RU2498185C1 - Barrel of automatic small arms, which is made using cold radial reduction method, and method for its local hardening - Google Patents

Abstract

FIELD: weapons and ammunition.

SUBSTANCE: barrel local hardening method consists in the fact that a barrel is installed in a device providing its vertical movement; a collar is oriented and aligned; cooling liquid is supplied to the barrel channel and a sprayer, heated without rotation above point A_C3 till the temperature of 880-900 °C, and then, it is cooled by abrupt movement of the heated zone under the inductor sprayer. Barrel (1) includes a channel with four grooves (2). In the breech end of the barrel there is a cartridge chamber with bullet inlet (3). On the breech part of the barrel there are two transverse cutouts for latch (4) of the barrel, as well as joves (5) for passage of the fame projection. On the breech face of the barrel there is annular projection (6) for supporting of a cartridge rim and cutout (7) for an extractor hook. On the chase there is flame arrestor (10). Barrel has finning (8) and four air supply channels. On the barrel there rigidly fixed is casing (12) with screen (13) and plate (14), gas chamber (15), gas regulator (16), ejector (17), shoe (18) muzzle-sight, and plain arm (19). On the outside of the barrel there is heat treated thrust shoulder (20) with two longitudinal slots (21).

EFFECT: elimination of barrel rolling.

2 cl, 13 dwg

Description

The group of inventions relates to the field of military equipment and can be used to create automatic small arms, for example, single machine gun barrels made by cold radial compression.

The well-known barrel with a bipod automatic small arms - machine gun 6P41 "Pecheneg" (PKP) (see 7.62 mm Kalashnikov infantry machine gun. Operation manual 6P41.000 RE. FSUE "TSNIITOCHMASH", 2000, pp. 9-16 ) adopted as a prototype. The trunk is an integral connection. The outer surface of the barrel in the middle part is made conical and ribbed to increase the cooling area and thermal radiation. Inside the trunk has a channel with four rifling. In the breech of the barrel is made a chamber with a bullet entrance. On the breech of the barrel there are two transverse cutouts for the barrel lock, as well as openings for the passage of the ledge of the frame and grooves for the protrusions of the receiver. On the breech section of the barrel, an annular protrusion is made to stop the flange of the sleeve and a cutout for the ejector hook. The trunk has a ribbing and four air ducts, with the upper and lower edges of the trunk wider than the side. On the muzzle of the barrel is made a flame arrester having an internal conical surface with longitudinal through grooves expanding to the outer surface of the barrel. In the wall of the barrel there is an opening for the removal of part of the powder gases from the barrel channel into the gas chamber. A barrel with a screen and a plate, a gas chamber, a gas regulator, an ejector, a fly block and a bipod are rigidly mounted on the barrel.

The main structural drawback of the prototype is the circular pitching of the barrel (more than 0.4 mm).

A known method of local surface hardening with a simultaneous method of heating by high frequency currents (hereinafter referred to as high frequency current) (see GF Golovin, MM Zamyatin. High-frequency heat treatment. Issues of metal science and technology. Edition 2, "Engineering", Leningrad, 1968 , p. 158-159), adopted as a prototype. The method consists in installing the part in an inductor with a technological gap, heating the entire portion of the part to be quenched, cooling the heated portion of the sprayer combined with the inductor.

The disadvantages of this method are:

- high copper consumption for the manufacture of a thick-walled inductor wire of the inductor;

- frequent maintenance of the inductor spray device due to the rapid formation of scale in the holes due to the periodic supply of coolant;

- the formation of zones with a burn during heating of thin elements of the type "shoulder" inductors equal in height to the width of the shoulder due to the high current density;

- there is no way to protect against deformation during local heating of the external elements of the parts in the form of a pipe with a small inner diameter;

- supplying the quenching unit with an additional device for supplying coolant after the end of the heating cycle.

The proposed group of inventions solves the problem: increasing the resource and reliability of weapons, stability in accuracy and accuracy throughout the life of the weapon.

The technical result obtained by the implementation of the group of inventions regarding the barrel of an automatic small arms is to eliminate the pitching of the barrel.

The specified technical result is achieved by the fact that on the barrel made by cold radial compression, having a conical and ribbed middle part outside, a front cylindrical part with four longitudinal air ducts with upper and lower ribs wider than the side ones, a breech part with two transverse cutouts for the contactor, openings for the passage of the ledge of the frame and the grooves for the protrusions of the receiver, an annular protrusion for stopping the edge of the sleeve, a cutout for catching the ejector, inside the channel with four grooves, pat window with a bullet inlet, a flame arrester with an internal conical surface and longitudinal through grooves expanding to the outer surface of the barrel, an opening in the barrel wall to divert part of the powder gases into the gas chamber, a casing with a screen and a plate mounted on the barrel, a gas chamber with a gas regulator, an ejector , a fly block, a bipod, a new one is that on the outside the barrel is equipped with a heat-treated thrust shoulder with two longitudinal grooves, the depth of the hardened layer being 2-3.5 mm.

The technical result obtained by the implementation of the group of inventions regarding the method of local hardening of the thrust shoulder of the barrel of an automatic small arms is to reliably ensure the quality of the contact surfaces of the thrust shoulder of the barrel by imparting mechanical properties to them that provide high strength and the ability to absorb shock loads.

The specified technical result is achieved by the fact that in the method of local hardening of the barrel of automatic small arms, including installation in an inductor with a technological gap, heating and cooling from the sprayer is new, that the barrel is installed in a device that provides its accelerated vertical movement, orient the shoulder in the center of the cylindrical parts of the induction wire, center relative to the inner diameter of the inductor, supply coolant to the bore and sprayer, heat without rotation above f points A _C3 to a temperature of 880-900 ° C in the inductor for continuous sequential hardening, cooled by abrupt movement of the heated zone under the sprayer of the inductor, and the coolant is fed into the bore under a pressure of 0.03-0.06 MPa.

Technical solutions with features distinguishing the claimed solution from the prototype are unknown and do not follow explicitly from the prior art. This suggests that the claimed group of inventions is new and has an inventive step.

The proposed group of inventions is illustrated by drawings, where

figure 1 - the barrel assembly;

figure 2 - section aa in figure 1;

figure 3 - section bB in figure 1;

4 is a view In figure 1;

5 is a barrel in the receiver;

6 is a section aa in figure 5;

7 is a diagram for determining pitching;

Fig. 8 is a diagram of the appearance of pitching during falls;

Fig.9 - remote element A in Fig.8;

figure 10 - diagram of the heat treatment of the shoulder shaft;

11 - centering the shoulder along the height of the induction wire;

Fig - centering collar along the diameter of the induction wire;

13 is a diagram of an implementation of the method.

The trunks are made according to the standard technological process of cold radial compression of 300KhN2MFA, 30KHN2MFA-Sh and others steel billets of 30KHN2MFA, 30KHN2MFA-Sh steel, etc., improved with a hardness of 300 ± 27 HB, with the final formation of the geometric dimensions of the chamber, the bullet entrance and the channel. Further heat treatment of the breech of the trunks, associated with an increase in hardness, is impossible, due to a change in the geometric dimensions of the chamber and the bullet inlet due to structural transformations occurring in steel during quenching.

The barrel liner is heat treated to a hardness of 38.5 ... 44HRC, and since the barrel is a softer part, its contact surfaces are crushed during operation. As a result, in an operating environment of 8-12 thousand shots, a circular pitching of the barrel of more than 0.4 mm occurs, which does not allow the machine gun to be operated.

The value of the pitching K (Fig. 7) is determined during a forced turn of the trunk until it is limited by the liner. Circular pitching during firing is formed:

- in connection with the movements of the barrel cantilever fixed in the liner in the vertical plane from the shot, leading to the collapse of the bearing pads of the barrel, which is facilitated by the presence of a clearance on the landing surfaces of the barrel and the barrel liner;

- in connection with the twisting of the barrel when the bullet moves along the screw cuts of the barrel;

- in connection with the occurrence of a bending load on the supporting platforms of the barrel when the machine gun falls on the bipod when taking a position, etc., leading to the crushing of the supporting platforms of the barrel (Fig. 8, where M is the bending moment).

It is impossible to repair the barrel of the 6P41 machine gun in order to eliminate the pitching due to the hard landing of the casing, which eliminates the filing, and the possibility of disassembling the barrel is fraught with certain difficulties, in particular with drilling the fastening pins, subsequent dismantling of parts included in the assembly, often leading to their rejection. Thus, the entire assembly unit is subject to replacement.

In order to increase the resource and reliability of weapons, optimize the mechanical properties of structural elements, the barrel is equipped with a thrust shoulder with local heat treatment of contact surfaces for a hardness greater than the hardness of the improved workpiece, namely 38.5 ... 44HRC (figure 10), which will significantly increase the mechanical the strength of the contact surfaces of the barrel shoulder. The main condition for local heat treatment is the absence of thermal effects on the bore in order to prevent its deformation and oxidation of the chrome coating. This condition can be fulfilled with a hardened layer depth h _{max of} not more than 0.1 (Dd) mm, in our case 2.64 mm without taking into account the transition zone, which can be (0.5-2) h mm, take 0.5h to prevent heating of the inner surface. The maximum depth of thermal influence should be no more than 3.96≈4 mm. The minimum depth of the hardened layer h _min = 0.1 R, that is, 1.7 mm, taking into account the transition zone - 2.5 mm. Considering that the hardness of a surface hardened layer is measured by a structure consisting of 50% martensite, the boundary zones of the depth of the hardened layer will be h = 2 ... 3.5 mm.

The barrel of an automatic small arms contains a barrel 1, the middle part of which is made conical and ribbed to increase the area of cooling and thermal radiation. Inside the barrel has a channel with four grooves 2. In the breech of the barrel there is a chamber with a bullet inlet 3. On the breech of the barrel there are two transverse cuts for the barrel closure 4, as well as openings 5 for the passage of the frame ledge. At the breech section of the barrel, an annular protrusion 6 is made for stopping the flange of the sleeve and a cutout 7 for catching the ejector. The barrel has a rib 8 and four air ducts 9, with the upper and lower edges of the barrel wider than the side. On the muzzle of the barrel there is a flame arrester 10 having an internal conical surface with longitudinal through grooves expanding to the outer surface of the barrel into the gas chamber. A casing 12 with a screen 13 and a plate 14, a gas chamber 15, a gas regulator 16, an ejector 17, a fly block 18 and a bipod are rigidly fixed to the barrel on the outside of the barrel. An abutment collar 20 with two longitudinal grooves 21 is made (FIGS. 1, 2 , 3, 4).

The barrel is placed in the receiver as follows. The barrel (figure 1) during assembly is installed in the liner 22 of the barrel until it stops in the shoulder 20. The liner 22 is placed in the receiver 23 (figure 5, 6). While the cylindrical breech of the barrel is placed in the cylindrical cavity of the liner, and the protrusions of the liner are placed in the longitudinal grooves 21 of the shoulder of the barrel.

When fired, the barrel 1 tends to rotate by the value of the structural clearance less than 0.4 mm In this case, the bearing pads of the barrel hit the protrusions of the liner 22 of the barrel, and since the thrust collar 20 is hardened to a hardness of 38.5 ... 44 HRC and a depth of 2 ... 3.5 mm, crushing of the bearing pads does not occur.

When firing from the bipod and from the hand with the occurrence of multidirectional bending moments on the thrust shoulder 20 are cyclic loads from the end surface of the liner 22 of the barrel.

According to the results of tests conducted, wear of the contacting surfaces does not occur.

The proposed method for local barrel quenching with simultaneous heating is implemented using a high-frequency generator with a frequency of 0.066 MHz, a hydraulic quenching machine made according to a single-cylinder circuit, an inductor for a continuous-sequential heating method combined with a sprayer, a device for supplying coolant to the barrel channel.

The use of an inductor collar for continuous-sequential hardening during heating is due to the simplicity of the design, its inexpensive and simple manufacture, which has proven to be highly reliable in operation. To prevent the coolant from pouring into the heating zone, the angle of inclination of the axis of the holes of the sprayer is made within 50-55 ° to the vertical.

In surface quenching practice, water cooling is most commonly used. It was noted that some alloy steels, which are usually subjected to oil quenching (after through heating in a furnace), can be cooled with water during surface hardening of a thin layer (up to 3 mm). With a small thickness of the heated layer, the low thermal conductivity of alloy steels is not an obstacle to the use of sharper cooling media due to the formation of compressive rather than tensile stresses.

With the simultaneous method of heating steel products with a height significantly lower than the height of the inductor, the maximum current density will be concentrated in the middle part of the inductor. Therefore, in order to obtain a uniformly heated layer of a given depth, to exclude burn-out at the edges of the collar, and to heat the body of the barrel, the collar is oriented at the center of height of the cylindrical part of the induction wire while the collar is centered on the inner surface of the induction wire.

Orientation of the collar in the center of height of the cylindrical part of the inductor wire of the inductor is carried out under the condition:

a = 0.5 (H-L), where

a - installation depth (distance from the upper plane of the induction wire to the upper end of the shoulder);

H is the height of the cylindrical part of the induction wire;

L is the shoulder width, and is controlled using a ruler or visually.

Since the collar has two sections in the cross section at an angle of 17 ° with an apex R15 mm (see Fig. 11), in order to balance the compressive stresses and reduce barrel deformation during heating and cooling, the collar is centered on the inner diameter of the inductor inductor wire.

Given that the current flows through the inductor along the path of least resistance, that is, at the incision site of the induction wire, its density will be minimal and, taking into account the wear pattern of the end surface, limited by sections and radius, the shoulder is centered, as shown in Fig. 11. A surface bounded by a circle (experiencing less load) faces the cut of the induction wire.

In order to prevent the appearance of discoloration colors in the fields and grooves of the bore in the heating zone and to avoid deformation of the bore, additional water cooling of the bore is used. Coolant is supplied through six holes ⌀ 1.5 mm at an angle of 55-60 ° to the surface of the first cone of the chamber, made in the upper supporting center of the hydraulic quenching machine. The water supply system is equipped with a pressure gauge and a control valve.

The critical point A _C3 for steel 30XH2MFA is 830 ° C. Taking into account that the preform has undergone preliminary improvement and that the depth of hot current penetration into the metal at a frequency of 0.066 MHz is 2 mm, then the shift of the critical point A of the _NW does not occur. A slight increase in temperature to 880-900 ° C is necessary to achieve quenching temperature at a depth of 3-3.5 mm due to the thermal conductivity of steel.

An example implementation of the method (Fig. 13): a high-frequency generator is prepared for operation by setting the anode voltage and the heating time on it according to the technological process, the position of the inductor relative to the centers of the hydraulic quenching machine is adjusted. The barrel 1 is installed by a muzzle cut into the lower center 24 of the hydraulic quenching machine, the breech is introduced into the inductor 25, combined with the sprayer and fixed by a spring-loaded supporting center 26. The hydraulic quenching machine is turned on and the height of the shoulder relative to the induction wire is centered by adjusting the position of the rod upper stop 27 hydraulic cylinder, while achieving placement of the collar in the center of the cylindrical part of the induction wire. Control the size of "a". Check the alignment of the shoulder relative to the internal diameter of the induction wire. If necessary, carry out the adjustment by turning the barrel. Water is supplied to both branches of the inductor combined with the sprayer. Adjust the flow of water by the valve 28 so that it does not fall into the heating zone. Open the valve 29 of the water supply to the bore and the pressure gauge 30 set the pressure of 0.03-0.06 MPa. The magnitude of the set water pressure depends on the design of the lower center 24. Water flows into the bath 31 of the hydraulic quenching machine through the grooves of the flame arrester. The high-frequency generator is turned on and the surface of the shoulder to be hardened is heated for 8-9 seconds. After turning off the time relay of the high-frequency generator, the heated zone of the barrel is sharply transferred under cooling by the water shower from the inductor sprayer. Cool for 3-4 seconds. Shut off the valves 28 and 29 of the water supply. The hardened barrel is removed from the centers and the next one to be hardened is installed. Thus, the batch of barrels is tempered.

The height of the shoulder with respect to the induction wire is centered periodically.

Claims (2)

1. The barrel of an automatic small arms manufactured by cold radial compression, having an outside conical and ribbed middle part, a front cylindrical part with four longitudinal air ducts with upper and lower ribs wider than the side, a breech part with two transverse cutouts for the contactor, openings for the passage of the ledge frames and grooves for the protrusions of the receiver, an annular protrusion for stopping the edge of the liner, a cutout for the ejector hook, inside a channel with four grooves, a chamber with a bullet in a house, a flame arrester with an internal conical surface and longitudinal through grooves expanding to the outer surface of the barrel, an opening in the barrel wall to divert part of the powder gases into the gas chamber, a casing with a screen and a plate mounted on the barrel, a gas chamber with a gas regulator, an ejector, a fly block , a bipod, characterized in that the outside of the barrel is equipped with a heat-treated thrust shoulder with two longitudinal grooves, the depth of the hardened layer being 2-3.5 mm. 2. The method of local hardening of the barrel of automatic small arms, including installation in an inductor with a technological gap, heating and cooling from a sprayer, characterized in that the barrel is installed in a device with accelerated vertical movement, the shoulder is oriented in the center of the cylindrical part of the induction wire, centered relative to the inner diameter inductor, coolant is fed into the bore and the sprayer is heated without rotation above point A _c3 to a temperature of 880-900 ° C in the inductor for continuous In order to quench it, it is cooled by a sharp movement of the heated zone under the inductor sprayer, and the coolant is supplied to the bore under pressure of 0.03-0.06 MPa.

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