DE2846658A1 - Powder filled capsule for use as extrusion blank - for making stainless steel or nickel-chromium alloy tubes, is isostatically pressed after filling - Google Patents

Abstract

The blanks are extruded into tubes or bars made of stainless steel or alloy steel with high Ni content, and esp. heat resisting tubes contg. 80% Ni, 20% Cr, and used in heat exchangers. The capsules are made of sheet metal, 1-2mm thick, contg. 0.015% C, esp. 0.004% C, and have a peripheral bulge. The capsule is filled withspherical grains of metal or alloy powder made by shotting, esp. in Ar atmos and the powder may include ceramics. The filled capsule is vibrated at 80-100 Hz, so that powder has 60-71% of the theoretical density, and is then sealed and cold isostatically pressed at >=4000 bars, pref. 4500-5000 bars, to attain min. 80-93% density. The bulge on the capsule disappears during the pressing operation. Defects are reduced due to the use of a bulge-free blank and the tubes have precise dimensions.

Description

description

Capsules and pellets for extruding objects, esp.

Tubes, and Methods of Making the Capsules and Compacts Additive to P 24 19 014.5-24 The present invention be frt a development of the main patent ................ (patent application P 24 19 014.5-24).

The main patent ............. (patent application P 24 19 014.5-24) concerns a method of making stainless steel pipes that are uniform Structure as well as uniform physical and chemical properties and good Have further processability, with powder from such steel in metallic Capsules filled and the closed capsules by means of pressure acting on all sides are compressed and the compact thus obtained is extruded into tubes, and steel powder produced by atomizing melt in inert gas from predominantly spherical particles are used, thin-walled capsules made of a ductile metal are used whose wall thickness a maximum of about 5% of the outer diameter of the capsule is the density of the steel powder filled in the capsule Vibration and / or ultrasound increased to about 60 to 70% of the theoretical density 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%, preferably 80 z to 93 t of the theoretical density is increased, the compact is heated and then hot, preferably at temperatures of at least about 12000C to the desired one Semi-finished product is extruded.

According to the main patent (patent application P 24 19 014.5) it can be advantageous be that you have the metallic capsules, which are filled with the steel powder, before after closing evacuated and / or with a gas, in particular an inert gas, e.g. argon. Furthermore, according to the main patent ...........

(Patent application P 24 19 014.5-24) preferably metallic capsules used whose wall thickness is less than 3%, in particular less than 1% of the outer diameter the capsule is and in particular metallic capsules used, their wall thickness is between about 0.1 to 5 mm, preferably between about 0.2 and 3 mm.

According to the procedure according to the main patent ....................

(Patent application P 24 19 014.5-24) composite pipes can also be produced, where one uses thin-walled metallic capsules, which by one or more concentric partitions in two or more areas separated are and one is the predominantly spherical powder particles of the various steel grades filled in one of these areas while vibrating at the same time, then the partitions removed and the capsules sealed, followed by cold isostatic pressing and the extrusion is carried out at an elevated temperature. When extruding the compacts glass is usually used as a lubricant for pipes. There big demands to the lubricant during extrusion, especially of stainless steel grades If higher temperatures are used, it is necessary to have an essentially flat surface To have the face of the compact, so that in the form of a glass washer on the End face of the compact given lubricant is really used.

It has now been shown that surface defects can be found in the extrusion received, in the front part of the extruded product, for what its reason had in it that there was a strong disturbance at the transition between the cover and the jacket of the flow profile, which can be attributed to the disruptive effect of the weld was.

This caused a significant loss in the yield of the finished product.

The object of the present invention is to improve the yield, i. H. the to reduce the percentage of defective products after extrusion.

According to the invention, this object is achieved in that the capsule is designed in this way that a funnel-shaped insert at the end face of the capsule is inserted. This training offers the advantage that the flow properties are improved during extrusion and that the yield of stainless material is increased.

According to the invention, the inserts are preferably made of electrical conductive metal, especially soft iron or some other cheap metal.

According to the invention, the inserts can be used to close the capsule on the end face Lid be formed, the inserts with the capsule outer shell and the capsule inner shell can be welded tightly. Advantageously, between uses and sheet metal inserts are also arranged in the interior of the capsule, which act as a cover are formed and sealed to the outer jacket and the inner jacket by welding get connected.

According to the invention for capsules for the production of compacts for Extruding tubes used inserts for the front face of the capsule are funnel-shaped and provided with a central bore are, the angle t between the wall of the central bore for the inner jacket the capsule and the conical surface of the funnel-shaped insert about 400 to 600, preferably about 400 to 500, especially about 450.

According to the invention it can be advantageous for pipe production, that at least one with a central bore on the front end face of the capsule provided annular insert is provided which has a substantially planar Has end face, and its boundary surface between the wall of the central Bore and its largest outer diameter an approximately circular arc-shaped cross-sectional profile having, the center point of the circular arc profile approximately in the area of the cutting line lies between the flat face and the central bore.

Another major improvement of the capsules and those made from them Compacts and the extruded articles, in particular the extruded tubes, can be designed according to the invention in combination with those described above Deposits or achieved independently of these deposits according to the invention that at least the shell of the capsule is approximately the same over the entire circumference Has strength properties in the axial direction. Preferably is at least the outer jacket of the capsule according to the invention by a thin-walled, spiral-welded one or extruded pipe. Such a design of the outer jacket Capsule offers the advantage that extruded products, in particular tubes, are obtained in which the error rate and thus the reject rate are markedly reduced.

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

The present invention is applicable to capsules and compacts for extruding objects, especially pipes, rods or similarly profiled, elongated, dense, metallic objects, in particular made of stainless Steel or high-alloy nickel steels, especially heat-resistant steels for heat exchangers, E.g. high-alloy nickel steels with 80% nickel and 20% chromium, whereby in the invention Capsule powder made of metal or metal alloys or mixtures thereof or mixtures of powders made of metals and / or metal alloys filled with ceramic powders will. The powder used is preferably spherical or predominantly spherical Powder used, with an average diameter preferably below about 1 mm. According to the invention, spherical powder is used, which is in a protective gas, preferably Argon atmosphere, from the desired starting material, i.e. the desired metal and / or metal alloy has been made by atomizing. Powder grains are preferably used here with a diameter greater than 1 mm, at least for the most part, screened off, because there is a risk that in powder grains with a diameter greater than 1 mm Argon is included. Such inclusion of argon can occur during atomization e.g. caused by turbulence. An inclusion of argon would be unfavorable during extrusion Induce properties of the extruded articles and lead to inclusion lines.

According to the invention, the capsule for producing the compacts for the tubes to be extruded filled with the powder, the density of the in the capsule filled powder by vibration to about 60 to 71% of the theoretical density is increased and wherein the frequency of the vibration is preferably at least about 70% Hz, advantageously 80 to 100 Hz is chosen. By vibrating at 80 to 100 Hz, a density of about 68 to 71% of the theoretical density can be obtained.

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

It has been shown that capsules, which are generally made of thin sheet metal, preferably about 1 to 2 mm thick sheet metal, especially about 1.5 mm thick sheet metal, especially are beneficial.

The material used for this capsule is preferably low-carbon iron, especially with a carbon content of less than 0.015%, especially less than 0.004%, to prevent carburization of the powder during heating and extrusion.

Due to the pressure on all sides during cold isostatic pressing, the Capsule compressed uniformly both longitudinally and radially and then forms a compact. This compact should not have any irregularities as far as possible have, since these lead to difficulties during extrusion, especially during extrusion of pipes, lead.

In order to produce a compact for extruding a pipe, a capsule is used, which is designed as an annular body, the outer jacket this ring body is formed by a spiral-welded pipe section which e.g.

is made of an approximately 1.5 mm thick sheet.

Inside this outer jacket, an inner jacket, e.g.

used in the form of a longitudinally welded pipe section, the one smaller diameter, but the same wall thickness as the outer jacket. An annular cover is attached to one side between the outer and inner casing and the annular space between the two tubes is closed on one side. Then it will be spherical powder is filled into the annulus and vibrated with e.g. 80 Hz compressed to about 68% of the theoretical density. Then it is evacuated and the other one End face of the annular body 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. The all-round pressure gives you one Compact with a density of e.g. 88% of the theoretical density.

In the case of the capsule according to the invention, the aim is that the spiral-shaped The weld seam is as smooth as possible and, if possible, the properties of the sheet metal changed significantly.

Therefore, the weld seam is preferably by means of rolling and / or by means of Loops smoothed. The smoothing of the weld seam by means of rollers can be carried out immediately to the welding process.

In the case of capsules for making tubes, it may not be useful only the outer jacket, but also the inner jacket from a pipe to manufacture that along its circumference approximately the same strength properties in the axial direction Has direction. The inner jacket can either consist of a spiral-welded one Pipe or consist of an extruded pipe. Applying an extruded or spiral-welded pipe for the inner jacket is particularly important for large dimensions expedient. For smaller dimensions, it is generally sufficient if the According to the invention, the outer casing of the capsule is made from a pipe section, which along its circumference has approximately the same strength properties in the axial direction having.

In the following the invention is based on a schematic drawing explained in more detail using an exemplary embodiment.

1 shows a top view of a capsule open at the top; Fig. 2 shows a modified embodiment of the capsule in longitudinal section; and Fig. 3 is a partial section another embodiment.

The capsule is denoted generally by 1 in FIG. 1. The capsule has an outer jacket 2 and an inner jacket 4. The outer jacket 2 consists of a spiral-welded pipe section with the length L. The weld seam 5 runs in a spiral over the circumference of the outer jacket 2, the spiral having a pitch angle ot, which is dimensioned so that the spiral forms approximately one complete turn.

It has been shown that it is useful to arrange the weld 5 so that they are between the weld 16, by means of the one not shown in FIG Lid of the capsule is welded to the outer shell 2, and that indicated at 16 Weld seam, by means of which the bottom of the capsule is attached to the outer shell, forms a complete turn. The distance between the welds 16 and 26 is designated by L 'in FIG. 1. This length L 'can be used as the effective length of the Are called capsule. It is useful to set the helix angle ot of the spiral weld to be chosen so that tg oc = n IT D, where D is the diameter of the capsule and n is the The number of turns desired is that the spiral weld seam 5 should have. It has proven to be useful to choose n = 1. But it can also be beneficial be to choose n = 2, 3, 4 or equal to a larger whole number.

The outer shell 2 and also the inner shell 4 of the capsule 1 passed in a practical example made of sheet metal with a thickness of 1.5 mm and a carbon content less than 0.004%. The cover not shown in Fig. 1 was along the weld seam 16 welded in. To produce the compact was powder, which was predominantly Part made of spherical Grains with a medium diameter under 1 mm and that by atomization in an argon atmosphere from the desired starting material made of stainless steel, for example, was filled into the capsule. To the powder was filled with vibration at a frequency of 80 Hz a density of about 68 t of the theoretical density. It was then evacuated and the capsule closed by means of a lid. The lid was made by welding connected approximately along the line 16 in FIG. 1 to the outer wall 2 of the capsule. the Capsule had a length of 600 mm and a length in the embodiment mentioned Outside diameter of 150 mm. The inner diameter of the inner jacket 4 was approximately 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 determined by cold isostatic pressing increased with a pressure of 4700 bar to about 85% of the theoretical density. Of the The compact obtained in this way was, as in the main patent application P 24 19 014.5-24 described, extruded to the pipe.

In the embodiment according to FIG. 2, both in the area of the cover 10 like the bottom 20 each have an insert 30 or

40 arranged, which is the front or rear end face of the capsule form. The front insert 30 is generally tapered and has a central bore 32 for receiving the inner shell 4 of the capsule. The surface of the cone 36 of the conical or funnel-shaped insert 30 forms with the wall of the bore 32 an angular p, which is preferably in the range between approximately 400 and 600, advantageously is in the range between about 400 and about 500 and in particular about 450. Of the Insert 30 has an essentially flat end face 34. However, it is on its outer edge beveled or rounded at 35 and then initially has a cylindrical section 37, which merges into the conical lateral surface 36. At 39 is the transition from the conical surface 36 to the wall of the central Bore 32 rounded. The cover 10, which is designed as a sheet metal insert, corresponds in its contour exactly that of the adjacent parts of the insert 30. In particular has the lid 10 on the outer edge of a cylindrical portion 17, the one ensures good contact of the lid 10 on the outer jacket 2, the outer edge this cylindrical section 17 by means of a weld 16 with the outer jacket 2 is connected. In the inner area too, the cover 10 has a short, essentially cylindrical portion 19 which rests against the inner shell 4 of the capsule and at 18 is tightly welded to the inner jacket 4 by means of a weld seam. Even the cover 10 has a rounding corresponding to the rounding 39 of the insert 30 on.

In the area of the rear face of the capsule 1 is a approximately Flat plate forming insert 40 having 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 an outer cylindrical Section 47 on. The shape of the capsule base 20 corresponds to the shape of the insert 40 and also has an outer cylindrical portion 27 and an inner cylindrical Section 29 on. The bottom 20 is connected to the outer jacket by means of welds 26 and 28 2 or the inner jacket 4 welded tightly. The inserts 30 and 40 are preferably made made of soft iron.

In Fig. 3 a modified embodiment of the capsule is shown, wherein an insert 130 provided on the front end face of the capsule is an im has a substantially circular arc-shaped cross-sectional profile 136 and a plane End face 134 and a central bore 132. The center of the circular arc-shaped Cross-sectional profile 136 is preferably located approximately in the area of the cutting line between the flat face 134 and the wall of the bore 132, i.

in the area of the front boundary line of the bore 132, and this Center is indicated at 138 and 138 '. The approximately circular arc-shaped cross-sectional profile 136 has the advantage that when the compact is extruded from soft iron or a similar metal insert 130 together with the lid 110, the welds 116, 118 and the neighboring ones Parts of the outer jacket 102 and the Inner jacket 104 form the first part of the tube, which is cut off after extrusion will or even falls off by itself when the connection to the preferably off stainless steel, then made from the powder filling of the capsule Pipe has no or insufficient strength. Due to the roughly circular arc Formation of the boundary line 136 of the insert 130 is achieved that the parting line between the leading waste section of the extruded tube and the actual pipe made of high quality stainless material sharp and as a separating surface extending substantially perpendicular to the pipe's longitudinal axis is trained. The cover 110 also has an approximately cylindrical section 117, which is welded at 116 to the outer shell 102 of the capsule, and one approximately cylindrical inner section 119 which rests against the inner jacket 104 and at 118 tightly connected to the inner jacket by means of a circumferential weld seam is. The transition from the wall of the central bore 132 to the circular one Cross-sectional profile 136 is rounded at 139.

It can also be advantageous to place the inserts 30 and 40 directly to be welded tightly to the outer jacket 2 or the inner jacket 4. In this case cover 10 and base 20 can be omitted. In an analogous way, the use can after Fig. 3 directly with the outer jacket 102 and the inner jacket 104 tight be welded.

It can be useful when using sheet metal inserts as a cover or base be to attach the inserts 30, 40, 130 by spot welding. Multiple However, it is also sufficient to push 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 face of the capsule leads to Extruding to a kind of tunnel effect, if this insert is made of ductile material, e.g. ductile iron, soft iron, low-alloy carbon steel or cast iron, consists. The pressure in the container of the extrusion press for extruding the compact required is lowered if the front insert is made of ductile material exists and this material can be brought to flow more easily than the powder filling of the pressed part. Once the flow process that takes place during extrusion has started, in this way it also encroaches on the powder filling, even if the flow limit the powder filling is higher than the yield point of the ductile material of the insert; So there is a kind of tunnel effect.

All information and characteristics disclosed in the documents, in particular the disclosed spatial arrangement, insofar as they are used individually or in combination are new compared to the prior art, claimed as essential to the invention.

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Claims (20)

Claims 1. Capsules for compacts for extruding objects, esp. of pipes, rods or similarly profiled, elongated, dense, metallic Objects, especially made of stainless steel or high-alloy nickel steels, especially heat-resistant steels for heat exchangers, e.g. high-alloy nickel steels with 80% nickel and 20% chromium, the capsule made of thin, preferably 1 to 2 mm thick and preferably low in carbon, a carbon content less than 0.015%, preferably less than 0.004%, comprising sheet and in the Capsule powder made of metal or metal alloys or mixtures thereof or mixtures of powders made of metals and / or metal alloys filled with ceramic powders is, which is preferably made of spherical or predominantly spherical Grains consists in a protective gas, preferably argon atmosphere, from the desired starting material are produced by atomization and where the density of the powder filled in the capsule by vibration with preferably 80 to 100 Hz is increased to about 60 to 71% of the theoretical density and gradually Seal the capsule with the density of the powder by cold isostatic pressing a pressure of at least 4000 bar, preferably 4200 to 6000 bar, in particular 4500 to 5000 bar, further increased to at least 80 to 93% of the theoretical density is, as a result, that at the front and / or rear The end face of the capsule (1) is plate, cone, hemispherical or funnel-shaped Use (30, 40) made of solid material is provided. 2. Capsule according to claim 1, characterized in that g e k e n n z e i c h -n e t, that the insert or inserts (30, 40) as the capsule (1) closing at the end Lids are formed. 3. Capsule according to claim 2, characterized in that g e k e n n z e i c h -n e t, that the inserts (30, 40) with the capsule outer shell (2) and possibly with the capsule inner shell (4) are welded. 4. Capsule according to claim 1, characterized in that g e k e n n z e i c h -n e t, that between the inserts (30, 40) and the interior (8) of the capsule (1) sheet metal inserts (10, 20) are arranged. 5. Capsule according to claim 4, characterized in that g e k e n n z e i c h -n e t, that the sheet metal inserts (10, 20) are designed as a cover and with the outer jacket (2) the capsule (1) and, if necessary, with the inner jacket (4) by means of welds (16, 18, 26, 28) are connected. 6. Capsule according to one or more of claims 1 to 5, characterized it is noted that the inserts (30, 40) are made of electrically conductive Metal, preferably soft iron, exist. 7. Capsule for making pellets for extruding tubes according to one or more of claims 1 to 6, characterized in that e t that inserts (20) are used for the front face of the capsule (1), which are funnel-shaped and provided with a central bore (32) are, the angle (t) between the wall of the central bore (32) for the Inner jacket (4) of the capsule (1) and the conical jacket surface (36) of the funnel-shaped Insert (30) is about 400 to 500, preferably about 450. 8. Capsule according to one or more of claims 1 to 7, characterized it is not noted that at least on the front face of the capsule (1) an annular insert (130) provided with a central bore (132) is provided, which has a substantially planar end face (134), and its Boundary surface (136) between the wall of the central bore (132) and his largest outer diameter has an approximately circular arc-shaped cross-sectional profile (136), wherein the center point (138) of the circular arc profile (136) approximately in the area of the cutting line lies between the planar end face (134) and the central bore (132). 9. Capsule according to one or more of claims 1 to 8, characterized it is noted that at least the outer casing (2) of the capsule (1) is longitudinal its circumference has approximately the same strength properties in the axial direction. 10. Capsules according to claim 9, characterized in that they are e k e n n -z e i c h n e t that at least the outer jacket (2) is spiral welded. 11. Capsules according to claim 9, characterized in that they are e k e n n -z e i c h n e t that at least the outer jacket (2) is extruded. 12. Capsules according to claim 9 or 10, characterized in that g e -k e n n z e i c h n e t that the slope (c) of the spiral formed by the weld seam (5) in the Relation to the length (L, L ') of the capsule (1) is dimensioned so that the weld seam (5) forms about one, two or more complete turns. 13. Capsules according to one or more of claims 9, 10 and 12, characterized It is indicated that the spiral weld seam is made by means of rolling and / or grinding is smoothed. 14. Compact for extruding objects, especially pipes, rods or similarly profiled, elongated, dense, metallic objects, in particular stainless steel or high-alloy nickel steels, in particular heat-resistant steels for heat exchangers, e.g. high-alloy nickel steels with 80% Nickel and 20% chromium, in that it is a capsule (1) according to one or more of claims 1 to 13. 15. Method of making capsules according to one or more of claims 1 to 14, characterized in that at the front and / or the rear end face of the capsule is plate-shaped, conical, hemispherical or funnel-shaped Insert made of solid material is used. 16. The method according to claim 15, characterized in that it is e k e n n -z e i c h n e t that the insert (s) with the outer shell of the capsule and possibly with the inner shell of the capsule be welded. 17. The method according to claim 15, characterized in that g e k e n n -z e i c h n e t that arranged between the inserts and the interior of the capsule sheet metal inserts will. 18. The method according to one or more of claims 15 to 17, characterized it is noted that at least the outer casing of the capsule consists of a spiral-welded or extruded pipe section is produced. 19. The method according to claim 18, characterized in that g e k e n n -z e i c h n e t that the slope of the spiral weld seam in relation to the length of the Pipe section is chosen so that the weld seam of the pipe section is about one, forms two or more complete turns. 20. A method for producing compacts according to claim 14, characterized it is noted that the capsule according to one or more of the claims 15 to 19 is produced, and at least the one provided on the front face Insert made of a ductile material, preferably ductile metal such as soft iron, low-carbon steel or cast iron, the yield point of which is in the container the extrusion press noticeably below the flow limit of the powder filling of the compact is such that the extrusion process is at that for the ductile material of the insert The required pressure begins and spreads to the powder filling through the tunnel effect.