RU2340418C1 - Tool for pressing of pipes with welding - Google Patents

Abstract

FIELD: technological processes, tool.

SUBSTANCE: tool contains container with heater, hollow press-stamp with pressure pad, movable holder and chamber matrix. Matrix splitter has central cylindrical opening for holder passage and alignment. Annular gap for pipe extrusion is formed with central cylindrical opening of splitter and working channel of matrix ring. Longitudinal grooves are arranged on the surface of splitter opening, and channels - feeders of welding chamber are formed with these grooves and holder.

EFFECT: quality of pipes is increased with reduction of pressing pressure.

1 dwg

Description

The claimed invention relates to the field of metal forming, and in particular to the manufacture of pipes by hot pressing.

During the pressing process, the workpiece placed in the container is squeezed out under the action of a punch into an annular gap formed by a matrix and a mandrel. The most efficient and common way to produce hot-pressed pipes is by pressing on special hydraulic presses (extruding presses) equipped with an independent drive for moving the mandrel (called the piercing system). So get pipes from steel, light and non-ferrous alloys.

However, when this method is used to produce thin-walled and small-diameter pipes (especially on horizontal presses), the quality of the products is significantly reduced due to an increase in their transverse and longitudinal differences, which are caused by deviations from the alignment of the mandrel and die when they are installed on the press and when moving the mandrel in the process of pressing, as well as the longitudinal bending of the mandrel under the influence of pressure uneven along the contour of its cross-section from the metal side of the workpiece.

In order to ensure the required quality of such pipes in terms of difference, they are pressed using a tool that includes the so-called combined dies with a short mounted needle. With the formation of an annular gap for extruding the pipe, this needle acts as a mandrel. Thus, the need for the use of long drive mandrels supplied to the matrix through a hollow die and blank is eliminated. Combined matrices by providing the best alignment of the needle and the working channel of the matrix in them allow you to get pipes with minimal difference. These dies also have other advantages: the use of a cheaper continuous blank for pressing, the possibility of using equipment that is simpler in design — bar-shaped extruding presses that do not have a special drive for the mandrel.

As an analogue of the invention, it is necessary to bring a pressing tool with a combined matrix made according to one of the possible variants of its design, namely, according to the version of the chamber matrix (Gildenngorn M.S., Kerov V.G., Krivonos G.A. Pressing with hollow welding products from aluminum alloys. - M., Metallurgy, 1975, p. 52-54, Fig. 7-d). The chamber matrix is a prefabricated design and consists of a base with a matrix ring installed in it (the matrix itself) and a short needle with a cylindrical divider placed in front of the base. The needle can be fixed in the divider or be made with it as one part. The base, divider and needle form a welding chamber, the entrance to which is provided by feed channels located concentrically around the circumference of the divider.

When pressing a pipe with this tool, the metal of a continuous heated billet, passing under the action of a punch through the feed channels of the divider, is divided into separate streams. Getting into the welding chamber, these flows occur; under the pressure of pressing, metal is welded at the points of contact of the flows and metal is extruded through the annular gap between the cylindrical surfaces of the working channel of the matrix and the needle. A pipe pressed in this way has longitudinal welds in the number of feeder channels, and therefore the method of manufacturing pipes using combined dies is called pressing with welding. Due to this welding, the use of technological graphite lubricant for the needle is excluded, which helps to improve the quality of the inner surface of the pipes and reduce the risk of defects associated with such lubrication. This process was most widely used in the manufacture of pipes and hollow profiles from light (mainly aluminum), as well as some non-ferrous alloys. Existing methods for calculating the optimal technological parameters of pressing with welding and calibration of combined dies provide high strength welds on extruded products from these materials.

The main disadvantage of the described analogue (chamber matrix) as well as of other types of combined dies with a built-in needle compared to the matrices of tube extruding presses is the reduced strength and, accordingly, the shortened service life of such dies, which is caused by their rather complicated design and increased pressures during welding pressing. In this regard, one of the main tasks of improving the pressing tool using combined dies is to reduce the workload on the die.

One of the other analogues of the present invention, providing a solution to this problem, is a tool in which the combined matrix divider is provided with a long cylindrical shank (false mandrel) that extends when pressing into the hole of the hollow press stamp (USSR author's certificate No. 275982 "Tool for the manufacture of hollow profiles ”, published on July 14, 1970, Bulletin No. 23). For pressing, a hollow billet is used. The effect of reducing the working loads on the matrix is achieved by reducing the degree of deformation (drawing) and due to the unloading from the significant force of the central zone of the divider.

However, this analogue has a serious drawback. The presence of a long shank on the divider significantly complicates the separation of the press residue after each pressing. The implementation of this operation in the usual way, namely with the help of a cutting knife on the front crosshead of the press, generally becomes impossible. It is necessary either to resort to pressing without separating the press residue, which is fraught with an increased risk of various defects appearing on the products (see below), or to perform this separation by tearing the press residue remaining in the container from the workpiece metal located in the welding chamber by the container running. In the latter case, firstly, it is necessary to increase the length of the press residue, secondly, it requires a significant increase in the drives for moving the container and pressing the matrix unit to the front crosshead of the press, and finally, thirdly, such separation, which usually occurs in the channels, divider feeders, is often the cause of the destruction of the latter.

The prototype of the claimed invention is a pressing tool according to US patent No. 3213662, 1965 (Gildengorn M.S., Kerov V.G., Krivonos G.A. Pressing with welding of hollow products from aluminum alloys. - M., Metallurgy, 1975, p. 68-69, fig. 26). In this tool, instead of the shank of the divider according to the analogue described above, a mandrel connected to the extruding press firmware system is used as a false mandrel. When pressing, this mandrel abuts against the flat end of the divider of the chamber matrix, and before the separation of the pressostat is retracted, which makes it possible to produce this separation at the end of the divider using the aforementioned knife.

It should be clarified that when pressing through combined dies with a built-in needle using false mandrels of any design, the central zone of the divider is only partially unloaded from the force. Instead of the pressure from the technological force on the punch, the force created by the friction of the workpiece metal on it acts on the false mandrel stationary during pressing.

And, finally, with any variant of pressing hollow products through combined dies with a built-in needle (including both when pressing with separation of the press residue and semi-continuous pressing "ingot by ingot"), there is an increased risk of defects on the products in the form bubbles, bundles and captivity. This is because here the welding chamber and the gap between the matrix ring and the needle forming the product section are always filled with metal. As a result, during upsetting in the container (pressing) of the next billet, it is extremely difficult to release the air in the container into the atmosphere, due to which individual air bubbles can enter the volume of the pressed metal.

The objectives of the invention for pressing pipes with welding are to reduce the pressing pressure, maximize the unloading of the central zone of the chamber matrix and simplify the design of the latter to increase the resistance of the dies, reduce the complexity of their manufacture and, accordingly, reduce the cost of a press tool, simplify the operation of separating the press residue, and enable pressing both with the separation of the pressostat and semi-continuous pressing, a significant reduction in the risk of defects on extruded pipes from pressing air, creating the possibility of using for extruding pipes through chamber dies from hollow billets, in addition to tube extruding presses with a piercing system, simpler in design and cheaper bar-shaped presses. With all this, of course, the conditions ensuring the production of pipes with a minimum difference should be preserved.

The achievement of these tasks when using the proposed device, first of all, is ensured by the fact that it is a pressing tool that combines pressing methods on conventional pressing mandrels and through chamber dies. It does not have a short needle mounted on the matrix divider, and uses the usual long-length mandrel. The pressing tool comprises a container with a heater, a hollow die with a press washer, a movable mandrel and a chamber matrix. The matrix consists of a base with a matrix ring installed in it and a cylindrical divider adjacent to the base on the side of the press stamp, forming a welding chamber together with the base and equipped with feed channels concentrically arranged around the circumference. The matrix divider has a central cylindrical hole for passage and alignment of the mandrel, which through this hole enters the working channel of the matrix ring, forming with the latter an annular gap for extruding the pipe. On the surface of the opening of the divider, longitudinal grooves are made. The feed channels of the welding chamber are formed by these grooves and the mandrel.

The decrease in pressing pressure in the proposed device is due to the presence of the mandrel and the use of a hollow billet. Full unloading of the central zone of the divider is ensured by making holes in it and using a movable mandrel, which eliminates friction on the metal of the workpiece. The simplification of the design and the increase in the strength of the matrix are associated with the absence of a needle mounted in its divider and the replacement of feeder channels in the form of holes in the divider body with open longitudinal grooves on the surface of its opening. The minimum difference in the extruded pipes is guaranteed by the fact that the alignment of the mandrel and the matrix ring is ensured by the centering of the mandrel in the bore of the divider in the immediate vicinity of this ring.

An example of the implementation of the inventive pressing tool in the form of pressing on a horizontal press with a piercing system and with the separation of the press balance is shown in the drawing. The tool is shown in the position corresponding to the moment of extrusion of the pipe.

The tool includes a container 1 with a heater 2, placed in the press container holder, a hollow press stamp 3, mounted on the press traverse of the press, a press washer 4 freely mounted in the container in front of the press stamp, fastened to the piercing rod through the hollow press stamp mandrel 5, and a chamber matrix placed in the holder of the matrix holder located on the front crosshead of the press. The matrix consists of a base 6 with placed in it a matrix ring 7 and located in front of the base of the hollow cylindrical divider 8 with open longitudinal grooves on the inner surface,

Pressing using the tool presented is as follows.

Before the first pressing, the container 1 is heated to a predetermined operating temperature using a built-in heater 2, as well as a chamber matrix and a press washer 4 in a separate furnace. The matrix is installed in the holder of the matrix holder. The container is pressed against the matrix unit. The stamp 3 and the mandrel 5 retracted to its extreme rear position. A heated hollow billet and a press washer are loaded into the cavity of the container. The stamp is connected to the press washer. The mandrel moves forward and stops before entering the hole of the matrix divider 8. Under the action of the press stamp (with a stationary mandrel), the workpiece is unpressed in the container. After this, the mandrel moves even further and is introduced into the working channel of the matrix ring 7 located in the base of the matrix 6. The working stroke of the press stamp is carried out, during which the mandrel moves forward with the latter. The metal of the workpiece through the feeder channels formed by the divider and the mandrel, is displaced in separate streams into the matrix welding chamber. Welding of flows occurs in this chamber under the pressure of pressing, and the workpiece metal is squeezed out through the annular gap formed by the matrix ring and the mandrel, forming a pipe with longitudinal welds. Pressing is done without mandrel lubrication. At the end of the stroke, after stopping the stamp and the mandrel, the underpressed part of the workpiece remains in the container — the press remainder.

The mandrel is removed from the matrix and returned to its rear position. When the stamp is stationary, the container moves away from the matrix block. As a result, the press residue and the adjacent press washer are released from the container. Then the stamp moves back. The separation of the press residue from the metal of the workpiece located in the longitudinal grooves of the divider and in the welding chamber is carried out at the end of the divider in the usual way - using a cutting device mounted on the front crosshead of the press with a knife-cutter. The container is pressed back against the matrix unit. The tool is ready for the next pressing.

Using such a tool, it is possible to manufacture pipes without separating the press residue - the so-called semi-continuous pressing "ingot by ingot". In this case, the press washer must be fastened to the press stamp, and with each subsequent (after the first) pressing during the process of pressing the workpiece, the end of the needle should be in front of the end face of the press residue of the previous pressing.

A significant reduction in the risk of defects in the pipes from pressing air during pressing using the described tool is achieved by the fact that during the process of pressing the workpiece in the container, the air in it can be forced out into the atmosphere through the channel created by the hole in the divider and the cylindrical cavity formed after the needle is removed in in the welding chamber, the mass of the pressed metal.

The inventive device can be used when pressing pipes with welding on extruding presses without a piercing system - bar-profile presses. In this case, the mandrel should be fixed on the stamp.

Claims (1)

A tool for pressing pipes with welding, containing a container with a heater, a hollow press stamp with a press washer, a movable mandrel and a chamber matrix consisting of a base with a matrix ring installed in it with a working channel and a cylindrical divider adjacent to the base from the press stamp forming together with the base a welding chamber and having channels concentrically arranged around the circumference - feeders, characterized in that the matrix divider is made with a central cylindrical hole for passage mandrels into the working channel of the matrix ring, its alignment and formation with the said working channel of the annular gap for extruding the pipe, longitudinal grooves are made on the surface of the central cylindrical opening of the divider, and the feed channels are formed by the said longitudinal grooves and the mandrel.