RU2532797C1 - Method of barrel production - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metal forming and may be used for production of rifled barrels. Initial billet is heat treated and machined to produce a pipe billet. Pipe billet has feed and drive parts for chuck and drive centres of radial squeezer. Pipe billet is subjected to radial reduction to produce semi with rifled guide part to be subjected to finish machining to get finished barrel. At radial reduction, forged piece bore is machined to get local conical surface to be reduced to get rifled guide part.

EFFECT: higher surface smoothness, lower labour input.

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Description

The invention relates to the field of metal forming and is suitable for the manufacture of trunks with threaded guiding parts.

A known method for the manufacture of trunks: the forgings are pre-treated on the outer surface, their ends are cut, centering necks and control belts are made and deep drilling is carried out. Then it is heat-treated, a deep hole is bored, grooves are made in it, then the chamber is finished and finally processed on the outer surface to obtain a finished barrel (see the book by N. Troitsky, Deep Drilling. - M.: Mechanical Engineering, 1971, pp. 140-141 )

With this method, the length of the initial billet is greater than the length of the barrel, taking into account the trimming of the ends and the separation of the template from the muzzle under the witness samples. Therefore, the volumes of preliminary and final machining are significant, and the metal utilization factor (KIM - the ratio of the mass of the barrel to the mass of the initial billet - η) is not more than 30%.

There is another method for the manufacture of trunks (see patent for the invention No. 215670 C1, 02.17.1999), adopted as a prototype containing the receipt and heat treatment of the original billet (rolled or forged). Then it is machined with the formation of a pipe billet having a lead-in under the retaining center and a lead part in the form of a large cylinder with the diameter of the initial workpiece and a small cylinder with a diameter ≥ of the external breech of the barrel under the lead center. A semi-finished product with a finished guide part is made from it by radial compression and its final processing is carried out with the input part removed.

Its advantage over the previous ones: CMM is increased by about 2 times and the workpiece-pipe is more technologically advanced than the previous one.

Disadvantage: due to the short duration of interaction of the metal of the channel layer with the forming part of the mandrel having protrusions and depressions, when the workpiece-pipe is radially crimped, the resulting roughness of the threaded guide part does not always correspond to that required and is improved by subsequent lead-making, which increases the complexity of the barrel.

The objective of the present invention is to remedy this drawback.

The problem is solved in that in the method of manufacturing the barrel, including the manufacture and heat treatment of the original billet, its preliminary machining to obtain a billet pipe with lead-in and drive parts for retaining and drive centers of the radial crimping machine, obtaining a semi-finished barrel with a threaded guide part by radial compression of the workpiece-pipe on a radial crimping machine and the final machining of the semi-finished product with the formation of the finished barrel,

Before the formation of the threaded guide part of the semi-finished product, a local conical surface is formed in the billet-pipe hole by radial compression, on which the threaded guide part is then formed by radial compression.

In the proposed method, when radially compressing the billet pipe in its hole, a local conical surface is first formed by compression, and then it is crimped into a threaded guide part.

This solution increases the duration of contact of the metal, located on the surface of the hole and in the zone adjacent to it, with the mandrel, on which it is first deformed on the conical part in 2 directions, and then in 3 directions (coordinates) on the forming part, having alternating protrusions and depressions, by ROM strikers with the formation in the forging of a threaded guide part and the outer surface of the barrel that is ready or as close as possible to it. Due to this, the cleanliness (roughness) of the surface of the guide part of the barrel channel is improved and there is no need for it to be lead after radial crimping.

Technical solutions with features distinguishing the claimed solution from the prototype are not known and do not follow explicitly from the prior art. This suggests that the proposed method is industrially applicable, has significant differences, is new and therefore meets the criterion of "invention".

The essence of the proposed is illustrated by the drawing, which shows the longitudinal section of the retaining center 1, obtained by radial compression by the strikers 2 from the workpiece-pipe forgings 3, fixed lead part 4 in the retaining center 1, the lead part 5 in the lead center 6 with internal radial teeth or end teeth.

The compression of the billet pipe by the strikers 2 is carried out on a mandrel 7 having a threaded part 8 of length l and parameters d _i along the protrusions and depressions to form grooves and fields, respectively, and a conical part 9 of length l ₀ and diameter d _k , which is smaller than the diameter d _{0 of} the billet hole -pipes (for the machine gun "Cord" d ₀ = 15 mm).

The diameter of the initial billet in the lead part is D ₀ = 57 mm, and the lead-in part of the strikers with their angles α ₁ -α ₄ (see OST B3-6011-85. Billets caliber 4,5 ÷ 30 mm. Typical cold process radial compression, sheet 30), form on the outside of the forgings of the barrel of the Kord machine gun a deformable section of length L ₀ not exceeding 40 mm.

Between the lengths of the conical surfaces of the forgings of the barrel, the condition L ₀ > l ₀ is fulfilled. And the same condition is fulfilled between d _to <d ₀ for the unimpeded movement of the mandrel along the billet-pipe hole into the area of the location of the ROM holes.

Compression is carried out as follows: it is fed by a manipulator, not shown in the drawing, into the zone of location of retaining 1 and lead 6 centers; the latter moves axially from left to right, and the shank of the lead part of the billet-pipe is in the socket of the center 1, after which the inner radius teeth of the lead center 6 are introduced into the intersection zone of the side and end surfaces of a large cylinder with a diameter D _{0 of the lead} part of the billet-pipe.

When it is crimped by the strikers 2, making reciprocating movements relative to it, a 2- and 3-dimensional deformation of its material occurs, as indicated earlier in the zones of the strikers and the mandrel, and when the strikers 2 move away from it, it rotates around with the teeth of the leashes of center 6 its longitudinal axis and is fed in the axial direction into the zone of the entry part of the strikers 2.

This part deforms the metal of the billet-pipe first on the conical part 9 of the mandrel 7, and then the gauge part of the strikers, this metal is deformed on the groove calibrating part 8 of it with the formation of alternating fields and grooves on the guide part with minimal roughness of the obtained forging 3 due to the increase the contact time of the metal with the mandrel having an additional conical part 9.

Gradual compression of the metal of the billet pipe from the base to the top of the conical part 9 of the mandrel increases the duration, improves the roughness of the corresponding section of the forging 3, which from the top of the conical part of the mandrel passes to the grooved calibrating part 8 of it, where the guide part is formed in the form of fields, grooves and faces of the latter .

In this case, the bottoms of future rifling have already formed on top of the conical part of the mandrel and have a corresponding roughness, which is improved by additional compression on the protrusions of the threaded part of the mandrel 7.

Future fields are also part of the perimeter of a conical surface of unit length at the aforementioned top of the mandrel 7 and, like the grooves, have an appropriate roughness and will be formed by the metal of this perimeter and will have minimal roughness on the rest of the mandrel, and the edges of the grooves will be formed metal zone adjacent to the billet-pipe hole.

When implementing this method in the barrel of a 12.7 mm caliber machine gun “Cord”, the dimensions along the bottoms of 8 grooves d _n = 13.0 mm, a width B _k = 2.82 mm, a depth h = 0.15 mm, and a width fields In _n = 2.15 mm (parameters of the chrome-plated guide part are indicated), we estimate the change in the perimeter of the guide part due to grooves and fields compared to the smooth perimeter of the hole obtained at the top of the conical part of the mandrel, assuming its diameter is ⌀13 mm.

The perimeters of the smooth hole P _hl = 3.14 × 13 = 40.82 mm,

the faces of the rifling P _g = 8 × 2 × 0.15 = 2.4 mm,

rifling P _n = 8 × 2.82 = 22.6 mm,

fields P _n = 8 × 2.15 = 17.2 mm.

The total perimeter of the threaded part

P _Σ = P _gr + P _n + P _p = 2.4 + 22.6 + 17.2 = 42.2 mm.

The increase in its perimeter compared to the perimeter of the hole on top of the conical part of the mandrel

. $$\Delta P=\frac{P_{\Sigma }-P_{gl}}{P_{gl}}=\frac{\mathrm{42,2}-40.82}{40.82}\cdot \mathrm{one\; hundred}\%=3.38\%$$

.

Therefore, the perimeter of the threaded guide part is formed in the forging mainly due to the perimeter of the smooth hole formed on the top of the conical part of the mandrel.

Thus, due to the increase in the contact time of the metal of the billet-pipe, first with the conical part of the mandrel, and then with the threaded part, the roughness of the threaded part of the channel of the obtained forgings improves and there is no need to lead it before chrome plating.

Claims (1)

A method of manufacturing a barrel, including the manufacture and heat treatment of the original billet, its preliminary machining to obtain a billet pipe with lead-in and lead parts for retaining and lead centers of a radial crimping machine, obtaining a semi-finished barrel with a threaded guide part by radially compressing the workpiece-pipe to radially crimping machine and the final machining of the semi-finished product with the formation of the finished barrel, characterized in that before the formation of the threaded guide of the prefabricated part in the billet-pipe hole by radial compression, a local conical surface is formed, from which then a threaded guide part is obtained by radial compression.