In the middle of August this year, there was a inconspicuous news on the Internet, but the content was closely related to domestic small arms - the scientific research team of Professor Fan Caihe of Hunan University of Technology successfully developed a new series of bullet case aluminum and aluminum shell products. If you remove the modified language in the news, its dry goods can be summarized as follows: 1, this "new type of small arms with high strength aluminum alloy shell" is designed for its own composition; 2, the aluminum alloy itself is "prepared based on 3D jet forming rapid solidification technology"; 3, the aluminum shell is cold-punched and formed by "self-developed molding mold"; 4, the 12.7 mm caliber shell made of new shell aluminum has passed the live ammunition test and acceptance of a military authority, and "the parameters have reached the military standard". A series of "self-reliance", "autonomy" and "authority" sound very exciting, and major media platforms also add headlines such as "the first in the country" when reprinting. Whether this is really the case, how big the gap between the ideal and reality, the actual equipment situation in the future will naturally give conclusions. In this regard, I think everyone feels the same way, and there have been many real-life examples in the past 20 years. Here I would like to help you find your own answers by asking yourself three questions.
Hunan University of Technology developed a 12.7 mm shell made of new aluminum alloy
The first question, is the aluminum alloy shell a completely new technology? What is its history?
The answer to the previous question must be no. Aluminum alloy shell shell (or cartridge) is already a very mature technology, with hundreds of years and thousands of kinds of ammunition application experience. The first to start the development and production of aluminum shells was the United States, as early as 1890, the Frankfurt Arsenal trial production of a variety of caliber aluminum shells from 7.62 mm to 10.16 mm. European powers during World War I, such as austria-Hungary, Great Britain, and Germany, also developed aluminum shell cartridges with the caliber of their mainstream military rifles, such as 8 mm, 7.7 mm and 7.92 mm. However, due to the lack of aluminum alloy materials with good strength and toughness, these early attempts failed. In particular, the aluminum shell of the military high-power rifle will have small holes and cracks in the side wall of the shell when fired, or the gunpowder gas leaks from around the bottom fire chamber, resulting in the shell burning through and deformation, so it is not practical.
A 7.92 mm aluminium-hued Mauser rifle cartridge produced on trial in Germany during World War II
By the time of World War II, aluminum alloys began to be widely used in aircraft, but there was still no breakthrough in the manufacture of gun shell casings. Although Germany and other countries still tested the aluminum shell many times, they finally abandoned it halfway because the performance was not significantly improved. However, the U.S. Army Ordnance Department persisted to the end, repeatedly testing and demonstrating the feasibility of various aluminum alloy shells. In 1933, the Frankfurt Arsenal produced a trial production of 11.43 mm aluminum-shell pistol cartridges. Due to the low chamber pressure, the operational performance of the tested cartridge is satisfactory. However, when applied to the type of ammunition with higher bore pressure, the aluminum shell is still prone to failure. In 1949, the plant tried to improve the manufacturing process, changing to stamping and then extrusion, and the performance of the aluminum shell produced was improved. In 1956, the factory used the most advanced 7075 aluminum alloy and the corresponding manufacturing process to produce and test 25,000 rounds of 7.62 mm aluminum shell rifle cartridges, but the test results found that its shell wall was mostly cracked during launch, and the bottom fire gas leakage ablation was still common. In 1968, the plant replaced the material with a better 7475 aluminum alloy, produced 20,000 rounds of 7.62 mm aluminum shell rifle cartridges again, and tested the high-velocity M134 "Minigang" machine gun, and the results were still not satisfactory.
The aluminum shell is used on pistol cartridges with relatively low chamber pressure, and the performance can generally be guaranteed
At the same time, for the application of aluminum alloys such as 6067 and 7075 in the manufacture of larger caliber ammunition cartridges, the United States has not stopped researching for a moment, and the main problems encountered include the phenomenon of "stagnation" in the aluminum alloy shell under the high chamber pressure, facing the problem of difficulty in returning the shell. Prior to the 1970s, the only two types of aluminum shells used in the M67 recoilless gun and the anti-personnel grenade used in the M79 individual grenade launcher were successfully tested side-by-side. Other aluminum cartridges or cartridges failed to achieve practical applications or mass production.
The 5.56 mm short-range training shell with an aluminum casing also has a low bore pressure
In 1969, the U.S. Army launched a three-year exploration program to determine the application feasibility of aluminum shells, and the U.S. Air Force and related military and metal companies continued to promote the research of aluminum shells and cartridges. At the same time, the emergence of new aluminum-zinc-magnesium-copper alloys with better comprehensive performance and the application of powder metallurgy in the production of high-strength aluminum alloys finally solved the problem of aluminum shell firing, and by the early 1970s, the practical application of aluminum shells was basically realized. In August 1972, the Frankfurt Arsenal tested 13,940 rounds of an improved version of the 5.56 mm aluminum shell made of 7475 aluminum alloy. The test was conducted with 3 M16A1 rifles, each firing 4000 rounds, and divided into three cases, one is fired at normal chamber pressure, one is fired under high chamber pressure conditions, and the other is pre-engraved with a longitudinal groove in the aluminum shell wall to simulate the shell with drawbacks in processing. However, none of the three rifles in the test stopped firing or other malfunctions, and after the test, there was no residue in the automatic mechanism and gas duct of the rifle, and it could continue to be used. Including 180 shells of pre-engraved longitudinal slots, 13940 shells were inspected, and no burn-through or rupture occurred, which proved that 7475 aluminum alloy was indeed feasible to make shells. In 1975, an aluminum cartridge, also made of 7475 aluminum alloy, was successfully applied to the 30 mm machine shell used in the A-10 attack aircraft GAU-8 aircraft gun. To this day, the U.S. Air Force uses aluminum casings for a variety of calibers of artillery shells.
In the U.S. military equipment sequence, the most widely used aluminum shells are aerial machine gun shells and low-pressure grenades
In terms of gun shells, there are still not many aluminum shells used today, but it is not nothing. For example, there is an ammunition company called CCI in the United States, as early as the 1980s launched the Blazer series of pistol cartridges, by 1997 has developed to provide 7 common calibers, 24 kinds of warhead configurations, including such as 10 mm AUTO, .357 Magnum, .44 Magnum and other high breech pressure varieties, now the U.S. civilian market is still easy to see, its price is about one-fifth cheaper than copper shell pistol bullets, but more expensive than steel shell bullets. The Blazer series of pistol cartridges are mainly used for civilian use, and police and military pistol cartridges are still mainly copper shells. Considering that aluminum alloys are prone to cracks or small holes under the action of high-pressure gas, these commodity aluminum shells are disposable and cannot be used for reassembly, which also limits its use surface.
Blazer 9mm aluminum-shelled pistol cartridge on the American civilian market
The second question is, what are the advantages of aluminum compared with steel and brass, which are more commonly used as shell materials?
It should be said that the advantages of aluminum are actually not obvious, if there is, the most important thing is only one, that is, light. The specific gravity of pure aluminum is 2.7 grams / cubic centimeter, the average specific gravity of steel is 7.85 / cubic centimeter, the former is only 34.4% of the latter, aluminum alloy because of the addition of copper, zinc, magnesium and other components, the average proportion is about 36% of steel, and brass is the heaviest of the three, the average proportion is 7.85 / cubic centimeter. The shells of the three materials are the lightest if they are of the same size. In other words, under the same weight conditions, more ammunition can be carried with aluminum shells. Taking the 6 mm SAW bullet in the United States as an example, the weight of the steel shell bullet is 15 grams, the aluminum shell bullet is only 11.6 grams, and the steel shell bullet carries 300 rounds is 4.5 kg. On the other hand, from the perspective of material consumption, the same manufacture of 6,000 rounds of 30 mm machine shells, if the use of aluminum shells, only need to consume 1 ton of aluminum, and if the use of steel shells, the weight of the shell alone will be nearly 3 tons. In addition to material consumption, lightweight ammunition is clearly more advantageous for airborne weapon systems.
The 6 mm SAW test ammunition in the United States began to use an aluminum shell (the first from the right), but eventually chose a steel case
In addition, compared with steel, the aluminum shell shell is relatively soft, the loss of the mold during processing is small, and the wear on the chamber, slope chamber and other places when used is also relatively small, which can reduce the wear of parts and improve the life of the weapon. At the same time, compared with steel, the chemical stability of aluminum is better, and the mechanical properties in long-term storage are not easy to change, and it is not easy to rust. However, in terms of these properties, the aluminum shell is significantly inferior to the copper shell. In particular, the heat capacity of aluminum alloy is poor, compared with the same copper shell, the empty shell absorbs and takes away less heat of gunpowder, if used in fully automatic weapons, the gun chamber is more likely to overheat, resulting in accidents such as spontaneous combustion of ammunition.
The manufacturing process of the shell cup formed by the aluminum stamping of the shell of Hunan University of Technology is not fundamentally different from the traditional process
In terms of economy, it should be said that aluminum is not as good as imagined. In nature, although the reserves of aluminum elements are large, but because of the relatively lively nature, the difficulty of refining is larger, the energy consumption is higher, the current price of electrolytic aluminum is 18,000-20,000 yuan / ton, as for the manufacture of bullet shells, the price of high-performance aluminum alloys is at least 50% higher. Correspondingly, brass is 45,000-53,000 yuan / ton, while carbon steel is only 3500 yuan / ton or even lower. It can be seen that the price of steel is still the lowest, and as the shell material of ordinary ammunition, the performance of steel fully meets the needs, and there are decades of mature experience in use, so China's long-term use of a large number of equipment used in the infantry, machine ammunition, long-term use of copper-coated steel, painted steel and copper-plated steel and other steel-based shell materials, only in recent years in sniper shells and other few types of ammunition that need to emphasize accuracy to switch to copper shells.
At present, the copper-clad steel shell is commonly used in China, which is inexpensive and can meet basic needs
Another restriction on the application of aluminum alloys is the difference in material properties. For the same kind of ammunition, the copper shell and the steel shell can be completely the same size, but the characteristics of aluminum and copper, steel and two materials are quite different, especially ductility, tensile resistance is low, so the wall thickness of the high-pressure resistance part of the shell bottom generally needs to be increased, if it is made according to the ready-made size, it is often impossible to ensure the basic performance, and it is easy to have problems. Therefore, even if it is the same kind of ammunition, after switching to an aluminum shell, it may need to be redesigned from the process to the structure, and the higher the bore pressure, the smaller the shell shell. For example, in August 1972, the Frankfurt plant successfully tested 14,000 rounds of aluminum shell rifle bullets, not only the shell shell has been specially heat treated in advance, but also the bottom of the shell is equipped with a special silicone rubber sealing cap, even if there are small holes or cracks in the housing, it will not affect the launch safety. Once such "specialization" is needed, the cost will often be high. Professor Fan's statement that "bullets made of new materials are 65% lighter than traditional shells, and the cost is about 75% cheaper" is only idealized laboratory data, which is difficult to achieve in practice.
If the aluminum shell lacks suitable storage conditions, its corrosion resistance is not superior to that of the steel shell
The third question is, what is the application level of aluminum alloy shells in China?
First of all, it should be pointed out that the domestic manufacturing and use of aluminum alloy material shells is not blank, and there have been many successful products and reference experience. According to public information, at least since 1981, the development of aluminum alloys for shell shells began in China, which was called "light alloy material" shells at that time. Through the cooperation between the relevant metal smelters and military enterprises, have successfully imitated high-performance aluminum alloy materials such as 7075 and 7475, on this basis, after more than ten years of exploration and a large number of tests, in the second half of the 1990s, they developed a certain grade of aluminum alloy with independent intellectual property rights, which is characterized by high yield strength, strong tensile resistance, and the shells processed with them are small affected by stress corrosion and rupture, and the storage time is long, which can meet the tactical and technical requirements. A casual search on the Internet can find the results of many papers such as "Research on the Optimization of Aluminum Alloy Shell Forming Process and Heat Treatment Process" written by Chongqing University and other units earlier. Therefore, even if the products of Hunan University of Technology are equipped, they will never be the "first in the country"
In domestic military ammunition, the proportion of aluminum shells used is already very high
The use of aluminum shells was first used in civilian and police products. As early as the 1980s, the domestic "Golden Ring Brand" shotgun shell of Suihua Forward Machinery Factory began to use aluminum shells. Subsequently, according to the imitation of foreign products, the 38 mm riot gun, which fired non-lethal ammunition such as tear gas, detonation bombs, smoke bombs, etc., also developed the corresponding aluminum shell. The real use of aluminum alloy shells on military ammunition began with the imitation of individual grenades. In the counterattack operation against Vietnamese self-defense, our army successively captured two kinds of grenade launchers, the US-made M79 single-shot and M203 guns, and the M406 high-explosive anti-personnel grenades used therein. The research and imitation of them, especially the muzzle safety design of the M406 with a clock mechanism, the internal prefabricated slot stamping warhead, and the aluminum alloy shell made by extrusion method, have played an important reference role in the development of the domestic single-soldier grenade launch system. At that time, the domestic related research had just started, after years of digestion and absorption, by the early 1990s had officially finalized the Type 91 riot grenade launcher and the supporting 35 mm series of riot munitions, although the caliber was reduced, but in the overall principle of the system, structural design, especially the barrel structure, manufacturing process, etc., the Type 91 riot bomb was greatly affected by the M406 grenade. On this basis, a series of 35 mm/40 mm grenade launchers with different structural layouts and automatic methods were subsequently developed in China, including the latest QLU11 35 mm sniper grenade launcher, whose shell casings are made of aluminum alloy material (in fact, other parts of the ammunition, including the launcher itself, also use a variety of aluminum alloys). Another domestic weapon that uses a large number of aluminum shells is the QBS09 military shotgun, because the supporting 09 shotgun fires heavier tungsten alloy projectiles, in order to reduce the weight of ammunition while maintaining better service performance, the bullet also uses aluminum alloy shells. In addition, in recent years, there have been some new attempts at aluminum/plastic mixed material shells, mainly in new types such as empty package bullets and coach bullets. Since it has long been widely used, the achievements of Hunan University of Technology claimed by relevant reports have solved the technical bottleneck of China's independent preparation of aluminum alloy special materials "card neck", which may be slightly exaggerated.
Gold Ring Aluminum Shell Shotgun Shell (Bottom) and Jialing Plastic Shell Shotgun Bullet (Top)
The aluminum shell of the domestic 38 mm tear gas canister is extruded and formed and then made by car
The US-made 40 mm grenades captured in the Vietnamese self-defense counterattack played a great role in the development of domestic grenades
Various aluminum alloy materials have been widely used in domestic automatic grenade launchers and their ammunition
The last thing to say is actually half a question, that is, where is the shortcomings of the domestic aluminum alloy shell application now? This gap is mainly reflected in the processing technology. Compared with foreign products, the extrusion surface of the domestic aluminum shell is obviously not smooth, leaving obvious processing marks, and the size cannot be accurate, especially the shell with a relatively large diameter, most of which must be made by car, which is also a common disease of the domestic shell. Of course, this does not hinder the quality of the use of domestic aluminum shells. Hunan University of Technology research and development of new materials of manufactured products, the main 12.7 mm large-caliber machine gun shell, the so-called "aluminum alloy shell chamber pressure of more than 400MPa, resistance to instantaneous high temperature of more than 1000 ° C, warhead velocity of more than 1200m / s, compared with the steel shell overall mass reduction of more than 20% (here and the aforementioned weight loss of 65% there is a contradiction)", all refer to this 12.7 mm shell. However, from the published photos alone, this batch of 12.7 mm shells uses a Boxel-style bottom fire chamber with low stamping or extrusion accuracy, and the surface processing quality of the shells is also very general. As for the three aluminum alloy cups used for display, the processing is even rougher. In fact, it is very simple to prove that the new process is effective, because 35 mm grenades and 09 shotgun shells are produced locally in Hunan, and if the process of Hunan University of Technology can effectively solve the quality problems in their current production, then these processes must be truly effective. Finally, please note that there is a sentence at the end of the news, "At present, the new material shell is undergoing conventional low temperature, high temperature and other tests, and striving to promote the direction of industrial production", that is, even if the performance is qualified, the problem of mass production has not been solved, whether it can be put into production, and how its cost is finally unknown.
The car design marks at the bottom of the domestic 09 shotgun shell are very obvious
Domestic 12.7 mm aluminum bottom plastic shell composite material empty wrapped bullet
As far as I am concerned, I still sincerely hope that these achievements of Hunan University of Technology really have a gold content and can be smoothly put into practical application. However, as far as aluminum alloy shells are concerned, individuals do not think that it is a promising scientific research direction. In summary, the existing steel and copper shell materials do not have an urgent need to replace them with aluminum alloy materials for the time being, and in the current situation, aluminum shells do not have special strategic significance or particularly broad application prospects. Even if it does need to be replaced in the future, it is more likely that the polymer shell that is currently in the ascendant, or even the shellless bullet, will not be an aluminum alloy shell that is still a metal material.
Polymer shells represent the most likely future directions for military cartridges