RU2818708C1 - Method of treating support surfaces of a clamping device of a press for upsetting pipe ends - Google Patents

Abstract

FIELD: processing of parts by pressure.

SUBSTANCE: invention can be used for upsetting pipe ends. Proposed method comprises production of rough layer on press clamping surfaces in contact with pipe. Press clamping device support surfaces are processed in the form of collet clamp central hole support surfaces, formed at convergence of collet halves. Rough layer is obtained by combined processing with a rotating lap with an abrasive material applied on it in the form of a finishing paste of fixed halves of the collet clamp for 30 s at smooth change of force of their pressing to lap from 0 to 50 N. For processing, lap is used, on external surface of which there are annular grooves with width of 5 mm, located every 5 mm from each other. As a workpiece for lap there used is a fragment of a pipe, the standard size of which corresponds to the pipe clamped in the collet clamp.

EFFECT: higher quality of pipe clamping for pipe ends upsetting without clamp force increase.

1 cl, 4 dwg, 1 tbl

Description

The invention relates to the processing of parts by pressure and can be used for upsetting pipe ends.

In various fields of mechanical engineering, in particular, in fuel equipment, pipes are used, the ends of which are deformed (upset) to give a given shape in the longitudinal section. Upsetting of pipe ends in mass production is carried out on presses. Before upsetting, the pipe must be secured against axial movement. A clamping device is often used as a fixing (clamping) element of the press design, which we will further conventionally call a collet clamp or collet. The need to increase the force to ensure a given plastic deformation of the end of the pipe in order to give it a given shape, on the one hand, and the requirement for reliable fixation of the pipe, on the other hand, are technically contradictory. The deformation force is largely determined by the mechanical properties of the pipe. For example, increasing the tensile strength of the pipe material while maintaining the clamping force of the press, in the applicant's experience, can lead to the pipe being pushed out of the collet during upsetting. Increasing the clamping force may require changes to the press design. Often the magnitude of the clamping force is unregulated during operation. This means that on a press with an increased clamping force, pipes with reduced mechanical characteristics will be impossible to press: the collet will deform them during clamping. Typically, the forces developed by the press to fix the pipe and upset its ends are constant and cannot be adjusted during operation. This means that when switching to pipes with increased mechanical characteristics, a situation may arise when the ends of the pipes become impossible to upset - the pipe will shift in the clamping element of the press structure.

A continuous collet is known, on the inner and outer surfaces of which screw recesses are made (A.S. 1060334, publ. 12/15/1983). According to a known solution, the direction of the outer helical groove is opposite to the direction of the inner helical groove, and one of them is offset relative to the other in the axial direction.

The disadvantages of the known solution include the impossibility of its use for fixing the pipe in a press on which the ends of the pipe are planted. This is due, firstly, to the fact that in the known solution the collet is continuous, that is, it has a very limited range between the “fully open” and “fully compressed” positions. Meanwhile, depending on the design of the upset end, the difference between the largest diameter of the upset part and the diameter along which the collet is clamped can exceed 37%. For example, for fuel pipelines of engines of KAMAZ PJSC, the applicant produces pipes in which the clamping during upsetting occurs along a diameter of ∅8 mm, and the largest diameter of the upset part is ∅11 mm. The disadvantages of the known solution also include the labor intensity of making external and internal helical grooves.

The closest in terms of the set of essential features - the prototype of the claimed invention - is a connecting device for pipes, including elements in contact with the pipe, made of a material having a hardness higher than the pipe material, forming part of a closed ring, partially equipped with a rough surface adjacent to the pipe and obtained using abrasive material (patent RU 2173425, published 09.10.2021). The pipe covered by the mentioned elements is inserted into the coupling part, where it is clamped by the mentioned elements. According to a known solution, a rough layer on the elements in contact with the pipe can be obtained, for example, using sand by gluing sand grains to the surface.

The disadvantages of the known solution include the difficulty of using it to fix the pipe in a press on which the ends of the pipe are planted. This is due to the fact that the pipe is clamped in a special coupling part, and the clamping force is created by axial contraction (bringing together) of the supporting surfaces. Implementing this on the press is problematic.

The technical problem to be solved by the present invention is the development of a method for processing the supporting surfaces of the clamping device of a press for upsetting pipe ends, ensuring reliable fixation of the pipe on a pipe press with increased mechanical characteristics.

The technical result of the implementation of the proposed invention is the production on the surfaces of the collet of successively located annular zones with different surface roughness, providing elastic deformation of the annular sections of the clamped pipe and thereby increasing the quality of clamping (fixing) of the pipe for upsetting its end on the press without increasing the clamping force.

The solution to the stated technical problem is achieved due to the fact that, when processing the supporting surfaces of the press clamping device for upsetting pipe ends, which includes obtaining a rough layer using an abrasive material on the supporting surfaces of the press clamping device in contact with the pipe, the processing of the supporting surfaces of the press clamping device is carried out in the form of the supporting surfaces of the central hole of the collet clamp, formed when the collet halves approach each other, and the rough layer is obtained by joint processing of a rotating lap with an abrasive material applied to it in the form of finishing paste of the stationary halves of the collet clamp for 30 s with a smooth change in the magnitude of the force of their pressing to the lap from 0 to 50 N, in this case a lap is used, on the outer surface of which there are ring grooves 5 mm wide, located 5 mm apart from each other, and a fragment of a pipe is used as a blank for the lap, the standard size of which corresponds to the pipe clamped in the collet clamp.

An example of the proposed method.

An example of the proposed method is illustrated by drawings.

In fig. Figure 1 shows a fragment of a pipe with an upset end, the shape of which meets the requirements agreed with the customer.

In fig. Figure 2 shows a top view of the loading window of the press, on which the ends of the pipes are planted.

In fig. Figure 3 shows the halves of the collet, the hole in which is processed according to the proposed method.

In fig. 4 schematically shows a lap for processing the supporting surfaces of the collet. The figures indicate:

1 - pipe,

2 - upset end of the pipe, having a given shape,

3 - collet halves,

4 - lap for processing the hole in the collet,

5 - finishing paste in the lap.

Both halves of the collet were made of HVG steel and had a hardness of 57 HRC. The hole roughness was Ra1.25. The outer diameter of the pipe, the ends of which needed to be upset, giving them a given shape, was ∅8 mm, the inner diameter was ∅3 mm (accepted designation: 8хвн.3). Samples of pipes made from steels St52 and St70BK were prepared for upsetting. The mechanical properties and chemical composition of steels are given in Table 1.

It was found that on the same press the ends of a pipe made of St52 steel can be upset, obtaining a given shape (see Fig. 1), but it is impossible to make pipes made of St70BK steel: the pipe moves in the collet, which indicates insufficient clamping.

We made a lapping. To make the lap, we used a piece of pipe 8хвн.3. A number of annular grooves 5 mm wide and 0.2 mm deep were machined on the outer surface, located 5 mm apart along the axis of the hole being machined. After this, AC4 200/160 abrasive grinding paste with AC4 diamond powder, which had a paste-like consistency, was applied to the lap. We installed the lap in the finishing head chuck, positioned both halves of the collet in such a way that the lap touched the supporting surfaces - the surfaces of the central hole of the collet clamp, formed when the collet halves come together.

By rotating the cartridge with the lap installed, we created a force compressing the collet halves and gradually increased it over 30 s from 0 to 50 N. After that, the compressive force was removed, the collet halves were moved away from the lap, and the rotation drive was turned off.

The parts were washed to remove any remaining wear and tear paste and installed in a press.

The collet halves were installed in the press. Conducted tests. It has been established that when using a modified collet, a pipe made of St70BK steel can be processed (upsetting) to ensure the desired shape of the ends.

Shiny ring bands correspond to the treated areas of the collet, matte ones correspond to untreated areas. In this case, the shiny areas have a diameter larger than the matte ones, that is, they are recessed into the body of the collet halves by an average of 0.05...0.10 mm. According to the applicant, when clamping the collet before upsetting the end of the pipe, elastic deformation of the clamped pipe occurs with “bulging” of the pipe material in the treated areas. The pipe within the collet acquires, relatively speaking, a wavy longitudinal profile. In addition to the frictional force acting on the pipe in areas not lapped, this increases the clamping effect. After releasing the collet, the pipe returns to its original shape.

The proposed method for processing the supporting surfaces of the clamping device of a press for upsetting pipe ends has been introduced into the manufacturing technology of collets of our own production and is used in LLC Management Company "AZPI".

Claims (2)

1. A method for processing the supporting surfaces of a press clamping device for upsetting pipe ends, including obtaining, using an abrasive material, a rough layer on the supporting surfaces of the press clamping device in contact with the pipe, characterized in that the supporting surfaces of the press clamping device are processed in the form of supporting surfaces of a central hole collet clamp, formed when the halves of the collets come together, and the rough layer is obtained by joint processing of a rotating lap with an abrasive material applied to it in the form of finishing paste of the stationary halves of the collet for 30 s with a smooth change in the magnitude of the force of pressing them to the lap from 0 to 50 N, in this case, a lap is used, on the outer surface of which there are ring grooves 5 mm wide, located 5 mm from each other, and a fragment of a pipe is used as a blank for the lap, the standard size of which corresponds to the pipe clamped in the collet clamp. 2. The method according to claim 1, characterized in that a finishing paste of a paste-like consistency is used.