RU2354488C2 - Method of rifled bore fabrication - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to pressurised metal treatment for producing rifled stepped bores. The fabrication method of rifled bore includes production of original work piece, hardening thermal treatment, mechanical treatment to the dimensions of pipe work piece for radial squeezing, forged piece production in two radial squeezing operations. As a result, plain channel is formed in forged piece during radial pre-squeezing operation, and threaded channel is formed in forged piece during the final radial squeezing and mechanical treatment operations. During rifled bore fabrication, the pipe work piece is subject to hardening thermal treatment after mechanical treatment but before the first squeezing operation, or forged piece is subject to hardening thermal treatment after the first squeezing operation.

EFFECT: reduced manpower effort, material and energy costs, and reduced consumption of tools and deterioration of used equipment during operations preceding final radial squeezing of forged piece.

Description

The invention relates to the processing of metals by pressure and can be used in the manufacture of rifled stepped trunks.

A known method of manufacturing a barrel according to OST VZ-6011-85, including the manufacture of the original billet, its heat treatment to hardness of the barrel, machining of the initial billet, including processing a deep hole and processing the external surfaces in the dimensions of the billet pipe with a volume equal to the forging volume after radial compression at the same time, a lead-in part is formed at one end of the billet-pipe, a lead part at the other, and a deformable part between them. Next, the billet-tube is subjected to radial compression on a radial crimping machine to obtain forgings with a threaded channel on the deformable part and then the final machining of the barrel is performed.

The disadvantage of this method is that the radial compression of the workpiece-pipe on the deformable section is possible with a degree of deformation, as a rule, not exceeding 30% due to the high hardness and strength of the metal being treated, while the deformable part also increases in length by no more than 30% and, as a result, you have to use the original workpiece of considerable length, there is a significant withdrawal of the tool when processing a deep hole, leading to the need to have significant allowances for machining the outer surface. All this leads to significant material, labor and energy costs.

A known method of manufacturing a rifled barrel, adopted as a prototype (see RU 2069594, IPC B21D 41/00, publ. 11/27/96). The method includes manufacturing the initial billet, hardening it to hardness of the barrel, machining the billet, including processing a deep hole and treating the outer surfaces to the dimensions of the pipe billet with a volume equal to the forging volume after radial compression, with the formation of a lead-in at one end of the pipe billet , on the other - the lead part, and between them the deformable part. Next, forgings are made by radially crimping the billet-pipe on a radial crimping machine in two operations with forming a smooth channel in the forging in the preliminary radial crimping operation and with forming a threaded channel in the deformable part of the forging in the final radial crimping operation, and after the preliminary radial crimping operation subjected to heat treatment to relieve internal stresses. Then carry out the final machining of the forgings to obtain the finished barrel.

The described method allows to reduce the length of the original billet, reduce the length of the deep hole, reduce machining allowances, reduce labor, material and energy costs in the manufacture of the barrel. The disadvantage of this method is that in the method the heat treatment of the initial billet is carried out for high hardness and strength of the metal, i.e. at the beginning of the process. In this regard, in all machining operations, including the preliminary radial reduction operation, low productivity and significant tool consumption due to the high hardness and strength of the metal.

The invention solves the problem of reducing the cost of manufacturing the barrel.

The technical result obtained by the implementation of the invention is to reduce labor, material and energy costs, reducing tool consumption and wear of equipment used in operations prior to the final radial compression.

The specified technical result is achieved by the fact that in the method of manufacturing a threaded barrel, including the manufacture of the original billet, hardening heat treatment, machining the billet into the dimensions of the billet-pipe for radial compression, the manufacture of forgings in two radial compression operations with the formation of a smooth channel in the forging on the preliminary radial operation compression and the formation of a threaded channel in forging on the final operation of radial compression, and the final machining, a new phenomenon The fact is that reinforcing heat treatment of the billet-pipe is carried out after machining before the first compression operation or hardening heat treatment of the forgings after the first compression operation.

The method is implemented as follows.

A drawing of a forgings with grooves in the channel on the deformable part, which is obtained after the final radial compression operation, is being developed. From the condition of equal volumes, a drawing of a forging with a smooth channel on the deformable part, which is obtained after the preliminary radial compression operation, is developed. A drawing of a workpiece-pipe is developed (for the operation of radial compression) with a lead-in, lead-out and deformable parts. From the standard series of hot-rolled round steel in the normalized state (in the delivery state), the closest circle is selected with minimal machining allowances, the rolled products are cut into piece billets with a length corresponding to the length of the billet-pipe and machined, namely, they process a deep hole, grind with a given beating from a deep hole the outer surface of the workpiece to the size of the workpiece-pipe with the formation of the lead-in, lead-in and deformable parts. Further, the manufacturing process of the threaded barrel can be carried out in two alternative ways. According to the first embodiment, the billet pipe is installed in a radial crimping machine and a preliminary radial crimping operation is performed to obtain a forging with a smooth channel. The resulting forging is subjected to hardening heat treatment to give it a given level of hardness and mechanical properties. Then the forging is again installed in the radial crimping machine and the final operation of the radial compression is performed to obtain the forgings with a threaded channel. In the second embodiment, the billet pipe is first subjected to hardening heat treatment, and then the preliminary and final radial compression operations are performed. Next, the final machining of the barrel. The second variant of hardening heat treatment is less preferable (they are forced to use it when the barrel length is too long for the thermal equipment available at the enterprise), because the preliminary operation of radial compression will be less productive due to the high hardness and strength of the billet pipe, as well as due to the need for heat treatment to relieve stress after preliminary radial compression.

An example of use in the manufacture of a rifled barrel caliber 7.62 mm

From the original billet with a diameter of ⌀50 mm, a billet 260 mm long is cut. By machining, including deep drilling of the hole and the hole of the outer surface with the formation of the lead-in, deformable, and lead parts, a billet-pipe with an outer diameter of ⌀48 mm and a hole diameter of ⌀13 mm is made. The billet-pipe is installed in a radial crimping machine and preliminary radial compression is performed on a smooth mandrel placed in the hole. After preliminary crimping, a forging is obtained with a hole diameter of ,812.8 mm with a complex external surface and a total length of more than 340 mm. The resulting forging is subjected to heat treatment at a given level of hardness and mechanical properties. After that, the forging is installed in a radial crimping machine, the final radial crimping operation is performed on the threaded mandrel and a forging is obtained with grooves in the barrel channel, a complex-profile cylindrical outer surface and a total length of more than 640 mm. After the final machining, a threaded barrel is obtained.

Alternatively, the aforementioned billet-pipe is thermally hardened to a predetermined level of hardness and mechanical properties, then the billet-pipe is installed in a radial crimping machine and a preliminary radial crimping operation is performed on a smooth mandrel placed in the hole. After preliminary radial compression, a forging with geometry is obtained as in the aforementioned embodiment. After preliminary radial compression, the forging is subjected to heat treatment to relieve stresses obtained in the process of radial compression. Then the forging is installed in a radial crimping machine and produce a radial compression on a threaded mandrel. After radial crimping, the final machining of the barrel is performed.

Thus, the invention allows to produce a threaded barrel with high quality and at the lowest cost.

Claims (1)

A method of manufacturing a threaded barrel, including the manufacture of the original billet, hardening heat treatment, machining the billet into the dimensions of the billet-pipe for radial compression, forging for two operations of radial compression with the formation of a smooth channel in the forging on the preliminary operation of the radial compression and the threaded channel in the forging on the final radial compression operations, and final machining, characterized in that they conduct hardening heat treatment of the workpiece pipe after th machining operation before the first compression forging heat treatment or hardening after the first crimping operation.