JP2008213001A - Method of extruding tubular product and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent misalignment of the axial center of a billet which is held with a die and extruding stem when inserting a mandrel into the billet. <P>SOLUTION: This method is an extruding method of a tubular product by which the billet 26 is extruded by moving the extruding stem 30 in the extruding direction after inserting the billet 26, which is held between the die 34 attached to the end platen 22 of an extruding shaft and the extruding stem 30 opposing to this die 34, into a container 20. The billet 26 is held between the extruding stem 30 and the die 34 at a preset holding pressure by moving the extruding stem 30 to the side of the die, and the holding pressure is maintained by eliminating the reaction force of the holding pressure which is produced by inserting the mandrel 38 into the held billet 26 from the inside of the extruding stem 30 by retreating the extruding stem 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for extruding a tubular product, and more particularly to a method and apparatus for extruding a tubular product in which a mandrel is inserted into a billet to extrude a tubular product such as an aluminum alloy.

  FIG. 4 shows an extrusion method for producing a conventional tubular product such as an aluminum alloy. For example, when an indirect extrusion press is used, the container 20 is first moved to the end platen 22 side as shown in the figure, and the die stem 24 is inserted into the container 20 to secure a supply space for the billet 26. In this state, the billet loader 28 is traversed until the axis of the billet 26 coincides with the axis of the container 20 (FIG. 4 (1)).

  Next, the length of the billet 26 inserted into the container 20 is automatically measured and stored in a control device (not shown). The movement distance of the extrusion stem 30 is measured by the linear scale 32, and the extrusion stem 30 is stopped when the billet 26 length stored in the control device is reached (FIG. 4 (2)).

  The billet 26 is sandwiched between the die 34 surface attached to one end of the die stem 24 and the extrusion stem 30 via the dummy block 36, and the container 20 is moved in the direction of the extrusion stem 30 (the direction opposite to the extrusion direction) to move the billet. 26 is inserted into the container 20. At this time, since the outer diameter of the billet is set to be slightly smaller than the inner diameter of the container, the billet 26 sandwiched between the tip end surface of the die stem 24 and the tip end surface of the extrusion stem 30 is in a floating state in the container 20. (FIG. 4 (3)).

The main ram that drives the extrusion stem 30 is provided with a piercer cylinder that drives the mandrel 38. As a result, the tip of the mandrel 38 attached on the extrusion shaft is inserted from one end of the billet 26 and moved to the opening of the die 34 and fixed at the set position of the mandrel 38. Thereafter, the extrusion stem 30 is advanced to press the billet 26 against the die 34, and the tubular product 40 is extruded from the opening. (FIG. 4 (4)).
JP 59-42118 A

  The billet of the conventional extrusion method uses a hollow billet having a hole (hollow) in the center in the cold, and there are cases where the billet hole diameter does not match the mandrel outer diameter. When the diameter of the hole provided in the center of the billet is slightly smaller than the outer diameter of the mandrel, according to the conventional extrusion method, when inserting the mandrel into the hole provided in the center of the billet, The billet deforms by expanding in the direction. For this reason, when the mandrel is inserted into the billet, the billet is deformed and the pressure oil in the main ram is compressed by the reaction force from the billet (the direction opposite to the extrusion direction), causing the extrusion stem to retreat, and the die surface of the die stem and the dummy There was a problem that the billet sandwiched between the extrusion stems through the block dropped in the container.

  The billet extrusion shaft is displaced due to the deformation of the billet, or the mandrel is inserted into a hole (hollow) provided in the center of the billet while the billet is dropped, and then the extrusion stem is advanced and extruded. In this case, there has been a problem that the tubular product is bent and uneven in thickness because the container and the billet are misaligned.

  Therefore, in order to solve the above-mentioned problems of the prior art, the present invention provides an extrusion method and an extrusion apparatus for a tubular product that prevent misalignment of the billet shaft center held by a die and an extrusion stem when a mandrel is inserted into the billet. It is intended to provide.

  In order to solve the above-mentioned problems, the tubular product extrusion method of the present invention inserts a billet sandwiched on an extrusion shaft between a die attached to an end platen and an extrusion stem facing the die into the container. And then, extruding the billet by moving the extruding stem in the extruding direction, the extruding stem being moved to the die side to move the billet between the extruding stem and the die. The reaction force of the billet that is generated by inserting the mandrel from the inside of the extrusion stem into the sandwiched billet by clamping with the clamping pressure set in step 1 is retracted to eliminate the reaction force. The holding pressure is maintained.

  The tubular product extruding method of the present invention includes inserting a billet sandwiched on an extruding shaft between a die attached to an end platen and an extruding stem facing the die into the container, and then inserting the extruding stem into the container. A method for extruding a tubular product that moves in an extrusion direction to extrude the billet, wherein the extruding stem is moved to the die side and the billet is set at a holding pressure set between the extruding stem and the die. The mandrel is inserted into the billet from the inside of the extrusion stem while being pinched and maintaining the holding position of the extrusion stem.

  In this case, the clamping pressure may be maintained until the insertion is completed after the mandrel is inserted into the billet.

  The tubular product extrusion apparatus according to the present invention includes a die stem attached to an end platen, an extrusion stem facing the die stem, and a mandrel attached to the inside of the extrusion stem, and the extrusion between the die stem and the extrusion stem. An extrusion apparatus for a tubular product that inserts a billet held on a shaft into a container and moves the extrusion stem in an extrusion direction to extrude the billet, wherein a decompression means is provided in a main cylinder that supports the mandrel. The pressure reducing means sets a holding pressure of the billet that is held between the extrusion stem and the die stem, and relieves pressure oil due to a reaction force of the billet generated by inserting the mandrel into the billet. Then, the holding pressure is maintained.

  The tubular product extrusion apparatus according to the present invention includes a die stem attached to an end platen, an extrusion stem facing the die stem, and a mandrel attached to the inside of the extrusion stem, and the extrusion between the die stem and the extrusion stem. An extrusion apparatus for a tubular product that inserts a billet held on a shaft into a container and moves the extrusion stem in an extrusion direction to extrude the billet, wherein a decompression means is provided in a main cylinder that supports the mandrel. The pressure reducing means sets a clamping pressure of the billet that is clamped between the extrusion stem and the die stem, and maintains the clamping position of the extrusion stem while the mandrel is inserted into the billet. It is characterized by that.

  The tubular product extrusion apparatus of the present invention includes a die attached to an end platen, an extrusion stem opposed to the die, and a mandrel attached to the inside of the extrusion stem, and the space between the die and the extrusion stem. An extrusion apparatus for a tubular product that inserts a billet held on an extrusion shaft into a container and moves the extrusion stem in an extrusion direction to extrude the billet, wherein the main cylinder supporting the mandrel has a pressure reducing means. And the pressure reducing means sets a clamping pressure of the billet that is clamped between the extrusion stem and the die, and pressure oil due to a reaction force of the billet generated by inserting the mandrel into the billet. It is characterized by relieving and maintaining the holding pressure.

The tubular product extrusion apparatus of the present invention comprises a die attached to an end platen, an extrusion stem facing the die, and a mandrel attached to the inside of the extrusion stem, and the extrusion between the die and the extrusion stem. An extrusion apparatus for a tubular product that inserts a billet held on a shaft into a container and moves the extrusion stem in an extrusion direction to extrude the billet, wherein a decompression means is provided in a main cylinder that supports the mandrel. The pressure reducing means sets a holding pressure of the billet that is held between the extrusion stem and the die, and maintains the holding position of the extrusion stem while the mandrel is inserted into the billet. It is characterized by that.
In this case, the billet may be a hollow billet.

  According to the present invention having the above-described configuration, the billet having the shaft center disposed on the extrusion shaft is nipped between the die and the extrusion stem with a set nipping pressure. That is, even if the billet is deformed by the insertion of the mandrel and the extrusion stem is pushed back, the billet does not fall in the container because the extrusion stem is retracted to eliminate the reaction force and maintain the holding pressure. Therefore, since the billet shaft center is held on the extrusion shaft, even when using a double stem type indirect double acting extrusion press or using a front loading type direct double acting extrusion press, there is little bending and uneven thickness. A tubular product with improved accuracy can be obtained.

  When inserting the mandrel into the hollow billet, the hollow billet is held with the holding pressure set between the extrusion stem and the die, and the mandrel is hollowed from the inside of the extrusion stem while maintaining the holding position of the extrusion stem. Inserted into billet. At this time, the reaction force due to the deformation of the hollow billet is smaller than the set holding pressure, and as a result, the position of the extrusion stem holding the hollow billet is controlled to be held. Then, the hollow billet is extruded as a rod material from the die side without retreating to the extrusion stem side. Therefore, the billet held between the extrusion stem and the die does not fall, and it is possible to prevent the displacement of the billet extrusion shaft. In addition, since the billet shaft center is held on the extrusion shaft by the position hold control, even when using a double stem type indirect double acting extrusion press or using a front loading type direct double acting extrusion press, it is bent. Therefore, it is possible to obtain a tubular product with less uneven thickness accuracy.

  The clamping pressure for clamping the billet between the die and the extrusion stem is configured to be maintained until the insertion is completed after the mandrel is inserted into the billet, and the clamping pressure is the billet material or type, diameter and length, It is set by the size of the hole (hollow) provided in the center, the extrusion ratio, and the like. For this reason, it is possible to obtain a tubular product that is less bent and is improved in uneven thickness accuracy without being affected by various extrusion conditions, and it is possible to improve the operation rate and product yield of the extrusion equipment.

  Since the billet uses a hollow billet that has been drilled in the center, a reaction force is unlikely to occur when the mandrel is inserted, and the billet extrusion shaft is not displaced. Even aluminum alloys that are hard and difficult to extrude, such as 2000 series alloys and 7000 series alloys, can be deformed from the center of the billet evenly, so that a tubular product with less uneven thickness can be obtained.

  A preferred embodiment of a method and apparatus for extruding a tubular product according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic structural view showing a first embodiment of an apparatus for extruding a tubular product according to the present invention. The same components as those in FIG. 4 will be described with the same reference numerals. As shown in the figure, the tubular product extrusion apparatus 10 of the present invention is mainly composed of a die stem 24, a container 20, a billet loader 28, an extrusion stem 30, and a driving means 60.

  One end of the die stem 24 is supported by the end platen 22, and a die 34 is attached to the other end. The container 20 mainly includes a container holder 20a, a container main body 20b, and a container liner 20c. The container body 20b has a through-hole through which the billet 26 is inserted at the center, and is fixed to the container holder 20a via a container liner 20c. The container 20 is configured to move forward or backward along the extrusion axis direction by a cylinder (not shown).

  The billet loader 28 places a cylindrical billet 26, which is an extruded material having a hole 21 processed at the center, and moves forward or backward along the direction intersecting the extrusion axis. It is configured to be concentric with the 20 axis.

  The push-out stem 30 is fitted with a closing plate 50 at the tip, and is attached to a main ram 54 serving as a main body of a piercer cylinder built in a main cylinder 52 as a driving device via a cross head 56. A mandrel 38 that is driven by the piercer piston 58 and is detachably disposed in the hole 42 at the center of the billet 26 is provided at the center of the extrusion stem 30.

  The hydraulic drive unit serving as the drive unit 60 mainly includes a hydraulic source 62, a first electromagnetic valve 64, a second electromagnetic valve 66, a pressure reducing valve 68 with a proportional electromagnetic relief valve serving as a pressure reducing unit, and a check valve 70. Has been. The hydraulic pressure source 62 is connected to the first electromagnetic valve 64. The first electromagnetic valve 64 is connected to the rod side oil chamber 76 via the oil passage 79a and the head side oil chamber 74 of the piercer piston 58 and the oil passage 79b. On the other hand, the pressure reducing valve 68 with a proportional electromagnetic relief valve is connected to a cylinder oil chamber 78 of the main cylinder 52 via an oil passage 79c. The second electromagnetic valve 66 is disposed between the oil passage 79d and the oil passage 79c branched in the middle of the oil passage 79a. A check valve 70 is disposed between the pressure reducing valve 68 with a proportional electromagnetic relief valve and the second electromagnetic valve 66 in the oil passage 79d. The check valve 70 is configured to allow the pressure oil to pass through only one from the second electromagnetic valve 66 to the pressure reducing valve 68 with a proportional electromagnetic relief valve. The drive means 60 supplies pressure oil to the piercer cylinder constituted by the piercer piston 58 housed in the main cylinder 52 and the main ram 54 described above.

  The operation of the tubular product extrusion apparatus 10 according to the first embodiment having the above-described configuration will be described below. When extruding a tubular product, first, the container 20 is moved to the end platen 22 side, and the die stem 24 is inserted into the container 20 to secure a supply space for the billet 26. In this state, the billet 26 has an axis centered on the container. The billet loader 28 is moved so as to coincide with the 20 axis. Next, the extrusion stem 30 is moved in the extrusion direction, the billet 26 is sandwiched between the die 34 surface at the tip of the die stem 24 and the extrusion stem 30 via the closing plate 50, and the container 20 is moved in the direction of the extrusion stem 30. The billet 26 is inserted into the container 20 to complete the preparation for extrusion. In this state, no external force is applied to the billet 26 and the billet 26 does not fall.

  After completion of the extrusion preparation, the solenoid a (Sola) of the first solenoid valve 64 is excited to supply the pressure oil from the hydraulic source 62 to the head side oil chamber 74 of the piercer piston 58 via the oil passage 79a. The supplied pressure oil moves the mandrel 38 forward along the extrusion direction, and inserts the mandrel 38 having the mandrel tip 39 into the hole 42 at the center of the billet 26.

  Further, by exciting the solenoid a (Sola) of the first solenoid valve 64 and the solenoid (Solb) of the second solenoid valve 66, the pressure oil from the hydraulic source 62 is reversed through the oil passage 79d and the oil passage 79c. It is also supplied to the cylinder oil chamber 78 of the main cylinder 52 through the stop valve 70 and the pressure reducing valve 68 with a proportional electromagnetic relief valve. The pressure oil supplied into the main cylinder 52 is depressurized by a pressure reducing valve 68 with a proportional electromagnetic relief valve, and the billet 26 is sandwiched between the die stem 24 and the extrusion stem 30 via the die 34 and the closing plate 50. The clamping pressure is set so as not to be deformed in the direction crossing the axis and contact with the container 20. At this time, the holding pressure is set according to the material or type of the billet, the diameter and length, the size of the hole (hollow) provided in the center, the extrusion ratio, and the like.

  FIG. 3 is an explanatory diagram of the gripping force of the extrusion stem and the force for pushing back the extrusion stem when the mandrel 38 is inserted into the center hole 42 of the billet 26. Since the hole 42 machined in the center of the billet 26 is machined slightly smaller than the outer diameter of the mandrel 38, the billet 26 whose tip is regulated by the die 34 as the mandrel 38 is inserted into the billet 26 is The central hole 42 is enlarged in diameter and deformed in the axial direction. That is, the deformation in the axial direction causes a billet reaction force in the direction opposite to the extrusion direction. Therefore, it tries to push back the extrusion stem 30 in the backward direction. Then, the reaction force of the billet acts on the pressure oil supplied to the head side oil chamber 74 of the piercer piston 58 behind the extrusion stem 30 to move the main ram 54 in the backward direction.

  Here, when the clamping force f1 of the billet 26 by the extrusion stem 30 is set to be larger than the force f2 by which the billet 26 expands in the extrusion direction and the extrusion stem 30 is pushed back, the billet 26 has a large diameter direction (direction intersecting the extrusion axis). Since the axis changes due to deformation, the wall thickness of the tubular product varies. Therefore, it is preferable that the extrusion stem 30 is retracted in the axial direction while holding the billet 26 with the set clamping pressure.

  Accordingly, the pressure oil pressurized in the cylinder oil chamber 78 of the main cylinder 52 is relieved (returned to the tank) from the pressure reducing valve 68 with a proportional electromagnetic relief valve, and the extrusion stem 30 is maintained while maintaining the set nipping pressure. Is pushed back in the direction opposite to the extrusion direction. As described above, by the pressure reducing action of the pressure reducing valve 68 with the proportional electromagnetic relief valve, the pressure oil is supplied and the inside of the cylinder oil chamber 78 is maintained at the set clamping pressure while the mandrel 38 is inserted into the billet 26. it can. For this reason, when the mandrel 38 is inserted into the hole 42 (hollow) provided in the center of the billet 26, the billet 26 held by the extrusion stem 30 through the die surface of the die stem 24 and the closing plate 50 may fall. Absent.

  In addition, since the reaction force for pushing back the extrusion stem 30 changes with the insertion length of the mandrel 38 into the billet 26, the insertion length of the mandrel 38 and the load pressure of the mandrel 38 are measured without making the clamping pressure constant. The setting may be such that the clamping pressure is changed based on the measured data.

  On the other hand, even if the mandrel 38 is inserted into the billet 26, there is almost no deformation in the axial direction. For example, a hollow billet in which the outer diameter of the mandrel 38 and the diameter of the hole 42 at the center of the billet 26 are set to substantially the same diameter is used. In some cases, the position of the extrusion stem 30 holding the billet 26 is maintained. In the position holding control of the extrusion stem 30, the pressure oil is supplied into the main cylinder 52 by the pressure reducing function of the pressure reducing valve 68 with the relief valve and then held at a constant pressure. When the mandrel is inserted into the hollow billet, the reaction force due to the deformation of the hollow billet is smaller than the set holding pressure, and as a result, the position of the extrusion stem holding the hollow billet is controlled. Then, the hollow billet is extruded as a rod material from the die side without retreating to the extrusion stem side. For this reason, the billet 26 held between the extrusion stem 30 and the die 34 does not fall, and it is possible to prevent the displacement of the billet extrusion shaft.

  Then, the mandrel tip 39, which is the tip of the mandrel 38, drives and moves the piercer piston 58 to a predetermined position set through the die 34, and the mandrel tip 39 is set. Next, the main ram 54 is driven to move the extrusion stem 30 forward along with the container, and the billet 26 is pressed against the die 34 to extrude the tubular product.

  After the end of the tubular product extrusion process, the solenoid b (Solb) of the first solenoid valve 64 is excited. The first solenoid valve 64 supplies pressure oil from the hydraulic source 62 to the rod side oil chamber 76 of the piercer piston 58 through the oil passage 79b, and pressure oil in the head side oil chamber 74 of the piercer piston 58 passes through the oil passage 79a. The first electromagnetic valve 64 is returned to the tank. Further, the cylinder oil chamber 78 is decompressed by the pressure reducing action of the pressure reducing valve 68 with the relief valve. As a result, the mandrel 38 moves backward.

  The tubular product extrusion method and the extrusion apparatus 10 of the present invention are based on the application to the double stem type indirect double acting extrusion press and the front loading type direct double acting extrusion press described above. The present invention can also be applied to a conventional direct and indirect double acting double action extrusion press.

  FIG. 2 is a schematic diagram showing a second embodiment of the tubular product extrusion apparatus. The same configuration as that of FIG. 1 has the same operational effects, and the same reference numerals are given and detailed description thereof is omitted. A configuration different from the first embodiment is shown below. As shown in the drawing, in the tubular product extrusion apparatus of the present invention, a die 34 a is fitted and fixed to the end platen 22. The extrusion stem 30 has a dummy block 80 attached to the tip. The outer diameter of the dummy block 80 is set so that it can be inserted into the through hole of the container 20.

  The operation of the extrusion apparatus 10A according to the second embodiment having the above configuration will be described below. When extruding a tubular product, the container 20 is first retracted toward the extrusion stem 30 to secure a supply space for the billet 26 between the die 34a and the extrusion stem 30. In this state, the axis of the billet 26 is the container. The billet loader 28 is moved so as to coincide with the 20 axis. Next, the container 20 is advanced in the extrusion direction together with the extrusion stem 30. The billet 26 is sandwiched between the tip end surface of the die 34 a and the extrusion stem 30 via the dummy block 80. Next, the billet loader 28 is retracted from the axial center, and the die 34a and the extrusion stem 30 hold the billet 26, the container 20 is advanced in the direction of the die 34a, and the billet 26 is inserted into the container 20 to prepare for extrusion. Complete. In this state, no external force is applied to the billet 26 and the billet 26 does not fall.

  After completion of the extrusion preparation, the step of inserting the mandrel into the billet is performed in the same manner as in the first embodiment.

  In the extrusion of the tubular product, the mandrel tip 39, which is the tip of the mandrel 38, is moved by driving the piercer piston 58 to a predetermined position set through the die 34a, and after setting the mandrel tip 39, the main ram 54 is moved. The extrusion stem 30 is driven to move forward along the through hole of the container together with the dummy block 80, and the billet 26 is pressed against the die 34a to extrude the tubular product.

  As explained above, when the center of the billet whose hole is processed in the center is sandwiched between the die and the extrusion stem at the same position as the axis of the container, and when the mandrel is inserted into the billet and inserted into the billet, The extrusion stem is retracted according to the reaction force due to the deformation of the billet. Further, when the mandrel was inserted into the billet, the extrusion stem was held in position. Thereby, a container and a billet can be ensured on the same axial center, without a billet falling. Therefore, in the pressurizing process of the extrusion stem after the mandrel is inserted into the billet, the billet is deformed symmetrically, so that the material flow becomes more uniform, so that the roundness accuracy and the thickness deviation accuracy of the tubular product are improved. Can do.

  Moreover, even if it is an aluminum alloy which is difficult to extrude, for example, a 2000 series alloy or a 7000 series alloy, the clamping pressure can be adjusted according to the load pressure of the mandrel, and a tubular product with less uneven thickness and excellent roundness accuracy can be obtained. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a structure schematic which shows 1st Embodiment of the extrusion apparatus of a tubular product. It is the structure schematic which shows 2nd Embodiment of the extrusion apparatus of a tubular product. It is explanatory drawing of the force which is going to push back a holding | grip force of an extrusion stem, and an extrusion stem. It is explanatory drawing of the extrusion method which obtains the conventional tubular product.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ......... Extruder of tubular product, 20 ......... Container, 22 ......... End platen, 24 ......... Die stem, 26 ......... Billette, 28 ......... Billette loader, 30 ......... Extrusion stem, 32 ......... Linear scale, 34 ......... Dies, 36 ......... Dummy block, 38 ......... Mandrel, 39 ...... Mandrel tip, 40 ......... Tubular product, 42 ......... Hole, 50 ......... Closed Plate 52 ......... Main cylinder 54 ......... Main ram 56 ......... Cross head 58 ... Piercer piston 60 ... Drive means 62 ... Hydraulic power source 64 ... First electromagnetic Valve, 66 ......... Second solenoid valve, 68 ......... Pressure reducing valve with electromagnetic relief valve, 70 ......... Check valve, 74 ......... Head side oil chamber, 76 ......... Rod side oil chamber, 78 ……… Cylinder oil chamber, 79 ……… Oil passage, 80 ...... dummy block.

Claims (8)

After inserting the billet held on the extrusion shaft between the die attached to the end platen and the extrusion stem facing the die into the container, the extrusion stem is moved in the extrusion direction to extrude the billet. A method for extruding a tubular product, comprising:
The extruding stem is moved to the die side, and the billet is held with a holding pressure set between the extruding stem and the die,
With respect to the reaction force of the billet generated by inserting a mandrel from the inside of the extrusion stem into the sandwiched billet, the extrusion stem is retracted to cancel the reaction force and maintain the holding pressure. Extrusion method for tubular products. After inserting the billet sandwiched on the extrusion shaft between the die attached to the end platen and the extrusion stem facing the die into the container, the extrusion stem is moved in the extrusion direction to extrude the billet. A method for extruding a tubular product, comprising:
The extruding stem is moved to the die side, and the billet is held with a holding pressure set between the extruding stem and the die,
A method for extruding a tubular product, wherein a mandrel is inserted into the billet from the inside of the extrusion stem while maintaining the holding position of the extrusion stem.   The method for extruding a tubular product according to claim 1 or 2, wherein the clamping pressure is maintained until the insertion is completed after the mandrel is inserted into the billet. A die stem attached to the end platen, an extrusion stem facing the die stem, and a mandrel attached to the inside of the extrusion stem, and a billet sandwiched on an extrusion shaft between the die stem and the extrusion stem inside the container An extruding device for a tubular product, which is inserted through the extruding stem and moves the extruding stem in the extruding direction to extrude the billet,
The main cylinder that supports the mandrel is provided with pressure reducing means, and the pressure reducing means sets a holding pressure of the billet to be held between the extrusion stem and the die stem, and inserts the mandrel into the billet. An apparatus for extruding tubular products, wherein pressure oil generated by a reaction force of the billet is relieved to maintain the holding pressure. A die stem attached to the end platen, an extrusion stem facing the die stem, and a mandrel attached to the inside of the extrusion stem, and a billet sandwiched on an extrusion shaft between the die stem and the extrusion stem inside the container An extruding device for a tubular product, which is inserted through the extruding stem and moves the extruding stem in the extruding direction to extrude the billet,
The main cylinder that supports the mandrel is provided with pressure reducing means, and the pressure reducing means sets a holding pressure of the billet to be held between the extrusion stem and the die stem, and while the mandrel is inserted into the billet. An apparatus for extruding a tubular product, characterized in that the holding position of the extrusion stem is maintained. A die attached to an end platen, an extrusion stem facing the die, and a mandrel attached to the inside of the extrusion stem, and a billet sandwiched on an extrusion shaft between the die and the extrusion stem inside the container An extruding device for a tubular product, which is inserted through the extruding stem and moves the extruding stem in the extruding direction to extrude the billet,
The main cylinder that supports the mandrel is provided with pressure reducing means, and the pressure reducing means sets a holding pressure of the billet to be held between the extrusion stem and the die, and inserts the mandrel into the billet. An apparatus for extruding tubular products, wherein pressure oil generated by a reaction force of the billet is relieved to maintain the holding pressure. A die attached to an end platen, an extrusion stem facing the die, and a mandrel attached to the inside of the extrusion stem, and a billet sandwiched on an extrusion shaft between the die and the extrusion stem inside the container An extruding device for a tubular product, which is inserted through the extruding stem and moves the extruding stem in the extruding direction to extrude the billet,
The main cylinder that supports the mandrel is provided with a pressure reducing means, and the pressure reducing means sets a holding pressure of the billet to be held between the extrusion stem and the die, and inserts the mandrel into the billet. An apparatus for extruding a tubular product, characterized in that the holding position of the extrusion stem is maintained.   8. The apparatus for extruding a tubular product according to any one of claims 4 to 7, wherein the billet is a hollow billet.

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