RU2333067C1 - Method of reverse extrusion and device for its implementation - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method of reverse extrusion includes deformation of billet with puncheon in movable container, which is installed in matrix holder, in the process of which active friction forces are applied to billet by container movement to the side of billet metal outflow. Deformation is carried out continuously in two stages, separation of which is determined by the moment of the first cracks appearance at internal surface of billet. At the first stage active friction forces are applied to billet by means of container movement to the side of metal outflow, and at the second stage - they are transformed into reactive friction forces by container movement in reverse direction. Device for reverse extrusion consists of the top plate, on which puncheon is fixed, bottom plate with matrix holder fixed in it. Container, which is installed in matrix holder, is moved by means of two levers of the 1^st type that are installed on both sides of container. Counterpunch is installed in container with the possibility of displacement. Levers with their one end interact with movable container, and with their other end - with wedges that are installed on the top plate. Device is installed with pushers that affect lever arms that are closest to container for container displacement in reverse direction.

EFFECT: increase of produced parts quality and increase of tool resistance.

2 cl, 4 dwg, 1 ex

Description

The invention relates to the field of mechanical engineering, in particular to the field of metal forming, and can be used for the manufacture of thin-walled cases of shock absorbers, pneumatic cylinders, etc. using cold extrusion forging.

The known method S.Sh. Yayashaeva (Yashayayev S.Sh. The method of reverse extrusion of parts of the type "glass". A.S. No. 160931 from 09/13/62, BI No. 5, 1964), in which the operation of extrusion is performed in a composite matrix (counter-punch + container) on the falling counter-punch with a stationary container and the wall of the extruded product. At the same time, active friction forces are created at the contact boundaries of the container with the non-deformed part of the preform and its plastic region, due to which the specific extrusion force is reduced compared to conventional reverse extrusion.

The disadvantage of this extrusion method is that it reduces the deformation force slightly (not more than 10%) with a significant complication of the stamp for forming the workpiece.

There is also known the method of Yu.P. Mozheiko and N.K. Rosenthal (Mozheiko Yu.P., Rosenthal N.K. The method of backward extrusion of parts of the "glass" type. A.S. No. 173107 from 07.12.62, BI No. 14, 1965), in which active friction is created by forced movement of the container towards the expiration of the extruded metal with a stationary counter-punch. At the same time, the active friction force is added in the contact zone of the container with the extruded product element, significantly reducing the total deforming force (by 30% compared to conventional reverse extrusion).

The disadvantage of this extrusion method is the poor-quality manufacture of a semi-finished product, which consists in the fact that with increased degrees of deformation of the non-plastic preforms, cracks occur on the inner surfaces of the products, which begin to appear from a certain moment of deformation of the preform.

Later, these and similar processes with active friction S.Sh. Yayashayev (Yasayayev S.Sh. Basics of differentiated extrusion. // Forging and stamping, No. 9, 1966, pp. 4-6) suggested calling differential extrusion, which strengthened in the technical literature.

The prototype adopted the method of E.I. Semenov and A.G. Ovchinnikov (Semenov E.I., Ovchinnikov A.G. The method of extrusion of hollow products A.S. No. 326997 from 03.07.70, BI No. 5, 1972) consisting in the fact that during the deformation of low-plastic metals and alloys in the deformation zone due to forced movement of the container in the opposite direction of the metal outflow, increased reactive friction is created at the contact boundary with the workpiece and the part. At the same time, an additional compressive hydrostatic pressure arises in the focus of plastic deformation, which increases the plasticity of the workpieces being deformed and contributes to the process of “healing” of emerging macro- and microcracks due to the intensification of diffusion processes.

The disadvantage of this method is the increased specific forces acting on the tool during deformation, which significantly reduces its resistance.

For the implementation of extrusion with forced friction, a device is known, which is a stamp with a hydraulic drive of the container [V.E. Favorsky. Extrusion cold stamping. M. - L.: Engineering, 1966, p.118, Fig. 74].

However, this device, usually mounted on a hydraulic press, is inefficient and cannot be used when extruding workpieces with high degrees of deformation, since in this case high productivity of the hydraulic system is required, which complicates the design of the stamp and its metal consumption.

A device for cold extrusion, adopted as a prototype. [A.G. Ovchinnikov. Fundamentals of extrusion press theory. - M .: Mashinostroenie, 1983, p.187, Fig. 7.1], which has autonomous hydraulic drives for the punch and container, the latter being equipped with two hydraulic cylinders with a control system for carrying out its working and idling.

The disadvantage of this device is its excessive metal consumption and high cost due to the fact that in practice it is a specialized press. In addition, it is impossible to carry out continuous extrusion with alternating friction during deformation of workpieces made of low-plastic materials.

The task of the invention is to improve the quality of the parts and increase the durability of the tool, reducing its metal consumption and cost.

The task is achieved as follows.

In the method of backward extrusion of a workpiece into a hollow part by a punch in a composite matrix with a container driven, to which additional friction is applied by this container during deformation, the extrusion process is carried out continuously in two stages, the separation of which is determined by the moment the first cracks appear on the inner surface of the part, at the first stage, active friction forces are applied to the workpiece by moving the container towards the expiration direction, and at the second stage, they are converted into additional reactive friction forces by moving the container in the opposite direction.

In addition, the moment of appearance of the first cracks in the details, depending on the degree of deformation, is determined experimentally by extrusion in a matrix with a fixed container, and finally clarified by extrusion in a matrix with a moving container. In the extrusion device, consisting of an upper and lower plate, a punch attached to them and a composite matrix including a container mounted on a counter punch with the possibility of axial movement, a drive interacting with the container, the container drive is made in the form of two levers of the first kind located on both sides of the matrix, each of which is mounted on a fixed support of the bottom plate and at one end interact with the container, and at the other end with wedges mounted on the top plate of the device, which It is also plunged by pushers acting on the leverage shoulders closest to the container.

It is also provided that the levers, wedges and pushers are fixed on the device plates with the possibility of adjustment in the horizontal plane.

To clarify the described objects, the drawings show: an experimental graph in the form of an oscillogram of the dependence of the deforming force on the working stroke of the punch (curve 1 in figure 1, a), experimental samples obtained by cold extrusion (figure 1, b, c), a diagram of possible movement tool elements (figure 2), a diagram of the method with alternating friction (figure 3), a device for implementing the proposed method (figure 4).

Implementation example

Figure 1 a) shows an experimental graph of the dependence of the deformation force of the aluminum alloy AMg2 on the stroke of the punch from the workpiece with a diameter of D = 38 mm and a height of H = 45.1 mm, the diameter of the inner cavity of the cup d = 26 mm and the bottom thickness t = 5, 7 mm, which corresponds to a reduction of R = 0.7 and the stroke of the punch L = 39.4 mm. Experimental data were obtained on samples squeezed out by a punch with a bevel angle α = 30 ° (Fig. 1 a), and strain-gauge curves using an H-107 oscilloscope when extruding on a modernized hydraulic press with an accelerated stroke of the P100 slider.

It can be seen from the oscillogram (curve 1 of Fig. 1, a) that the beginning of extrusion begins with a surge in the deforming force (its growth in the form of a peak), which is explained by the transition from one type of deformation to another, i.e. the draft of the workpiece when filling the working space with a deformed metal is replaced by cold extrusion. The jump in strength can reach 10-15% of the main value.

Then, when extruding, the force stabilizes, and in the end we observe a certain drop in its value and a subsequent increase (not shown) at the final unsteady stage. Given that the extrusion process itself is energy-intensive, this surcharge created by a surge of force often leads to increased wear and fatigue failure of the tool.

Despite the fact that the extrusion takes place under conditions of high hydrostatic pressure, there are materials that do not withstand large plastic deformations and are destroyed. These fractures can be in the form of through, internal and surface cracks. During the reverse extrusion of cups of aluminum alloys, the most frequent are internal surface cracks. Such cracks were obtained on the given samples from the AMg2 alloy during extrusion by a plane-conical punch (Fig. 1, b). The enlarged picture of crack formation (Fig. 1, c) shows that the inclination of cracks and the step of their occurrence are almost constant throughout the deformation of the workpiece and do not depend on the geometry of the working profile of the punch. The depth of cracks in one product is not constant and increases with deformation. In some cases, when the lubricating layer is greatly thinned, the depth of the cracks begins to decrease, which also proves the dependence of crack formation on hydrostatic pressure.

Measurements of the samples showed that cracking along the inner surface of the product begins when the punch enters the workpiece at 40-50% of its full stroke. Moreover, the peak of strength occurs at about 20% of its course. These data were the basis for the development of a new method called alternating differentiated extrusion.

From the foregoing, it becomes clear how it is possible to control the value of the deformation force and the elimination of cracking, creating respectively active and reactive forced friction on the outer surface of the workpiece. If, for example, you start to extrude according to the scheme of Yu.P. Mozheiko and N.K. Rozental (lowering the hydrostatic pressure), and end according to E.I.Semenov and A.G. Ovchinnikov (increasing the hydrostatic pressure), changing the direction of friction a little earlier If the product cracks, it is possible to reliably obtain high-quality products with increased tool wear resistance, since there will be no peak force in this case, which especially affects tool wear, and the increase in hydrostatic pressure will be in the zone of technological force drop.

For the given parameters of the tool and the deformable material, the theoretical values of the deformation force were determined, superimposed on the experimental schedule 1 (figure 2). It can be seen from it that, using the corresponding coefficient of friction (m = 0.5), it is possible to select a design force that is close to the experimental force for backward extrusion (curve 2), and other calculations will have the same coefficient. Then the obtained curves will be placed on the graph, respectively: for the method of Yu.P. Mozheyko and N.K. Rosenthal - curve 3; for the method of EI Semenov and A. G. Ovchinnikov - curve 4. The moment of transition, in accordance with the experiment, is equal to the working stroke of the punch L = 17.1 mm. The general scheme of the transition of one movement to another is shown in Fig.3.

A device for implementing the proposed kinematics of moving a container using two levers and a movable matrix container inside a rigid bandage is shown in FIG. 4. When designing the device, the calculated and experimental data of the technological force were incorporated into the strength calculations of the lever system.

The device is designed to receive parts such as a glass by differential extrusion, capable of realizing various elements of active friction. The device is a block that includes the upper plate 1, guide columns 2 and bushings 3 and the lower plate 4. A matrix holder 5 is attached to the lower plate 4, in which a movable container 6 is installed, as well as a counter punch 7 consisting of a base 7 and an ejector 8 . In the matrix holder 5, slots 9 were made for the entrance of the pivoting levers 10. In the container 6, recesses 11 were made to accommodate the working ends 12 of the pivoting levers 10.

In addition, a ledge 13 is made inside the matrix holder 5, the length of which corresponds to the move of the movable container 6. In the cavity of the ledge 13 of the matrix holder 5, a movable container flange 14 is placed 6. The rotary arms 10 are fixed in the forks 15, spring-loaded on both sides and are designed for axial movement of the movable container 6. In addition, columns 16 are installed on the bottom plate 4, along which the spring-loaded plate 17 of the puller moves. To control the rotation of the levers 10, the pushers 18 and the wedges 19 are attached one at a time to the upper plate 1, the wedges 19 having spring-loaded dogs 20. A punch holder 21 is fixed in the center of the stamp, which has a punch 22 with a thrust plate 23 and a collet 24 that locks the punch 22 with nuts 25 of the punch holder 21.

The method of reverse differential extrusion with alternating friction forces is as follows. When the plate 1 is in the upper position, the workpiece in the form of a continuous cylinder is fed into the movable container 6. When the press slide moves downward, the punch 22 begins to deform the workpiece. At this moment, the wedges 19 through the dog 20 act on the levers 10, which, turning, raise the movable container 6, implementing the reverse extrusion mode with active friction. After the dog 20 of the wedge 19 passes the lever 10, pressure 18 begins to press on it, moving the container 6 down and performing a reverse extrusion mode with reactive friction. During the reverse stroke, the wedges 19 pass through the levers 10 with the reclined dogs 20, and the obtained part is removed by the puller plate 17 if it remained on the punch 22, or by the ejector 8 of the counter punch 7 if it remained in the movable container 6. The released part is removed from the working area of the device tweezers or blower.

The moment of transition of the application of additional active friction forces to the reactive one is determined experimentally from the first part during a test reverse extrusion. Adjustment of the stamp is carried out by the underlay plates placed under the clino holders (not shown).

The proposed method and device allows to obtain high-quality parts from workpieces made of low-plastic metals and alloys, with increased tool wear resistance.

Claims (2)

1. The method of backward extrusion of a workpiece, comprising deforming the workpiece with a punch in a movable container placed in a holder matrix, during which active friction forces are applied to the workpiece by moving the container toward the flow of the workpiece metal, characterized in that the deformation is carried out continuously in two stages, separation which is determined by the moment the first cracks appear on the inner surface of the workpiece, and at the first stage, active friction forces are applied to the workpiece by moving the container in the side well, the expiration of the metal of the workpiece, and in the second stage they are converted into reactive friction by moving the container in the opposite direction. 2. A device for backward extrusion of a workpiece, comprising an upper plate on which a punch is fixed, a lower plate with a matrix holder fixed to it, in which a container with a counter punch placed in it with the ability to move and levers located on both sides of the container is installed, characterized in that the container is placed in the matrix holder with the possibility of movement by means of two levers of the first kind located on both sides of the container, each of which interacts with the movable container at one end, and the other end - with wedges mounted on the top plate to move the container in the direction of the metal flowing out of the workpiece, the device is equipped with pushers acting on the arms of the arms closest to the container to move the container in the opposite direction.

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