RU2176573C1 - Method for manufacture of small arms cartridge case - Google Patents

Abstract

FIELD: plastic metal working, applicable in production of cartridges of small arms of various purpose. SUBSTANCE: method consists in punching of a disk, manufacture of a hollow semi-finished item, drawing of the hollow semi- finished item with thinning of the wall, chemical heat treatment and a complex of shape-changing operations for formation of the primer cap seat, formation of the flange in the bottom part of the cartridge case and facing of the cartridge case and facing of the cartridge case in length, the volume of the disk equals 1.12 to 1.30 of the volume of the finished item, and the thickness exceeds 0.7 of the bottom thickness of the semi-finished item of the last drawing. A cup-shaped semi-finished item is produced by volume punching with a bottom external band having a diameter equal to 0.95 to 1.1 of the cartridge case diameter in its bottom part, the band height not exceeding 0.9 of the thickness of the source disk, and bottom thickness equal to 1.0 to 1.3 of the thickness of the bottom of the semifinished item of the last drawing. The outer surface of the cup-shaped semifinished item is made tapered with the taper angle equal to 8 to 60 deg. The wall of the cup-shaped semi-finished item has a thickness uniformly converging from the bottom part to the edge with a varying cross-section area in height. The obtained cup-shaped semi-finished item is subjected to a recrystallizing softening annealing and pickling, after that one or two drawings are accomplished with a thinning of the walls, which form the mechanical properties of the cartridge case body. EFFECT: improved quality of cartridge case, reduced waste for facing of cartridge case, preset distribution of the mechanical properties in height of the cartridge case walls with its reduced value from the bottom to the neck, reduced number of shape-changing operations. 2 cl, 6 dwg, 1 tbl

Description

 The invention relates to the processing of metals by pressure and can be used in the manufacture of small arms cartridges for various purposes and similar parts when used as the initial blank strip (tape) from which the circle is cut.

 A known method of manufacturing glasses cartridge cases (US patent N 2028996 from 01/28/1936). According to this method, it is proposed to use round steel as an initial billet, from which to cut off the billet. The billet is stamped without heating, obtaining a semi-finished product having an upper cylindrical girdle and a lower cylindrical ledge, necessary to ensure coaxiality of the semi-finished product and the tool. This semi-finished product, stamped in the second operation, also without heating, in the form of a glass, has a greater height than the workpiece, and the same upper diameter and a predetermined bottom thickness.

The disadvantages of the proposed solution include:
- the need to use round rolled products - since the domestic industry does not produce round rolled products that would not have surface defects (hairs), and since their depth is commensurate with the wall thickness of the finished sleeves, the probability of cracking with the subsequent breakthrough of powder gases during firing is very high;
- the difficulty of obtaining blanks from the bar - since at a low relative height obtaining a high-quality cut is very difficult;
- unfavorably oriented texture of the metal (fiber) - the axial direction of the fibers weakens the strength of the bottom of the sleeve and increases the likelihood of a cut of the flange of the sleeve during extraction after firing;
- the presence of two structural elements of the upper cylindrical girdle and the lower cylindrical ledge requires the use of a guide ring, which unnecessarily complicates the design of the tool.

 At present, at the enterprises of the industry, for the manufacture of cartridges of small arms cartridges, a technological process is used in which the strip from which the circle is cut down is used as the initial blank. The latter can be annealed, followed by a set of operations to remove the scale formed during annealing - etching. When using steel as the liner material, it is necessary to apply a lubricant coating of iron and zinc phosphates to the surface of semi-finished products - phosphating. Next, one to three hoods are produced, followed by annealing, etching, and when using steel as the material of the liner by phosphating. Then one or two other hoods follow, during which the shell metal is given the appropriate mechanical properties to ensure the normal functioning of the shells (strength, extraction and obturation). The number of hoods, both intermediate and forming mechanical properties, is determined by the sleeve material, the ratio between the wall and bottom thickness, the required accuracy, the specified mechanical properties of the sleeve body, equipment capabilities, tool geometry, etc. Subsequently, the bottom of the liner is formed, including a nest for the igniter capsule, crimping, machining and applying an anti-corrosion coating. (Malov A.N. Production of small arms cartridges. - M .: Oborongiz, 1947, tab. 20, p. 31 and tab. 21, p. 35). This method is taken as a prototype.

 With this method of manufacturing sleeves, an initial billet (strip or tape) is used, the thickness of which does not exceed 75% of the thickness of the bottom of the last hood, which allows you to increase the diameter of the cup to facilitate the first hood and reduce the number of hoods to obtain the desired thickness of the barrel. At the same time, to obtain the bottom of the required thickness in the process of hoods, material from the walls has to be moved to the bottom. The disadvantage of this process is the formation of a bottom fold, which reduces the strength of the liner.

In the manufacture of pistol cartridges, the length of which does not exceed 2-4 diameters, the ratio of the volumes of the wall and bottom metal is less than 2 - 3. With this ratio, if you use conventional trimming allowances, a relatively small diameter of the circle D ₀ with a thickness of t _{0 is} obtained, from which it is necessary during the first drawing with thinning through (one or more) matrices, form a cap with a diameter of D ₁ .

It is believed that if D ₀ -D ₁ <2 • t ₀ , then the normal course of the first drawing process is not possible, since the first drawing process is performed in this case with metal cutting, the semi-finished products have increased difference, skew and curvature. To ensure the normal course of the first drawing process, usually:
increase the diameter of the cup by increasing the allowance for cutting in order to eliminate inequality, however, this leads to an increase in waste and, consequently, a decrease in the utilization rate of the material, since in this case the volume of the cup is 1.3-1.7 volume of the sleeve;
reduce the thickness of the circle, however, this leads to the necessity of surging the metal into the bottom and, as a consequence, to increase the bottom fold, which affects the quality of the manufactured sleeve.

 The present invention solves the problem of improving the quality of the liner (eliminating the formation of a bottom fold), reducing waste for trimming the liner, ensuring a predetermined distribution of mechanical properties (hardness HV) along the height of the walls of the liner with decreasing its value from the bottom to the shaft, and also reducing the number of forming operations.

где

и

- площади поперечных сечений стенок, отсекающих равные объемы стенок чашеобразного полуфабриката и полуфабриката последней вытяжки соответственно, мм²;
HV_i - твердость металла готовой гильзы в i-ом сечении, безразмерная;
A, B и n - безразмерные коэффициенты выражения, аппроксимирующего кривую упрочнения металла гильзы вида: HV_i = A + B ψ $\genfrac{}{}{0ex}{}{\text{n}}{\text{i}}$ , где ψ_i - относительное поперечное сужение металла гильзы в i-ом сечении. Полученный чашеобразный полуфабрикат подвергают рекристализационному смягчающему отжигу и травлению, после чего осуществляют одну или две вытяжки с утонением стенок, которые формируют механические свойства корпуса гильзы. Затем проводят комплекс формоизменяющих операций.The present problem is solved in that in a method for manufacturing a cartridge case of a small arms, including cutting a circle from a strip, manufacturing a hollow prefabricated product, drawing a hollow prefabricated product with thinning the wall, chemical-thermal treatment and a set of shaping operations to form a capsule socket, forming a flange in the bottom of the cartridge case and trimming the sleeve along the length, the circle is cut down with a volume equal to 1.12-1.30 of the volume of the finished product, and a thickness t ₀ greater than 0.7 of the bottom thickness t _{p the} semi-finished product of the last hood. A cup-shaped semi-finished product with a bottom outer belt with a diameter of D _p equal to 0.95-1.1 of the diameter of the sleeve D _g in the bottom part thereof, a belt height h _p not exceeding 0.9 of the thickness t _{0 of the} original circle is made from a cut-out die forging, and bottom thickness t _d equal to 1.0 ... 1.3 bottom thickness t _p semi-finished product of the last hood. The outer surface of the cup-shaped semi-finished product is made conical with a taper angle α equal to 8 - 60 ^o . In this case, the wall of the cup-shaped semi-finished product is performed with a thickness uniformly tapering from the bottom to the edge with a varying cross-sectional area in height, determined by the dependence:

Where

and

- the cross-sectional area of the walls, cutting off equal volumes of the walls of the cup-shaped semi-finished and semi-finished products of the last hood, respectively, mm ² ;
HV _i - metal hardness of the finished sleeve in the i-th section, dimensionless;
A, B and n are dimensionless coefficients of an expression approximating the hardening curve of a metal of a sleeve of the form: HV _i = A + B ψ $\genfrac{}{}{0ex}{}{\text{n}}{\text{i}}$ where ψ _i is the relative transverse narrowing of the sleeve metal in the i-th section. The resulting cup-shaped semi-finished product is subjected to recrystallization softening annealing and etching, after which one or two hoods with thinning of the walls are carried out, which form the mechanical properties of the sleeve body. Then carry out a set of shaping operations.

- площадь в i-го поперечного сечения стенки чашеобразного полуфабриката; в) - то же, но полученный с использованием рабочего торца выталкивателя, который формирует предварительный контур гнезда под капсюль-воспламенитель; г) - полуфабрикат первой вытяжки, формирующей механические свойства корпуса гильзы; д) - полуфабрикат последней (второй) вытяжки, формирующей механические свойства корпуса гильзы, где D_п и t_п - диаметр и толщина дна полуфабриката последней вытяжки,

- площадь i-го поперечного сечения стенки полуфабриката последней вытяжки отсекающего объем стенки от дна полуфабриката последней вытяжки, равный объему стенки от дна до i-го сечения чашеобразного полуфабриката.The essence of the proposed method is illustrated by drawings, where in FIG. 1 shows a diagram of the flow of metal during volumetric stamping of a circle in the process of forming a cup-shaped semi-finished product: a) before the start of deformation; b) after the end of deformation. In FIG. 2 - semi-finished products of the technological process of manufacturing a sleeve, implemented in accordance with the proposed method: a) a circle cut from a strip (tape), where: D ₀ is the diameter and t ₀ is the thickness of the circle; b) - a cup-shaped semi-finished product obtained as a result of volumetric stamping of a circle using a flat working end of the ejector, where: D _p and h _p are the diameter and height of the outer belt; t _d - bottom thickness; α is the taper angle of the outer surface, D _h is the outer diameter of the upper edge of the cup-shaped semi-finished product,

- the area in the i-th cross section of the wall of the bowl-shaped semi-finished product; c) - the same, but obtained using the working end of the ejector, which forms the preliminary contour of the socket under the igniter capsule; g) - a semi-finished product of the first hood, forming the mechanical properties of the sleeve body; d) - the semi-finished product of the last (second) hood, forming the mechanical properties of the shell body, where D _p and t _p - the diameter and thickness of the bottom of the semi-finished product of the last hood,

- the area of the i-th cross section of the wall of the semi-finished product of the last hood cutting off the wall volume from the bottom of the semi-finished product of the last hood, equal to the volume of the wall from the bottom to the i-th cross section of the cup-shaped semi-finished product.

 In FIG. 1, position 1 represents the punch, 2 — the die, 3 — the ejector, 4 — the circle, 5 — the cup-shaped semi-finished product obtained as a result of volumetric stamping of the circle.

The introduction of the operation of volumetric stamping with the formation of a cup-shaped semi-finished product allows you to remove the restriction on the ratio of the thickness of the cup to its diameter and thereby reduce the ratio of the volume of the cup to the volume of the finished sleeve from 1.3-1.7 by known technologies to the minimum required values of 1.12-1 , 30 and increase the thickness t ₀ circle to values> 0.7 of the bottom thickness of the last hood.

The selected range of values of the diameter of the outer belt D _p = (0.9-1.1) • D _g due to the need to center the semi-finished product in the matrix on subsequent hoods. The upper value of the specified range is limited by the condition that the influence of deformation of the bottom of the semi-finished product in the drawing process on its hardening is reduced. In addition, exceeding this value leads to an unreasonable increase in effort when forming the bottom of the finished sleeve.

The height of the outer belt h _p <0.9 • t ₀ determines the presence of a cylindrical surface in the bottom of the semi-finished product, necessary for centering it in the matrix on the last hood. Exceeding this value leads to a decrease in the wall thickness in the bottom part of the bowl-shaped semi-finished product and, therefore, to a decrease in the mechanical properties of the bottom part of the semi-finished finished sleeve and the inability to provide the specified mechanical properties of the walls of the finished sleeve formed on subsequent hoods.

The choice of the bottom thickness of the bowl-shaped semi-finished product from the range t _d = (1,0 ... 1,3) • t _p due to the following. When t _d <1,0 • t _p for drawing operations, it is necessary to use a surge of metal from the walls of the semi-finished products to the bottom, which leads to the appearance of a bottom fold. When t _d > 1,3 • t _{p the} specific forces on the tool in the process of bottom formation unreasonably increase. The selected range of values of t _d provides the specified strength properties of the material of the bottom of the sleeve with a satisfactory tool life. The bottom thickness of the cup-shaped semi-finished product is provided by the geometrical dimensions of the tool and the magnitude of the force when performing the volumetric stamping of the circle, and depending on the size of the tool and the force, it is possible to obtain a thickness t _{p of a} larger or smaller thickness of the circle t ₀ .

The execution of the outer surface of the cup-shaped semi-finished product is due to the condition of ensuring coaxiality of the semi-finished product relative to the working surface of the exhaust matrix. Based on the fact that the outer diameter of the upper edge of the bowl-shaped semi-finished product is D _h ≤ D ₀ , the choice of the taper angle α from the range α = 8-60 ^o is determined by the ratio of the wall and bottom volumes of the manufactured sleeve. With an increase in the relative volume of its walls, the angle α decreases and vice versa.

и стенки чашеобразного полуфабриката

, и оценивают величиной твердости, замеряемой на приборе Виккерса (HV). Поскольку для обеспечения обтюрации необходимо в дульце гильзы иметь минимальную прочность, соотношение площадей поперечных сечений полуфабриката последней вытяжки

и чашеобразного полуфабриката

по кромке должно быть минимальным, что и определяет толщину стенки чашеобразного полуфабриката, равномерно сужающейся от донной части к кромке.The operational properties of the sleeves are determined by the mechanical properties of the bottom and especially the walls, since the strength of the sleeve during firing, obturation of the sleeve of powder gases and the possibility of removing the sleeve from the chamber after the shot depend on the ratio of their strength and ductility. The mechanical properties of the sleeve wall are obtained in the process of drawing with thinning due to the hardening of the metal during deformation, the value of the latter being determined by the ratio of the areas of the corresponding cross sections of the semi-finished product of the last drawing

and the walls of the bowl-shaped semi-finished product

, and evaluate the value of hardness measured on a Vickers device (HV). Since to ensure obturation, it is necessary to have a minimum strength in the sleeve barrel, the ratio of the cross-sectional areas of the semi-finished product of the last hood

and bowl-shaped semi-finished product

along the edge should be minimal, which determines the wall thickness of the cup-shaped semi-finished product, evenly tapering from the bottom to the edge.

 An example of the production of cartridge cases in this way is the manufacturing processes of steel and brass cartridge cases of 9 mm Luger cartridge (9x19) and 40 S&W (10x22), implemented at the Tula Cartridge Plant OJSC.

As the initial billet, a steel or brass strip with a thickness of t ₀ = 3.2 _-0.1 (instead of the previously used 2.9 _-0.1 ) was used, from which a circle with a diameter of D ₀ was cut. Next, the steel circle was phosphated and saponified, after which the circle was stamped to obtain cup-shaped semi-finished products, the geometric parameters of which are given in the table.

 The resulting cup-shaped semi-finished products were subjected to recrystallization softening annealing and etching (steel was additionally phosphated), saponified, and then two hoods were made with thinning of the wall (Fig. 2 g) and e)), forming the mechanical properties of the sleeve body. Then, a generally accepted technological process was implemented, which included such shaping operations as stamping the bottom, punching the pilot hole (s), crimping, grooving and grooving along the length.

 Data on the technological processes of the above products, used as an example, are summarized in table.

 The claimed method was obtained corresponding to the drawing of the sleeve of two pistol cartridges, which did not have a bottom fold and had a more favorable distribution of the mechanical properties of the wall along the length. The cartridges successfully passed the tests of shooting.

Compared with existing technologies for the manufacture of cartridge cases for small arms, the use of the proposed method provides the following advantages:
- allows you to use as the initial blank a strip with a thickness> 0.7 of the bottom thickness of the semi-finished product of the last hood;
- provides a reduction in the mass of the workpiece by an average of 14 percent;
- eliminates the formation of a bottom fold, which is impossible using traditional technology;
- provides a more favorable distribution of the mechanical properties (hardness HV) of the sleeve body with a decrease from bottom to dulce, while the existing process technology provides the opposite;
- the number of form-changing operations is reduced, - since the proposed technological process uses cutting, volumetric stamping of a cup, two hoods, while the existing one uses cutting and four hoods.

 This method can be widely used in the manufacture of cartridge cases of small arms of various calibers.

Claims (2)

1. A method of manufacturing a cartridge case for a small arms cartridge, including cutting a circle from a circle, manufacturing a hollow prefabricated product, drawing a hollow prefabricated product with thinning the wall and forming the mechanical properties of the cartridge case, chemical-thermal treatment and a set of shaping operations to form the capsule socket, forming the flange of the bottom of the cartridge case and trimming the sleeve in length, characterized in that the circle is cut out with a volume equal to 1.12-1.30 of the finished product, and with a thickness greater than 0.7 of the bottom thickness of the semi-finished product her hoods, in the manufacture of a hollow semi-finished product from a mug by volumetric stamping, a cup-shaped semi-finished product with a bottom outer girdle with a diameter equal to 0.95-1.1 of the diameter of the sleeve in its bottom part, a girdle height not exceeding 0.9 of the thickness of the original circle, and with a thickness the bottom, equal to 1.0-1.3 the thickness of the bottom of the semi-finished product of the last hood, while the outer surface of the cup-shaped semi-finished product is tapered with a taper angle of 8-60 ^o and with a wall thickness that tapers uniformly from the bottom to the edge, after which the chemical -those mical treatment comprising recrystallization annealing softening, etching the cup-shaped intermediate product, its subsequent drawing and ironing formation wall and the mechanical properties of the sleeve body, and then the complex shaping operations. 2. The method according to claim 1, characterized in that the cup-shaped semi-finished product is performed with a cross-sectional area that varies in height, determined by the dependence

Where

and

-the area of the cross-sections of the walls, cutting off equal volumes of the walls of the bowl-shaped semi-finished and semi-finished products of the last hood, respectively, mm ² ; НV _i - metal hardness of the finished sleeve in the i-th section, dimensionless; A, B and n are dimensionless coefficients of an expression approximating the hardening curve of a metal sleeve type:
HV _i = A + Bψ $\genfrac{}{}{0ex}{}{\text{n}}{\text{i}}$ ,
where ψ is the relative transverse narrowing of the sleeve in the i-th section.

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