RU2570265C1 - Method of stabilisation of electroplated chrome coating of barrels of automatic small arms, and shaft-type resistance furnace for its implementation - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method of stabilisation of barrels of automatic small arms with electroplated chrome coating includes the barrels internal cavities filling with dry quartz sand and their installation in shaft-type resistance furnace, equipped with heat insulating partition with two heat zones at temperature in bottom heat zone 150-200°C, made in form of disk with holes for barrels installation using bushings with height 10-123 mm. At that breech end of the barrel is located above the heat insulating partition, and muzzle part under it are heated, and breech end is held at tempering temperature of hardened stub for hardness 38-44HRC, and muzzle part is held at temperature not exceeding tempering temperature of the barrel blank. The shaft-type furnace is equipped with heat insulating partition dividing the heating chamber to two sections, having individual electric heaters and creating two heat zones, made out of steel plates, and lined inside with light weight refractory material. In partition through holes are made for the barrels installation, and for their removal from the furnace on the partition the disk with eye lug is installed and aligned by kingpins. The furnace has second control cabinet.

EFFECT: increased wear resistance of the electroplated chrome coating of barrels, and absence of coating chips on the muzzle part of the barrels.

3 cl, 2 dwg, 1 ex

Description

The group of inventions relates to the field of mechanical engineering and can be used for stabilizing tempering of galvanic chrome plating of trunks of automatic small arms 6P6M, 6P7K, 6P41 etc.

A known method of stabilizing the chrome coating of the barrel of 6P49 machine guns (see patent RU No. 2367689 C1, C21D 1/76, F27B 1/09, F27 / B 5/04, 09/20/2009), in which the stabilization of the galvanic chrome coating is carried out in a vacuum furnaces with a retort, providing dual-zone heating with different temperatures in the zones (for example, 570 ° C in the upper zone and 500 ° C in the middle and lower zones). In this case, the trunks are installed vertically in the fixture (chamber down), which is attached to the lid of the container, then the fixture is loaded into the container and sealed with this lid with a rubber gasket, after loading the container, water is supplied to the heated retort of the furnace to cool the lid with a rubber gasket and stop water supply before unloading the device with the barrels from the container into the air at a barrel temperature of not higher than 200 ° C. Argon is used as the working medium during the process during heating and cooling of the charge and vacuum when it is held at the technological temperature. Vacuum can be used as a working medium during the process.

The disadvantages of this method are:

- the use for placing cages of parts of a massive container made of austenitic class thick-walled steel reduces the heating rate of parts;

- before loading, the furnace must be warmed up at the technological temperature, which leads to additional energy consumption;

- hygiene of vacuum equipment requires thorough washing of the trunks after the chrome channel operation.

There is a method of heating the barrel of machine guns DP after chromium plating in electric furnaces in a nitrogen atmosphere or in loose bodies (for example, in sand) for 4 hours at a temperature of 500 ° C (see Arefyev MG, Karpov LI "Production of small barrel weapons ”under the editorship of A. A. Blagonravov, NKAP OboronGIZ, Main edition of weapons and ammunition, Moscow, 1945, p. 211), adopted as a prototype.

The disadvantages of the prototype are:

- the use of protective environments, such as nitrogen, implies the use of sealed electric furnaces and leads to additional consumption of protective environments, which increases the cost of products;

- heating the barrel in a furnace with one thermal zone can lead to tempering hemp.

A well-known periodic resistance shaft furnace СШ3-6.6 / 7, consisting of a welded metal casing lined with refractory and heat-insulating materials forming a heating chamber, on the inner surface of which spiral electric heaters of one thermal zone are placed, pipes for supplying and removing gas are welded into the casing, closed sealed caps, lined cover, with a fan installed in it, the bearing of which is cooled by water, manual lever-eccentric lifting mechanism opening the lid, the sand shutter to seal the casing and the lid, the cabinet for supplying electricity to the furnace, monitoring and on-off temperature control of the basket device for loading and heat treatment of parts (see "Electric furnace СШ3-6.6 / 7З УХЛ4 Operational documentation. Technical description." IDFA . 681114.001 TO, l. 4-6, 1989, the manufacturer - JSC "Electric furnace" Biysk). The well-known design of the electric furnace is taken as a prototype.

The disadvantages of the prototype are:

- the presence of one thermal zone does not allow simultaneous tempering for different hardness of two sections of lengthy (about 800 mm) parts;

- water cooling of the fan bearing involves finding water supply and sanitation systems near the furnace, which leads to additional costs during installation and operation of the electric furnace.

The proposed group of inventions solves the problem of improving the quality and resource of barrels of automatic small arms.

The technical result obtained by the implementation of the group of inventions regarding the method of heating the trunks of automatic small arms with galvanic chrome plating is to provide increased wear resistance of the galvanic chrome plating, the absence of chips on the muzzle of the trunks.

The specified technical result is achieved by the fact that in the method of heating the trunks of automatic small arms with a galvanic chrome coating, including heating, holding the trunks in a shaft furnace using protective media, it is new that dry quartz sand is poured into the internal cavities of the shafts, and resistance is installed in the shaft furnace equipped with a heat-insulating partition with two thermal zones at a temperature in the lower thermal zone of 150-200 ° C, made in the form of a disk with holes for installing trunks at bushes of bushings with a height of 10-123 mm, while the breech of the barrel is located above the heat-insulating partition, and the muzzle is under it, the breech is heated and held at the tempering temperature of tempered hemp to a hardness level of 38-44 HRC, and the muzzle is not at a temperature above the tempering temperature of the barrel stock.

The breech and muzzle parts of the shafts made of steel with a high position of the critical point A _C1 are heated to a temperature not higher than the tempering temperature of the barrel billet.

The technical result obtained by the implementation of the group of inventions regarding a shaft resistance furnace for heating the barrels of automatic small arms with galvanic chrome plating consists in creating a furnace design that provides for the simultaneous implementation of a dual-zone with different temperatures in the heating zones of the barrels of automatic small arms in an oxidizing environment (air).

The specified technical result is achieved by the fact that in a shaft furnace, resistance to heat the trunks of automatic small arms with a galvanic chrome coating containing a welded metal casing lined inside with refractory and heat-insulating materials, a heating chamber, a lined cover, a manual lever-eccentric mechanism for lifting and opening the lid, sand shutter for sealing the casing and cover, control cabinet for power supply, control and on / off control of the pace Atura, it is new that the furnace is equipped with a heat-insulating partition that divides the heating chamber into two sections, having individual electric heaters and forming two thermal zones, made of steel sheets and lined inside with lightweight refractory material, through holes for installing trunks are made in the partition, and for removing them from the furnace on the partition, a disk with an eye is installed and centered by the pivots, while the furnace is equipped with a second control cabinet.

The trunks of automatic small arms 6P6M, 6P7K, 6P41, made by the method of cold radial compression, in the breech are the same, the differences are in the geometric dimensions of the muzzle and the design of the outer part. On all models in the breech of the barrel, the chamber end is hardened - a stump to a depth of 5-10 mm. The operation of hemp tempering for the hardness HRC 38-44 specified by the drawing is combined with the operation of stabilizing the chrome coating in an electric furnace with two thermal zones.

A galvanic chrome coating having a microhardness of 950-1000 HV is applied to the barrel of automatic small arms. The stabilizing tempering of a galvanic chrome coating at temperatures of 490-520 ° C does not ensure the absence of chips in the muzzle of the trunks during acceptance tests due to the high 580-650 HV microhardness of the coating. Raising the temperature of the stabilizing tempering of the electroplated chrome coating to 560-580 ° C reduces the microhardness of the coating in the muzzle to 450-550 HV. In this case, the ductility of chromium increases sharply with a simultaneous improvement in the adhesion of the coating to steel. Closer to the breech, the hardness gradually increases to the level of 600-700 HV, which positively affects the survivability of the trunks.

The specified distribution of microhardness of galvanic chrome plating is achieved in a specially designed shaft resistance furnace, which has two thermal zones. The zones are separated by a thermal insulation partition with a total thickness of 110 mm. When setting the control temperature in the upper thermal zone 425 ± 5 ° C in the lower thermal zone 570 ± 5 ° C during the process, the temperature along the barrel is distributed as follows: in the muzzle 575 ° C, on the upper boundary of the lower thermal zone - 540-550 ° C, above the septum in the upper thermal zone 465-475 ° C, in the hemp zone 428-435 ° C. Thus, the muzzle of the barrel is in the furnace at an elevated temperature, but not higher than the tempering temperature of the barrel stock, and the chamber with hemp at the tempering temperature for a given CD hardness HRC 38-44. In a short section, limited by the height of the baffle, the temperature along the barrel drops by 75-80 ° C, which favorably affects the distribution of microhardness of the coating.

When installing trunks on a sleeve of various heights ranging in size from 10 to 123 mm, it is possible to regulate the hardness of the barrel cover in the most loaded zone (120-250 mm from the cut of the breech) by temperature.

The electric heater of the furnace consists of two independent sections. The height of the heat zone of the upper section after installing the heat-insulating partition is 320 mm, which is quite enough to heat the barrel at a distance of 250-270 mm from the breech cut. The height of the thermal zone of the lower section from the partition is 500 mm, which ensures the heating of the muzzle of the trunks of existing products.

To accelerate the transfer of trunks from the furnace to the well, a disk with an eye is used, in which holes are made corresponding to the holes in the heat-insulating partition. The disk is centered relative to the baffle holes with pivots.

Due to the fact that the proposed design of the resistance shaft furnace provides a difference in temperature zones up to 160 ° C, the fan located in the cover and its cooling system are dismantled, and the remaining holes are lined.

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:

FIG. 1 - section of an electric furnace;

FIG. 2 is a diagram of a barrel installation in a furnace.

The furnace contains a welded metal casing 1, lined with refractory and heat-insulating materials, a heating chamber 2, divided by a partition 3 made of steel sheets and lined inside with a lightweight heat-insulating material. In the partition 3, holes 4 are made for installing trunks. A nichrome heater 5 is mounted on the walls of the heating chamber 2, divided into two independent sections. A disk with an eyelet 6 is installed on the heat-insulating partition 3. Holes 6 are also made in the disk 6, similar to those made in the partition 3. The disk 6 is centered on the partition by pivots 7. The electric furnace is closed by a lever-eccentric mechanism (not shown conditionally) with a lid 8 and sealed with a sand lock 9.

Each of the thermal zones has its own control system, consisting of a thermoelectric converter 10 connected to a temperature regulator 11 (automatic recording potentiometer), which controls the power circuit. Control systems are mounted in individual cabinets 12.

An example of the implementation of the method for stabilizing the galvanic chrome coating of the barrel of an automatic small arms.

In the open furnace, a disk 6 is mounted on the heat-insulating partition 3 and pivoted by pivots 7 to match the holes 4. Using a lever-eccentric mechanism, close the furnace with a lid 8.

Trunks 13 are prepared for loading into the furnace, for which a cap 14 is attached to the muzzle part using wire ends. A funnel 15 sleeve is mounted on the breech part. Trunks 13 are installed into the fixture with the muzzle part down and the channel and the chamber are filled with dry quartz sand. Turn on the oven and warm it to a temperature of 150-200 ° C. Turn off the oven and open the lid with a manual lever-eccentric mechanism 8. The trunks 13 are installed in the furnace using the mounting sleeves 16. With a manual lever-eccentric mechanism, the furnace is closed with a lid 8 and sealed with a sand shutter 9. On the thermostats 11 (automatic recording potentiometers), the process temperature . In the upper thermal zone - 435 ± 15 ° C, in the lower thermal zone - 570 ± 10 ° C. Turn on the heating of the furnace. The trunks in the furnace are heated and maintained according to the requirements of the process. At the end of the holding time, the furnace is turned off and opened with a manual lever-eccentric mechanism. Using the electric hoist for the eye of the disk 6, the barrel cage is transferred to the well and closed with a lid. Cool for two hours. Then the lid of the well is opened and the trunks 13 are cooled to the temperature of the workshop. When measuring the stabilization temperature regimes along a control shaft with thermoelectric converters minted in it, it is allowed to cool the charge with the furnace lid 8 ajar.

The tests carried out by shooting in the scope of acceptance tests showed the absence of chips in the muzzle of the trunks made by the proposed method, and the resource tests showed an increase in barrel survivability.

Claims (3)

1. The method of heating the trunks of automatic small arms with a galvanic chrome coating, including heating, holding the trunks in a shaft furnace using protective media, characterized in that dry quartz sand is poured into the internal cavities of the shafts, installed in a shaft furnace equipped with a heat-insulating partition with two thermal zones at a temperature in the lower thermal zone of 150-200 ° C, made in the form of a disk with holes for installing trunks using bushings with a height of 10-123 mm, while the breech ol is placed above the heat-insulating partition, and the muzzle under it is heated and the breech is maintained at tempering temperature of tempered hemp at a hardness level of 38-44HRC, and the muzzle at a temperature not higher than the tempering temperature of the barrel stock. 2. The method according to p. 1, characterized in that the breech and muzzle parts of the trunks made of steel with a high position of the critical point A _C1 are heated to a temperature not higher than the tempering temperature of the barrel billet. 3. A resistance shaft furnace for heating the trunks of automatic small arms with a galvanic chrome coating, comprising a welded metal casing lined inside with refractory and heat-insulating materials, a heating chamber, a lined lid, a manual lever-eccentric mechanism for lifting and opening the lid, a sand shutter to seal the casing and covers, a control cabinet for power supply, control and on-off temperature control, characterized in that it is equipped with thermal insulation an ionic partition separating the heating chamber into two sections, having individual electric heaters and forming two thermal zones, made of steel sheets and lined with lightweight refractory material inside, and through holes for installing barrels are made in the partition, and installed to remove them from the furnace on the partition and the disc with the eye is centered by the pivots, while the furnace is equipped with a second control cabinet.

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