DE2526818A1 - METHOD AND DEVICE FOR LUBRICATING A HEATED ALUMINUM COMPRESSION DURING EXTRUSION - Google Patents

Description

Method and device for lubricating a heated aluminum compact during extrusion.

Priority: June 17, 1974, V.St.A., No. 480 047

The invention relates to a method and a device for lubricating a heated compact from Aluminum or an aluminum alloy in an extrusion press, consisting of a container with one on one Flat extrusion mold arranged at the end and with a movable plunger arranged at the opposite end, through which the compact inserted into the container can be pressed through the mold.

Extrusion is widely used for shaping aluminum. In direct extrusion, an aluminum bolt is placed in a cylindrical container which is provided at one end with an extrusion die having a wall of the appropriate size for the end product. Extrusions with a flat surface are usually used. A piston is inserted into the container from the opposite end by applying a force

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moves enough to get the aluminum through the mold opening to be forced to flow in the extrusion mold. The aluminum is usually at one temperature extruded hot above its recrystallization temperature. Characteristic of aluminum extrusion, what is done with flat face extrusions is that the material that goes through the mold flows from the center of the extrusion billet in the early stages of the extrusion process. The surface of the extrusion bolt, which is usually contaminated with alumina is the last part of the extrusion bolt that is extruded. In general, the extrusion process is interrupted before the surface portion of the extrusion bolt is extruded will. Usually a colloidal graphite mixture is sprayed onto the extrusion die prior to extrusion. This Mixture prevents the extrusion billet from sticking to the mold and reduces that required to initiate extrusion Pressure. However, the graphite is only used as a lubricant for a small fraction of the material to be extruded effective.

It is therefore desirable to achieve continuous lubrication so that the force required for extrusion is reduced that is, reduced pressure is required to initiate and complete extrusion is. This would enable the production of larger extrusions on a press of a given size.

^lichen 509881/0445

In common practice, the friction of the aluminum flowing through the extrusion mold creates a localized high level of friction Temperature, especially when an accumulation of aluminum has formed on the surface of the mold. This temperature can be sufficient to reduce the hardness of the mold. It can also cause local rapid grain growth in the material on the surface of the extruded product. The combination of higher Temperatures and an aluminum structure of the mold lead to cracking and poor surface quality extruded product. Because you use the conventional metal flow pattern would like to maintain the extrusion bolt during extrusion, it is not advisable to use a lubricant between the Bring the wall of the container and the bolt surface. According to the invention, these difficulties are caused by the Lubrication process in the extrusion of aluminum and with the help of a device for implementation of the procedure solved.

The present invention is based on the object of the previously known methods and devices for lubrication to avoid the above-described disadvantages adhering to a heated aluminum compact during extrusion.

This object is achieved according to the invention by a method in which a thin, uniform layer of a heated, liquid lubricant the gap-shaped space

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- 4 is fed between the extruded material and the wall of the extrusion opening with the application of pressure will.

The device for carrying out the method is marked by a continuous, thin, radially uniform film of lubricant at the gap-shaped space between the mold wall and the extruded product, the lubricant being liquid at the extrusion temperature, im essentially does not react with the molding material, is applied under pressure and has good film strength and Has lubricity.

In a preferred embodiment of the device, one of the surfaces is between the metal plate and the grooved or knurled flat shaped surface. In this space formed by the corrugation or knurling a suitable lubricant is introduced under pressure. The lubricant emerges from the one formed by the grooves Space and flows into the gap-shaped space between the extrusion mold and the extruded product.

According to the invention there is thus a method and a device for introducing a lubricant between the surfaces of the mold of the extruded product in hot extrusion made of aluminum. This method also becomes a preferred technique for delivery and distribution of the lubricant at the interface between the mold and

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Press bolt used. According to the invention for this Process a number of lubricants used for aluminum extrusion. Further advantageous method examples and embodiments of the device are shown in FIG can be found in the following description.

The invention is explained in more detail, for example, with the aid of the accompanying drawings.

Fig. 1 shows schematically in section a direct-acting extruder.

FIG. 2 shows in section an extrusion mold which is similar to that in the press of FIG. 1.

Fig. 3 shows schematically a flow pattern during hot extrusion and when using an extrusion mold with a flat surface.

Fig. 4 shows a metal flow pattern during extrusion under lubrication using an extrusion die with a tapered surface.

5 shows an embodiment of the device according to the invention.

Fig. 6 shows a preferred embodiment of an embodiment of the invention.

Fig. 7 shows different shapes for the plate according to the invention.

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Fig. 8 shows a preferred embodiment with which a more uniform lubricant coating can be achieved.

The method according to the invention and the method according to the invention Devices are useful in conventional direct-acting extrusions such as those used for direct extrusion of aluminum and aluminum alloys at high temperature using extrusion dies with flat surfaces can be used. Such a press is shown schematically in FIG. The press consists of a hollow cylindrical Container 1, at one end with a suitably designed extrusion mold 2 (or die) at the other end is provided with a movable piston 3. The piston moves accordingly to the movement of a punch 4, to which in turn a force F is usually given via some hydraulic device. The one to be extruded The bolt 5 is arranged in the container 1. When the piston 3 moves into the container 1, the bolt is through the Opening printed in the extrusion mold and the extruded product 6 assumes the overall shape of the extrusion mold opening.

Fig. 2 shows in section a typical extrusion mold for Aluminum with flat surfaces. The mold 2 has an opening 7 which is delimited by the walls 8 of the mold. The flat surface the mold 9 is in contact with the bolt to be extruded. This shape area extends essentially

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- 7 right to the center line of the extruder and meets the wall of the container at an angle of essentially 90. The wall 8 of the extrusion mold essentially forms a 90 degree angle on the mold surface and is arranged parallel to the center line of the extrusion device.

The extrusion die geometry described above is characteristic of the hot extrusion of aluminum.

Fig. 3 shows schematically the flow diagram or flow pattern of the metal during the hot extrusion of aluminum. the Lines shown on extrusion pin 5 illustrate the deformation during an intermediate section of the extrusion.

These lines were drawn on the die in a uniform square pattern prior to extrusion. It can be seen that the metal extruded first comes from the center of the bolt 10, while the outer surfaces 11 of the bolt are extruded last. In Fig. 3, an extrusion mold D with a flat surface F is shown. This procedural measure is desirable because any surface oxides and other surface contaminants remain effectively isolated to the last portion of the extruded product. The surface 12 of the main part of the extruded product 13 is a pure, light metal which has no relation whatsoever to the original surface condition of the extrusion bolt.

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For comparison, Fig. 4 shows a conventional hot extrusion process, as it is used for most non-aluminum materials. One sees, that in this method, the surface of the bolt 11 roughly seen at the same speed as the center 10 of the bolt is extruded and that is why the surface condition of the bolt is reflected in the surface condition of the extruded product 13. The extrusion mold D according to FIG. 4 has a tapering surface T instead of the flat surface shown in FIG.

With these two types of metal flow, there is a fundamental difference, which can be attributed to the container and shape geometry, but which is also due to the Presence of a lubricant is affected. The lubrication between the bolt and the container wall leads to the fact that one - the extrusion metal shown in Fig. 4 while the lack of lubricant results in the flow pattern as shown in FIG. At the Extrusion of aluminum, however, would like to have the flow pattern shown in FIG. 3 for the reasons mentioned above to have. Heretofore it has been thought that it is impractical to use any form of lubricant during extrusion of aluminum because of the undesirable and inevitable change to a metal flow pattern like it shown in Fig. 4 to admit.

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Considerable force is required to extrude metals. One therefore wants the required Power both from the point of view of economy, namely the reduction of energy consumption, as well as reduce from the point of view that through the Reduction of the required force Extruded products with larger cross-sections on existing extrusion presses can be shaped.

The flow of metal through the extrusion die generates a significant amount of heat due to the frictional forces between the extruded metal and the mold wall. This generation of heat is undesirable for several reasons. Firstly, there is accelerated wear of the extrusion mold if the temperature of the mold is excessive increases. Second, the shape, usually made of heat-treated steel, becomes soft and loses its shape desired properties achieved by the heat treatment. Third, the excess heat can lead to one increased grain growth on the surface of the extruded product, resulting in an undesirable duplex structure shows what problems cause the further surface treatment of the extruded product.

A 'further problem that occurs in extrusion, is that the extruded metal tends to form on the mold wall an order. this contract

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- Io leads to a change in the dimensions as well as to objectionable

surface defects of the extruded product.

The method according to the invention and the method according to the invention Apparatus now provide a lubricant on the walls or surfaces of the mold opening. By using the invention can significantly reduce the force required to produce a given extrusion be realized. The device according to the invention comprises a metal plate with an opening which essentially corresponds to the size and shape of the extrusion opening. The metal plate is placed on the surface of the extrusion die so that the die opening and the opening in the plate align with each other. At least one of the abutting surfaces between the metal plate and the mold has a knurled pattern which serves to establish intimate contact between the metal plate and the mold surface to prevent. A lubricant is forced into the groove space under pressure, which is directed and guided so that it exits and coats the mold cavity walls, so that the friction between the metal to be extruded and the mold wall is reduced. This reduction in friction leads to a Reduction of heat generation in the extrusion die and a reduction in the amount of metal that is on the Extrusion mold wall settles, as well as a reduction in mold wear.

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In Fig. 5, an embodiment of the invention is shown. On the extrusion mold 2 is by fastening devices 17 a metal plate 16 is attached. The plate 16 sits between the flat surface 9 of the extrusion mold and the bolt to be extruded. At least one of the associated surfaces of the metal plate 16 and the mold surface 9 has a grooved or knurled pattern 18 which provides intimate contact between the metal plate 16 and the mold surface 9 prevented. Details of the grooved surface will be described later.

A hollow lubricating channel 19 is guided through the extrusion mold 2 in such a way that lubricant can enter the space between the plate 16 and the mold surface 9 is fed. In order to direct the flow of lubricant towards the mold wall surface 8, a Seal 20 is used, which seals the opening between the grooved channel 18 and the container wall 1. In the In the embodiment shown in FIG. 5, the plate 16 covers the entire mold surface 9.

In practice, during extrusion the container is removed in order to remove the non-extruded part of the bolt residue, before a new bolt is extruded. Preferred in that it is necessary to provide a removable mold mani the metal plate 16 in the mold surface 9, as shown in Fig. 6 is shown to use. In the embodiment shown in FIG. 6, the molding surface 9 has a recess directly adjacent to the mold wall 8. The metal plate 16 is so loaded

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measure that it fits into this insertion portion of the mold surface. Then the gasket 20 is used to create a seal used between the metal plate 16 and the mold itself. In this embodiment, the shape can be used without deterioration the seal 20 can be removed. In Fig. 6 is also the lubrication channel 19, the groove surface 18 and the Fastening device 17 shown.

Fig. 7 shows a variety of possible designs of the edge of the metal plate, which is directly on the mold wall borders.

Fig. 7A shows that the edge of the opening of the metal plate 16 can have a square shape, so for example Flat sides of the metal plate 16 at right angles into the boundary wall pass the opening. In this embodiment, the metal plate 16 then mainly serves as an extension the form 2 itself.

7B shows a metal plate with a rounded leading edge 21. The rounded edge reduces and reduces the shear of the aluminum as it enters the mold 2 so are the frictional forces that are exerted on the aluminum before it enters the lubricated section of the mold entry.

Fig. 7C shows a metal plate with a beveled one

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Leading edge 22 which has essentially the same function as the rounded edge of Fig. 7B.

The lubrication channel 19 is also shown in FIGS. 7A, 7B and 7C and the sealing device 20 is shown.

The corrugation consists of a pattern of fine grooves on the surface of a solid object. The grooves are in essentially straight and parallel. It can be a pattern or several patterns can be superimposed so that the desired pattern is generated. The Piofelung resp. Knurling is conventionally created by a stamping process, but are below the term used here Corrugation means all indented patterns made by any process. The groove patterns suitable for the purposes according to the invention have the following dimensions: The depth of the individual grooves is generally between 0.013 mm and 0.51 mm (0.0005 to 0.020 "). The number of grooves per cm is between 4 and 20 (10 to 50 per in). The function of the grooves is to keep the lubricant evenly around the circumference of the extrusion around to distribute. To achieve this, it is necessary that the lubricant is reduced to a minimum Meng von Riefen passes through it before it comes into contact with the pellet. The minimum amount of scoring required in order to obtain a satisfactory lubricant distribution can be defined as follows: The dem

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- 14 dispensed fluid lubricant as it flowed through the grooves Pressure drop must be more than five times the pressure drop the lubricant is exposed to when it is flows from the reservoir to the grooves. A more uniform one Lubricant distribution can be achieved in that an enlarged groove is provided that the grooved Surrounds section and into which the lubricant is introduced. This embodiment is shown in Fig. 8, in which the groove 15 surrounds the section 13 provided with grooves. A more uniform lubricant distribution is also achieved when there are transverse channels which connect the groove grooves with one another, as in a preferred embodiment is the case.

The metal from which the plate is made advantageously has approximately the same composition as that from which the mold is made, so one is the same mechanical and the same thermal properties, for example the same thermal expansion. The thickness of the plate is generally between 5 mm and 25 mm. Preferably the plate is made of steel and is heat treated after scoring.

A large number of suitable lubricants are already available. In general, these lubricants can be characterized as follows:

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1) They must be at extrusion temperature, usually at about 510 C (950 F) at maximum at the pressure at which the lubricant is supplied, be thermally stable.

2) They must be liquid in the temperature range between 455 and 510 C (850 and 950 ° F).

3) They must have adequate lubricity and film strength under the conditions prevailing in the mold have or they have to react with the aluminum surface to form a reactive product, which can act as a solid lubricant.

4) There should be no reaction between the lubricant and the material of the mold.

Examples of inorganic compounds which meet these criteria are water-free B ₂ O and mixtures of alkali metal and alkaline earth chlorides, the liquidus of which is not higher than 230 C (450 F). Systems in this latter area, which are particularly favorable, are KCl-LiCl, NaCl-MgCl ₂ , LiCl-NaCl-MgCl ₃ , LiCl-KCl-MgCl and NaCl-KCl-MgCl _2. In addition, the above mixtures CaCl ₃ , SnCl ₃ , ZnCl ₂ and PbCl ₂ added or optionally replace one of the constituents of these mixtures in whole or in part. Stable alkali nitrates and alkaline earth nitrates can also be used. Selected organic and organometallic compounds can also meet the above criteria. Organizational

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See compounds belonging to the general family of polynuclear aromatics are suitable because of their good thermal stability. Examples are ^C ₂ 2 ^H 14 ' ^C lo ^H 7 ^NHC lo ^H 7' C _1n H ₇ C _1n H ₇ and compounds of this general family which have ester or amide bonds, for example tricresyl phosphate.

Most of the above lubricants are at room temperature Solids. Accordingly, the solid lubricants must be melted prior to being used in extrusion molding will. This heating is preferably carried out in a container. The lubricant is then over the extrusion die an insulated connecting line supplied. Because of the difficulty in pumping molten material, it can in a preferred embodiment, compressed air or another gas is applied to the top of the memory to press the liquid into the extrusion mold. ■ It may be necessary to preheat the mold in order to to prevent the lubricant from solidifying in the grooved space.

The required lubricant pressure varies greatly, depending on the operating conditions and the composition of the chosen lubricant depends. The pressure required

However, 2 is generally above 35 kgf / cm (500 psi). The one possible for an appropriate work according to the invention Lubricant pressure can be determined using the criterion that the lubricant pressure is greater than

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- 17 the yield stress of the metal under the conditions encountered by the metal in the extrusion die opening. That means/ that the desired lubricant pressure is the pressure that causes the pressurized lubricant to to deform the aluminum to be extruded. The compressive flow stress changes depending on the alloy

composition, grain size, temperature and hydrostatic pressure to which the alloy is exposed in the mold is. Generally prints are between 35 and

350 kp / cm (500 to 5000 psi) as measured on the extrusion

mold opening, and preferably between 40 and 210 kp / cm " (600 to 3000 psi) required.

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Claims (20)

- 18 claims 1.J Procedure for lubricating a heated pellet Aluminum or an aluminum alloy in an extrusion press, consisting of a container with one on one Flat extrusion mold arranged at the end and with a movable one arranged at the opposite end Press piston, through which the pressed part inserted in the containers can be pressed through the mold, thereby characterized in that a thin uniform layer of a heated, liquid lubricant the gap-shaped Space between the extruded material and the wall of the extrusion opening under the application of pressure is fed. 2. The method according to claim 1, characterized in that the lubricant is supplied under a pressure which reduces the compressive flow stress of the aluminum in the mold exceeds, the lubricant pressure at the gap-shaped Space between the mold wall and the extruded material is measured. 3. The method according to claim 1 or 2, characterized in that 2 that the pressure is between 42 and 210 kgf / cm (600 to 3000 psi). 509881/0445 4. The method according to any one of claims 1 to 3, characterized in that the lubricant is selected from the following group, which mixtures of alkali metal and alkaline earth chlorides with a liquid which is not higher than 230 ⁰ C (450 ° F), including KCl -LiCl, NaCl-MgCl ₂ . LiCl-NaCl-MgCl ₂ , LiCl-KCl-MgCl and KCl-MgCl. 5. The method according to claim 2, characterized in that at least one material from the group consisting of CaCl, SnCl », ZnCl ₂ and PbCl _{2 is} added to the chloride mixtures. 6. The method according to any one of claims 1 to 3, characterized in that the lubricant is selected from the group comprising polynuclear aromatic organic compounds, including ^C 22 ^Ii i4 ^/ C. H-NKC ₁ H ₇ , C ₁₀ H ₇ CH and compounds of this general family with ester or amide bonds. 7. The method according to any one of claims 1 to 3, characterized in that the lubricant has anhydrous B ₀ O ^ . 8. The method according to any one of claims 1 to 3, characterized in that the lubricant comprises tricresyl phosphate . 5G9881 / 0445 9. Device for performing the method according to claims 1-8, characterized by a continuous, thin, radially uniform lubricant film on the gap: shaped space between the mold wall and the extruded Product in which the lubricant is liquid at extrusion temperature, essentially with the form material "^ rial does not react, is applied under pressure, and has good film strength and lubricity. 10. The device according to claim 9, characterized in that the lubricant film on the interface between the V7and and the extruded product is distributed in that it is between the flat mold surface and a Metal plate in the container is guided adjacent to the mold surface, one of the adjacent surfaces has a grooved surface between the mold surface and the plate which has grooves, through which the lubricant flows. 11. The device according to claim 9 or 10, characterized in that the grooves have a depth between 0.013 and 0.51 mm (0.0005 to 0.020 "), which is the distance between the metal plate is between 0.013 and 0.51 mm. 609881/0445 12. Device according to one of the preceding claims 9 - 11, characterized in that the number of grooves the score is between 4 and 20 scores per cm (10 to 50 per inch). 13. Device according to one of the preceding claims 9 - 12, characterized in that between the groove grooves Connecting grooves are provided. 14. Device according to one of the preceding claims 9 - 13, characterized in that the lubricant is supplied in heated form. 15. Device according to one of the preceding claims 9 - 14, characterized in that the lubricant pressure on the gap-shaped space between the mold wall and the extruded product goes beyond the value of the compressive flow stress of the extruded aluminum. 16. The device according to claim 15, characterized in that 2 That the lubricant pressure is between 42 and 210 kgf / cm (600 and 3000 psi) where the lubricant is is in contact with aluminum. 17. Device according to one of the preceding claims 9 16, characterized in that the lubricant is a 509881/0445 Is subject to pressure drop as it flows through the grooves, at least the magnitude of the pressure drop in the grooves is five times larger than the size of the The lubricant pressure drops before it enters the groove, creating a uniform lubricant distribution is achieved. 18. Device according to one of the preceding claims 9-17, characterized in that the lubricant having anhydrous BO. 19. Device for direct extrusion of aluminum or aluminum alloys at high temperature with a hollow cylindrical container in which to do so extruding metal is introduced, with a planar extrusion die at one end of the container and a movable piston is arranged at the other end of the container, in particular after one of the preceding claims, characterized by a metal plate with an opening which is the same Dimension as the extrusion die opening, where the plate in the container to the flat surface of the mold is positioned adjacent and aligned the aperture of the plate with the mold opening, a _fluted: surface on at least one of the adjacent surfaces of the plate and the planar surface of the mold upstream 509881/0445 is seen to create a regulated space between the plate and the mold, and taking a flow a suitable lubricant in the grooved space between the plate and the mold is directed so that the lubricant in the mold opening as continuous thin layer emerges. 20. The device according to claim 19, characterized in that the metal plate is inserted into the flat surface of the mold ₇ and that a sealing device is used to direct the flow of lubricant into the opening of the mold. 509681/0445