetite or hematite iron ores was fairly well in ample supply all over Europe, from even Stalin's iron mines for a while, and iron ore from Finland, Sweden, and most likely other countries as well, but copper was many times more scarce in the supply of metals a hi-tech war machine would require both for the building of heavy machine tools as well as the thousands of products German industry would have to make out of those raw materials.

Copper in the United States was more plentiful, and my Uncle, who was on a 105mm Howitzer battery for 3-1/2 years during WWII told me they always recieved brass cases for the ammunition they were issued, and they were supplied in the millions, but America had the resources. Had Germany had the natural wealth of the USA, they would have had all they needed and more.

Germany needed copper for many other uses besides the fairly wasteful use as cartridge cases when submarines and battleships and communications to name just a few could not do without copper for the wire that would conduct electricity by the hundreds of miles. So cartridge cases needed to be made from something that would not matter if tons and tons were wasted every day as the army required millions of rounds of all types of disposable ammunition cartridge cases.

Thus came the need by the munitions industry to find a suitable replacement for brass as a cartridge case metal, and the most plentiful metal Germany had was iron. The requirements for a cartridge case metal is probably a high degree of ductility but I honestly do not know the specifics of what the Germans had to create out of a very low carbon steel besides ductility, iron is almost certainly not as ductile as brass. But as I read, the demands for such specific properties for low carbon steel as was required for the forming of cartridge cases were so particular and pure that the making of a steel of such properties as were necessary for these cartridge cases , the German industrial arm had to build foundry and smelting infrastructure specially designed for the purity and precise analysis of additives to the molten iron that the finished cases would always perform in many or all of the precise behaviors a cartridge case had to endure for just a half second or so of their useful life!

So I finally get to my question!!

Does anybody have any knowledge of the metallurgical properties, and all the processes the German's had to build into the manufacturing of steel cartridge cases that would meet the many requirements a steel billet would need to have both in it's chemical analysis and it's heat treatment to go from cartridge cases 3 inches long for a 7.92x57 Mauser Rifle to some cases probably for the case of the 88mm 40/43 cases that were a meter or so in length and used in the Tiger II ??


I've not been able to find very much technical info, but when you consider the tens of millions of 88mm FLAK cases required for Anti Aircraft defenses fired by over 15,000 guns intended as a defensive shield against Allied bombers, as well as the ammunition for another 8,000 Flak 18,36,37 canons used in anti-tank and direct fire applications, there was a great deal of steel being used in this essential ammunition application.

Has anybody found any source of info on the technology required to make a steel that could act effectively as brass in this substitution?

Thanks
Walt

 

[Alpini]

Hi,

I think the metallurgy of drawn steel cases is not extremely complex and requires very few imported metals. But the production process itself is much more complicated and requires better tools and stronger presses compared to brass cases.

More complicated was the substitution of imported metals for (hardened) armor piercing shells. After many research they found alloys without imported metals with almost the same performance as peace time alloys.

 

[Kilroy]

Hi,

I think the metallurgy of drawn steel cases is not extremely complex and requires very few imported metals. But the production process itself is much more complicated and requires better tools and stronger presses compared to brass cases.

More complicated was the substitution of imported metals for (hardened) armor piercing shells. After many research they found alloys without imported metals with almost the same performance as peace time alloys.

Hi, thanks for your reply. I agree that nowadays, the technology required for doing the cartridge case manufacturing challenge would not be difficult as compared to what was known about the physical properties of iron in the 1930's. Even the vocabulary of metallurgy , with words like Pearlite, Martensite or Austenite and all the other innumerable names and microscopic crystalline states iron and steel posses may not have been invented or widely taught at that time. It did represent real challenges at the time as I understand. I had dealt with a fuse designer Engineer from Germany who worked for the DOD in the States, and he had told me that the steel rifle cartridge case type sizes were not the problem, the real headaches came in for the 88mm KWK/PAK 43 cases used in the jumbo towed anti-tank and Panzer Tiger II guns that were a very difficult problem to fashion with that neck, and not get cracking and other problems in that neck. The Flak 41 case never did get a suitable steel case, and for as many as were made, they were withdrawn from Africa service, and brought back to Germany and supplied with brass cases in home defense.

I follow what you say about substitution for known hardening agents to alloy with a basic starting carbon steel. What they would have preferred in alloy metals even then would have required and did get a great deal of science when metals such as a preferred alloy combination of nickel-chromium-molybdenum had to be reformulated ,probably at great time and expense, into a new formula consisting for instance, of silicon-manganese-and chromium. I just looked this formula up again, but years ago I had done some research into the alloying challenges of making a steel that could withstand the new demands of armor penetration that became necessary for war, and the choices for making just the right alloy were infinite maybe at first.
At one time I had become baffled by a specialty steel application we faced in work, and even with late 20th century metallurgy to take advantage of, it took about 6 trial runs of what were all considered steels with properties of strength that we needed, and still the time, effort and metallurgical experience that became involved was really fascinating to me, but was a major headache for the engineer who had to get a steel that would really do the job!! I gained a real respect for the almost infinite variability and versatility that steel could be alloyed into and then possibly hardened and tempered into the most fussy but effective alloy. I had supposed making a specialty steel was a fairly simple process. I learned that it could be a very difficult exercise even now. It's as challenging a science as any.