RU2151369C1 - Armor-piercing bullet and method of manufacture of armor-piercing slugs - Google Patents

Abstract

FIELD: small arms ammunition. SUBSTANCE: armor-piercing bullet has an envelope secured in which are a jacket and a steel armor-piercing slug installed with projection of the tapered nose behind the open envelope end and overlapping the slug nose. The slug core has a structure of troostite with a hardness of 350 to 380 HB, and the external layer of the slug lateral and tail sections to depth h=(0.1-0.3)dslug is made with a hardening to a hardness of 55 to 60 HRC. The method of manufacture of armor-piercing slugs consists in cutting-off of blank from a steel rod of easily deformable low-carbon steel, slug shaping by cold stamping simultaneously of the tapered nose, central and tail sections of the slug, after that hardening of the external layer of the armor-piercing slug is accomplished by casehardening in the medium of carburizer at a temperature of 900 to 1000 C to depth h= (0.1-0.3)dslug, and the final heat treatment of the slug is accomplished by hardening and tempering of the slug external layer to a hardness of 55 to 60 HRC, and of the slug core to the structure of tempering troostite with a hardness of 350 to 380 HB. EFFECT: enhanced armor-piercing effect of bullet, reduced ricochet of slugs, enhanced capacity of process. 5 cl, 3 dwg, 2 tbl, 1 ex

Description

 The invention relates to ammunition for small arms, mainly to pistol cartridges and cartridges for automatic weapons and other weapons with armor-piercing bullets intended for firing at armored targets, as well as for the production of armor-piercing cores.

 Known is an armor-piercing bullet containing a shell in which a steel heat-strengthened armor-piercing core is placed in a shirt of a material with low density (RF patent N 2018781, IPC6 F 42 B 30/02, 12/06; 08/30/94). High armor-piercing properties of a bullet of this design are provided, first of all, by increasing the relative mass of the core, reaching 70% of the mass of the bullet. In addition, the bullet has a good layout: the shell of the core is installed on the side of the tail of the bullet with the protrusion of the head of the core above the end of the shell, which eliminates the energy consumption of the core when interacting with the armor to break through the hard shell. However, the implementation of the core of the bullet of high-carbon steel with high hardness when it interacts with the armor leads to a breakaway of the tail, that is, to its destruction and thereby reduce the armor-piercing properties of the bullet. In addition, the implementation of the core of the bullet from high carbon steel with high hardness complicates the manufacture of the core with a nasal tip. The manufacture of a core with nasal blunting also significantly reduces its piercing properties.

 Known is an armor-piercing bullet selected as a prototype, containing a shell, in which a shirt and armor-piercing core are fixed, installed with a pointed head part protruding beyond the open end of the shell (RF patent N 2077021, IPC6 F 42 B 30/02, 12/06; 10.04. 97).

 Despite the fact that this bullet has higher penetration properties than the previous one, due to the pointed nose protruding beyond the shell, it is also possible to destroy the armor core when it interacts with an obstacle. In addition, the manufacture of a pointed core of high strength steel significantly complicates the technology of its manufacture.

A known method of manufacturing steel armor-piercing cores, including chopping off measured billets, induction heating of the semi-finished product to a temperature of 750 - 780 ^o C, half-hot stamping in demountable dies with the final formation of the head, central and tail parts of the core with the release of metal allowance in the annular cavity, which is removed after cooling prefabricated core in air (RF patent N 2094161, IPC6 B 21 K 3/00, 10.27.97).

 The disadvantages of this method include the fact that for the manufacture of armor-piercing core is used difficult to deform tool steel U10. This leads to a significant complication of the core stamping process, as well as a decrease in the durability of expensive dies operating at elevated temperatures. In addition, the choice of high-carbon steel for the manufacture of the core, which is prone to crack formation after hardening heat treatment, will significantly reduce the bulletproof penetration due to chipping of the pointed nose of the core.

 A known method of manufacturing steel armor-piercing cores, which is selected as a prototype (RF patent N 2110353, IPC 6 B 21 K 3/00, F 42 B 12/04, 05/10/98). According to this method, an armor-piercing core is made in several transitions, including cutting the workpiece into size, preliminary deformation by rotational compression of the head part at one of its ends, intermediate chemical processing and final shaping of the head and tail parts of the core by simultaneous precipitation with extrusion of the head part and direct extrusion of the tail part core.

 The disadvantages of this method include the fact that, as in the above method, as the initial billet, hard-to-deform high-carbon steel is used, which significantly complicates the manufacturing technology of armor-piercing core. In addition, during the functioning of an armor-piercing core of high-carbon steels with armor, it is destroyed by chipping the bow, which reduces the bulletproof properties of the bullet.

 The objective of the present invention is to increase the armor-piercing properties of bullets and reduce the rebound of the cores, as well as increasing the productivity of the process and reducing the complexity of manufacturing armor-piercing cores.

The problem is solved in that in a pool containing a shell in which a shirt and steel armor-piercing core are fixed, the pointed head part protrudes beyond the open end of the shell partially overlapping the head part of the core, the core core has a troostite structure with a hardness of 350-380 HB, and the outer layer of the core to a depth of h = (0.1 - 0.3) d _{heart is} made with hardening to a hardness of 55 - 60 HRC, where d _heart is the diameter of the bullet core (mm).

где d_серд - диаметр сердечника пули (мм),
β - параметр взаимодействия сердечника с преградой, определяемый из выражения:

где m - масса сердечника (г),
V - скорость взаимодействия сердечника с преградой (м/с),
V^* = 5000, скорость дислокационного деформирования сердцевины сердечника, равная скорости звука в сталях (м/с),
Δ - толщина пробиваемой сердечником преграды (мм),
σ_в - прочность материала преграды (кг/мм²).The optimal depth of the outer hardened layer of armor-piercing core, providing maximum penetration while maintaining its integrity, is determined by the mathematical dependence:

where d _heart - the diameter of the core of the bullet (mm),
β is the parameter of the interaction of the core with the barrier, determined from the expression:

where m is the mass of the core (g),
V is the speed of interaction of the core with the barrier (m / s),
V ^* = 5000, the rate of dislocation deformation of the core of the core, equal to the speed of sound in steels (m / s),
Δ is the thickness of the barrier pierced by the core (mm),
σ _in - the strength of the barrier material (kg / mm ² ).

In this case, the nose of the core can be hardened to a height of up to 0.42 _{d heart} .

Moreover, in the method of manufacturing armor-piercing cores, including cutting a workpiece in size from a steel bar, forming the core by cold stamping and final heat treatment of the core by quenching and tempering, the cutting is made from a steel bar from easily deformable low-carbon steel. In this case, the formation of the pointed head, central and tail parts of the core is carried out simultaneously, after which the outer layer of the armor-piercing core is hardened by chemical-thermal treatment in a carburizer at a temperature of 900 - 1000 ^o C to a depth of h = (0.1 - 0.3) d _heart . The final heat treatment of the core is carried out by quenching and tempering of the outer layer of the core to a hardness of 55-60 HRC and the core of the core to the structure of tempered troostite with a hardness of 350-380 HB.

где h - глубина упрочненного внешнего слоя бронебойного сердечника, (мм);
D₀ = 3,8•10^-11, диффузионная константа процесса насыщения поверхностного слоя стального сердечника углеродом, (см²/с);
T - температура процесса химико-термической обработки стального сердечника, (^oC), определяемая по зависимости: T = 870 + 370 • %C, где: %C - исходное содержание углерода в заготовке сердечника до химико-термической обработки;
H = 32000, энергия активации диффузии углерода в поверхностном слое стали при цементации,

R = 1,98, газовая постоянная,

На фиг. 1 показана конструкция пули в разрезе; на фиг. 2 - бронебойный сердечник, на фиг. 3 - схема взаимодействия пули с броней.The duration of the operation of chemical-thermal treatment t of the armor-piercing core in the environment of the carburetor is determined by the dependence:

where h is the depth of the hardened outer layer of the armor-piercing core, (mm);
D ₀ = 3.8 • 10 ^-11 , diffusion constant of the process of saturation of the surface layer of the steel core with carbon, (cm ² / s);
T is the temperature of the process of chemical-thermal treatment of the steel core, ( ^o C), determined by the dependence: T = 870 + 370 •% C, where:% C is the initial carbon content in the core preform before chemical-thermal treatment;
H = 32000, the activation energy of carbon diffusion in the surface layer of steel during cementation,

R = 1.98, gas constant,

In FIG. 1 shows a sectional view of a bullet construction; in FIG. 2 - armor-piercing core, in FIG. 3 is a diagram of a bullet interacting with armor.

 The bullet consists of armor-piercing steel core 1 with a pointed head part 2, shirt 3 and shell 4 mounted on the core 1 from the side of its tail. The pointed head part 2 of the core 1 protrudes beyond the open front end 5 of the shell 4, the shell partially overlapping the head of the core 1 and can form a cavity 6 with the core and the front end of the shirt 3.

The material of the core 7 of the "capsule" armor-piercing core 1 is made with a troostite structure with a hardness of 350 - 380 HB, the outer layer 8 of the core 1 is made with hardening to a hardness of 55 - 60 HRC to a depth of h = (0.1 - 0.3) d _heart , and the nose of the core is hardened to a height of 0.42 _{d heart} .

 At the beginning of the interaction of the bullet with the armored barrier 9, the pointed hard nose 2 of the core 1 penetrates the barrier 9. Due to the fact that the pointed nose 2 is protruded from the shell 4, the bullet does not spend energy on breaking through it. Subsequently, at the beginning of the interaction of the front end 5 of the shell 4 with the barrier 9, due to the presence of a void 6 in the head of the bullet, the shell 4 is deformed with a loss of stability, it is easy to open and separate from the shirt 3. The destruction and separation of the shell 4 occurs with minimal loss of kinetic energy of the core . Subsequently, the core 1 penetrates into the barrier 9.

 The armor-piercing properties of the claimed bullet in comparison with the known ones are increased due to the structural design of the material of the armor-piercing core, taking into account the peculiarity of the dynamic interaction of the core with a rigid armor barrier in collision.

 In the initial phase of the interaction of the core 1 with the barrier, the majority of the impact energy of the sharp and solid nose 2 of the core 1 is perceived by the core 7 as being plastic with a troostite structure, preventing chips and cracking in the surface solid layer 8. However, under conditions of an unchanged core volume limited by a hardened solid surface layer 8, and at high interaction rates of the order of several hundred meters per second, conditions are created for the homogeneous nucleation of dislocations in the ferrite matrix t oostitnoy core 7 of the core 1. Thus there is a "bouncy platoon" troostite structure core interaction by accumulating energy in the core of the core 7 and creating thus the volume-stressed state, including in the outer solid layer 8.

 At the second stage of piercing the barrier, the inertial penetration of the first pointed nose of the core 1 into the barrier 9 begins due to the displacement of its material to the periphery and the subsequent penetration of the entire core. The driving force of this phase is the elastic consequence of the core – hardened surface layer system accumulated in the first phase of the interaction with constant “back up” of kinetic energy from the side of the core mass in the middle and back parts.

 Example.

For the manufacture of an armor-piercing core for a PBM type pool of a Makarov pistol with a caliber of 5.7 mm with a core (d _heart = 5 mm, from a bar with a diameter of d _pr = 4.9 mm from mild steel with stamped steel with a carbon content of 0.2% and a hardness of 130 - 180 HB (for example, steel 20X), chopped off a workpiece with a mass of m = 1.7 grams. On the cold-heading dies in two transitions without heating and intermediate thermochemical operations, the sharpening of the pointed head, central and tail parts of the core was carried out simultaneously.

To harden the outer layer of the armor-piercing core to a predetermined depth to a hardness of 55-60 HRC, the obtained core products were subjected to chemical-thermal treatment by carburization in a solid carburetor, for example, based on charcoal with normalized additives of Ca, Na, Ba carbonates. The carbon potential was 0.8% C, and the diffusion constant of the process of saturation of the surface layer of the steel core with carbon was D ₀ = 3.8 • 10 ^-11 cm ² / s.

The process temperature was:
T = 870 + 370 •% C = 870 + 370 • 0.2 = 944 ^o C.

 To ensure maximum armor penetration during the interaction of a bullet with an obstacle of thickness Δ equal to 5; 8 and 15 mm and taking into account the weapons used, ensuring the interaction of the core with the barrier with speeds of 300; 500 and 800 m / s according to dependence (3), taking into account the values of the above parameters, the duration of the chemical-thermal treatment process was determined, which ensures the optimum depth h of the hardened outer layer. The calculation results are given in table. 1.

 Simultaneously, experiments were carried out to saturate with carbon the outer surface of the cores of steel 20X under the same conditions over time: 1.3; 3.0; 4.7; 5.8 and 8.0 hours. In this case, the deviation of the experimental thicknesses of the outer hardened layer h from the calculated ones did not exceed 18%.

However, it should be noted that in the pointed nose of the core, due to its shape, the depth of carburization exceeds the depth of the hardened outer layer on its lateral and tail parts. The height L of the hardened nose of the core reached values of up to 0.42 _{d heart} .

In order to obtain hardness of the outer layer of the core 55 - 60 HRC and hardness of the troostite core 350 - 380 HB, after cementation, the core was quenched in the traditional way at a temperature T _AC3 + (30-50) ^o C, i.e. 830 - 890 ^o C, and subsequent annealing at a temperature of 200 - 220 ^o C for an hour.

 After the manufacture of the armor-piercing core, the bullet was assembled. To do this, they pressed the core 1 with the jacket 3 from the side of its tail into the sheath 4. Subsequently, the head of the sheath was crimped, with a partial overlap of the head of core 2 1. The pointed nose of the core was protruded beyond the front end 5 of the sheath 4. Moreover, the crimping of the head of the shell was made in such a way that a cavity 6 was formed between the core 1, the front end of the shirt 3 and the inner surface of the shell.

 Conducted comparative tests of bullets for armor penetration.

 The test was subjected to bullets like PBM Makarov pistol, the core of which was made of U10 steel according to the standard technology outlined in the prototype. Moreover, the hardness of the entire core was 60 - 63 HRC.

The proposed bullets core was made of steel 20X according to the claimed technology. Moreover, the core of the core had a troostite structure with a hardness of 363 HB, and the outer layer to a depth of h = 1.1 mm (h = 0.22d _core ) was made with an HRC of 59 units, the pointed nose of the core was made with hardening to a height L = 2.1 mm.

Test conditions:
The number of cartridges in each batch of tests is 30 pieces;
The barrier was made of steel 3 thicknesses Δ equal to 5 and 10 mm;
Shot distance - 10 m;
The initial velocity of the bullet V, which actually coincides with the velocity of interaction between the bullet and the obstacle, was 500 and 600 m / s.

 The results of comparative tests of PBM type bullets and those proposed are given in table. 2.

Thus, the use of developed bullets with a stamped and cemented core allows you to:
- increase the penetration rate by 20% for thin barriers and up to 40 ... 50% for thick barriers compared to prototype bullets;
- by reducing the number of stamping operations and reducing energy costs for core shaping, the developed method significantly increases the productivity of low-waste bullet production technology in mass production.

Claims (5)

1. Armor-piercing bullet containing a shell, in which a shirt and armor-piercing core are fixed, installed with the pointed head part protruding beyond the open end of the shell partially overlapping the head part of the core, characterized in that the core is made of steel, the core of the core has a troostite structure of hardness 350 - 380 HB, and the outer core layer is formed by hardening a hardness of 55 - 60 HRC, the outer layer side and tail portions of the core is hardened to a depth h = (0,1 - 0,3) d _{serd, serd} where d - diameter of cardiac a. 2. The bullet according to claim 1, characterized in that the optimal depth h of the hardened outer layer of the armor-piercing core is determined by the dependence

where d _heart - the diameter of the core of the bullet, mm;
β is the dimensionless parameter of the interaction of the core with the barrier, determined from the expression

where m is the mass of the core, g;
V is the speed of interaction of the core with the barrier, m / s;
V ^* = 5000 - the rate of dislocation deformation of the core of the core, equal to the speed of sound in steels, m / s;
Δ is the thickness of the barrier pierced by the core, mm;
σ _in - the strength of the barrier material, kg / mm ² . 3. The bullet according to claim 1, characterized in that the nose of the core is hardened to a height of up to 0.42 _{d heart} . 4. A method of manufacturing armor-piercing cores, including cutting the workpiece to the size of a steel bar, forming the core by cold stamping and final heat treatment of the core by quenching and tempering, characterized in that the cutting is made from a steel bar of easily deformable low-carbon steel, shaping is carried out simultaneously with a pointed central, central and the tail parts of the core, after which hardening of the outer layer of the armor-piercing core is carried out by chemical-thermal treatment in a carburizer at 900 - 1000 ^o C to a depth of h = (0.1 - 0.3) d _heart , and the final heat treatment of the core is carried out by quenching and tempering of the outer layer of the core to a hardness of 55 - 60 HRC and the core core to the structure troostite tempering hardness 350 - 380 HB. 5. The method according to claim 4, characterized in that the duration of the chemical-thermal treatment of the armor-piercing core in the environment of the carburetor is determined by the dependence

where h is the depth of the hardened outer layer of the armor-piercing core, mm;
D ₀ = 3.8 • 10 ^-11 - diffusion constant of the process of saturation of the surface layer of the steel core with carbon, cm ² / s;
T is the temperature of the process of chemical-thermal treatment of the steel core, ^o C;
H = 32000 - activation energy of carbon diffusion in the surface layer of steel during cementation,

R = 1.98 - gas constant,

s

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