KR840001303B1 - Capsules and pressings for extruding objects partieularly tubes,ana a process for producing the capsules and pressings - Google Patents

Abstract

As a blank manufacturing capsule for extruding high-density metal tube, especially of stainless steel or Ni-Cr alloy, the capsule has a thin outer wall in a circular cone shape and an inner wall, which does not contact the outer wall. Metal or alloy powder, a mixture of these powders, or a mixture of metal powder and ceramic powder are poured into the tube space. the capsule itself can be extended and then returned to normal site after condensation, and is constructed to allow an inner core to be inserted into its inner wall.

Description

Capsule for making blanks for use in extrusion of high density metal tubes

1 is a perspective view of an open top capsule.

2 is a longitudinal sectional view showing a modified form of the capsule.

3 to 6 are longitudinal cross-sectional views similar to those of FIG. 2 showing various modification forms.

The present invention relates to a blank manufacturing capsule for use in extruding high-density metal pipes, in particular stainless steel pipes or nickel chromium alloy pipes, wherein the capsule forms an empty space forming an annular cross section between the cylindrical outer wall and the inner wall. It consists of a thin cylindrical metal container configured to fill a space with a metal powder or metal alloy powder or a mixture thereof or a mixture of the metal and metal alloy powder and porcelain powder and seal both ends of the capsule with an annular stopper.

German patent application DE-AS 24 19 014 discloses a method for producing stainless steel pipes with uniform structure, uniform physical and chemical properties, and good processing characteristics. The capsules are pressed from all sides and pressed, and the blank thus obtained is extruded again to produce an extruded tube, wherein the metal powder is made of mainly spherical fine particles made by spraying molten stainless steel in an inert gas and atomizing them. Powder is used and the capsule used here is a flammable thin walled metal capsule whose maximum wall thickness is about 5% of the capsule outer diameter and vibrates the density of the steel powder filled in the capsule or Use ultrasound to increase the density to about 60% -70% of theoretical density By applying uniform cold compression under a pressure of at least 1500 bar, the blank obtained by increasing the density of the steel powder to at least 80% of the theoretical density, in particular 80% to 90% is heated and hot-extruded at a high temperature, especially at about 1200 degrees Celsius. To produce the desired semifinished product.

According to German patent application DE-AS 24 19 014, it may be advantageous to vacuum the metal capsule filled with steel powder or to fill it with an inert gas, in particular a gas such as argon.

According to German patent application DE-AS 24 19 014, the wall thickness of the capsule is 3% or less, in particular 1% or less of the outer diameter, the wall thickness of which is about 0.1 to 5 mm, especially 0.2 to 3 mm.

Using a method according to the German Patent Application Publication DE-AS 24 19 0.14 using a thin walled metal capsule divided into two or more compartments using one or more concentric partitions, It is possible to manufacture. At this time, the various spherical powders having different steel properties are filled in one of the divided compartments while vibrating, and then the partitions are removed, and both ends of the capsules are sealed to give uniform cold compression and extruded under high temperature.

Glass is used as a lubricant when the blank is extruded to produce an extruded tube. In particular, since the importance of the lubricant is greatly required when extruding the type of stainless steel, it is desirable to fundamentally flatten the cross section of the blank in order to effectively operate the lubricant attached to the cross section of the blank in the shape of a round glass tube.

Today, it has been found that surface defects occur in the front part of the extruded product because the adverse effects of the weld on the execution of the steel pipe extrusion are large in the flow mode. This leads to huge losses in the yield of the final product.

An object of the present invention is to reduce the incidence of defective products after extrusion to increase the yield and to improve the accuracy of the product quality and dimensions.

This object is to make the outer shell of the capsule convex outward by the expected shrinkage in order to offset the shrinkage phenomenon during even cold pressing according to the present invention so that it disappears again after the pressing.

The structure of the capsule according to the invention has the advantage that it does not have a "hourglass" shape in which the blank is narrow after the uniform cold pressing. This so-called "hourglass" type is usually due to the fact that both ends of the capsule, sealed with a stopper or similar lid, have less shrinkage than the middle part during cold even compression. The compression requires trimming both ends of the "hourglass" type blanks, since a blank is required to form an essentially uniform outer wall of the cylinder, which is very expensive and risks cracking. The structure of the capsule according to the invention offers the advantage that no trimming is necessary to make the blank a uniform cylinder shape. The present invention also makes it possible to produce blanks with diameters which exactly match the desired diameter values. According to the invention an accuracy of ± 0.2%, in particular ± 0.1%, can be obtained. In other words, blanks of exact diameter up to ± 0.2 mm, in particular ± 0.1 mm, can be produced.

The outer wall and the inner wall of the capsule according to the present invention are manufactured to have a cylindrical shape in which the diameters of both ends of the capsule exactly match the diameters of both ends of the desired blank and gradually become convex while going toward the central part of the capsule.

According to the present invention, the outer wall and the inner wall of the capsule continue to gradually open from the concave portion of the outer side toward the central portion in the axial direction from the angular cylinder portions at both ends of the capsule, wherein the inclination angles of the outer wall and the inner wall with respect to the capsule axis are also gradually In addition, the inclined angle between the outer wall and the inner wall is formed again, and after the conical portion, the outer wall and the inner wall are convex outwardly, and the diameter is made constant by gradually forming a central portion parallel to the axial direction.

According to the present invention, the plug of the disc, cone, hemispherical or funnel-shaped solid is inserted into the front and rear ends of the capsule, thereby improving the accuracy of the blank dimensions and reducing the number of defects. By attaching the stopper as described above, the flow characteristics are greatly improved when the blank is extruded, and the capsule stoppers form both ends of the extruded tube to be cut after extrusion, thereby increasing the yield of the stainless material. They consist of a conductive material, in particular soft iron or low carbon mild steel.

In addition, by inserting a stopper made of a conductor at the front and rear ends of the capsule in this way, it can be heated more easily by induction heat before extruding the blank. Because the stopper is easily heated by induction heat and transfers heat into the remainder of the blank, in particular the blank filled with metal powder, thereby facilitating rapid heating of the entire blank.

It was proved to be very advantageous to insert the above-mentioned stopper at the front end and the rear end of the capsule, and at the same time to make the outer and inner walls of the capsule swell outward to offset the shrinkage of the blank during cold compression.

By using the two methods according to the invention, the dimensions of the blank can be maintained more accurately. In particular, the dimensions of the blanks can be accurately maintained to ± 0.5%, ie up to ± 0.1 mm, which is very useful for the production of extruded products, especially extruded tubes, without defects.

According to the invention the closures can be made in the form of a lid which closes both ends of the capsule or can be firmly welded to the outer and inner walls of the capsule. In addition, a metal plate in the form of a lid may be installed between the cap and the inside to be firmly welded to the outer wall and the inner wall.

In the manufacture of a blank manufacturing capsule for extruding a metal tube according to the present invention, a stopper punched in the center of the funnel shape for the front end face of the capsule may be used, wherein the cylindrical inner wall of the central hole of the funnel stopper And the angle r between the conical outer surface is about 40 ° to 60 °, in particular about 40 ° to 50 °.

In the manufacture of the metal tube according to the present invention, at least the front end of the capsule is advantageously inserted into the annular stopper having a hole in the center, wherein the annular stopper forms a flat annular front part on the front side, and between the center hole and the outer circumference at the rear side. An annular curved surface portion forming a circular arc cross section is formed in the center, and the center of the circular arc cross section is located near the circumference where the annular front surface portion and the central hole intersect.

Another important improvement in capsules for producing blanks for use in the extrusion of high-density metal tubes according to the invention is that the outer wall of the capsule is axially through the entire outer circumferential surface, whether or not to use a capsule stopper having the structure according to the invention. Is to have the same strength. According to the invention at least the outer wall of the capsule is preferably formed of a spirally welded or extruded metal tube which is a thin wall. By forming the outer wall of the capsule as described above it provides an advantage that the extruded product, that is, the extruded tube can be obtained that is characterized in that the occurrence of bonding is small and thus the rate of defective products is significantly reduced.

Primarily, the pitch for the capsule length of the spiral joint formed by welding is calculated such that the weld joint forms approximately one complete turn. The outer wall with such a weld seam has only one weld seam at every point on the outer periphery in the axial direction and thus exhibits the same strength characteristics in the axial direction. Alternatively, it is possible to form two or more complete turns of the weld seam.

The present invention is a capsule for producing blanks, mainly for use in the extrusion of high-density metal tubes consisting of stainless steel or nickel-chromium alloys, especially heat-resistant steels for heat exchangers, for example alloys containing about 60% nickel and 20% chromium. And metal or metal alloy powders or mixtures thereof or mixtures of metal and metal alloy powders and porcelain powders in a capsule according to the invention. The powder used is usually a spherical powder having an average diameter of usually 1 mm or less. It is suitable according to the invention to use spherical powders which are granulated by spraying the desired raw material, ie the desired metal or metal alloy, in an inert gas mainly in an argon gas. At this time, the powder particles with a diameter of 1mm or more are sieved to the maximum. This is because there is a risk that argon gas will be included between powder particles larger than 1 mm in diameter. Inclusion of such argon gas may occur during atomization, ie by disturbing motion. The inclusion of argon gas can lead to the separated nature of the extruded product and will lead to indentations.

The blank preparation capsule to be used for metal tube extrusion according to the invention is filled with metal powder. Next, the powder density filled in the capsule is increased by vibration to about 60% to 71% of the theoretical density, where the vibration frequency is mainly used at a minimum of about 70 Hz, in particular 80 to 100 Hz. By vibrating at a frequency of 80 to 100 Hz, up to about 68 to 71 of theoretical density can be achieved.

After filling and vibrating the powder to increase its density, the capsule is vacuumed or filled with an inert gas and then sealed. The density of the powder is then increased to at least 80% to 93% of theoretical density by cold even compression under pressure of at least 4000 bar, roughly 4200 to 6000 bar, especially 4500 to 5000 bar.

It has been proved particularly advantageous for the capsules to be made of thin metal plates, usually about 1 to 2 mm in thickness, in particular thin metal plates of about 1.5 mm. As a material of such a capsule, low carbon mild steel having a carbon content of 0.015% or less, particularly 0.0046% or less is used to prevent the carbonization of the powder during heating and extrusion.

The capsule is uniformly compressed not only in the long axis direction but also in the radial direction by the pressure applied from all directions during cold uniform compression to form a blank. The blank thus obtained should not be irregular. This is because when extrusion, in particular during extrusion of the metal tube will cause difficulties.

Cylindrical capsules are used to produce a blank for metal tube extrusion, the outer wall of which is made of a spiral welded cylinder with a metal tube about 1.5 mm thick. A cylindrical inner wall is then inserted into the cylindrical outer wall which is fused in the longitudinal direction with a smaller diameter and the same wall thickness. An end cap is then attached to one end between the outer wall and the inner wall, so that one side of the annular space between the two metal tubes is sealed. The spherical metal powder is then charged into the annular space and compacted by vibrating a frequency of about 80 to increase the density to about 68% of theoretical density. The capsule is then evacuated and sealed on the other side with a suitable second lid. The capsule is then cold evenly compressed by applying a pressure of about 4700 bar in a liquid such as water. In this way, pressure is applied from the face to obtain a blank having a density of about 85% of the theoretical density.

In the capsule according to the present invention, it is desired to make the spiral weld joint as smooth as possible so that the properties of the steel sheet are not changed as much as possible. Therefore, the welded joint is mainly finished by rolling or polishing. Grinding the weld seam mainly by rolling may be done immediately after the end of the weld.

In the capsule for manufacturing an extruded tube, it is advantageous to make the outer wall and the inner wall a metal tube having the same strength characteristics in the axial direction along the outer circumferential surface. At this time, the inner wall can be used as a spiral weld tube or an extrusion tube. The use of extruded tubes or spiral welded tubes for inner walls is particularly preferred for producing large metal tubes. In manufacturing a relatively small metal tube, according to the present invention, it is sufficient that the outer wall of the conventional capsule is made of a metal tube having substantially the same strength characteristics in the axial direction along the outer circumferential surface.

An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, 1 denotes a capsule, which consists of an outer wall 2 and an inner wall 4. The outer wall 2 is comprised from the spiral welded tube which has length L. As shown in FIG. The weld joint 5 spirals around the outer wall 2 in which the helix forms a helix angle α to allow approximately one full turn.

Welding between a weld joint 16 used to weld and fix the lid of the capsule (not shown in FIG. 1) to the outer wall 2 and a weld joint 26 to attach the capsule under lid to the outer wall. It has proven advantageous to adjust the joint (5) to make one complete turn. The distance between the weld joints 16 (, 26) is indicated by L 'in FIG.

이때 D는 캡슐의 직경기고, n은 나선용접이음(5)의 요망선회수이다. 여기서 n=1로 하는 것이 유리하다는 것이 증명되었다. 그러나 n=2,3,4 또는 보다큰 정수를 선택하는 것이 유리할 수도 있다.This length L 'can be regarded as the effective length of the capsule. The spiral angle α of the spiral welding is determined by the following formula,

Where D is the diameter of the capsule, n is the desired number of turns of the spiral welded joint (5). It was proved to be advantageous here that n = 1. However, it may be advantageous to choose n = 2,3,4 or a larger integer.

In one experiment, the outer wall (2) and inner wall (4) of the capsule (1) consisted of a 1.5m thick steel plate with a carbon content of 0.004% or less. A lid (plug) not shown in FIG. 1 was welded by welding the weld joint 16. In order to prepare the blank, a powder containing mainly spherical particles having an average diameter of 1 mm or less, which was prepared by atomizing a desired material, ie, stainless steel, in argon gas was filled into a capsule. The powder was then vibrated at a frequency of 80 Hz to increase the density to about 68% of theoretical density. The capsules were then vacuumed and sealed with a lid. The lid was welded to the outer wall 2 of the capsule by extending the weld seam 16 of FIG. In this example, the capsule had a length of 600 mm and an outer diameter of 150 mm. The inner diameter of the inner wall 4 was about 55 mm. The inner wall 4 was made of a longitudinal weld tube having a longitudinal point joint 6. The powder was then cold-compressed under pressure of about 4700 bar and pressed to about 85% of theoretical density. The blank thus obtained was extruded into a tube as described in DE-AS 24 19 014, above.

In the embodiment shown in FIG. 2, the capsule plugs 30 and 40 are inserted into the lid 10 and the bottom 20 to form the front and rear ends of the capsule, respectively. The capsule stopper 30 is usually conical and has a central hole 32 into which the capsule inner wall 4 enters.

The circumferential surface 36 of the conical or funnel stopper 30 forms an angle r with the inner wall of the central hole 32, which is usually about 40 ° to 60 °, more advantageously about 40 ° to 50 °. °, in particular about 45 °. The capsule stopper 30 has a mainly flat cross section 34. However, its outer edge 35 is obliquely cut or rounded, and the outer edge 35 is formed next to the cylinder portion 37, which in turn is adjacent to the surface 36. The portion 39 leading from the conical surface 36 to the central hole 32 is rounded. The lid 10 made of a metal plate is formed so that its shape exactly matches the contact portion of the capsule stopper 30. In more detail, the lid 10 extends the outer edge to form a cylinder portion 17, and the portion 17 is in intimate contact between the lid 10 and the outer wall 2. The outer edge of the portion 17 is attached to the wall 2 of the capsule by a weld seam 16. The lid 10 also has a short cylinder portion 19 in the inner portion, which is in contact with the capsule inner wall 4 and is firmly welded to the capsule inner wall 4 by a welding joint 18. The lid 10 also has a rounded portion coinciding with the rounded corner portion 30 of the capsule stopper.

At the rear end of the capsule 1 is attached a flat disc shaped capsule cap 40 having a central hole 42 and an outwardly directed cross section 44. This disc-shaped capsule stopper 40 is also made with rounded corners 45 and has an outer cylinder portion 47. Lower lid 20 has a shape corresponding to the shape of the capsule stopper 40 also has an outer cylinder portion 27 and the inner cylinder portion 29. The lower lid 20 is firmly welded to the capsule outer wall 2 and the inner wall 4 by welding joints 26 and 28, respectively. The capsule stopper 30, 40 is mainly made of soft iron or low carbon mild steel.

3 shows another embodiment of the capsule, in which the capsule plug 130 inserted into the front end of the capsule is a curved portion 136, a flat cross-section 134 and an arc-shaped arc cross section. It has a central hole 132. The center point of the curved portion 136 having the arcuate section is located on the circumference near the intersection where the flat cross section 134 and the central hole 132 meet, ie near the front boundary of the central hole 132. The circumference is indicated by two x marks 138 in FIG. The curved portion 136 is a capsule stopper 130 made of soft iron or similar metal during extrusion of the blank is cap 110, welding joints 116, 1118 and outer wall 102 and inner wall 104 It is made of stainless steel by forming the front end of the extruded tube together with the adjacent part of and it is cut after the extrusion or automatically falls off when the connection with the extruded extruded tube made by powder filling of capsule is not strong enough. Have As the boundary line 136 of the capsule plug 130 forms a curved surface, the interface between the front end of the extruded tube to be separated into the waste and the extruded tube made of expensive stainless steel is clearly distinguished. It is vertical.

In addition, the lid 110 is also in contact with the cylinder portion 117 and the inner wall 104 welded to the capsule outer wall 102 by welding to the welding joint 116 and firmly connected to the inner wall 104 by connecting to the welding joint 118. It has the inner cylinder part 119 welded. A portion 139 which transitions from the wall of the central hole 132 to the annular curved portion 136 is made round. It is also advantageous to weld the capsule plug 30, 40 directly to the outer wall 2 and the inner wall 4. In this case, the upper lid 10 and the lower lid 20 can be omitted. In a similar manner, the plug shown in FIG. 3 can also be welded directly to the outer wall 102 and the inner wall 104. When the metal plate is used as the upper lid 10 and the lower lid 20, it will be beneficial to attach these lids to the caps 30, 40 and 130 by spot welding. However, in most cases, it is sufficient to fix the capsule stoppers 30, 40, 130 to the flange ends 15, 25, 115 of the outer walls 2, 110.

The plug inserted into the front end of the capsule during extrusion causes a kind of tunnel effect if it is made of combustible metal material, ie combustible iron, soft iron, low alloy carbon steel or cast iron. If the capsule plug of the front end portion can be more easily dissolved than the metal powder filled in the blank, the pressure inside the extrusion container of the extrusion press for extruding the blank can be reduced. Once the dissolution occurs during extrusion, even if the yield point of the powder filler is higher than the yield point of the flammable material of the cap, the dissolution phenomenon is propagated to the powder filler. In this way, a tunnel effect is obtained.

In FIG. 3, the outer wall 102 has an inflation portion 103 to counteract the shrinkage that occurs during cold even compression. As shown in FIG. 3, the capsule plug 140 may also be made of a curved portion 146 having an arcuate cross section in the lower lid 120. Near the central hole 142, the curved portion 146 passes through the rounded corner portion 149 to the wall of the central hole 142. The capsule stopper 140 is in contact with the cylinder portion 127 and the outer side of the lower lid 120 in the cylinder portion 147. The cylinder portion 127 is welded to the cylinder portion 102 of the outer wall 102 in connection with the weld joint 126. The lid 120 is welded to the inner wall 104 by contacting the inner wall 104 along the cylinder portion 120 to connect the weld joint 128. The outer end portion 144 of the capsule stopper 140 rounds the outer edge 145 so that the lower flange end 125 of the outer wall 102 firmly fixes the capsule stopper 140. The size of the inflation portion 103 of the capsule is made so that after cold uniform compression the inner surface of the outer wall 10 contracts up to the line 170 in the desired cylinder shape. Accordingly, the cylinder portions 156, 166 of the outer wall 102 are also contracted by rolling so that they are also in line with the line 170.

In order to prevent wrinkles and to accurately center the blank, it is advantageous to limit the diameter change of the outer wall 102 to the portion of the stopper 130 and 140 according to the invention. The central portion 150 of the outer wall 102 between the capsule plugs 130 and 140 has a constant diameter. According to the present invention, the cylinder portions 156, 166 are formed toward the middle of the capsule, and then connected to the recessed portions 157, 167, which are concave outwardly, from the recessed portions 157, 167 to the truncated cone portion. It is proved to be particularly advantageous to form outwardly convex portions 159 and 169 after forming 158 and 168, from which the central portion 150 of the cylinder is parallel to the axis. It became. It is important that the concave recesses 157 and 167 are symmetrical with respect to the cross-sections 136 and 146 of the capsule stopper, and the line 170 becomes the line of symmetry and the inclination angle β of the outer wall is the adjacent capsule stopper. It was made small in proportion to the shrinkage ratio with respect to the inclination angle δ of.

4 shows another embodiment similar to the embodiment of FIG. 3, wherein all identical or similar parts are denoted by reference numerals of 200 units. Here, the main difference is that the capsule cap 230, 240 is formed by the pointed portion (239), (249), respectively, the upper lid 210 and the lower lid 220 formed in the same way as the capsule cap to the inner wall 203 It is in full contact to form an obtuse angle (a, a '). This shape proved to be advantageous for correct centering of the blank. In the embodiment shown in FIG. 4, the inner wall 204 does not need to form an expanded portion, while in Embodiment 5 it may be advantageous to expand the inner wall slightly outward. According to the invention it is advantageous to form an expansion in the outer wall and the inner wall of any type of capsule plug.

5 is another embodiment similar to Example 4, wherein all the same or similar parts are denoted by reference numerals of 300 units. An important difference here is that the capsule stoppers 330 and 340 have pointed portions 339 and 349 and do not have a metal plate lid. Starting from the first concave portions 157 and 367 from the respective cylinder portions 156 and 366, the inflation portion 303 continues to increase gradually in the axial direction, starting from the first concave portions 157 and 367. Gradually increases against. The inclination angle of the outer wall 302 then becomes constant as it passes through the conical portions 358 and 368 and the capsule intermediate portion gradually parallel to the axis past the portions 359 and 369 where the outer wall 302 is outwardly convex. Proceed to 350. The portion where the cross-sectional diameter of the outer wall 302 changes in this way forms the change portions 355 and 365 located within the range of the capsule plugs 330 and 340 portions. The cross-sections 336 and 346 of the capsule plugs 330 and 340 are approximately symmetrical with respect to the outer wall within the range of the change portions 355 and 365, the symmetry of which forms the cylinder wall of the desired blank. It is symmetrical with respect to the line 370 but is located at a radially extending distance. Considering the change in the cross section with the reduction of the radius, the extent of extension coincides with the ratio of the reduction in the capsule diameter of the outer and inner diameters of the blank.

The capsule plugs 330 and 340 are welded to the outer wall and the inner wall by connecting the welding joints 316, 318, 326 and 328. The cylinder portions 337, 347 of the capsule plugs 330, 340 coincide with the cylinder portions 137, 147, 237, 247 of FIGS. 3 and 4.

EXAMPLE

Rolling or rolling both ends of a welded 600mm deep metal tube to be used as an outer wall of a capsule with an outer diameter of 154mm and a wall thickness of 1.5mm to produce a blank capsule of 144mm in diameter to extrude stainless steel pipe with an outer diameter of 50mm and a pipe thickness of 5mm. Pinching formed a cylinder portion with an outer diameter of 144 mm, which coincided with portions 156, 166, 256, 266, 356, and 366 of FIGS. 3 and 4, followed by the change portion 155. 165, 255, 265, and 355, 365 are formed. The end of the outer wall was then ground flat. At one end, a lower lid made of a metal plate similar to the metal plate lid shown in FIG. 3 is welded and sealed to the outer wall and the inner wall. At this time, the inner wall is a metal tube welded with a wall thickness of 1.5 mm, an inner diameter of 40 mm, and a length of 590 mm.

Then, an annular or funnel shaped capsule stopper similar to the capsule stopper 1 40 made of low alloy carbon steel containing about 0.004% of carbon was inserted from the front end of the outer wall to the lower lid and fixed by spot welding. The capsule is placed on a plate and filled with metal powder, and then vibrated at 80 Hz to increase the density to about 60% of the theoretical density and simultaneously press the funnel-shaped metal plate 110 to serve as a lid as shown in FIG. It was inserted between the outer wall and the inner wall from the top while applying. Then, the metal plate lid was firmly welded to the inner wall and the outer wall by connecting to the weld joints 116 and 118. A cyclic or funnel capsule stopper 130 of low alloy carbon steel containing about 0.004% carbon was then inserted from above. This annular stopper was spot welded to a funnel lid or to the inner and outer walls.

The capsules were cold evenly compressed under water at 4700 bar to increase the density to 88% of theoretical density. At this time, the blank was shrunk to have the same diameter as the contracted cylinder portion at both ends, that is, the outer diameter of 144 mm. This 144 mm diameter coincided with the inner diameter in the extrusion press vessel at the same time. Thus, complete centering was guaranteed. The blanks were also completely straight and immediately extruded after induction heating up to 1200 degrees Celsius to form the desired seamless stainless steel tube, with no additional cutting. The front end of the extruded tube made of low alloy carbon steel was cut out. The stainless part was not cut at all. Since the capsule plug is conical, a vertical interface was formed between the extruded plug and the stainless steel against the axis of the extrusion tube. The extruded tube portion made of stainless material had a flawless surface. Therefore, material loss is reduced to a minimum. In order to be able to easily separate between the front end of the extruded tube made of low alloy carbon steel and the desired seamless stainless steel extruded tube, a glass film layer may be formed on the surface of the front plug facing the entire metal powder layer 308 according to the present invention. Can be. For this purpose, it is appropriate to heat the front cap 330 and spray the glass powder onto the surface 336. At this time, the temperature of the cap is heated so that the glass powder can melt. This intermediate glass film layer facilitates the separation of low-alloy carbon steel and stainless steel so that the two steels are completely separated from each other and do not mix with each other. In a similar manner, a glass film layer is formed on the surface adjacent to the entire metal powder layer 308 of the capsule cap 340 at the bottom to facilitate the separation of the stainless steel and the low alloy carbon steel.

Capsule caps 30, 40, 130, 140, 230, 240 (330, 340) may also be pressed into powdered metal materials. For this purpose, for example, soft iron may be underwater or low carbon steel. The metal powder prepared by atomizing it into water can be used, which can be cold-compressed to form the desired stopper and then sintered. The compression may be made at a higher or at least the same pressure, mainly for cold even compression applied to the capsules described above, followed by high temperature sintering to obtain a high density product. In this case, it is also possible to obtain a sealing effect by forming an outer glass layer on the front face 34, 134, 234, 334 and the rear face 44, 144, 244, 344 and the surrounding surface. have.

The embodiment shown in FIG. 6 is almost identical to the embodiment shown in FIG. Only capsule stoppers have a modified form. The front plug 330 'is composed of two rings 380 and 381 attached to each other at several spots. Instead of two rings 380 and 381, of course, three or more rings may be formed, the appearance of which is curved in FIG. 5 and arc cross section 236 in FIG. It forms a shape close to the ideal shape of the front closure device is determined by the arc cross section (136). In Example 6, the stopper 340 'at the lower end of the capsule is an annular disc. Again, if desired, multiple rings can be superimposed while increasing or decreasing the outer or inner diameter stepwise to approximate the ideal shape, i.e., to approach the shape 346 shown in FIG.

Claims (1)

Capsules for making blanks (1) (101) (201) (301) to be used for extruding high-density metal tubes, in particular metal tubes of stainless steel or nickel-chromium alloy, the capsules (1) (101) (201) (301) Is composed of a thin cylindrical outer wall (2) 102 (202) 302 and an inner wall (4) (104) 204 (3 04), and has an empty space (8) having an annular cross section between the outer wall and the inner wall ( 108) (208) 308 to form a metal powder or metal alloy powder or a mixture thereof or a mixture of the metal and metal powder and porcelain powder in the space, and both ends of the capsule cap 30 (40) (130) (140) (230) (240) (330) (340) (330 ') (340'), and at least to compensate for the shrinkage that occurs during cold uniform compression of the outer wall of the capsule. Inflate outwards to form inflation (103) (203) (303) which, after contraction, return to the desired capsule size again. Capsules 30, 40, 130, 140, 230, 240, 330, 340, 330 'and 340' to be inserted into the back and back ends are disc, conical, hemispherical or funnel-shaped. And a central hole (32) (4 2) (132) (142) (232) (242 (332) 342) into which the inner wall of the capsule is to be inserted.

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