CH652054A5 - PRESSLING FOR EXTRUDING OBJECTS AND METHOD FOR THE PRODUCTION THEREOF AND CAPSULE FOR IMPLEMENTING THE METHOD. - Google Patents

Abstract

A casing for isostatically pressed pieces, which are intended for the extrusion of metal articles, in particular stainless steel metal pipes. The outer and inner envelopes (302, 304) of the casing (301) are comprised of a thin metal sheet: the outer envelope (302) at least has, along the periphery thereof, resistance characteristic substantially uniform in the axial direction and it consists of, in particular, a spiral welded pipe and is provided, preferably, with a bulge directed outwardly, opposed to the narrowing. It is provided, at least at the front part of the casing an intermediary piece which is made of one or several parts; this piece is obtained from ductile material or from a material obtained by compression of a powder. It is also provided a method for producing such casings and pressed pieces and a method for the extrusion of pipes as well as pipes obtained by such method.

Description

The present invention relates to a compact according to the preamble of claim 1. Furthermore, the invention relates to a method for its production and a capsule for carrying out the method.

DE-AS-2 419 104 describes a method for producing stainless steel tubes which have a uniform structure and uniform physical and chemical properties and are easy to process, powders of such steel being filled into metallic capsules and the sealed capsules by means of all-round action Compressed pressure and the pellet thus obtained is extruded into tubes, and using steel powder made of predominantly spherical particles produced by atomizing melt in inert gas, thin-walled capsules made of a ductile metal are used, the wall thickness of which is at most about 5% of the outer diameter of the Capsule, the density of the steel powder filled into the capsule is increased to about 60 to 70% of the theoretical density by vibration and / or ultrasound and the density of the steel powder by cold isostatic pressing of the capsule by means of a pressure of at least 1500 bar to at least 80%, in front is preferably increased from 80% to 93% of the theoretical density, the compact is heated and then hot, preferably extruded to the desired semi-finished product at temperatures of at least about 1200 ° C.

According to DE-AS 2419 014, the metallic capsules, which are filled with the steel powder, can be evacuated before closing and / or with a gas, in particular an inert gas, e.g. Argon, fill.

According to DE-AS 2419 014, metallic capsules are preferably used, the wall thickness of which is less than 3%, in particular less than 1% of the outer diameter of the capsule and in particular metallic capsules are used, the wall thickness of which is between approximately 0.1 to 5 mm, preferably between approximately 0.2 and 3 mm.

According to DE-AS 2 419 014, composite pipes can also be produced, using thin-walled metallic capsules which are separated into two or more areas by one or more concentric partition walls and the predominantly spherical powder particles of the different steel qualities being in one of these areas at the same time Vibrate filled, then the partitions removed and the capsules closed, whereupon the isostatic cold pressing and the extrusion takes place at elevated temperature. Glass is normally used as a lubricant when extruding the compacts into tubes. Since high demands are placed on the lubricant during extrusion, in particular of stainless steel qualities, at higher temperatures, it is necessary to have an essentially flat end face of the compact so that the lubricant which is placed on the end face of the compact in the form of a glass rondelle is really used becomes.

It has now been shown that surface flaws were obtained during the extrusion, namely in the front part of the extruded product, which was due to the fact that at the transition between the lid and the jacket there was a strong disturbance in the flow, which is a problem Effect of the welding was due. This caused a significant loss in yield on the finished product.

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The object of the present invention is to provide a compact in which the yield is increased, i.e. the percentage of defective extruded products is reduced and the quality and dimensional accuracy of the extruded products is increased.

This object is achieved according to the invention by the means specified in claim 1. For this purpose, in the process for the production of the compact, at least the outer shell of the capsule is provided with a bulge which is shrunk by isostatic pressing and directed outwards and which is dimensioned such that it is essentially eliminated again by the shrinkage.

The production of the compact according to the invention offers the advantage that after the capsule is cold-isostatically pressed, the compact does not show an “hourglass shape” with a constricted central region. This so-called “hourglass shape” often arises from the fact that the ends of the capsule, which are closed by means of a lid or the like, show less shrinkage when subjected to cold isostatic pressing than the central region of the capsule. Since a compact is required for the extrusion process, the outer surface of which is cylindrical as precisely as possible, it is necessary to trim the ends of an «hourglass shape» of the compact, which is a very expensive process, with the risk of cracks occurring . The production according to the invention offers the advantage that there is no need for processing or trimming the compact to achieve a cylindrical shape. In addition, the invention makes it possible to produce compacts whose diameters correspond very precisely to the desired diameter dimensions. Accuracies of ± 0.2%, in particular ± 0.1% can be achieved. The diameter dimensions of the compact can be produced with an absolute accuracy of + 0.2 mm, in particular + 0.1 mm.

In a preferred embodiment, the outer casing and / or the inner casing of the capsule in the area of the capsule ends are produced as essentially cylindrical sections in the capsule according to the invention, the diameter dimensions of which correspond exactly to those of the desired compact and which continuously merge into a bulged central capsule area.

In a preferred embodiment, the shape of the outer and / or inner shell of the capsule is designed in such a way that the bulge from each of the cylindrical sections at the capsule ends in the axial direction, as seen in each case towards the center of the capsule, initially has a concave cross-sectional profile on the outside Range increases gradually and steadily, the inclination of the outer and / or inner casing against the capsule axis also gradually and steadily increasing, then preferably follows a conical intermediate area in which the inclination of the outer and / or inner casing remains substantially constant, whereby an area adjoins this conical intermediate area, in which the outer and / or inner casing has a convex cross-sectional profile and gradually and continuously merges into an axially parallel central section which preferably has a substantially constant diameter.

An improvement in the dimensional accuracy of the compact and a reduction in the reject rate can also be achieved in a preferred embodiment in that a plate, cone, hemisphere or funnel-shaped insert made of solid material is arranged on the front and / or rear end of the capsule. The provision of such inserts significantly improves the flow properties during extrusion of the compact and increases the yield of rustproof material, since the inserts, which preferably consist of electrically conductive metal, in particular soft iron or a low-carbon soft steel, form the ends of the extruded tubes. that have to be cut off anyway. Furthermore, the inserts, which preferably consist of an electrically conductive metal, in the area of the front and / or rear end face of the capsule considerably facilitate the heating of the compact prior to extrusion by means of inductive heat, since the metal inserts can be easily inductively heated and their heat to the Dispense the remaining parts of the compact, especially to the powder-filled interior, and thus contribute to the rapid heating of the entire compact.

The combination of the above-mentioned inserts in the area of the front and / or rear end face of the capsule with the formation of the outer and / or inner shell of the capsule with a bulge which is opposed to and outward from the shrinkage during isostatic pressing has proven to be particularly advantageous is such that it is essentially eliminated again by the shrinkage. With this combination, the dimensions of the compact can be maintained much more precisely. In particular, it is possible to maintain the dimensions of the compact to ± 0.05% or absolutely to ± 0.1 mm or more precisely, which is of the greatest importance for the faultless manufacture of extruded objects, in particular of extruded tubes.

In a preferred embodiment, the inserts can be designed as caps that close the end of the capsule, wherein the inserts can be welded tightly to the capsule outer jacket and the capsule inner jacket. Advantageously, sheet metal inserts can also be arranged between the inserts and the interior of the capsule, which are designed as lids and are tightly connected to the outer jacket and the inner jacket by welding.

In a preferred embodiment, inserts are used for the front end of the capsule, which are funnel-shaped and have a central bore, the angle y between the wall of the central bore for the inner shell of the capsule and the conical outer surface of the funnel-shaped insert being about 40 ° to 60 °, preferably about 40 ° to 50 °, in particular about 45 °.

It can be advantageous for the tube production that at least on the front end face of the capsule an annular insert provided with a central bore is provided, which has an essentially flat end face, and its boundary surface between the wall of the central bore and its largest outside diameter has an approximately circular arc-shaped cross-sectional profile, the center point of the circular arc profile lying approximately in the region of the intersection between the flat end face and the central bore.

A further substantial improvement of the capsules and the compacts produced therefrom and the objects extruded therewith, in particular the extruded tubes, can be achieved in combination with the above-described inlays or independently of these inlays according to one embodiment of the invention in that at least the jacket of the Capsule has approximately the same strength properties in the axial direction over the entire circumference. According to one embodiment of the invention, at least the outer shell of the capsule is preferably formed by a thin-walled, helically welded or extruded tube. Such a design of the outer shell of the capsule offers the advantage that extruded products, in particular tubes, are obtained.

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where the error rate and thus the scrap are significantly reduced.

The pitch of the helix formed by the weld seam in relation to the length of the capsule is preferably dimensioned such that the weld seam forms approximately one complete turn. An outer jacket provided with such a weld seam has only one weld seam at each point along its circumference in the axial direction and approximately the same strength properties in the axial direction. Alternatively, the weld seam can form two, three or more complete turns.

The present invention is applicable to capsules for the formation of compacts for extruding objects, in particular pipes, rods or similarly profiled, elongated, dense, metallic objects, in particular made of stainless steel or high-alloyed nickel steels, in particular heat-resistant steels for heat exchangers, e.g. B. high-alloy nickel steels with 80% nickel and 20% chromium, in the capsule powder of metal or metal alloys or mixtures thereof or mixtures of powders of metals and / or metal alloys with ceramic powders is filled. Spherical or predominantly spherical powder is preferably used as the powder, with an average diameter preferably below about 1 mm. Advantageously, spherical. used powder which is produced in an inert gas, preferably argon, atmosphere from the desired starting material, i.e. the desired metal and / or metal alloy has been produced by atomization. Powder grains with a diameter greater than 1 mm are preferably sieved, at least for the most part, since there is a risk that argon is enclosed in powder grains with a diameter larger than 1 mm. Such inclusion of argon can be used in atomizing z. B. done by turbulence. Argon confinement would cause unfavorable properties of the extruded articles during extrusion and lead to confinement lines.

The capsule for forming the compacts for the pipes to be extruded is filled with the powder, the density of the powder filled in the capsule being increased by vibration to about 60 to 71% of the theoretical density and the frequency of the vibration preferably being at least about 70 Hz, advantageously 80 to 100 Hz is selected. A density of about 68 to 71% of the theoretical density can be obtained by vibration at 80 to 100 Hz.

After the powder has been filled in and compacted by means of vibration, the capsule is closed, preferably after evacuation and / or filling with inert gas. The density of the powder is then increased by isostatic cold pressing with a pressure of at least 4000 bar, preferably 4200 to 6000 bar, in particular 4500 to 5000 bar, with at least 80 to 93% of the theoretical density.

It has been shown that capsules which are generally made of thin sheet metal, preferably sheet metal approximately 1 to 2 mm thick, in particular sheet metal approximately 1.5 mm thick, are particularly advantageous. Low-carbon soft steel, in particular with a carbon content of less than 0.015%, in particular less than 0.004%, is preferably used as the material for this capsule in order to prevent carburization of the powder during heating and during extrusion.

Due to the all-round pressure during cold isostatic pressing, the capsule is compressed uniformly both in the longitudinal direction and in the radial direction and then forms a compact. The pellet should have as few irregularities as possible, since these lead to difficulties during extrusion, especially when extruding pipes.

In order to produce a compact for extruding a tube, a capsule is used which is designed as an annular body, the outer jacket of this annular body being formed by a pipe section which is welded by a helix and which, for. B. is made from an approximately 1.5 mm thick sheet.

Inside this outer sheath, an inner sheath e.g. used in the form of a longitudinally welded pipe section that has a smaller diameter but the same wall thickness as the outer jacket. An annular cover is attached between the outer and inner jacket on one side and the annular space between the two tubes is closed on one side. Then spherical powder is poured into the annular space and vibrated with e.g. 80 Hz compressed to about 68% of the theoretical density. Then it is evacuated and the other end face of the ring-shaped body is sealed by a corresponding second cover. This is followed by cold isostatic pressing in a liquid, e.g. Water, with a pressure of e.g. 4700 bar. Due to the all-round pressure, a compact with a density of z. B. 85% of theoretical density.

In the compact according to the invention, the aim is that the helical weld seam is as smooth as possible and that the properties of the sheet do not change as much as possible. Therefore, the weld seam is preferably smoothed by means of rollers and / or by grinding. The welding seam can be smoothed by means of rollers immediately after the welding process.

In the case of compacts for the production of pipes, it may be expedient not only to produce the outer casing of the capsule but also the inner casing from a pipe which has approximately the same strength properties in the axial direction along its circumference. In this case, the inner jacket can either consist of a pipe welded by helix or of an extruded pipe. The use of an extruded or helically welded tube for the inner jacket is particularly useful with large dimensions. With smaller dimensions, it is generally sufficient if the outer casing of the capsule is produced from a tube section which has approximately the same strength properties in the axial direction along its circumference.

The invention is explained in more detail below with the aid of a schematic drawing using an exemplary embodiment.

Fig. 1 shows a capsule open at the top after pressing in view;

Fig. 2 shows a modified embodiment of the capsule after pressing in longitudinal section;

3 to 6 longitudinal sections similar to FIG. 2 of further modified embodiments before pressing.

The capsule is generally designated 1 in FIG. 1. The capsule is shown after pressing, i.e. without bulging. The capsule has an outer casing 2 and an inner casing 4. The outer jacket 2 consists of a helically welded pipe section with the length L. The weld seam 5 runs helically over the circumference of the outer jacket 2, the spiral having a pitch angle α which is dimensioned such that the screw line forms approximately a complete turn.

It has been shown that it is expedient to arrange the weld seam 5 such that it is welded between the weld seam 16, by means of which the capsule's cover (not shown in FIG. 1) is welded to the outer jacket 2, and the weld seam indicated at 26 the bottom of the capsule is attached to the outer shell, forms a complete turn. The distance between the weld

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ten 16 and 26 is designated in Fig. 1 with L '. This length L 'can be called the effective length of the capsule. It is expedient to choose the pitch angle a of the helical weld so that where D is the diameter of the capsule and n is the number of desired turns that the helical weld 5 should have. It has proven expedient to choose n = 1. However, it can also be advantageous to choose n = 2, 3.4 or a larger whole number.

In a practical example, the outer jacket 2 and also the inner jacket 4 of the capsule 1 consisted of 1.5 mm thick soft steel sheet with a carbon content of less than 0.004%. The lid, not shown in FIG. 1, was welded along the weld seam 16. To produce the compact, powder was used, the majority of which consisted of spherical grains with an average diameter of less than 1 mm and which was obtained from the desired starting material, for example by atomization in an argon atmosphere. B. had been made of stainless steel, filled into the capsule. After filling, the powder was compacted by vibration at a frequency of 80 Hz to a density of about 68% of the theoretical density. It was then evacuated and the capsule closed with a lid. The lid was connected by welding approximately along line 16 in Fig. 1 with the outer wall 2 of the capsule. In the exemplary embodiment mentioned, the capsule had a length of 600 mm and an outer diameter of 150 mm. The inner diameter of the inner jacket 4 was about 55 mm. The inner jacket 4 consisted of a longitudinally welded pipe section with a longitudinal weld seam 6. The density of the powder was then increased to about 85% of the theoretical density by isostatic cold pressing at a pressure of 4700 bar. The compact thus obtained was extruded into the tube as described in DE-AS 2 419 014.

In the embodiment of the capsule according to FIG. 2, which is also already shown in the pressed state, an insert 30 or 40 is arranged both in the area of the lid 10 and the base 20, which form the first and second end faces of the capsule. The first insert 30, hereinafter referred to as the front insert, is generally conical and has a central bore 32 for receiving the inner shell 4 of the capsule. The conical outer surface 36 of the conical or funnel-shaped insert 30 forms an angle y with the wall of the bore 32, which is preferably in the range between approximately 40 ° and 60 °, advantageously in the range between approximately 40 ° and approximately 50 ° and in particular approximately 45 ° lies. The insert 30 has an essentially flat end face 34. However, it is bevelled or rounded at its outer edge at 35 and then initially has a cylindrical section 37 which merges into the conical outer surface 36. At 39, the transition from the conical outer surface 36 to the wall of the central bore 32 is rounded. The contour of the cover 10, which is designed as a sheet metal insert, corresponds exactly to that of the adjacent parts of the insert 30. In particular, the cover 10 has a cylindrical section 17 on the outer edge, which ensures that the cover 10 is in good contact with the outer jacket 2. the outer edge of this cylindrical section 17 being connected to the outer jacket 2 by means of a weld seam 16. Also in the inner region, the cover 10 has a short, essentially cylindrical section 19, which bears against the inner casing 4 of the capsule and is welded to the inner casing 4 by means of a weld seam at 18. The cover 10 also has a rounding corresponding to the rounding 39 of the insert 30.

In the area of the second end face of the capsule 1 there is an insert 40 forming an approximately flat plate, which has a central bore 42 and an outwardly facing end face 44. This plate-shaped insert 40 is also beveled or rounded at the edge at 45 and has one outer cylindrical portion 47. The shape of the capsule base 20 corresponds to the shape of the insert 40 and also has an outer cylindrical section 27 and an inner cylindrical section 29. The base 20 is welded tightly to the outer jacket 2 and the inner jacket 4 by means of weld seams 26 and 28. The inserts 30 and 40 are preferably made of soft iron or low-carbon soft steel.

FIG. 3 shows a modified embodiment of the capsule in the unpressed state, an insert 130 provided on the front end of the capsule having an essentially circular cross-sectional profile 136 and a flat end face 134 and a central bore 132. The centers of the circular cross-sectional profile 136 lie on a circle that approximately in the area of the intersection between the flat end face 134 and the wall of the bore 132, ie lies in the region of the front boundary line of the bore 132, and is indicated by two crosses 138 in FIG. 3. The approximately circular cross-sectional profile 136 offers the advantage that when the compact is extruded, the insert 130 consisting of soft iron or a similar metal together with the cover 110, the weld seams 116, 118 and the adjacent parts of the outer jacket 102 and the inner jacket 104 form the first part of the tube which is cut off after the extrusion or even falls off by itself if the connection to the subsequent tube, which is preferably made of stainless steel and made from the powder filling of the capsule, has no or no sufficient strength. The approximately circular arc of the boundary line 136 of the insert 130 ensures that the dividing line between the front section of the extruded pipe, which is produced as waste, and the actual pipe, which is made of high-quality stainless material, is formed sharply and as a separating surface which extends essentially perpendicular to the longitudinal axis of the pipe . The lid 110 also has an approximately cylindrical section 117, which is welded at 116 to the outer casing 102 of the capsule, and an approximately cylindrical inner section 119, which bears against the inner casing 104 and at 118 by means of a circumferential weld seam sealingly to the inner casing connected is. The transition from the wall of the central bore 132 to the circular cross-sectional profile 136 is rounded off at 139.

It can also be advantageous to seal the inserts 30 and 40 directly to the outer jacket 2 and the inner jacket 4, respectively. In this case, cover 10 and bottom 20 can be omitted. In an analogous manner, the insert according to FIG. 3 can be tightly welded directly to the outer jacket 102 and the inner jacket 104.

When using sheet metal inserts as a lid or base, it may be expedient to attach the inserts 30, 40, 130 to them by spot welding. In many cases, however, it is also sufficient to fix the inserts 30, 40 and 130 through the flanged ends 15, 25 and 115 of the outer jacket 2 and 102, respectively.

The use in the area of the front end face of the capsule leads to a kind of tunnel effect when extruding, if this insert is made of ductile material, e.g. B. ductile egg 5

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sen, soft iron, low-alloy carbon steel or cast iron. The pressure that is required in the container of the extrusion press to extrude the compact is reduced if the front insert is made of ductile material and this material is easier to flow than the powder filling of the compact. Once the flow process, which takes place during extrusion, is initiated, it also spreads to the powder filling, even if the flow limit of the powder filling is higher than the flow limit of the ductile material of the insert; so there is a kind of tunnel effect.

In FIG. 3, the outer jacket 102 has a bulge 103 which is opposite to the shrinkage during cold isostatic pressing. In FIG. 3, the insert 140 in the area of the capsule bottom 120 also has an approximately circular cross-sectional profile 146, which in the area of the central bore 142 merges into the wall of the bore 142 via a rounded area 149. On the outside, the insert 140 has an essentially cylindrical section 147, against which a cylindrical section 127 of the base 120 comes to rest. The cylindrical section 127 is welded at 126 to a substantially cylindrical section 166 of the outer casing 102. The cover 120 lies with its cylindrical section 129 on the inner casing 104 and is welded to the inner casing at 128. The outer end face 144 of the insert 140 has a flat design and is rounded or beveled on the outer edge at 145, so that the flanged lower edge 125 of the outer jacket 102 can hold the insert 140 in place. The bulge 103 is dimensioned such that the inner surface of the outer shell 102 shrinks after the cold isostatic pressing up to the line 170, which corresponds to the ideal cylindrical shape. Accordingly, the cylindrical sections 156 and 166 of the outer jacket 102 are preferably drawn in by rolling until they are aligned with the line 170.

In order to avoid wrinkling and to achieve a compact that is centered as precisely as possible, it is advantageous according to the invention to essentially restrict the change in the diameter of the outer casing 102 to the area of the inserts 130 and 140, respectively. Between these inserts, the outer jacket 102 essentially has a constant outer diameter in the region indicated at 150. It has proven to be particularly advantageous to connect to the cylindrical sections 156, 166 towards the center of the capsule a region 157 or 167 with an outwardly concave cross-sectional profile and an intermediate region 158 or 168 in the shape of a truncated cone and to allow this to be followed by a region 159, 169 which is a has a convex cross-sectional profile on the outside and merges into the cylindrical, axially parallel central region 150. It is essential that the outwardly concave areas 157 and 167 are approximately mirror images of the cross-sectional profile 136 and 146 of the inserts, the line 170 representing the mirror symmetry axis and the angle of curvature of the outer shell indicated at β approximately in the ratio of the percentage shrinkage to the angle of curvature 5 of the neighboring mission is reduced.

FIG. 4 shows a modified embodiment, similar to FIG. 3, in which all the same or similar parts are provided with reference numbers increased by a hundred. The main difference is that the inserts 230 and 240 have a cross-sectional profile that is substantially tapered at 239 and 249, so that the appropriately designed lid 210 and the appropriately designed bottom 220 extend directly to the inner jacket 204 and form an obtuse angle with them form a or a '. It has been shown that this design is advantageous for exact centering of the compact. In the embodiment according to FIG. 4, bulging of the inner jacket 204 is not necessary. In contrast, in the embodiment according to FIG. 3, a slight outward bulging of the inner jacket can be advantageous. The bulge of the outer and / or inner jacket can be advantageous according to the invention in connection with any insert. The bulge in combination with a spiral welded outer and / or inner tube can also be advantageous.

FIG. 5 shows a modified embodiment, similar to FIG. 4, in which all the same or similar parts are provided with reference numbers increased by a hundred. The main difference is that the inserts 330 and 340 are provided with tips 339 and 349 and that no sheet metal inserts are provided. The bulge 303 from each of the cylindrical sections 356, 366 in the axial direction, viewed in each case towards the center of the capsule, initially gradually and steadily increases in a region 357, 367 with a concave cross-sectional profile, the inclination of the outer jacket 302 towards the capsule axis also gradually and continuously increases, then the inclination of the outer casing 302 remains substantially constant over a conical intermediate area 358, 368 and an area 359, 369 adjoins in which the outer casing 302 has an outwardly convex cross-sectional profile and gradually and continuously merges into an axially parallel central area 350 . The regions with a changing cross section of the outer jacket 302 each form a transition region 355, 365 which is arranged in the region of an insert 330 or 340. The cross-sectional contour 336, 346 of the inserts 330, 340 is approximately a reflection of the contour of the outer jacket in the transition regions 355, 365, which is mirrored on the line 370 of the desired cylindrical shape of the compact, but is stretched in the radial direction, the extent of the stretch being approximately corresponds to the ratio of the difference between the outer and inner diameter of the compact to the shrinkage of the capsule, preferably taking into account the change in the cross-sectional area as the radius becomes smaller.

With 316, 318, 326 and 328, the inserts 330 and 340 are directly welded to the outer and inner jacket. 337 and 347 are cylindrical portions of the inserts 330 and 340, respectively, which correspond to the cylindrical portions 137, 147 and 237.247 of Figures 3 and 4, respectively.

example

In order to produce a compact with an outer diameter of 144 mm for extruding a stainless steel tube with an outer diameter of 50 mm and a wall thickness of 5 mm, a screw-welded 600 mm long tube with an outer diameter of 154 mm and a wall thickness of 1.5 mm at both ends constricted by rolling or rotary pressing, such that cylindrical sections with an outer diameter of 144 mm correspond to the sections 156, 166; 256, 266; 356, 366 of FIGS. 3 to 4 were present, to which transition areas adjoined, which correspond to transition areas 155, 165; 255.265; 355, 365 were molded. Then the ends of the outer jacket were ground flat. At a first end, a sheet-metal insert forming a bottom was welded similarly to insert 120 in FIG. 3, on the one hand tightly to the outer jacket and on the other hand tightly to an inner jacket, which consisted of a 590 mm long, welded tube with a wall thickness of 1.5 mm and an inner diameter of 40 mm.

Until it touched the floor panel, an annular or funnel-shaped insert, similar to insert 140, was used

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low-alloy carbon steel with approx. 0.004% carbon stock inserted from the first end of the outer jacket and fastened by means of spot welding.

The capsule was placed upright on a plate, filled with powder and vibrated at 80 Hz and compressed to about 68% of the theoretical density and at the same time provided with a funnel-shaped sheet-metal insert similar to 110 in FIG. 3, which is between the inner and outer shells of was pushed in at the top with great pressure. Then the sheet metal insert was tightly welded to the inner and outer jacket, as indicated in FIG. 3 at 116 and 118. Then the front ring-shaped or funnel-shaped insert was inserted from above, which was designed similarly to 130 in FIG. 3 and consisted of low-alloy carbon steel with approx. 0.004% C. This ring-shaped insert was advantageously welded onto the funnel-shaped sheet metal insert or the inner or outer jacket by means of spot welding.

The capsule was cold isostatically pressed at 4700 bar in water to a density of 88% of the theoretical density. The compact shrank to an outside diameter of 144 mm, i.e. to the same dimension as the retracted cylindrical sections at the ends. The dimension of 144 mm also corresponded to the inner diameter of the container of the extrusion press. This ensured perfect centering. In addition, the inner diameter of the compact was almost exactly 40 mm.

The pellet was also completely straight and, after induction heating to 1200 ° C, could be extruded directly into the desired seamless tube made of stainless steel, without further processing being necessary. The front section of the tube made of low-alloy carbon steel was cut off. Nothing was cut from the stainless steel. Because the insert is tapered, a line of separation between the extruded insert and the stainless steel, which is approximately perpendicular to the pipe axis, was maintained in the extruded tube. The part of the pipe made of stainless material had a flawless surface. The material loss was thereby reduced to a minimum.

In order to achieve a good separation between the front section of the extruded tube, which is made of low-alloy carbon steel, and the desired seamless tube made of stainless steel, a glass layer can be applied to the surface of the front insert facing the powder filling 308. For this purpose, it may be expedient to heat the front insert 330 and to sprinkle the surface 336 with glass powder, the temperature of the insert being selected so that the glass powder softens and sticks. Such an intermediate glass layer makes the separation between the low-alloy carbon steel and the stainless steel considerably easier when the extruded tube is obtained, so that the two types of steel are obtained completely separately from one another and without mixing.

In an analogous manner, the surface of the bottom-side insert 340 adjoining the powder filling 308 can also be provided with a glass layer which facilitates the separation of stainless material and low-alloy carbon steel.

The inserts 30, 40, 130, 140, 230, 240, 330 and 340 can also be pressed from powdered starting material. For this purpose, e.g. B. water-atomized soft iron or water-atomized low-carbon steel can be used, which is cold isostatically pressed to the desired shape of the inserts mentioned and then sintered. The pressing of the soft iron powder can be carried out cold isostatically in a plastic mold, the pressure preferably being chosen to be at least as high, if not higher, than the pressure for the cold isostatic pressing which is used for the production of the capsules. Subsequent hot sintering can result in a dense material. Alternatively or additionally, a seal can be obtained by applying an outer glass layer, in this case also on the end faces 34, 134, 234, 334 or 44, 144, 444 and 344 and the peripheral surfaces.

The embodiment according to FIG. 6 largely corresponds to that according to FIG. 5. Only the insert pieces have a modified shape. The front insert 330 'consists of two rings 380 and 381, which are held together by means of several spot welds 382. Instead of two rings 380, 381, three or more rings can of course also be provided, the outer contour of which approximates the ideal contour of the front insert, which is represented by curve 336 in FIG. 5 or circular cross-section 236 in FIG 4 or 136 of FIG. 3 is given. In the embodiment according to FIG. 6, the bottom-side insert 340 'consists of an annular plate. Also here, if desired, additional rings with a stepped outer diameter and / or stepped inner diameter can be provided in order to approximate the desired ideal profile, e.g. B. to achieve an approximation to the profile 346 of FIG. 5.

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Claims (29)

652 054 2nd PATENT CLAIMS 1. compact for extruding objects, characterized by a capsule made of sheet metal filled with powder of metal and / or metal alloys or with mixtures of powders of metals and / or metal alloys with ceramic powders, the capsule provided at its ends for closing the one outer and has a capsule sleeve and a cover having inner liner and / or inserts, is cylindrical and the density of the powder in the capsule is at least 80% of the theoretical density. 2. Pellet according to claim 1, characterized in that the density of the powder in the capsule is 80% -93% of the theoretical density. 3. compact according to claim 1, characterized in that the front edge (35, 135; 235, 335) of the front insert (30; 130; 230; 330; 330 ') is chamfered in such a way that to achieve good lubrication when Extrusion process for lubricating glass, which can be placed in the form of a glass rondelle on the front side (34, 134; 234, 334) of the pressing in the container or recipient of the extrusion press, by the interaction of the bevelled front edge (35, 135; 235; 335) of the front insert (30; 130; 230; 330; 330 ') with the container or recipient can be fed approximately uniformly in the circumferential direction between the tool and the extruded object during the entire extrusion process. 4. The method for producing the compact according to claim 1, characterized in that a capsule sleeve with powder of metal and / or metal alloys or with mixtures of powders of metals and / or metal alloys is filled with ceramic powders, the density of the filled powder by vibration with 80 Hz to 100 Hz is increased to 60% to 71% of the theoretical density, open ends of the capsule sleeve are closed with an appropriate insert and the density of the powder isostatically cold pressed with a pressure of at least 4000 bar to at least 80% of the theoretical density is increased, at least the outer casing of the capsule being provided with a bulge which is opposite to the shrinkage during isostatic pressing and which is dimensioned such that it is eliminated again by the shrinkage during cold isostatic pressing. 5. The method according to claim 4, characterized in that the density of the powder is increased by isostatic cold pressing to 80% to 93% of the theoretical density. 6. The method according to claim 4, characterized in that the outer and / or inner shell of the capsule sleeve in the region of the capsule ends are provided with essentially cylindrical sections such that the outer and / or inner diameter of the cylindrical sections of the corresponding diameters of the compact to be produced deviate by + 0.2% or less or + 0.2 mm or less and that the bulge of the outer or inner jacket opens tangentially into these cylindrical sections. 7. The method according to claim 6, characterized in that the outer and / or inner diameter of the cylindrical sections of the corresponding diameter of the compact to be produced by + 0.1% or less or Deviate ± 0.1 mm or less. 8. The method according to claim 4 or 5, characterized in that at least one of the inserts for closing the capsule sleeve has a plate, cone, hemisphere or funnel-shaped one-part or multi-part body made of solid material or of pressed powder. 9. The method according to claim 7, characterized in that the body or bodies with the capsule sleeve outer tel and / or are welded to the capsule sleeve inner jacket. 10. The method according to claim 8, characterized in that glass layers are arranged between the inserts and the interior of the capsule. 11. The method according to any one of claims 4 to 10, characterized in that at least the outer shell of the capsule is made from a helical welded or extruded tube section. 12. The method according to claim 11, characterized in that the slope of the helical weld in relation to the length of the pipe section is selected so that the weld of the pipe section forms one or more complete turns. 13. The method according to any one of claims 4 to 12, characterized in that at least the insert provided on one end face of the capsule sleeve made of a ductile material, preferably ductile metal, such as e.g. Soft iron, low-carbon steel or cast iron is produced, the flow limit of which is noticeably below the flow limit of the powder filling of the compact in the container of the extrusion press, in such a way that the extrusion process begins at the pressure required for the ductile material of the insert and overlaps the powder filling due to the tunnel effect. 14. Capsule for performing the method according to claim 4 with an outer and an inner shell capsule sleeve made of sheet metal with a carbon content of less than 0.015 wt .-%, characterized in that at least the outer shell (102; 202; 302) of the capsule (101; 201; 301) is provided with a bulge (103; 203; 303) directed towards and outwardly from shrinkage by isostatic pressing such that it can essentially be eliminated again by the shrinkage. 15. Capsule according to claim 14, characterized in that a plate, cone, hemisphere or funnel-shaped body (30, 40; 130, 140; 230, 240, 330, 340, 330, 330 ') on at least one of the inserts provided for closing the capsule sleeve. , 340 '), one or more parts, made of solid material or pressed from powder, is provided. 16. Capsule according to claim 15, characterized in that the body or bodies (330, 340) as the capsule sleeve (301) are formed on the end-closing cover and are covered at least towards the interior of the capsule with a layer of glass. 17. Capsule according to claim 16, characterized in that the inserts (330, 340) are welded to the outer casing (302) and inner casing (304). 18. Capsule according to claim 14 or 15, characterized in that the inserts (30, 40; 130, 140; 230, 240) against the interior (8; 108; 208) of the capsule (1; 101; 201) are sheet metal inserts (10, 20; 110, 120; 210, 220). 19. Capsule according to one of claims 14 to 18, characterized in that the inserts (30.40; 130.140; 230.240, 330; 340; 330 ', 340') consist of electrically conductive metal, preferably soft iron. 20. Capsule according to one of claims 14 to 19, characterized in that funnel-shaped inserts (30) are provided for a first end face of the capsule sleeve (1) which have a central bore (32), the angle (y) between the wall the central bore (32) for the inner jacket (4) of the capsule (1) and the conical jacket surface (34) of the funnel-shaped insert (30) is 40 ° to 60 °, preferably about 45 °. 21. Capsule according to one of claims 14 to 20, characterized in that at least on a first end face 5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 3rd 652 054 the capsule sleeve (101; 201) is provided with an annular insert (130; 230) which is provided with a central bore (132; 232) and which has an essentially flat end face (134; 234), and the boundary surface (136; 236) between The wall of the central bore (132; 232) and its largest outer diameter has an approximately circular cross-sectional profile (136; 236), the center of the circular profile (136; 236) preferably approximately in the area of the circular cutting line (138; 238) between the plan End face (134; 234) and the central bore (132; 232) or within this circle (138; 238). 22. Capsule according to one of claims 14 to 21, characterized in that at least the outer casing (2; 102; 202; 302) of the capsule sleeve (1; 101; 201; 301) has approximately the same strength properties in the axial direction along its circumference . 23. Capsule according to claim 22, characterized in that at least the outer casing (2; 102; 202; 302) is welded by screw lines. 24. Capsule according to claim 22, characterized in that at least the outer casing (2; 102; 202; 302) is extruded. 25. Capsule according to claim 23, characterized in that the slope (a) of the helix formed by the weld seam (5) is dimensioned in relation to the length (L, L ') of the capsule (1; 101; 201; 301) so that the weld seam (5) forms one or more complete turns. 26. Capsule according to one of claims 23 and 25, characterized in that the helical weld seam is smoothed. 27. Capsule according to one of claims 14 to 26, characterized in that the outer and / or inner shell of the capsule sleeve in the region of the capsule ends has essentially cylindrical sections (156, 166; 256, 266; 356; 366), the outer and / or inner diameter of which essentially exactly, preferably up to about + 0.1% of the diameter or + 0.2 mm, in particular ± 0.1 mm, corresponds to the diameter dimensions of the compact and that the bulge (103; 203; 303) of the outer shell is tangential in this cylindrical sections opens. 28. Capsule according to claim 27, characterized in that the bulge (103; 203; 303) from each of the cylindrical sections (156,166; 256,266; 356, 366) in the axial direction, in each case as seen towards the center of the capsule, first in a concave Area having a cross-sectional profile (157.167; 257.267; 357, 367) increases gradually and steadily, the inclination of the outer casing (102; 202) towards the capsule axis also increasing gradually and then, preferably over a conical intermediate area (158.168; 258.268; 358, 368 ) the inclination of the outer casing (102; 202; 302) remains essentially constant and that preferably an area (159, 169; 259, 269; 359, 369) adjoins in which the outer casing (102; 202; 302) is convex to the outside Has cross-sectional profile and gradually and continuously merges into an axially parallel central region (150; 250) and that the regions with a changing cross-section of the outer casing (102; 202; 302) each have a transition region i (155.165; 255.265; 355, 356), which is preferably arranged in the region of an insert, the cross-sectional contour (136, 146; 236, 246; 336, 339; 346, 349) of which approximately reflects the contour of the transition region, which is marked on the line (170; 270; 370) of the cylindrical shape of the compact is mirrored, but is enlarged in the radial direction in the ratio of the diameter of the compact to diameter shrinkage. 29. Capsule according to claim 28, characterized in that the cylindrical central region (150; 250; 350) of the outer casing (102; 202; 302) and / or the inner casing (104; 204; 304) has a substantially constant diameter extends essentially over the entire area between the inserts (130, 140; 230,240).