CN100366354C

CN100366354C - Method and device for manufacturing tube with high dimensional accuracy

Info

Publication number: CN100366354C
Application number: CNB2004800030567A
Authority: CN
Inventors: 剑持一仁; 长滨拓也; 坂田敬; 菅野康二; 大西寿雄; 依藤章; 丰冈高明
Original assignee: NKK Corp
Current assignee: JFE Engineering Corp
Priority date: 2003-04-11
Filing date: 2004-04-08
Publication date: 2008-02-06
Anticipated expiration: 2024-04-08
Also published as: CN1744956A; JP2004314083A; JP4285053B2

Abstract

There are provided a high dimensional accuracy pipe and a manufacturing method thereof, the pipe being in response to wide requirements of sizes, being manufactured at inexpensive cost, and having a sufficient fatigue strength. The detailed structure thereof is as follows. A push-to-pass process is performed in which, while a plug 1 is being charged in a metal pipe 5 , the metal pipe is pushed in a hole provided in a die 2 and is then allowed to pass therethrough. As a result, a high dimensional accuracy pipe can be obtained in which at least one of the deviation of the outer diameter, the deviation of the inner diameter, and the deviation of the thickness in the circumferential direction is 3.0% or less as processed.

Description

Method and apparatus for manufacturing high dimensional accuracy tube

Technical Field

The present invention relates to a high dimensional accuracy pipe, a method and an apparatus for manufacturing the same. To a high dimensional accuracy tube suitable for a member requiring high dimensional accuracy, such as a driving member for an automobile, a method for manufacturing the high dimensional accuracy tube, a manufacturing apparatus, and a manufacturing equipment set.

Background

Metal pipes such as steel pipes are classified into general welded pipes and seamless pipes. Welded steel pipes, such as electric welded steel pipes, are manufactured by rounding the width of a strip-shaped plate material and welding the two ends of the rounded width. On the other hand, a seamless steel pipe is produced by piercing a solid billet at a high temperature and then rolling it with a mandrel mill or the like. When welding steel pipes, the dimensional accuracy of the pipes is improved by grinding the projection bead of the welded portion after welding, but the wall thickness variation thereof exceeds 3.0%. In the case of seamless steel pipes, eccentricity is likely to occur in the piercing step, and large wall thickness variations are likely to occur due to the eccentricity. Although the subsequent steps are attempted to reduce the wall thickness variation, the wall thickness variation cannot be sufficiently reduced, and 8.0% or more remains in the final product stage.

Recently, as a solution to environmental problems, weight reduction of automobiles is strongly desired. Drive components such as drive shafts are being replaced with hollow metal tubes from solid metal rods. In these metal pipes for automobile driving parts and the like, high dimensional accuracy is required in which the variation in wall thickness, inner diameter, and outer diameter is 3.0% or less, and more strictly 1.0% or less.

The drive-type components must withstand the fatigue caused by long-distance driving of the motor vehicle. If the accuracy of the wall thickness, inner diameter, and outer diameter of the metal pipe is not high, the irregularities existing on the inner and outer surfaces of the pipe as initiation points inevitably tend to accelerate fatigue failure, and the fatigue strength is significantly reduced. In order to ensure sufficient fatigue strength, the metal pipe must have good wall thickness, inner diameter, and outer diameter accuracy.

The high dimensional accuracy tube of the present invention described below is a tube in which at least one or two or more of the outer diameter variation, the inner diameter variation, and the circumferential wall thickness variation are 3.0% or less, and each variation is derived from the following equation.

Deviation = variation width/(target or average) × 100%

Range of variation = max-min

As means for improving the accuracy of the wall thickness, inner diameter, and outer diameter of a metal pipe, the following two methods are generally known. The following describes welded steel pipes and seamless steel pipes (hereinafter referred to as steel pipes or pipes). One method is a method of cold-drawing a steel pipe using a die and a mandrel bar (referred to as a cold-drawing method) (see patent document 5). Another method is a method of pressing a steel pipe into a die hole by using a rotary forging machine equipped with a circumferential segment die (referred to as a rotary forging press-fitting method) (see

patent documents

1, 2, and 3).

Patent document 1: japanese unexamined patent publication No. 9-262637

Patent document 2: japanese unexamined patent publication Hei 9-262619 (JP-A)

Patent document 3: japanese unexamined patent publication Hei 10-15612

Patent document 4: japanese patent No. 2858446

Patent document 5: japanese patent publication No. 2812151

However, in the cold drawing method, when the equipment capacity is insufficient, or when the wall thickness and the diameter of the tube are large, the drawing stress cannot be sufficiently obtained and the reduction ratio has to be reduced, the contact between the die and the tube and between the drawing plug and the tube becomes insufficient in the working gap (the gap between the core rod and the inner surface of the die hole). This is because the tube stress is a pulling force in the cold drawing process. In this case, the inner surface and the outer surface of the pipe are not sufficiently smoothed, and unevenness is likely to remain. In contrast, the diameter reduction ratio of the tube is increased during cold drawing, and the contact between the inner and outer surfaces of the tube and the mandrel bar and the die is increased in the machining gap. However, when the pipe is cold-drawn using the die, the larger the diameter reduction ratio of the pipe, the larger the roughness of the pipe due to the irregularities of the inner surface. As a result, it is difficult to obtain a high dimensional accuracy tube by the cold drawing method. Therefore, the fatigue strength of the pipe is insufficient, and a pipe having a better dimensional accuracy is strongly required. Since the front end of the tube is clamped in order to apply a tensile force in the cold drawing method, the front end of the tube is required to be narrow. As a result, the drawing has to be performed one by one, and there is a problem that the processing efficiency is significantly lowered.

Further, even if the diameter reduction ratio can be made large in spite of sufficient facility capacity, the work deformation due to the diameter reduction becomes large, and the pipe is easily work hardened. After the tube is drawn, the tube is subjected to a process such as bending or swaging. The work hardening by the drawing has a problem that cracks are likely to occur in a subsequent bending step or the like. In order to prevent this problem, it is necessary to perform a long-time heat treatment at a high temperature after drawing, and the manufacturing cost is significantly increased.

Further, the metal pipe pressing device described in patent document 4 is an auxiliary device for reducing a necessary pulling force because grooves are formed on the inner surface of the pipe by preventing the pipe from being broken due to the metal pipe being pulled by another device, and does not smooth the inner and outer surfaces of the pipe.

In the rotary forging press-fitting method described in patent documents 1 to 3, the die of the rotary forging machine is separated and swung, and as a result, a step difference is likely to occur in the combined portion, the outer surface is insufficiently smoothed, or uneven deformation is caused due to the different die rigidity in the circumferential direction. As a result, the wall thickness accuracy is also insufficient, and the target final dimensional accuracy cannot be obtained sufficiently, and the fatigue strength of the steel pipe is also insufficient, and improvement is required.

In the rotary forging press-fitting method, the wall thickness after press-fitting of the steel pipe is thicker than that before press-fitting. Because of the complicated structure, the use of a rotary forging machine which is difficult to increase the load is restricted. In order to increase the thickness, the tube is more easily deformed as the gap is increased in the machining gap closer to the outlet side, and thus, when the tube is easily deformed due to the presence of the gap, irregularities are generated on the inner surface of the tube. When the wall thickness is further increased, the gap becomes large, and the tube and the die surface or the core rod surface become insufficient in contact. The result is the following drawbacks: the smoothing of the tube surface does not progress, and it is difficult to obtain a tube with high dimensional accuracy.

Further, when manufacturing a high dimensional precision tube, if the frictional force between the outer surface of the mandrel bar and the inner surface of the tube, and between the inner surface of the die and the outer surface of the tube is not reduced to the extent possible, defects such as seizure occur on the tube surface during the processing, and the surface quality of the tube after the processing is low, and not only is the tube not finished, but also the load during the processing is significantly increased, and the processing itself is not possible, and as a result, the production efficiency is significantly reduced.

Therefore, in order to obtain a desired thickness after press-fitting, the thickness before press-fitting can only be designed to be thin. Therefore, in order to prepare pipes of various finished sizes and improve the fatigue strength and other properties of these pipes, it is necessary to prepare various tube blank sizes. However, since it is impossible to prepare tube blanks of various sizes due to the constraints of the tube blank manufacturing facility, it is difficult to obtain a good size over the entire required size of the tube. In addition, in the automobile parts, the degree of processing of the pipe is changed and used. For example, it is considered that the degree of working is reduced in a certain member and the heat treatment after the working is omitted, and the degree of working is significantly increased in another member to increase the strength.

However, in the conventional cold drawing method or rotary forging press-fitting method, since only diameter reduction is performed, the outer diameter of the tube after the working is uniquely determined by the outer diameter of the die, the wall thickness is also uniquely determined by the die and the mandrel bar, and only a unique degree of working can be obtained from the same mother tube, and it is almost impossible to manufacture tubes of the same size having different degrees of working from the same mother tube. Therefore, in order to manufacture pipes having the same size and different degrees of working, it is necessary to prepare blank pipes of various sizes and change the reduction ratio, and it takes much time and effort to manufacture the blank pipes.

As described above, in the conventional technique, it is difficult to obtain a tube with high dimensional accuracy, and in manufacturing tubes having the same size and different degrees of working, there is a problem that a plurality of blank tubes having different sizes must be prepared.

In order to solve the above problems, the present inventors have studied a processing method for producing a pipe with higher dimensional accuracy than the drawing method, and have concluded that pressing is a preferred alternative method. In the press working, as shown in fig. 10, the mandrel bar 1 is fitted into the tube 4, and the tube 4 is press-fitted into the die 2 by the tube press-fitting machine 3 while floating the mandrel bar 1, so that all the compressive stress acts in the working gap. As a result, the tube can sufficiently contact the mandrel and the die at both the inlet side and the outlet side of the machining gap. Further, even with a slight reduction ratio, since the inside of the working gap is in a compressive stress state, the pipe and the mandrel, the pipe and the die are likely to be in sufficient contact with each other, and the pipe is likely to be smoothed, compared with drawing, so that a pipe with high dimensional accuracy can be obtained.

In addition, when press working is performed, the mandrel bar is pushed into the pipe, and the load increases, and as a result, buckling occurs in the pipe blank that is being pushed in, and working may become impossible. The reasons for this include insufficient lubricant application amount, change in surface properties of the blank tube, deformation of the mandrel bar or die due to frictional heat during press working or heat dissipation during press working, and the like.

Conventionally, an operator determines the vibration sound of a pipe press or the deflection of a hydraulic gauge by feel, or performs a working with difficulty, stops the working when a die is broken, resets the press working conditions, and performs the working again. That is, since the condition is changed in a workable state rather loose from the press working limit or when the die starts to break in a very severe working state, the working time is wasted, the die is replaced with a troublesome work, and the productivity is low.

In conventional drawing, in order to improve the dimensional accuracy of a pipe, it is necessary to apply a metal soap to the pipe before drawing and then to form a sufficient lubricating film. Therefore, it takes a sufficient time to form the lubricating film, and the pipe needs to be pretreated by pickling or the like, and the drawing equipment set needs to have a plurality of grooves for pretreatment such as pickling or a plurality of grooves for lubrication treatment. In addition, in order to perform the drawing process, it is necessary to perform a joint process on the tube tip by a rotary forging machine or the like. Further, when these units are arranged on the inlet side of the drawing apparatus on a line, since the productivity is greatly lowered, the pipe is subjected to a lubricating treatment in another step and then is fed into the drawing line unit to be processed.

That is, in the conventional manufacturing facility group of high dimensional accuracy tubes, it is difficult to improve the manufacturing efficiency, since it is assumed that the drawing process requiring a long pretreatment step is required.

In the conventional cold drawing method or rotary forging press-fitting method described above, there have been unsolved problems that it is difficult to obtain a pipe with high dimensional accuracy and the surface quality of the pipe is low. In view of the problems in the prior art described above, an object of the present invention is to provide a high dimensional accuracy pipe having sufficient fatigue strength, which can be manufactured at low cost over a wide range of required dimensions of the pipe, a manufacturing method thereof, and a manufacturing equipment set for high efficiency production.

Disclosure of Invention

The present invention for achieving the above object is as follows.

1. A high dimensional accuracy pipe in a pressed state, characterized in that the pipe is manufactured by pressing a metal pipe into a die hole and passing the metal pipe through the die hole in a state in which a core rod is incorporated into the metal pipe, and that any one or two or more of the variation in outer diameter, the variation in inner diameter, and the variation in wall thickness in the circumferential direction is 3.0% or less.

2. The high dimensional accuracy tube in a press state according to claim 1, characterized in that it is produced by performing a press in which a metal tube is pressed into a die hole and passed therethrough in a state in which a core rod is fitted into the metal tube and the metal tube wall thickness on the exit side of the die is set to be equal to or less than the wall thickness on the entry side; and any one or more of the outer diameter variation, the inner diameter variation and the circumferential wall thickness variation is 3.0% or less.

3. The high dimensional accuracy tube according to

claim

1 or 2, wherein the punching is performed by circumscribing the entire circumference of the mandrel and inscribing the entire circumference of the die with the metal tube in the same cross section of the tube.

4. The high dimensional accuracy pipe according to any one of claims 1 to 3, wherein the mold is an integral type and/or a fixed type mold.

5. A method for manufacturing a high dimensional accuracy pipe, characterized by performing a press-fitting process in which a metal pipe is pressed into a die hole and passed through the die hole with a mandrel bar fitted into the metal pipe.

6. The method of manufacturing a high dimensional accuracy pipe as set forth in claim 5, wherein the pipe wall thickness at the outlet side of the die is set to be smaller than or equal to the same pipe wall thickness at the same inlet side.

7. The method of manufacturing a high dimensional accuracy tube as set forth in claim 5 or 6, characterized in that the pressing is performed by circumscribing the entire circumference of the mandrel and inscribing the entire circumference of the die in the same cross section of the tube.

8. The method for manufacturing a high dimensional accuracy pipe as set forth in any one of claims 5 to 7, wherein the mold is an integral type and/or fixed type mold.

9. The method of manufacturing a high dimensional accuracy pipe as set forth in any one of claims 5 to 8, wherein the mandrel is a traveling mandrel.

10. The method for efficiently producing a high dimensional accuracy pipe as set forth in claim 5, wherein when the high dimensional accuracy pipe is formed by improving one or more of the variation in the outer diameter, the variation in the inner diameter, and the variation in the wall thickness in the circumferential direction of the pipe by press working, the mandrel is set in the pipe so as to float, and the pipe is continuously fed into the die by a pipe feeding device on the inlet side of the die.

11. The method for efficiently manufacturing a pipe with high dimensional accuracy as set forth in claim 10, wherein the pipe feeding means is a crawler for clamping the pipe before the processing.

12. The method for efficiently manufacturing a high dimensional accuracy pipe according to claim 10, wherein said pipe feeding means is an endless belt which compresses the pipe before the processing.

13. The method for efficiently manufacturing a high dimensional accuracy pipe as set forth in claim 10, wherein said pipe feeding means is an intermittent conveyor which grips the pipe before processing and alternately and intermittently conveys the pipe.

14. The method for efficiently manufacturing a high dimensional accuracy pipe according to claim 10, wherein the pipe feeding device is a press machine that sequentially presses the pipe before the machining.

15. The method for efficiently manufacturing a high dimensional accuracy pipe as set forth in claim 10, wherein said pipe feeding means is a hole roll for nipping a pipe before processing.

16. The method for efficiently manufacturing a high-dimensional accuracy pipe according to claim 15, wherein the hole roll is a hole roll having two or more rolls.

17. The method for efficiently manufacturing a high dimensional accuracy pipe as set forth in

claim

15 or 16, wherein said hole roll is provided with two or more frames.

18. The method of producing a high dimensional accuracy pipe having a good surface quality as described in claim 5, characterized in that after the lubricating coating is formed on the inner surface and/or the outer surface of the pipe, a mandrel bar is fitted into the pipe, and the pipe is pressed with a die.

19. The method of manufacturing a high dimensional accuracy pipe having a good surface quality as described in claim 18, wherein the pipe on which the lubricating film is formed is a steel pipe in a state where scale is attached.

20. The method for producing a high dimensional accuracy pipe having a good surface quality as described in 18 or 19, wherein the lubricating film is formed with a liquid lubricant.

21. The method for producing a high dimensional accuracy pipe having a good surface quality as set forth in claim 18 or 19, characterized in that the lubricating coating is formed with a lubricating grease lubricant.

22. The method of producing a high dimensional accuracy pipe having a good surface quality as described in 18 or 19, wherein the lubricating film is formed of a drying resin.

23. The method of producing a high dimensional accuracy tube having a good surface quality as described in 22, wherein the lubricating film is formed by coating the dry resin on the tube, or by diluting a liquid of the dry resin or an emulsion of the dry resin with a solvent, and then drying or air-drying the coated tube in warm air.

24. A method of manufacturing a high dimensional accuracy pipe as described in claim 5, wherein pipes of a predetermined size having different degrees of finish are manufactured from a raw pipe of the same size with high dimensional accuracy, wherein a mandrel bar capable of expanding and reducing the diameter is fitted into the pipe, and the pipe is pressed with a die.

25. The method of manufacturing a high dimensional accuracy tube according to claim 24, wherein the mandrel is floated within the tube, and the tube is continuously fed into the die.

26. The method of manufacturing a high dimensional accuracy pipe according to claim 24 or 25, wherein the mandrel is a mandrel in which a taper angle of the enlarged diameter portion is smaller than a taper angle of the reduced diameter portion.

27. The method of manufacturing a high dimensional accuracy pipe as set forth in any one of claims 24 to 26, wherein a target outer diameter of the pipe on an outlet side of the die is smaller than an outer diameter of the pipe on an inlet side thereof.

28. The method for stably producing a high dimensional accuracy pipe according to claim 5, wherein, when the high dimensional accuracy pipe is produced by press working in which a pipe having a mandrel bar fitted therein is pressed into a die hole and passed through, the mandrel bar is used such that an angle formed by a surface of a reduced diameter portion and a machining center axis is 5 to 40 ° and a length of the same reduced diameter portion is 5 to 100mm, and the die is used such that an angle formed by an inner surface of the hole on the inlet side and the machining center axis is 5 to 40 °.

29. The method of stably manufacturing a high dimensional accuracy pipe according to claim 28, wherein a length of the supporting portion of the mandrel bar is 5 to 200mm.

30. A stable manufacturing method of a high dimensional accuracy pipe as set forth in

claim

28 or 29, wherein the thickness of the pipe wall at the outlet side of the die is set to be smaller than or equal to the thickness of the pipe wall at the same inlet side.

31. The method for stably producing a high dimensional accuracy pipe according to any one of claims 28 to 30, wherein an integral type fixed die is used as the die.

32. A method for stably manufacturing a high dimensional accuracy pipe according to any one of claims 28 to 31, wherein the mandrel is floated within the pipe.

33. The method for stably manufacturing a high dimensional accuracy pipe according to claim 5, wherein a high dimensional accuracy pipe is manufactured by performing press working in which a mandrel bar is fitted into a pipe, the mandrel bar is floated, and the pipe is pressed into a die to pass through the pipe, wherein a load in a press working direction is measured during the press working, a calculated load is calculated from material characteristics of a pipe blank before the press working by using any one of the following expressions 4 to 6, the measured load and the calculated load are compared, and whether the press working can be continued or not is determined based on the result;

formula 4 sigma _k Cross sectional area of tube blank

Wherein σ _k ＝YS×(1-a×λ)，a =0.00185 to 0.0155, L: tube blank length, k: secondary radius of cross section, k ² ＝(d ₁ ² +d ₂ ² ) 16, n: tube end state (n = 0.25-4), d ₁ : outer diameter of tube blank, d ₂ : tube blank inner diameter, YS: yield strength of pipe blank

Formula 5 tube blank yield strength YS multiplied by tube blank sectional area

Formula 6 tensile strength of the tube blank TS × cross-sectional area of the tube blank.

34. A method of stably manufacturing a high dimensional accuracy pipe according to claim 33, wherein if the measurement load is equal to or less than the calculation load, it is determined that continuation is possible, and the machining is continued, and if the measurement load exceeds the calculation load, it is determined that continuation is not possible, and the machining is suspended, and the die and/or the mandrel bar is replaced with a die and/or a mandrel bar having another shape corresponding to the same finished pipe size, and then the machining is resumed.

35. The method for stably manufacturing a high-dimensional-accuracy pipe according to claim 34, wherein an angle of the die and/or the core rod used after the replacement is smaller than an angle of the die and/or the core rod used before the replacement.

36. The method of stably producing a high dimensional accuracy pipe as set forth in any one of claims 33 to 35, wherein a lubricant is applied to the pipe blank before the press working, and only when the measured load exceeds the calculated load, the type of the lubricant is changed.

37. An apparatus for manufacturing a high dimensional accuracy pipe, comprising: a mandrel contactable with the inner surface of the metal pipe in the full circumference, a die having a hole contactable with the outer surface of the same pipe in the full circumference, and a pipe extruder for extruding the same pipe; and a press may be performed in which a metal pipe is pressed into the die hole by the pipe press and passed through in a state where the mandrel bar is fitted into the pipe.

38. The apparatus for manufacturing a high dimensional accuracy pipe as set forth in claim 37, wherein said mold is an integral type and/or fixed type mold.

39. The apparatus for manufacturing a high dimensional accuracy pipe as set forth in claim 37 or 38, wherein said mandrel is a traveling mandrel.

40. The apparatus for manufacturing a high dimensional accuracy tube as set forth in any one of claims 37 to 39, wherein said tube extruding machine continuously extrudes said tube.

41. The apparatus for manufacturing a high dimensional accuracy tube as set forth in any one of claims 37 to 39, wherein said tube extruder intermittently extrudes said tube.

42. A method for manufacturing a high-efficiency high-dimensional precision tube as described in 37, wherein a mandrel is inserted into the tube, the mandrel is floated, and the tube is continuously or intermittently pressed into dies and passed through the dies, wherein a plurality of dies having different hole patterns are arranged on the same circumference, and any one of the dies is moved in the circumferential direction of the arrangement according to the product size so as to be arranged in the rolling line for pressing.

43. A method for efficiently manufacturing a high-dimensional-accuracy pipe according to claim 37, wherein a high-dimensional-accuracy pipe is manufactured by performing a press process in which a mandrel is inserted into a pipe so as to float and the pipe is continuously or intermittently pressed into dies and passed through the dies, wherein a plurality of dies having different hole patterns are arranged on the same straight line, and any one of the dies is moved in the linear direction of the arrangement according to a finished product size so as to be arranged in a rolling line for the press process.

44. The method for efficiently manufacturing a high-dimensional accuracy pipe as set forth in 42 or 43, wherein, when the final dimension is changed between the front pipe and the rear pipe, the rear pipe is stopped at the inlet side of the die after the front pipe is pressed, and the mandrel bar corresponding to the final dimension is inserted into the rear pipe before, after, or during the movement of the die corresponding to the final dimension of the rear pipe.

45. The high-efficiency manufacturing apparatus for a high-dimensional-accuracy pipe according to claim 37, comprising: the die rotating table supports a plurality of dies in a state where the plurality of dies are arranged on the same circumference, conveys the plurality of dies in the circumferential direction, and places any one of the plurality of dies in the rolling line.

46. The high-efficiency manufacturing apparatus for a high-dimensional-accuracy pipe according to claim 37, comprising: a die through which the tube passes, an extruder that presses the tube into the die in the mill pass line, and a die straightening station; the die linear motion stage supports the plurality of dies in a state in which the plurality of dies are aligned on the same straight line, and conveys the dies in the straight line direction, and any one of the dies is arranged in the pass line.

47. The method of manufacturing a high dimensional accuracy pipe as set forth in claim 5, in a method of manufacturing a high dimensional accuracy pipe by performing a press in which a mandrel is fitted into a pipe to float the mandrel and the pipe is pressed into a die to pass therethrough, characterized in that bending of the pipe is prevented by passing the pipe on the die outlet side through a hole pattern which is arranged immediately at the die outlet side and whose position in a plane perpendicular to the pipe passing direction has been adjusted in advance.

48. The method of manufacturing a high dimensional accuracy pipe as set forth in claim 47, wherein the pipe on the inlet side of the die and/or on the outlet side of the hole pattern is passed through a guide cylinder.

49. A method of manufacturing a high dimensional accuracy tube as claimed in

claim

47 or 48 wherein the tube is pressed into the die continuously.

50. The manufacturing apparatus of high dimensional accuracy tube as set forth in claim 37, having a die for passing the tube and an extruder for pressing the tube into the die, characterized in that a tube bending fine adjustment device having a hole pattern for passing the tube, a support base plate for supporting the hole pattern movably in a plane perpendicular to the direction of the through-tube, and a hole pattern moving mechanism for moving the hole pattern supported on the support base plate is provided in the vicinity of the exit side of the die.

51. The apparatus for manufacturing a high dimensional accuracy pipe as defined in claim 50, wherein the hole-type moving mechanism presses one position or two or more positions of the hole-type outer peripheral portion in a direction perpendicular to the pipe passing direction by a tapered surface of the wedge mold moving in the pipe passing direction.

52. The manufacturing apparatus of a high dimensional accuracy pipe as set forth in claim 51, characterized in that a screw is used to urge the movement of said wedge mold.

53. The apparatus for manufacturing a high dimensional accuracy pipe as defined in claim 50, wherein the hole-type moving mechanism presses or pulls one or more positions of the hole-type outer circumferential portion in a direction perpendicular to the pipe passing direction.

54. The manufacturing apparatus of a high dimensional accuracy pipe as set forth in claim 53, wherein said pushing or pulling type pushing or pulling force is applied by a fluid pressure cylinder.

55. The apparatus for manufacturing a high dimensional accuracy pipe as set forth in any one of claims 50 to 54, wherein the hole diameter of said hole pattern is equal to or larger than the exit hole diameter of said die.

56. The apparatus for manufacturing a high dimensional accuracy pipe as set forth in any one of claims 50 to 55, wherein said hole type hole is a straight hole or a hole with a tapered shape.

57. The apparatus for manufacturing a high dimensional accuracy tube as set forth in any one of claims 50 to 56, wherein a guide cylinder is provided for passing the tube on the inlet side of said die and/or on the outlet side of said tube bending fine adjustment means.

58. The apparatus for manufacturing a high dimensional accuracy pipe as set forth in any one of claims 50 to 57, wherein said extruder is a continuous extruder capable of continuously extruding the pipe.

59. A manufacturing facility group of high dimensional accuracy pipes, comprising the press working device described in 37, characterized in that a pipe end surface grinding device capable of grinding an end surface of a pipe to be perpendicular to a pipe axial direction, a lubricant dip coating tank for dip coating a lubricant on the pipe, a drying device for drying the pipe coated with the lubricant, and the press working device are arranged in this order.

60. The set of high-dimensional-accuracy pipe manufacturing facilities according to claim 59, wherein a cutting device for cutting the pipe into short lengths is disposed on an inlet side of the pipe end surface grinding device.

61. The group of manufacturing facilities for a high-dimensional-accuracy pipe according to 59 or 60, characterized in that a lubricant spraying device for spraying a lubricant onto a pipe or a lubricant spraying and drying device for spraying a lubricant onto a pipe and then drying it is arranged on the die inlet side of the press working device, instead of the lubricant dip coating tank and the drying device.

62. The manufacturing facility group of high dimensional accuracy tubes as recited in any one of claims 59 to 61, wherein at least one of a die exchanging device for exchanging said die, a mandrel bar exchanging device for exchanging said mandrel bar, and a bending preventing device for preventing bending of the tube on the exit side of said die is disposed at the same time as said press working device.

Drawings

Fig. 1 is an explanatory view showing an embodiment of the present invention in which pressing is used.

FIG. 2 is an explanatory view showing an embodiment in which drawing is performed.

Fig. 3A is an explanatory view showing an embodiment of press-fitting using a conventional rotary forging machine in which a segment die is attached and oscillated, and is a sectional view including a pipe center axis.

Fig. 3B is an explanatory view showing an embodiment of press-fitting usingbase:Sub>A conventional rotary forging machine in whichbase:Sub>A segment die is attached and oscillated, and isbase:Sub>A view along the directionbase:Sub>A-base:Sub>A.

Fig. 4 is a characteristic diagram showing the relationship between the stress and the number of times of endurance in the fatigue test.

FIG. 5 is a longitudinal sectional view showing an example of the present invention using a crawler as a pipe feeding apparatus.

FIG. 6 is a longitudinal sectional view showing an example of the present invention using an endless belt as a tube feeding device.

Fig. 7 is a longitudinal sectional view showing an example of the present invention using an intermittent conveyor as a tube feeding device.

FIG. 8 is a longitudinal sectional view showing an example of the present invention using a hole roller as a tube inserting device.

Fig. 9 is an explanatory view of a taper angle of a portion of the mandrel.

Fig. 10 is a cross-sectional view showing an outline of press working.

FIG. 11 is a schematic diagram showing an embodiment of the method of the present invention using example 1 of the apparatus of the present invention.

FIG. 12 is a schematic diagram showing an embodiment of the method of the present invention using example 2 of the apparatus of the present invention.

Fig. 13 is an explanatory view of a comparative example (mold is replaced by a worker).

Fig. 14 is a perspective view showing one embodiment of the present invention.

Fig. 15 is a plan view showing an example of the pipe bending fine adjustment apparatus of the present invention.

Fig. 16 is a sectional view showing an example of the hole pattern moving mechanism of the present invention.

Fig. 17 is a perspective view showing one embodiment of the present invention.

FIG. 18 is a plan view showing an example of the pipe bending fine adjustment apparatus of the present invention.

Fig. 19 is a perspective view showing a comparative example.

Fig. 20 is a perspective view showing a comparative example.

Fig. 21 is a perspective view showing a comparative example.

Fig. 22 is a schematic diagram showing a configuration of a device group as an embodiment of the present invention.

Fig. 23 is a schematic diagram showing the arrangement of the equipment set and the pre-processing steps necessary for the drawing process as a comparative example.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

In the conventional cold drawing method, it is difficult to improve the dimensional accuracy of a metal pipe when the pipe is drawn with a die and a plug. This is because the drawing force acts as a tensile force, and contact between the die and the tube outer surface and between the mandrel and the tube inner surface becomes insufficient in the machining gap. As shown in fig. 2, when the mandrel bar 5 is inserted into the tube 4 and the tube 4 is drawn from the hole of the die 6, the drawing force 10 applied to the exit side of the die 6 generates a tensile stress in the machining gap, and the inner and outer surfaces of the tube are formed with irregularities and increase from the entrance to the exit side of the machining gap. Also, at the inlet side in the machining gap, the tube outer surface does not contact or only slightly contacts the die 6 because the inner surface of the tube is deformed along the mandrel 5. On the exit side in the machining gap, since the tube outer surface contacts the die 6 and deforms, the tube inner surface does not contact or only slightly contacts the core rod 5. Therefore, there are freely deformable portions on both the inner and outer surfaces of the tube, and the irregularities cannot be sufficiently smoothed, and the dimensional accuracy of the tube obtained after drawing is degraded. Reference numeral 7 in the drawings denotes a tube drawing machine.

In contrast, in the press-forming method of the present invention, as shown in fig. 1, a mandrel bar 1 is inserted into a tube 5, and the tube 5 is pressed into a hole of a die 2 to pass therethrough. By means of the pressure 8 applied on the inlet side of the die 2, all the compressive stresses act inside the machining gap. As a result, the tube 5 can sufficiently contact the core rod 1 and the die 2 in the same cross section over the entire circumferential direction, whether on the inlet side or the outlet side of the machining gap. Even with a slight reduction, the inside of the working gap becomes compressive stress, and the tube and the mandrel, the tube and the die are in contact with each other in the same cross section in the entire circumferential direction as compared with drawing. Therefore, the tube can be easily smoothed, and a tube with high dimensional accuracy can be obtained.

As a result, when the fatigue strengths of these pipes are compared, the pipes produced by pressing can obtain a desired sufficient fatigue strength as compared with the conventional pipes produced by drawing. Further, since the inner and outer surfaces of the tube can be smoothed even if the diameter reduction ratio is small at the time of pressing, the work strain does not become large as compared with that at the time of drawing, and therefore, the heat treatment work after diameter reduction is reduced, and the manufacturing cost is reduced.

In the press-fitting using the conventional rotary forging machine 8 shown in fig. 3, since the combined die 9 in which the integral die is divided in the circumferential direction is used and the die is oscillated (as shown in fig. 12) to perform the working, a step is generated, and the wall thickness accuracy is not sufficiently good. In the present invention, for example, the step height difference may not be present in the mold formed as an integral mold, or the step height difference due to the swing rotation may be prevented in the mold formed as a fixed mold. Of course, the step height difference can be prevented by integrally forming the mold and fixing the mold.

Further, in the present invention, as compared with a method of swinging a die using an existing rotary forging machine, it is possible to simplify the apparatus structure, apply a sufficient load during machining, set the thickness on the outlet side to be the same as or smaller than the thickness on the inlet side of the die, and even if the load is increased by this, it is possible to obtain a pipe having a satisfactory dimensional accuracy and a sufficient fatigue strength with respect to a wide range of required dimensions by sufficient machining.

Conventionally, as a method for making the deviation of the outer diameter, the deviation of the inner diameter, and the deviation of the wall thickness in the circumferential direction of the metal pipe to be 3.0% or less, a machining method (a machining method involving the removal of a material portion) has been known, but the machining cost is increased, the working efficiency is lowered, and it is difficult to machine a long metal pipe having a small diameter. Thus, it is difficult to apply to a drive shaft of an automobile part or the like.

As a method for distinguishing the machined metal pipe from the present metal pipe (the metal pipe in a pressed state of the present invention), a method of observing the surface of the pipe and distinguishing the pipe from the scale is mentioned, in which the scale adhered to the surface of the present metal pipe by heating, rolling, or the like in the pre-manufacturing step is removed from the metal pipe obtained by machining.

Further, the metal pipe is improved by several times in wall thickness variation as compared with a pipe manufactured by a method of pressing a steel pipe into a die by a conventional rotary forging machine (see, for example,

patent documents

1, 2, and 3). That is, in the past, it was impossible to obtain a steel pipe having one or two or more of the outer diameter variation, the inner diameter variation, and the circumferential direction variation of 3.0% or less in the pressed state.

In the present invention, the outer diameter variation, the inner diameter variation, and the circumferential wall thickness variation are obtained as the dimensional accuracy indicators as follows.

The tube is rotated by contacting a micrometer with the outer surface (or inner surface) of the tube, and the outer diameter (or inner diameter) deviation, which is the maximum deviation from the target outer diameter (or target inner diameter), is calculated from the measured outer diameter (or inner diameter) distribution data in the circumferential direction, or the outer surface (or inner surface) of the tube is irradiated with a laser beam, and the outer diameter (or inner diameter) deviation, which is the maximum deviation from the target outer diameter (or target inner diameter), is calculated from the measured distribution data of the distance between the tube and the laser vibration source in the circumferential direction. Alternatively, the tube may be image-analyzed in circumferential direction in cross section, and the deviation from the perfect circle may be calculated in the circumferential direction to calculate the deviation of the outer diameter (or inner diameter).

The circumferential wall thickness deviation is calculated as the difference between the circumferential distribution data of the outer diameter and the circumferential distribution data of the inner diameter, or the circumferential wall thickness deviation is directly measured as the maximum deviation from the target wall thickness from the image of the wall thickness section by image-analyzing the circumferential section of the tube.

Then, measurement was performed at an arbitrary position except for the front and rear end portions of the tube by a distance of not more than 10mm, and the deviation was determined from the measurement point values of not less than 10 points.

That is, the outer diameter variation, the inner diameter variation, and the wall thickness variation (= circumferential wall thickness variation) are defined as follows.

Deviation of outer diameter: (maximum outer diameter-minimum outer diameter)/target outer diameter (or average outer diameter) × 100 (%)

Inner diameter deviation: (maximum inner diameter-minimum inner diameter)/target inner diameter (or average inner diameter) × 100 (%)

Wall thickness variation: (maximum wall thickness-minimum wall thickness)/target wall thickness (or average wall thickness) × 100 (%)

The high dimensional accuracy pipe of the present invention is a metal pipe in which one or two or more of the three dimensional accuracy indexes are 3.0% or less, and therefore can be used as a metal pipe such as a vehicle drive component requiring 3.0% or less of high dimensional accuracy.

In addition, according to the conventional rotary forging press-fitting method shown in fig. 3A and 3B, since the die 4 is assembled and the die is swung (as shown in fig. 12), the circumferential wall thickness variation cannot be sufficiently improved due to the step height difference caused by the die assembly or the uneven deformation caused by the circumferential rigidity difference under high stress.

In contrast, in the press of the present invention, since the die is integrated and does not need to be swung at all times, the uneven deformation does not occur, and as a result, both the inner surface and the outer surface of the pipe can be smoothed.

In the conventional rotary forging press-fitting method, since the pipe 5 must be fed in conjunction with the oscillation (as indicated by 12) of the die 4, the oscillation speed cannot exceed a certain value or more due to the impact load of the die, and the machining efficiency is low. In addition, in the conventional drawing, since the front end of the tube must be strongly gripped and tensioned, the front end of the tube must be narrowed to draw the tube, and therefore, the tube must be processed in a single piece, which significantly reduces the processing efficiency.

In contrast, according to the present invention, since the mandrel bar is floated by pressing, the tube can be continuously fed into the die by applying the pushing force 15 to the tube from the inlet side of the die by using the tube feeding device 3. Particularly high efficiency processing can be achieved compared to the prior art. The term "continuously feeding" as used herein means that, as shown in fig. 1, one pipe 5 and the next pipe 5 are fed without interruption, and the pipe body may be moved in the pipe-passing direction in a state of continuous movement or intermittent movement with a minimum stop time.

Examples of suitable tube feeding devices 3 include: a crawler conveyor 13 for gripping the pipe 5 before the processing (see fig. 5 in which small pieces of the gripped pipe are connected in a crawler shape), an endless belt 14 for pressing the pipe 5 before the processing (see fig. 6), an intermittent conveyor 15 for gripping the pipe before the processing and alternately and intermittently conveying the pipe, a press (not shown) for sequentially pressing the pipe before the processing, and a hole roller 16 for gripping the pipe before the processing (see fig. 8). The tube feeding device 3 may be constituted by one or a combination of two or more of the above.

It is also important to prevent defects at the time of clamping or pressing and to secure a necessary pressing force by appropriately selecting the tube feeding device according to the size (diameter, length, wall thickness) of the tube, the necessary force for pressing the tube, the required length of the tube after pressing, and the like.

Further, when the tube before the processing is nipped by the hole-type rollers, it is preferable to use a method of using 2 or more hole-type rollers and/or a method of providing 2 or more hole-type rollers in a frame because the punching force can be easily secured without causing defects in the tube.

Further, when the mandrel bar is floated, even if the pressing conditions relating to the complicatedness such as the angle between the die and the mandrel bar, the lubrication of the surface of the die and the mandrel bar are changed, since the mandrel bar is present at a position where a stable compressive stress is always applied, it is possible to stably obtain a good dimensional accuracy.

Further, in the case of manufacturing a high dimensional accuracy pipe, when lubricating the gap between the outer surface of the mandrel bar and the inner surface of the pipe, and between the inner surface of the die and the outer surface of the pipe, defects such as seizure do not occur on the pipe surface during the processing, and therefore, a pipe having a good surface quality can be manufactured. Further, since the frictional force is reduced by lubrication, the load necessary for machining can be reduced, the machining energy consumption can be saved, and the productivity can be improved.

As a result of the inventors' study of various lubrication methods, the following methods were obtained, which are important achievements of the present invention. That is, a lubricating film is formed in advance on either or both of the inner surface and the outer surface of the pipe, and pressing is performed. The lubricant for forming the lubricating film is preferably any of a liquid lubricant, a grease lubricant, and a drying resin. Examples of the liquid lubricant include mineral oil, synthetic ester, animal or vegetable fat and oil, and the above-mentioned lubricant mixed with additives. Examples of the lubricant-based lubricant include Li-based grease lubricants, na-based grease lubricants, and the above-mentioned lubricants containing additives such as molybdenum disulfide. Examples of the drying resin include polypropylene resins, epoxy resins, polyethylene resins, and polyester resins.

The method of forming a lubricating film using the resin is to coat the resin on a pipe, or to dilute the resin in a liquid or emulsion with a solvent. And then dried, preferably in warm air, or air dried. Examples of the solvent for diluting the resin include ethers, ketones, aromatic hydrocarbons, and linear and side chain hydrocarbons. Examples of the dispersant for obtaining the resin emulsion include water, alcohols, and a mixture thereof.

Further, when a high dimensional precision pipe is efficiently produced, it is possible to process an electric resistance welded steel pipe or a seamless steel pipe obtained by direct electric resistance welding a hot rolled steel plate without removing an oxide scale in an original state, and if so, it is possible to reduce the processing cost.

In the conventional cold drawing method or rotary forging press-fitting method, only diameter reduction is performed. Only a single degree of working can be obtained from a single size of tube blank, and it is almost impossible to manufacture tubes of the same outside diameter having different degrees of working. In contrast, in the present invention, as shown in fig. 1, an expanded pipe portion 1A for expanding a pipe 4 and a reduced diameter portion 1B for reducing the diameter of the expanded pipe 4 in cooperation with a die 2 are provided in a mandrel bar 1. Thus, pipes of a certain size having different degrees of working can be produced from the same size of raw pipe. Even if the dimensions of the raw pipe and the pipe after press working are fixed, the expansion ratio of the expanded portion of the mandrel bar is adjusted, and the reduction ratio of the reduced portion of the mandrel bar is inevitably increased or decreased, resulting in different degrees of working of the pipes to be obtained.

Expansion ratio =1-D0/D1

Diameter reduction ratio =1-D2/D1

Wherein,

d0: external diameter of tube blank

D1: target outer diameter after pipe expansion

D2: reduced target outer diameter

Further, according to the present invention, it is preferable to supply the tubes to the molds sequentially and continuously from the viewpoint of improving the production efficiency. In this case, when the mandrel bar is supported on the inlet side or the outlet side of the die, a device such as a rod or a wire for supporting the mandrel bar becomes an obstacle, and it becomes difficult to continuously supply the tube. Thus, it is preferable to float the core rod within the tube.

In order to stably perform the press working of the present invention, the mandrel bar must be stabilized during the working process. I.e. must not deviate from the proper position relative to the mould. Studies have been made in this regard. By expanding and reducing the diameter, the mandrel is subjected to the surface pressure of the tube. It is found that when the surface pressure on the diameter reduction side is higher than the surface pressure on the diameter expansion side, the stabilization of the mandrel bar can be achieved. In order to increase the surface pressure on the diameter reduction side to be higher than the surface pressure on the diameter expansion side, it is effective that the taper angle θ a of the expanded pipe portion 1A of the mandrel bar 1 is smaller than the taper angle θ B of the reduced pipe portion 1B, as shown in fig. 9. Here, the taper angle of the mandrel segment means an angle formed between the segment surface and a straight line 17 parallel to the central axis of the mandrel in the traveling direction of the tube. Further, θ a =0.3 to 35 ° and θ B =3 to 45 ° are preferable. On the other hand, the diameter reduction ratio may be made larger than the tube expansion ratio, and for this reason, it is effective to make the outer diameter of the tube on the outlet side of the die smaller than the outer diameter of the tube on the inlet side.

In the present invention, since the integrated fixed mold can be used, the step height difference and the uneven deformation in the circumferential direction due to the mold combination are not generated at all. As a result, both the inner surface and the outer surface of the pipe can be smoothed. Further, by using the integrated fixed mold, a sufficient load can be applied during processing. Even if the load is increased by setting the wall thickness on the outlet side of the die to be equal to or smaller than the wall thickness on the inlet side, sufficient processing can be performed. As a result, a tube having excellent dimensional accuracy can be obtained. The size range of the finished pipe which can be manufactured by one pipe blank is expanded.

However, in order to stably perform the press working, it is necessary to use a mandrel bar and a die which satisfy the points proposed by the inventors. The point is that the angle formed between the surface of the reduced diameter portion of the mandrel bar and the machining center axis (the mandrel bar reduced diameter portion angle) is 5 to 40 °, the length of the portion (the mandrel bar reduced diameter portion length) is 5 to 100mm, and the angle formed between the inner surface of the hole on the die inlet side and the machining center axis (the die angle) is 5 to 40 °. Further, it is preferable that the length of the mandrel bar supporting portion (the length of the mandrel bar supporting portion) is 5 to 200mm. Here, the machining center axis is an axis that is perpendicular to a cross section in a diameter direction of the mandrel and passes through a center of the cross section, an axis that is perpendicular to a cross section in a diameter direction of the die hole and passes through a center of the cross section, and the support portion is a cylindrical portion that is connected to a minimum diameter portion of the reduced diameter portion.

The reason why the mandrel bar and the die are defined as described above is as follows.

(angle of the reduced diameter portion of the mandrel: 5 to 40 DEG)

When the angle of the reduced diameter portion of the mandrel is less than 5 °, the mandrel and the material (pipe) may be drawn out at the same time, and when the angle of the reduced diameter portion of the mandrel exceeds 40 °, the mandrel and the material may be jammed in the die and press working may not be performed.

(core rod reducing part length: 5 to 100 mm)

If the length of the reduced diameter portion of the mandrel is less than 5mm, the mandrel may be drawn together with the material, while if the length of the reduced diameter portion of the mandrel exceeds 100mm, the frictional force between the mandrel and the material increases, and both may jam in the die and make the press working impossible.

(mold angle: 5-40 degree)

When the die angle is less than 5 °, the plug tends to be drawn simultaneously with the material in a state of being sunk into the material, and on the other hand, when the die angle exceeds 40 °, the plug and the material tend to be jammed in the die and the press working cannot be performed.

(core rod support part length: 5 to 200 mm)

The force of withdrawal to the die inlet side acts on the mandrel due to the reaction force from the material on the reduced diameter portion and the die, and in balance with this, a force of pressing the mandrel to the die outlet side must be applied to stabilize the mandrel. A bearing portion may be provided on the core rod so as to utilize the frictional force acting on the surface thereof. According to the studies of the inventors, in order that the frictional force contributes to sufficient stability of the mandrel, the length of the mandrel bar supporting portion should be 5 to 200mm. When the length of the mandrel bar supporting portion is less than 5mm, the frictional force for extruding the mandrel bar is insufficient, and the material and the reaction force of the die tend to push back the mandrel bar toward the die entrance side. On the other hand, if the mandrel bar supporting portion length exceeds 200mm, the frictional force becomes too large, and the mandrel bar becomes easy to be pressed toward the die exit side. Either destabilizes the position of the core rod.

In addition, in the present invention, by floating the mandrel bar, even if the pressing conditions are changed, which are complicated in terms of angles between the die and the mandrel bar, surface lubrication of the die and the mandrel bar, the mandrel bar can be positioned at a position where a generally stable compressive stress state can be obtained. In addition, when the thickness of the die exit side is set to be equal to or less than the thickness of the die entrance side wall, the stability of the press working is further improved, which is preferable.

In the case of press working, since there is a possibility that the mandrel bar is jammed in the pipe to increase the load, and as a result, the pressed-in raw pipe is buckled to make the working impossible, it is necessary to prevent buckling of the raw pipe before stable press working is performed. Therefore, the inventors paid attention to the load at the time of pressing. That is, since the load in the press working direction is significantly increased when the plug is jammed by the plug, when the load is equal to or less than a certain specific value, the press can be performed, and when the load exceeds the specific value, the press cannot be performed, and of course, the press condition may be changed to the most appropriate condition. This specific value is called the press limit load.

When the pressing is impossible, if a pressing limit load is set by a formula representing the buckling of the tube due to buckling of the tube blank being pressed in, the pressing can be stabilized when the load is below the limit load. Although it is known that the formula representing the buckling of the tube is an euler formula obtained from the elastic modulus of the material, the values represented by the study of the present inventors deviate from the actual phenomena, and thus the application is not possible at all. Therefore, as a result of studying various buckling formulas different from this, it was found that the following formula 4 best represents the actual phenomenon.

(formula 4) σ _k X cross sectional area of tube blank

Wherein

σ _k ＝YS×(1-a×λ)，

a＝0.00185-0.0155

L: the length of the tube blank is as long as,

k: the secondary radius of the cross-section,

k ² ＝(d ₁ ² +d ₂ ² )/16，

n: tube end state (n = 0.25-4)

d ₁ : the outer diameter of the tube blank is as follows,

d ₂ : the inner diameter of the tube blank is less than the inner diameter of the tube blank,

YS: yield strength of pipe blank

In order to stably press the workpiece, when the measured load in the press direction (measured load) does not exceed the value (calculated load) of expression 4, the press can be continued in a holding state, and when the measured load exceeds the calculated load, the press can be temporarily stopped, and the press can be restarted by changing the conditions.

However, equation 4 is slightly complicated, and equation 5, which is a simplified equation 4, may be used to make the determination easier.

(equation 5) yield Strength YS X tube sectional area

Although the press limit load is expressed by an increase of 10% at the maximum in expression 5 compared to expression 4, the present inventors considered that the determination can be made sufficiently easily.

Further, when a blank tube that is too short (for example, 0.2m or less) is press-worked, or when the working speed is increased even if the tube is slightly buckled and the working is continuously performed to increase the load to such an extent that the die does not break, the following formula 6 can be used.

(formula 6) tensile Strength TS of tube blank X tube blank sectional area

The method of measuring the load (actual load in the press working direction) is preferably a method of measuring with a load cell provided in the press punch or a method of measuring with a load cell integrated with the die by raising the die from the frame.

When the measured load exceeds the calculated load calculated by any one of the equations 4 to 6, that is, when it is determined that machining is impossible, the press working is temporarily interrupted, the die and/or the mandrel bar are replaced with another shape corresponding to the same finished pipe size, and then machining is resumed. Here, since the dies and/or the mandrel bars having other shapes corresponding to the same finished pipe size can process the same raw pipe, they can be selected from dies and mandrel bars having the same diameter reduction ratio.

Further, in order to set more stable processing conditions, according to the study of the present inventors, it is considered that it is preferable that the angle between the die and the mandrel used after the replacement (see fig. 10) is smaller than the angle before the replacement.

In order to more stably set the working conditions, the type of the lubricant applied to the material tube may be changed. However, when the lubricant is applied by a method of immersing the raw pipe in the lubricant in the application tank from a so-called simple point of view, it is difficult to change the type of the raw pipe frequently because of the trouble of replacing the lubricant in the application tank. Therefore, it is important to select a lubricant having excellent performance for significantly reducing the load in the press working direction by performing a preliminary test as the lubricant.

In contrast, in the press working according to the present invention, as shown in fig. 1, a mandrel bar 1 is inserted into a tube 4, and the tube 4 is pressed into a hole of a die 2 and passed therethrough. The mandrel may contact the inner surface of the tube over the entire circumference within the machining gap, and the hole may contact the outer surface of the tube over the entire circumference within the machining gap. By the action of the pressing force 11 applied on the inlet side of the die 2, all the compressive stresses act in the machining gap. As a result, the tube 4 can be sufficiently contacted with the mandrel bar 1 and the die 2 at both the inlet side and the outlet side in the machining gap. Further, even if the diameter reduction ratio is light, the inside of the working gap becomes compressive stress, and thus the tube and the core rod, the tube and the die are likely to be in sufficient contact with each other, and the tube is likely to be smoothed, whereby a tube with high dimensional accuracy can be obtained. Further, even if the diameter reduction ratio is small at the time of pressing, the inner and outer surfaces of the pipe can be smoothed, and since the working deformation is small as compared with that at the time of drawing, the heat treatment load after diameter reduction is reduced, or the heat treatment can be omitted, and the manufacturing cost can be reduced.

Accordingly, the apparatus structure of the present invention is characterized by comprising: the following pressing operations are performed by a mandrel 1 which can be brought into full circumferential contact with the inner surface of a metal pipe 4, a die 2 having a hole which can be brought into full circumferential contact with the outer surface of the same pipe 4, and an extruder 3 which extrudes the same pipe 4: in a state where the mandrel bar 1 is fitted into the metal tube 4, the metal tube 4 is pressed into the hole of the die 2 by the extruder 3 and passed therethrough.

Further, in the press working by the conventional rotary forging machine 8 shown in fig. 3, since the split die 9 obtained by splitting the one-piece die in the circumferential direction is used and the split die 9 is swung (as shown by 12), a step height difference due to the splitting or uneven deformation due to the die rigidity different in the circumferential direction under high stress is generated, and therefore, the wall thickness accuracy cannot be sufficiently improved. In contrast, in the apparatus of the present invention, which is configured to be capable of performing pressing, since the die has the hole that contacts the outer surface of the pipe over the entire circumference in the same cross section and the metal pipe is passed through the hole of the die, the step difference caused by the split die does not occur at all, and as a result, the inner and outer surfaces of the pipe can be smoothed.

In the present invention, an integral fixed mold is used. The apparatus is simpler in structure than a method using a combination die mounted on an existing rotary forging machine. When a sufficient load is applied during the processing, the thickness of the outlet side is set to be equal to or less than the thickness of the inlet side of the die, so that the processing can be performed sufficiently even if the load is increased. Within a wide range of finished product required dimensions, a metal tube with significantly good dimensional accuracy can be obtained.

Further, in the present invention, the mandrel is floated. Even if the pressing conditions such as the angle of the die and the mandrel, lubrication of the surfaces of the die and the mandrel, and the like are changed complicatedly, the mandrel can be located at a position where the compressive stress is stably applied. Therefore, stable and good dimensional accuracy can be obtained.

Further, in the conventional drawing, the tip of the tube must be tapered and the portion must be drawn, and the tube cannot be processed individually. In contrast, in the present invention, since the tube is extruded, it is not necessary to taper the front end of the tube, and the tube can be continuously extruded. If the core rod is floated, continuous punching is possible, and productivity is remarkably improved. Further, when the length of the tube is short, a tube extruder which performs an intermittent extrusion operation is used, whereby a high productivity can be maintained and a high-precision tube can be manufactured. Further, the pipe extruder may support and extrude the middle portion of the pipe, or may extrude the end portion of the pipe.

In the case of tubes to be stamped, the finished dimensions are varied. In the press, in order to change the outer diameter of the product, dies having different hole patterns are prepared, and each time the outer diameter of the product is changed, the dies must be replaced. In addition, the hole pattern size of the mold is generally expressed by a diameter, an angle, and a taper length.

However, the outer diameter of the finished product is different for each small lot of the minimum number of tons, and each time the change is made, the mold that has been used previously must be removed and the mold to be used must be mounted, and considerable time and labor are required to make the mold mounting accuracy strictly in units of ± 0.1 mm.

In order to reduce the time and labor required for changing the dies, the present inventors have proposed that dies of various hole patterns corresponding to the outer diameter of the finished product be prepared, arranged in line, and changed sequentially.

In a method for producing a high dimensional accuracy pipe by loading a mandrel into a pipe, floating the mandrel, and continuously or intermittently pressing the pipe into a die and passing the pipe through the die, a plurality of dies having different hole patterns are arranged on the same circumference. Only the dies having the hole pattern corresponding to the target product size are rotated and moved in the circumferential direction of the array, and arranged in the pass line for pressing. When the target finished size of the rear pipe is different from that of the front pipe, the dies corresponding to the pass and the pipe outer diameter are also rotated and moved to be arranged in the pass line so as to be used for punching.

One example is shown in FIG. 11, which uses a die 2 for supporting and conveying a tube 4 in a circumferential direction while arranging a plurality of dies 2, 20, \ 8230;, 20 in a circumferential direction, an extruder 3 for pressing the tube 4 into the die 2 in a rolling line, and a plurality of dies 2, 20, \8230;, 20. The use of an apparatus having a die turret 19 in which any one of the dies 2 is arranged in the rolling line can be easily performed.

In another example, a plurality of dies having different hole patterns may be arranged on the same straight line, and any one of the dies may be moved in the direction of the arranged straight line in accordance with the product size so as to be arranged in the pass line for pressing.

As shown in FIG. 12, a plurality of dies 2, 20, \ 8230;, 20 are supported in a manner that the dies 2 are aligned on a straight line, and a die 2 through which a tube 4 is passed is conveyed in the straight direction, an extruder 3 for pressing the tube 4 into the die 2 in a pass line, and a plurality of dies 2, 20, \\8230;, 20 are used. The apparatus having the die linearly-moving table 19 in which any one of the dies 2 is arranged in the pass line can be easily implemented.

Further, it is also necessary to efficiently perform the core rod loading. In the die replacement, if the mandrel bar can be easily replaced, the efficiency is further improved. Since the core rod 1 used for the previous working remains in the die, it is removed at the same time as the die is replaced. The mandrel 22 necessary for the next process can be inserted into the tube during the die change.

For this reason, in either of the above-described

methods

1 and 2 of the present invention, when the finished size is changed between the front pipe and the rear pipe, the rear pipe is stopped at the die inlet side after the front pipe is pressed. The mandrel 22 corresponding to the finished size of the rear pipe is fitted into the rear pipe before, after, or during the movement of the die corresponding to the finished size of the rear pipe. This enables efficient replacement of the mandrel as well as efficient replacement of the die.

When the press working is performed, the pipe at the exit side of the die is easily bent. Since the tube cannot be finished as soon as it is bent, a processing technique that does not bend the tube is required. In the conventional drawing, the working efficiency is low because the pipe is drawn in the drawing direction, and the pipe is not easily bent, because the pipe is drawn in the drawing direction. However, the pipe on the exit side of the die is automatically moved during the press, and the pipe is easily bent due to the machining accuracy of the die, the wall thickness accuracy and surface condition of the pipe before machining, the uneven lubrication condition of the die and the mandrel, and the like. Therefore, a technique for preventing the bending of the pipe on the die outlet side is strongly demanded.

Therefore, the inventors conducted experiments in which guide tubes were provided on the inlet side and the outlet side of the die to guide the tube for bending of the tube after the press. When the guide cylinder is provided at either of the inlet side and the outlet side of the die, the tube becomes difficult to bend, and when provided at both of them, the tube becomes more difficult to bend, and further, the guide cylinder becomes more difficult to bend as it is positioned closer to the outlet side of the die.

Thus, guide cylinders may be provided immediately at the die inlet side and die outlet side. I.e. may be arranged at the exit side of the mould and very close to the mould. However, it is known that this cannot sufficiently prevent bending due to the difference in the bending direction of the tube. In order to sufficiently prevent bending regardless of the bending direction of the tube, the clearance between the tube outer surface and the guide cylinder inner surface must be set to almost zero. However, when the above arrangement is adopted, there is a problem that the contact between the pipe and the guide cylinder is excessive, thereby causing a defect or a significant increase in the punching force.

The inventors learned that the tube bending started immediately at the exit side of the die. That is, residual stress is generated in the tube due to the machining accuracy of the die, the wall thickness accuracy or surface condition of the tube before machining, the lubrication unevenness of the die and the mandrel bar, and the residual stress is suddenly released in the vicinity of the die exit side, so that the tube is naturally likely to be bent. Therefore, if a device capable of finely adjusting the bending direction of the tube is provided immediately at the die exit side, the tube can be sufficiently prevented from being bent.

As a result of intensive studies, the present inventors have provided a pipe bending fine adjustment device having a hole pattern through which a pipe passes, a support base plate which movably supports the hole pattern in a plane perpendicular to a pipe passing direction, and a hole pattern movement mechanism which moves the hole pattern by being supported by the support base plate, at the side close to the exit side of the mold. By finely moving the hole pattern in the support substrate by the hole pattern moving mechanism, the position of the hole pattern in a plane perpendicular to the pipe passing direction is finely adjusted in advance, and the pipe on the outlet side of the die is passed through the hole pattern, whereby the pipe can be sufficiently prevented from being bent.

In order to finely adjust the hole pattern position, for example, a press working experiment in which the hole pattern position is changed at multiple points is performed with a standard pipe several times before actual production, and the pipe bending is measured to find the relationship between the amount of change in the hole pattern position and the amount of change in the pipe bending after the press. In actual production, when the pipe bend exceeds a predetermined threshold, it is preferable to move the hole pattern to a direction in which the bend becomes small in accordance with the above-described relationship.

As the hole pattern moving mechanism, it is preferable that one position or two or more positions of the outer peripheral portion of the hole pattern are pressed in a direction perpendicular to the pipe-passing direction by means of, for example, a tapered surface of a wedge-shaped mold moved in the pipe-passing direction by a screw. Alternatively, it is preferable that, for example, a fluid pressure cylinder (hydraulic cylinder, air cylinder, or the like) directly push one position or two or more positions of the hole-shaped outer circumferential portion in a direction perpendicular to the pipe-passing direction.

When the hole diameter of the hole pattern is set to be larger than or equal to the hole diameter of the die exit, it is preferable that the tube is smoothly processed without being jammed on the die exit side in the press working process. In particular, it is more preferable because fine adjustment is easy when the hole diameter is within the range of +0mm to +3mm of the die exit hole diameter. In addition, the hole of the hole type may be a straight hole or a hole with a taper.

It is needless to say that a large hollow portion having a sufficient clearance to allow the passage of the tube is provided in the support substrate at a position intersecting the passage of the tube coming out of the die.

Further, when a guide cylinder through which a tube entering the die and/or a tube exiting from the tube bending micro-adjustment apparatus passes is provided on the inlet side of the die and/or the outlet side of the tube bending micro-adjustment apparatus, the tube enters the die substantially perpendicularly and/or exits from the tube bending micro-adjustment apparatus substantially perpendicularly, and therefore, the tube can be more easily prevented from bending, which is preferable.

Further, in the present invention, it is preferable to continue the tube and press it into the mold. By the continuous tube feeding, the mold or the core rod is subjected to the frictional heat or the working heat more smoothly than the working with a single piece, and thus the bending is easily further prevented. Further, in the press, since the interface processing for causing the drawing machine on the die outlet side to pinch the tube end as in the drawing is not required, the leading end can be continuously fed in a form of pressing the leading end by the leading end of the following tube, and the production efficiency can be improved.

In the case of conventional drawing, in order to obtain high dimensional accuracy, it is necessary to apply a sufficient lubricating film, and for this purpose, an adhesion treatment is performed with good lubrication. In this method, the tube is previously subjected to acid washing to remove oxide scale, and alkali washing and water washing are performed again in order to neutralize the acid. Then, the tube was immersed in a tank in which the adhesion treatment was performed to form a lubricating film, and the tube was further immersed in a metal soap tank to form a film, and then dried with hot air. Therefore, these steps take several hours or more, and when these steps are incorporated into a plant group for drawing a tube, productivity is significantly impaired, and therefore, the steps are required to be performed in a separate step.

In contrast, according to the press working, since high dimensional accuracy is easily obtained even if the diameter reduction ratio is small, lubrication of the pipe can be simple. That is, the tube may be not acid-washed, and may be hot-air dried after the lubricant is dip-coated. However, in order to continuously perform the punching, a right angle of the end face of the tube is necessary, and a grinding device for forming the right angle is necessary.

Among these treatments before press working, the processes of squaring of the end face, dip coating with a lubricant, and drying are most effective in this order. From these viewpoints, in the present invention, a pipe end surface grinding device for grinding an end surface of a pipe to be perpendicular to a pipe axial direction, a lubricant dip coating tank for dip coating a lubricant on the pipe, and a drying device for drying the pipe coated with the lubricant are disposed in this order on an inlet side of a press working device as a set of equipment, and a high dimensional accuracy pipe can be efficiently manufactured.

Further, since it is more efficient to form the right angle of the end face of the pipe directly after cutting the pipe into a short size, it is preferable that a cutting device for cutting the pipe into a short size is disposed at the inlet side of the pipe end face grinding device in the equipment set of the present invention.

Further, if a lubricant which is easily formed into a film by drying is used as the lubricant, instead of performing dip coating on the inlet side of the press working and then drying, spraying may be performed on the inlet side of the die in the press working apparatus and then drying may be performed, or if the lubricity is more excellent, drying may be omitted and the press working of the pipe may be performed in a wet state. Therefore, instead of the lubricant-impregnated coating tank and the drying device, a lubricant spraying device for spraying a lubricant onto a pipe or a lubricant spray drying device for spraying a lubricant onto a pipe and drying the lubricant may be disposed on the die inlet side of the press working device in the equipment set of the present invention.

Further, in order to further improve the press working efficiency, it is preferable that the die and the mandrel can be easily replaced on line, and that the pipe is not bent on the die exit side. From these viewpoints, in the equipment set of the present invention, it is preferable that one or more of a die exchanging device for exchanging the die, a mandrel bar exchanging device for exchanging the mandrel bar, and a bending preventing device for preventing bending of the pipe on the exit side of the die are disposed simultaneously with the press working device.

The die (or mandrel) exchanging device is preferably configured to sequentially transfer and arrange the dies (or mandrels) at predetermined positions in the pass line while holding a plurality of dies (or mandrels) of different sizes (and/or shapes in the order of use. The bending prevention device is preferably configured to apply a force in a direction opposite to the bending direction of the pipe at the outlet side of the die, for example, using a movable disk or the like having a pipe through hole.

In addition, in both drawing and pressing which have been used in the present invention, since a tube whose surface has been pickled after processing is often required, it is possible to carry out pickling by other steps and then shipment. In drawing, the tube blank needs to be pickled in order to form a strong film of the lubricant during the adhesion treatment before the drawing, and pickling is required again to remove the lubricant after the drawing is continued, so that pickling must not be performed twice. In contrast, in the press, the lubrication treatment before the working is simple, and the scale can be adhered, so that the lubrication treatment can be incorporated into the equipment group on line, and the equipment group can be inexpensive and efficient.

Example 1

The present invention will be described in more detail with reference to examples.

In example 1.1, a steel pipe having an outer diameter of 40mm × a wall thickness of 6mm was subjected to press working in the manner shown in FIG. 1. Here, a mandrel whose surface contacting the inner surface of the tube is a mirror surface and a die whose surface contacting the outer surface of the tube is a mirror surface are used, and the die is an integral fixed die. One end of the core rod is fixed and is arranged in the tube. The processing conditions were outlet side wall thickness = inlet side wall thickness and diameter reduction =10%.

In example 1.2, the same processing as in example 1.1 was performed except that the diameter reduction = 5%.

In example 1.3, the same working as in example 1.2 was carried out except that the mandrel bar was floated.

As comparative example 1, processing was performed in the same manner as in example 1.2, except that drawing in the form shown in fig. 2 was used instead of pressing in the form shown in fig. 1, and the outlet-side plate thickness was made smaller than the inlet-side plate thickness.

In comparative example 2, the same processing as in example 1.2 was performed except that the integrated fixed die was replaced with the split die of the embodiment shown in fig. 3, the split die was used by being set in a rotary forging machine and oscillated, and the press-fitting was used instead of the press-fitting.

In comparative example 3, the processing was performed in the same manner as in comparative example 2, except that the processing conditions were outlet-side wall thickness = inlet-side wall thickness +1mm (= 7 mm).

The three dimensional accuracy indexes of the steel pipes after diameter reduction were obtained, and the steel pipes were subjected to a fatigue test. The results are shown in Table 1.

Further, the outer diameter and inner diameter deviations shown in table 1 were obtained by measurement using the laser beam, and the circumferential wall thickness deviation was obtained from the difference in the circumferential distribution of the measurement data.

Further, as shown in fig. 4, in a test in which the number of repetitions until cracking occurs (i.e., the number of times of endurance) is determined with stress kept constant, the stress level is variously changed, and the relationship between the stress and the number of times of endurance is graphically shown, and the number of times of endurance limit in the fatigue test shown in table 1 is the number of times of endurance in which the stress starts to change from a downward trend to a substantially constant yield point as the number of times of endurance increases. The larger the value, the better the fatigue strength. That is, in this example, the number of times of durability is set at a stress of about 150 MPa.

From table 1, the dimensional accuracy of the finished pipes of examples 1.1 to 1.3 was remarkably good, the fatigue strength was also the best, and the dimensional accuracy was particularly good when the mandrel bar was floated (example 1.3). In contrast, in the conventional drawing, the fatigue strength was remarkably reduced as a result of the low dimensional accuracy of the finished pipe (comparative example 1). Even in the case of press-fitting using a rotary forging machine, the dimensional accuracy of the finished pipe is low (comparative example 2), and when the thickness is increased, the dimensional accuracy is further poor (comparative example 3), and sufficient fatigue strength cannot be obtained.

Example 2

In the present example, a steel pipe of phi 40mm × 6mmt × 5.5mmL was used as a billet, a mirror-faced mandrel bar and an integral fixed die were used, the mandrel bar was floated and fitted into the steel pipe, the steel pipe was extruded from the die inlet side at a reduction ratio of 5%, the thickness of the steel pipe on the die outlet side was made equal to the thickness of the steel pipe on the die inlet side and was set to 6mmt, and the press was performed. In addition, an intermittent conveyor of the form shown in fig. 7 was used as a tube-feeding device to continuously feed the tube inside the mold.

Further, as comparative example 1, drawing in the form of fig. 2 was performed. In this example, the same steel pipe was used as a billet, the same mandrel bar and the same die were used, the mandrel bar was set in the steel pipe, the steel pipe was pulled from the die exit side at the same diameter reduction ratio, and the steel pipe wall thickness on the die exit side was reduced to 5.5mmt.

As comparative example 2, the rotary forging press-fitting method of the embodiment of fig. 3A and 3B was performed. In this example, the same steel pipe was used as a billet, and a rotary forging machine was used, in which the same mandrel bar was inserted into the steel pipe using a split die instead of the integrated fixed die, and the rotary forging press-fitting was performed at the same reduction ratio, and the thickness of the steel pipe on the outlet side of the forging machine was increased to 7mmt.

The dimensional accuracy (variation in outer diameter, variation in inner diameter, and variation in wall thickness in the circumferential direction) of the steel pipes produced by the methods of the examples was measured, and the machining efficiency was examined. The results are shown in Table 2. Further, the outer diameter deviation and the inner diameter deviation are obtained by analyzing the circumferential cross section of the tube with an image and calculating the deviation from the perfect circle in the circumferential direction. Then, the circumferential cross section of the tube is image-analyzed, and the circumferential wall thickness variation, which is the maximum variation from the average wall thickness, is directly measured from the image of the wall thickness cross section.

According to table 2, the steel pipes produced by the press working of the present invention example had remarkably good dimensional accuracy and good working efficiency. On the contrary, the steel pipe manufactured by drawing of comparative example 1 had low dimensional accuracy. Further, the steel pipe manufactured by press-fitting by rotary forging of comparative example 2 also had low dimensional accuracy. In addition, the drawing and rotary forging press-in processing efficiency is obviously reduced.

Example 3

Comparative example 3.1 an electric resistance welded steel pipe having a hot rolled scale on the surface and having a diameter of 40 mm. Times.6.0 mmt. Times.5.5 mL was worked under the following condition A by punching as shown in FIG. 1.

(Condition A) mandrel: the mirror surface core rod is arranged in the steel pipe to float

A mould: integrated fixed die

Diameter reduction: 5 percent of

Wall thickness of steel pipe on the outlet side of die: 6.0mmt (= inlet sidewall thickness)

(invention example 3.1) the steel pipe was processed in the same manner as in comparative example 1, after applying a liquid lubricant (mineral oil) to both the inner and outer surfaces of the pipe and forming a lubricating film.

(invention example 3.2) the steel pipe was coated with a grease lubricant (molybdenum disulfide was added to the Li grease lubricant) on both the inner and outer surfaces of the pipe, and after a lubricating coating was formed, the steel pipe was processed in the same manner as in comparative example 1.

(inventive example 3.3) the steel pipe was coated with a drying resin (polyalkyl resin) on both the inner and outer surfaces of the pipe, dried in hot air (about 200 ℃ C.), and then processed in the same manner as in comparative example 1.

(inventive example 3.4) the steel pipe was similarly processed in the same manner as in comparative example 1, after applying a liquid obtained by diluting a drying resin (polyalkyl resin) in a solvent (acetone) to both the inner and outer surfaces of the pipe, and drying the resultant in warm air (about 50 ℃ C.) to form a lubricating film.

(inventive example 3.5) the steel pipe was similarly processed in the same manner as in comparative example 1, after coating the inner and outer surfaces of the pipe with a latex in which a drying resin (polyalkyl resin) was dispersed in a dispersion medium (water) and drying the latex in warm air (about 70 ℃).

Comparative example 3.2 the same liquid lubricant as in example 1 of the present invention was applied to both the inner and outer surfaces of the steel pipe to form a lubricating film, and then the steel pipe was processed by the cold drawing method shown in fig. 2 under the following condition B.

(condition B) mandrel, die, and reduction ratio: are the same as in condition A

Thickness of steel pipe on die outlet side: 5.5mmt (< inlet sidewall thickness)

Comparative example 3.3 the same liquid lubricant as in example 1 of the present invention was applied to both the inner and outer surfaces of the steel pipe to form a lubricating film, and then the steel pipe was processed under the following condition C by the rotary forging press-fitting method shown in fig. 3.

(Condition C) mandrel: same as in condition A

A mould: combined die

Diameter reduction: same as in condition A

Thickness of steel pipe on die outlet side: 7.0mm (> inlet sidewall thickness)

The surface defect state and the dimensional accuracy (outer diameter variation, inner diameter variation, and wall thickness variation) of the steel pipes produced by the methods of the above examples are measured, and the results are shown in table 3. Further, the maximum deviation from the perfect circle (that is, (maximum diameter-minimum diameter)/perfect circle diameter × 100%) is calculated in the circumferential direction by image-analyzing the circumferential cross section of the tube, and the outer diameter deviation and the inner diameter deviation are determined. Further, the circumferential direction cross section of the tube was image-analyzed, and the wall thickness deviation as the maximum deviation from the average wall thickness (i.e., (maximum wall thickness-minimum wall thickness)/average wall thickness × 100%) was directly determined from the image of the wall thickness cross section.

According to table 3, in all of the inventive examples in which the pressing was performed under the lubrication condition, no defect was generated on the surface of the steel pipe after the working, and good surface quality and dimensional accuracy were obtained. In contrast, in comparative example 1 in which pressing was performed under a non-lubricated condition, defects were generated on the surface of the steel pipe after processing. In comparative example 2 in which the working was performed by the cold drawing method under the lubrication condition, the dimensional accuracy was low. In comparative example 3 in which the working was performed by the rotary forging press-fitting method under the lubrication condition, the dimensional accuracy was further lowered.

In the present embodiment, although the case of so-called double-sided lubrication in which a lubricating coating is formed on both the inner and outer surfaces of the pipe is shown, it is clear that the present invention is not limited to this, and may include the case of so-called single-sided lubrication in which a lubricating coating is formed on either the inner surface or the outer surface, that is, the case of preventing the occurrence of a defect on the surface on the side on which the lubricating coating is formed during single-sided lubrication.

(example 4)

A steel pipe having a diameter of 40 mm.times.6.0 mmt.times.5.5 mL was used as a billet, and the pipe expansion and subsequent diameter reduction were performed on the billet in accordance with the present invention (press working using a mandrel bar capable of pipe expansion and diameter reduction) schematically shown in FIG. 1. The target wall thickness at the exit side of the die was the same as that at the entrance side and was 6.0mmt. The mirror-finished core rod was floated in the tube. The mold used was an integral fixed mold in which the inner surface of the mold hole was mirror-finished. The values shown in table 4 were set for each of the examples of the expansion ratio and the reduction ratio of the mandrel bar, the taper angles θ a and θ B of the expanded portion and the reduced portion, and the target outer diameter D2 of the pipe on the die outlet side (after reduction). The tube is continuously fed to the mold.

Comparative example A

The tube blank was reduced by the cold drawing method (diameter reduction only) shown in FIG. 2, as described above. The target wall thickness at the exit side of the die was the same as that at the entrance side and was 6.0mmt. The mirror-finished core rod was floated in the tube. The mold used was an integral fixed mold in which the inner surface of the mold hole was mirror-finished. The diameter reduction ratio of the mandrel bar and the target outer diameter of the pipe on the die outlet side were set to the values shown in table 4 for each of the examples. The tube is continuously fed to the mold.

Comparative example B

The pipe blank was reduced in diameter by the rotary forging press-in method (diameter reduction only) shown in FIG. 3, as described above. The target wall thickness at the exit side of the die was the same as that at the entrance side and was 6.0mmt. The mirror-finished core rod was floated in the tube. The used mold is a combined mold after mirror finish machining is carried out on the inner surface of the mold hole. Examples in which the diameter reduction ratio of the mandrel bar and the target outer diameter of the pipe on the die outlet side were set for each are shown in table 4. The tube is continuously fed to the mold.

The dimensional accuracy (outer diameter variation, inner diameter variation, wall thickness variation) was measured for the steel pipes produced under the conditions of the above examples. The maximum deviation from the perfect circle (i.e., (maximum diameter-minimum diameter)/diameter of perfect circle x 100%) is calculated in the circumferential direction by image-analyzing the circumferential cross section of the tube, and the outer diameter deviation and inner diameter deviation are determined. Then, the circumferential cross section of the tube was analyzed by image analysis, and the wall thickness deviation was directly measured as the maximum deviation from the average wall thickness (i.e., (maximum wall thickness-minimum wall thickness)/average wall thickness × 100%) from the image of the wall thickness cross section. Then, the section hardness was measured as an index of the degree of processing. As an index for determining whether or not a pipe of a predetermined size is obtained after machining, the average outer diameter and the average wall thickness of the pipe after machining, which are obtained while measuring the above dimensional accuracy, are used. These results are shown in table 4.

From table 4, in the present invention example, the dimensional accuracy after the working was remarkably good, and by changing the combination of the mandrel bar and the die, pipes having a constant size and different degrees of working could be obtained from the same size of the blank pipe. In contrast, in the comparative example, the dimensional accuracy was low, and when tubes having different degrees of processing were to be obtained from raw tubes of the same size, it was not possible to obtain an outer diameter or wall thickness of a certain size. In the present invention example satisfying one or both of θ a < θ B and D2 < D0, the floating state of the mandrel bar in the tube is further stabilized.

Further, the expansion ratio a (%) = (D1-D0)/D1 × 100

Reduction ratio of b (%) = (D1-D2)/D1X 100

Example 5

(inventive examples 5.1 to 5.4)

A press working as shown in FIG. 1 was attempted using a mirror-faced mandrel bar and an integral fixed die as a blank tube made of an electric resistance welded steel tube having an outer diameter of 40mm X a wall thickness of 6 mm. The shape conditions of the mandrel and the die used (the mandrel reduced diameter portion angle, the mandrel reduced diameter portion length, the mandrel receiving portion length, and the die angle) are shown in table 5. The mandrel is allowed to float within the tube. The thickness of the pipe wall on the die outlet side was set to 5mm.

Comparative examples 5.1 to 5.4

Press working was attempted in the same manner as in the present invention example except that the steel pipe of the same lot as in the present invention example was used as the raw pipe, and the shape conditions of the mandrel bar and the die used were changed as shown in table 5.

(conventional example 5.1)

A steel pipe of the same lot as that of the example of the present invention was used as a raw pipe, and a mirror-surface mandrel bar and an integrated fixed die were used to perform the cold drawing test shown in fig. 2. The shape conditions of the core rod and the die used are shown in table 5. The mandrel is allowed to float within the tube. The thickness of the die outlet side was set to 5mm.

(conventional example 5.2)

Steel pipes of the same lot as the example of the present invention were used as a blank pipe, and a mirror-finished mandrel bar and a rotary forging machine equipped with a combined die were used to perform a trial working according to the rotary forging press-in method shown in fig. 3A and 3B. The shape conditions of the core rod and the die used are shown in table 5. The mandrel is allowed to float within the tube. The wall thickness of the tube at the outlet side of the die was thickened to 7mm.

The production availability and the dimensional accuracy (outer diameter variation, inner diameter variation, and wall thickness variation) of the finished pipe measured when the pipe is produced by the methods of the above examples are shown in table 5. Here, the cross section of the image analysis tube in the circumferential direction is calculated as the maximum deviation from the perfect circle (i.e., (maximum diameter-minimum diameter)/diameter of the perfect circle × 100%) in the circumferential direction, and the outer diameter deviation and the inner diameter deviation are determined. On the other hand, the circumferential direction cross section of the tube was image-analyzed, and the wall thickness deviation as the maximum deviation from the average wall thickness (i.e., (maximum wall thickness-minimum wall thickness)/average wall thickness × 100%) was directly measured from the image of the wall thickness cross section.

According to table 5, in the present invention example, the press-forming can be stably performed, and the dimensional accuracy of the finished pipe is remarkably good. In contrast, in any of the comparative examples, the press working could not be completed, and a finished pipe could not be obtained. In the conventional example, the finished pipe that can be finished has low dimensional accuracy.

Example 6

(example 6.1)

A steel pipe having a diameter of 40mm × 6.0mmt × 5.5mL and YS400MPa was used as a billet, and a high dimensional accuracy pipe was produced by press working with a diameter reduction of 13% in the mode shown in FIG. 10. In the initial stage of production, a die having an angle of 21 DEG and a core rod having an angle of 21 DEG and a taper length of 11mm were used. The mandrel is allowed to float within the tube. The lubricant is applied to each of the pipe blanks before the working by immersing the pipe blanks in the lubricant in the coating tank. As the lubricant, a polymer lubricant diluted with a quick-drying solvent is used.

In the machining, the load in the press direction is constantly measured by the above-described measuring method, and pressing is performed while comparing the measured load with the calculated load calculated by the above-described equation 4. In equation 4 related to this example, the values of a and n are the optimum values experimentally derived in advance, and a =0.00185 and n =1 (corresponding to the case where the chip state is the freely rotatable state).

During the processing of a certain blank, since the measured load exceeds the calculated load, it is determined that the processing cannot be continued, the processing is interrupted, and then the processing conditions are changed, that is, the die is replaced by a die having an angle of 11 °, and the mandrel is replaced by a mandrel having an angle of 11 ° and a taper length of 20 mm. After the replacement, the machining is started, and the machining of the remaining plurality of blank pipes can be completed without difficulty.

Further, when the replacement and the machining are resumed, the die entrance side portion and the die exit side portion of the tube in process entering the die used first are cut and separated, the mandrel used first is mounted in the tube, the die used first including the die inside portion of the tube is removed from the predetermined mounting position, the die used later is mounted on the same predetermined mounting apparatus, the mandrel used later is mounted on the tube blank of the same size and the same YS for the post-machining, and the machining is resumed. Also, the die outlet side portion of the above-described separated tube can be used as a finished product. The die inlet side portion of the tube becomes scrap.

Comparative example 6.1

A steel pipe similar to that of example 6.1 was used as a raw pipe, and a high dimensional accuracy pipe was produced by press working with a diameter reduction of 13% in the mode shown in fig. 10. In the initial stage of production, a die having an angle of 21 ° and a mandrel having an angle of 21 ° and a taper length of 20mm were used. The mandrel is allowed to float within the tube. The pipe blanks before being processed are coated with the lubricant by immersing the pipe blanks in the lubricant in a coating tank. As the lubricant, a polymer lubricant diluted with a quick-drying solvent is used.

During machining, the load in the press direction is not measured, and the condition change during abnormality depends on the judgment of the operator.

During the processing of a certain pipe billet, the processing is interrupted due to the die breakage, the same die and mandrel bar as in the initial stage are replaced, and the lubricant in the lubricant application tank is entirely replaced with a polymer lubricant diluted with a quick-drying solvent having a larger molecular weight. When the machining is resumed thereafter, the die is broken again during the machining of a certain blank from the time of resumption. Therefore, the machining is interrupted and the machining conditions are changed as follows. That is, the die was replaced with a die having an angle of 11 °, and the mandrel was replaced with a mandrel having an angle of 11 °, and a taper length of 20 mm. After the replacement, the machining is started, and the machining of the remaining plurality of blank tubes can be completed without difficulty.

Comparative example 6.2

A high dimensional precision tube was produced by drawing the same steel tube as in example 6.1 as a parent tube with a diameter reduction of 13%. In the initial stage of production, a die having an angle of 21 ° and a mandrel having an angle of 21 ° and a taper length of 20mm were used. The mandrel is allowed to float within the tube. Each of the blank pipes before the working was subjected to an adhesion treatment and applied with a metal soap, and at the same time, a joint working of the pipe end, which is necessary for drawing, was performed (this joint working was not necessary for pressing).

During the machining, the load in the drawing direction is not measured, and the condition change during the abnormality depends on the judgment of the operator.

In the middle of processing a certain pipe blank, the die is broken, and the processing is interrupted, and the processing conditions are changed as follows. That is, the die was replaced with a die having an angle of 11 °, and the mandrel was replaced with a mandrel having an angle of 11 °, and a taper length of 20 mm. After the replacement, the machining is started, and the machining of the plurality of remaining blank pipes can be completed without difficulty.

Table 6 shows the results of the examination of the dimensional accuracy of the finished product and the conditions changed during the machining, the relative machining time, and the loss during the machining for the examples and comparative examples. The relative processing time is represented by the ratio of the time required for processing in each example (total processing time/total number of processed pieces) to that in comparative example 1. The dimensional accuracy is expressed in wall thickness variation and outer diameter variation. These deviations are obtained from data obtained from the circumferential cross-section of the tube by image analysis, the wall thickness deviation being obtained as a value relative to the average wall thickness, and the outer diameter deviation being obtained as a value relative to a perfect circle (target outer diameter).

As is clear from table 6, the present invention can stably and efficiently manufacture a high dimensional accuracy tube.

Example 7

The present invention will be described more specifically with reference to examples.

The apparatus of example 7.1 is an apparatus in which a mandrel bar 1, a die 2, and a pipe extruder 3 are combined as shown in fig. 1. The contact surface of the core rod and the inner surface of the tube is made into a mirror surface, the diameter of the inlet end of the mirror surface is 28mm, the diameter of the central part of the mirror surface is 30mm, and the diameter of the outlet end of the mirror surface is 28mm; the die is an integrated fixed die, the inner surface of the hole is made into a mirror surface, and the diameter of the outlet of the hole is 40mm; the tube extruding machine is composed of an oil hydraulic cylinder, and causes extruding force to act on the tube according to a set operation mode which can operate under either a continuous extrusion operation mode or an intermittent extrusion operation mode. The mandrel bar 1 is a fixed mandrel bar having one end fixedly fitted into a tube, and the operation mode of the tube extruding machine 3 is set to "intermittent extrusion". The carbon steel pipe having an outer diameter of 40mm X a wall thickness of 6mm was pressed by using this apparatus to obtain a finished pipe having an outer diameter of 38mm X a wall thickness of 6 mm.

In example 7.2, a carbon steel pipe having an outer diameter of 40mm × a wall thickness of 6mm was pressed in the same manner as in example 7.1 except that the fixed mandrel bar was replaced with a floating mandrel bar, to obtain a finished pipe having an outer diameter of 38mm × a wall thickness of 6 mm.

In example 7.3, a carbon steel pipe having an outer diameter of 40mm × a wall thickness of 6mm was pressed in the same manner as in example 7.2 except that the setting of the operation mode of the pipe extruding machine 3 was changed from "intermittent extrusion" to "continuous extrusion", thereby obtaining a finished pipe having an outer diameter of 38mm × a wall thickness of 6 mm.

As comparative example 1, a mandrel bar 5, a die 6, and a tube drawing machine 7 were combined as shown in fig. 2. The contact surface of the core rod and the inner surface of the tube is made into a mirror surface, the diameter of the inlet end of the mirror surface is 28mm, the diameter of the central part of the mirror surface is 28mm, and the diameter of the outlet end of the mirror surface is 26mm; the die is an integrated fixed die, the inner surface of the hole is made into a mirror surface, and the diameter of the outlet of the hole is 38mm; the tube drawing machine is composed of a hydraulic cylinder, and applies a drawing force to the tube according to a set operation mode capable of operating in an "intermittent drawing" mode. The mandrel 5 is a fixed mandrel having one end fixedly fitted into the tube. Using this apparatus, a carbon steel pipe having an outer diameter of 40mm and a wall thickness of 7mm was pressed to obtain a finished pipe having an outer diameter of 38mm and a wall thickness of 6 mm. In comparative example 1, it takes a little time to narrow the tip of the steel pipe and then pass through the die hole.

In comparative example 2, a carbon steel pipe having an outer diameter of 40mm × a wall thickness of 5mm was pressed in the same manner as in example 7.1 except that the mandrel bar 1 was replaced with the same mandrel bar 5 as in comparative example 1 and the apparatus shown in FIG. 3 was configured with a split die 9 (the exit-side inner diameter of which was the same as the hole exit diameter of the die 2) incorporated in a rotary forging machine 8 in place of the die 2, to obtain a finished pipe having an outer diameter of 38mm × a wall thickness of 6 mm.

The results of measuring the dimensional accuracy of these finished tubes are shown in Table 7. The measurement methods of the variations in the circumferential thickness, the inner diameter, and the outer diameter shown in table 7 are as follows.

The pipe is rotated by bringing a micrometer into contact with the outer surface (or inner surface) of the pipe, and the outer diameter (or inner diameter) deviation, which is the maximum deviation from a perfect circle, is calculated from the measured outer diameter (or inner diameter) distribution data in the circumferential direction. The circumferential wall thickness variation, which is the maximum variation from the target wall thickness, is directly measured from the image of the wall thickness cross section. Alternatively, instead of bringing the micrometer into contact with the tube, laser irradiation may be used to calculate the outer diameter deviation and the inner diameter deviation from the measured data of the circumferential distance distribution between the tube and the laser vibration source. The circumferential thickness variation may be calculated as a difference between the circumferential distribution data of the outer diameter and the circumferential distribution data of the inner diameter.

In addition, the wall thickness variation (= circumferential wall thickness variation), inner diameter variation, and outer diameter variation are defined as follows.

Wall thickness deviation = (maximum wall thickness-minimum wall thickness)/target wall thickness (or average wall thickness) × 100 (%)

Inner diameter deviation = (maximum inner diameter-minimum inner diameter)/target inner diameter (or average inner diameter) × 100 (%)

Outer diameter deviation = (maximum outer diameter-minimum outer diameter)/target outer diameter (or average outer diameter) × 100 (%)

From table 7, the dimensional accuracy of the finished pipes manufactured by the apparatuses of examples 7.1 to 7.3 was remarkably good, and particularly, the finished pipes were better when the mandrel bar was floated (example 7.2), and the finished pipes with high dimensional accuracy could be obtained even when the joining press was performed (example 7.3). On the contrary, in the conventional drawing, the dimensional accuracy of the finished pipe was low (comparative example 7.1). The dimensional accuracy of the finished pipe was low even when the pipe was press-fitted by the rotary forging machine (comparative example 7.2).

Example 8

(inventive example 8.1)

A steel pipe of phi 40mm x 6.0mmt x 5.5mL is used as a blank pipe, a plurality of dies 2, 20, \\8230:, 20 corresponding to the finished dimensions of the respective pipes are assembled in a die turret 19 in a predetermined pipe processing order as shown in FIG. 11, then the die 2 corresponding to the finished dimensions of the front pipe 4 is arranged in a rolling line, the front pipe 4 is pressed into the die 2 by an extruder 3 to complete the press working, the die turret 19 is rotated to sequentially convey the plurality of dies, the dies 2 are replaced, the die 20 corresponding to the finished outer diameter dimensions of the rear pipe 7 is arranged in the rolling line, at this time, a mandrel bar 22 is put into the rear pipe 5 before the die 20 is arranged in the rolling line, and then the rear pipe 7 is pressed into the die 20 by the extruder 3 to perform the press working. The above operations are repeated to manufacture high-dimensional precision tubes of various finished sizes.

(inventive example 8.2)

A steel pipe having a diameter of 40mm x 6.0mmt x 5.5mL is used as a blank pipe, a plurality of dies 2, 20, \ 8230:, 20 corresponding to the finished dimensions of the respective pipes are assembled in a predetermined pipe processing sequence on a die linear stage 23 as shown in FIG. 12, the die 2 corresponding to the finished dimensions of the front pipe 4 is then arranged in a rolling line, the front pipe 4 is pressed into the die 2 by an extruder 3 to complete the press working, the die linear stage 23 is linearly moved to sequentially convey the plurality of dies, the die 2 is replaced, and the die 20 corresponding to the finished outer diameter of the rear pipe 7 is arranged in the rolling line. At this time, the mandrel bar 22 is loaded into the rear tube 5 before the die 20 is disposed in the pass line. Next, the rear pipe 7 is pressed into the die 20 by the extruder 3 and press-worked. The above operations are repeated to produce high dimensional precision tubes of various finished product sizes.

Comparative example 8.1

A steel pipe having a diameter of 40 mm. Times.6.0 mmt. Times.5.5 mL was used as a blank pipe, and a plurality of dies having different hole patterns were prepared and pressed as shown in FIG. 13. The die 2 used at the start is arranged in the pass line, and first, the front pipe 4 is pressed into the die 2 by the extruder 3 to complete the press working. Next, the die 2 is manually replaced, and the die 20 corresponding to the finished outer diameter of the rear pipe 7 is disposed in the pass line. At this time, the mandrel bar 22 is fitted into the rear tube 7 before the die 20 is disposed in the pass line. Then, the rear pipe 7 is pressed into the die 20 by the press 3 and press-worked. The above operations are repeated to manufacture high dimensional precision tubes of various finished sizes.

Comparative example 8.2

A steel pipe having a diameter of 40 mm. Times.6.0 mmt. Times.5.5 mL was used as a blank pipe, and a plurality of dies having different hole patterns were prepared and pressed as shown in FIG. 13. The die 2 used at the start is arranged in the pass line, and first, the front pipe 4 is pressed into the die 2 by the extruder 3 to complete the press working. Next, the die 2 is manually replaced, and the die 20 corresponding to the finished outer diameter of the rear pipe 7 is disposed in the pass line. At this time, the rear pipe 7 is once moved out of the pass line, the mandrel bar 22 is installed, and thereafter, the rear pipe 7 is returned into the pass line again. Then, the rear pipe 7 is pressed into the die 20 by the extruder 3 and press-worked. The above operations are repeated to manufacture high dimensional precision tubes of various finished product sizes.

The processing efficiency and the dimensional accuracy of the finished products of the inventive examples and comparative examples are shown in table 8. The machining efficiency was evaluated by the number of steel pipe punches per unit working time, and in table 8, the machining efficiency of comparative example 2 was represented by 1 and its relative value. The dimensional accuracy is expressed by the wall thickness deviation and the outer diameter deviation. These deviations are obtained from data obtained by image analysis of the circumferential cross section of the tube, the wall thickness deviation being obtained as a deviation value from the average wall thickness, and the outer diameter deviation being obtained as a deviation value from the true circle (target outer diameter).

As can be seen from table 8, the press working efficiency can be particularly improved by the present invention.

Example 9

The present invention will be described in detail below with reference to examples.

(example 9.1)

As shown in fig. 14, a pipe bending fine adjustment device 24 is provided immediately at the exit side of the die 2. Although not shown, a continuous extruder is provided on the inlet side of the die 2 to continuously press the tube 4 into the die 2 while holding the tube 4 by a crawler.

As shown in fig. 15, the pipe bending fine adjustment device 24 movably supports a groove 26 having a hole 27 through which a pipe passes in a plane perpendicular to the pipe passing direction by a support base 28, and presses any one of 4 positions or 2 or more positions of an outer peripheral portion of the groove 26 in a direction perpendicular to the pipe passing direction (a groove moving direction 33) by a groove moving mechanism 29 supported by the support base 28, and as shown in fig. 16, brings a tapered surface of a wedge mold 30 into contact with the outer peripheral portion of the groove 26, and moves the wedge mold in the pipe passing direction 25 by an adjustment screw 31 screwed with the wedge mold 30, thereby applying a pressing force. In fig. 16, when the adjustment screw 31 is rotated rightward, the wedge mold 30 is lifted, and the groove pattern 26 in contact with the tapered surface moves leftward. After the hole position is finely adjusted, the fixing screw 32 is tightened to fix the hole 26 to the support base 28.

Using this apparatus, a steel pipe of phi 40mm × 6.0mmt × 5.5mL was used as a raw pipe, a mandrel bar 1 was inserted into the pipe to float the mandrel bar, and the raw material was continuously conveyed to be pressed into a die 2, thereby producing a high dimensional accuracy pipe by this press working. The steel pipe after press working penetrates through the hole 27 of the hole pattern 26 at the side of the outlet of the die 2. The holes 27 of the hole pattern 26 are straight holes having a hole diameter 0.5mm larger than the die exit hole diameter (35 mm in this example).

Before actual manufacturing, a press working experiment in which the hole pattern position was changed at multiple points was performed with a standard pipe several times, and the pipe bending was measured to obtain the relationship between the amount of change in the hole pattern position and the amount of change in the pipe bending after pressing. In actual manufacturing, when the pipe is bent beyond a predetermined threshold, the hole pattern is moved to a direction in which the bending becomes smaller in accordance with the above-described relationship, and fine adjustment of the hole pattern position is performed.

(example 9.2)

As shown in fig. 17, a pipe bending fine adjustment device 24 is provided in close proximity to the outlet side of the die 2, a guide cylinder 35 is provided in close proximity to the inlet side of the die 2, and a guide cylinder 36 is provided in close proximity to the outlet side of the pipe bending fine adjustment device 24. Although not shown, a continuous extruder is provided on the inlet side of the inlet-side guide cylinder 35 to continuously press the pipe 4 into the die 2 while holding the pipe with a crawler.

As shown in fig. 18, the pipe bending fine adjustment device 24 movably supports a groove 26 having a hole 27 for passing a pipe in a plane perpendicular to the pipe passing direction by a support base plate 28, and applies pressure by a small hydraulic cylinder 34 in contact with the outer periphery of the groove 26 at any one position or at 2 or more positions of 4 positions of the outer periphery of the groove 26 in a direction perpendicular to the pipe passing direction (groove moving direction 33) by a groove moving mechanism 29 supported by the support base plate 28. In fig. 18, by adjusting the pressure difference between the two opposing hydraulic cylinders 34, the orifice 26 moves in the direction in which the two hydraulic cylinders 34 oppose each other. After fine adjustment of the orifice position, the pressure difference between the opposing hydraulic cylinders 34 is set to zero, and the orifices 26 are fixed to the support base plate 28.

Using this apparatus, a steel pipe of phi 40mm × 6.0mmt × 5.5mL is used as a billet, a mandrel bar 1 is inserted into the pipe to float the mandrel bar, and the billet is continuously conveyed to be pressed into a die 2, whereby a high dimensional accuracy pipe is manufactured by this press working. The steel pipe before the press working penetrates the inlet-side guide cylinder 35, and the steel pipe after the press working penetrates the hole 27 of the pass 26 on the outlet side of the die 2 and the outlet-side guide cylinder 36 in this order. The hole 27 of the hole pattern 26 is a tapered hole whose maximum inner diameter portion (on the inlet side) has a hole diameter 2.5mm larger than the exit hole diameter (in this example, 33 mm) of the die 2. The minimum inner diameter (on the exit side) of the hole pattern 26 has the same diameter as the exit hole diameter of the die 2. Further, in order to prevent the occurrence of defects in the tubes, the inner diameters of the inlet-side and outlet-

side guide cylinders

35 and 36 are 0.5mm larger than the outer diameter of the tubes on the same side.

Before actual manufacturing, a press working experiment in which the hole pattern position was changed at multiple points was performed with a standard pipe several times, and the pipe bending was measured to obtain the relationship between the amount of change in the hole pattern position and the amount of change in the pipe bending after pressing. In actual manufacturing, when the pipe is bent beyond a predetermined threshold, the hole pattern is moved to an orientation where the bend becomes smaller in accordance with the above-described relation, and fine adjustment of the hole pattern position is performed.

Comparative example 9.1

As shown in fig. 19, a guide cylinder 35 is provided immediately at the inlet side of the die 2, and a guide cylinder 36 is provided immediately at the outlet side. Although not shown, a continuous extruder is provided on the inlet side of the inlet-side guide cylinder 35 to continuously press the pipe 4 into the die 2 while sandwiching the pipe with a crawler.

Using this apparatus, a steel pipe of phi 40mm × 6.0mmt × 5.5mL was used as a billet, and a mandrel bar 1 was inserted into the pipe to float the mandrel bar, and the billet was continuously conveyed to be pressed into a die 2 (in this example, the exit hole diameter was phi 35 mm), and a high dimensional accuracy pipe was manufactured by this press working. The steel pipe before press working penetrates the inlet side guide cylinder 35, and the steel pipe after press working penetrates the inlet side guide cylinder 36.

Comparative example 9.2

As shown in fig. 20, no device is provided immediately at the inlet side and immediately at the outlet side of the mold 2. Although not shown, a continuous extruder is provided on the inlet side of the die 2 to continuously press the pipe 4 into the die 2 while holding the pipe with a crawler.

Using this apparatus, a steel pipe of phi 40mm × 6.0mmt × 5.5mL was used as a billet, and a mandrel bar 1 was inserted into the pipe to float the mandrel bar, and the billet was continuously conveyed to be pressed into a die 2 (in this example, the exit hole diameter was phi 35 mm), and a high dimensional accuracy pipe was manufactured by this press working.

Comparative example 9.3

As shown in fig. 21, no device is provided immediately at the inlet side and immediately at the outlet side of the mold 2. The extruder is not provided on the inlet side of the die 2, but the drawing machine 37 is provided on the outlet side of the die 2.

Using this apparatus, a steel pipe having a diameter of 40mm × 6.0mmt × 5.5mL is used as a billet, a plug 1 is inserted into the pipe to float the plug, and the pipe tip is gripped by a drawing machine 37, and the steel pipe is drawn in a drawing direction 38 from a die 2 (in this example, the exit hole diameter is 35 mm), thereby manufacturing a high dimensional accuracy pipe by such drawing.

The results of examining the bending and dimensional accuracy of the pipes manufactured by the methods of the above examples and comparative examples are shown in table 9. The pipe was bent by contacting a straight gauge with the pipe and evaluating the maximum value of the clearance between the straight gauge at the center of the pipe and the pipe at a pipe length of 500 mm. The dimensional accuracy of the tube was expressed by the thickness deviation and the outer diameter deviation (each of which is the maximum value of data of a plurality of tubes manufactured). These deviations are obtained from data obtained from the circumferential cross section of the tube by image analysis, and the wall thickness deviation is obtained as a deviation value from the average wall thickness, and the outer diameter deviation is obtained as a deviation value from a perfect circle (target outer diameter).

As can be seen from table 9, remarkably good dimensional accuracy can be obtained with the present invention, and bending of the tube after punching can be sufficiently prevented.

Example 10

Embodiments of the present invention constitute a group of devices as shown in fig. 22. Reference numeral 39 denotes a press working apparatus which performs press working in which the mandrel bar 1 is inserted into the tube and floated, and the tube is continuously pressed into the die 2 by the continuous pressing apparatus 43 and passed through. The die exchanging device 45, the mandrel bar exchanging device 44, and the bending prevention device 46 configured as described above are preferably provided in the press working device 39 at the same time.

The pipe end surface grinding device 40, the lubricant-impregnated coating tank 41, and the drying device 42 are arranged on the inlet side of the press working device 39 in this order from the upstream side. The pipe end surface grinding device 40 is configured to grind and form a right angle by aligning the end surfaces of pipes arranged on a table at right angles to the pipe axial direction with a grinding tool. The lubricant-dipping tank 41 stores a dry liquid lubricant emulsion, and the tube is dipped in the emulsion bath to apply the lubricant to the tube. The drying device 42 is configured to dry the lubricant-coated tubes arranged in parallel on the stage by blowing hot air. A pipe receiving table 47 for receiving the raw pipe fed from the previous step and transferring the raw pipe to the pipe end surface grinding device 40 is disposed on the inlet side of the plant group, and a pipe discharging table 48 for discharging the pipe to the subsequent step, which is a finished pipe by press working, is disposed on the outlet side.

The use of this equipment set successively performed the formation of a right angle at the end face of a tube blank having various sizes and scale deposits within the size ranges of 25 to 120mm phi in the outer diameter, 2 to 8mm in the wall thickness and 5 to 13m in length, followed by dip coating with a lubricant, drying and press working to obtain a finished tube.

On the other hand, fig. 23 shows a manufacturing equipment set according to the existing drawing as a comparative example. The apparatus set includes a pipe receiving table 47 provided on the entrance side of a drawing apparatus 50, a pipe discharge table 48 provided on the exit side, and the drawing apparatus 50 for floating a mandrel bar 1 by loading the mandrel bar into a pipe and drawing the pipe from a die 2 by the drawing apparatus 50. The drawing apparatus 39 is provided with a plug replacing apparatus 44 and a die replacing apparatus 45 which are configured in the same manner as in the embodiment. In this equipment group, the same raw pipe having the oxide scale as in example could not be directly drawn, and it was necessary to use a pipe subjected to the 1 st pretreatment step and the subsequent 2 nd pretreatment step shown in fig. 23 as a raw pipe.

The 1 st pretreatment step is a step of forming a strong lubricating film for drawing, and includes the following steps in sequence: the tube blank with the scale is cut into short sizes → the scale is removed by acid washing → alkali neutralization of acid → water washing → adhesion treatment → application of metal soap → drying. When the plurality of immersion tanks or devices for performing the 1 st pretreatment step and the drawing device 50 are arranged in the same line, productivity is lowered, and therefore, the immersion tanks or devices need to be arranged in a different line. In addition, in order to allow the drawing apparatus 50 to grip the pipe, the 2 nd pretreatment step is required to be a step of performing the joint processing of the pipe end by, for example, a rotary forging machine, and when the rotary forging machine is also arranged on the same line as the drawing apparatus 50, productivity is low, and therefore, the rotary forging machine needs to be arranged on a different line.

The same raw tube with oxidized scale as in example was processed in the order of

pretreatment steps

1 and 2 using the equipment line of this comparative example, and only the processed tube was subjected to drawing to obtain a finished tube.

The time required for production and the dimensional accuracy of the finished pipes obtained in the study examples and comparative examples are shown in Table 10. The total treatment time/total number of treatments from the start of a predetermined batch of raw tubes with oxide scale to the end of obtaining finished tubes was used to evaluate the time required for production, and the evaluation value of the comparative example is 1 and is expressed as a ratio to the evaluation value in table 10. Dimensional accuracy is expressed by wall thickness variation and outer diameter variation. These deviations are obtained from data obtained from the circumferential cross section of the image analysis tube, the wall thickness deviation being obtained as a deviation value from the average wall thickness, and the outer diameter deviation being obtained as a deviation value from a perfect circle (target outer diameter).

As can be seen from table 10, the present invention enables efficient production of a high dimensional accuracy tube.

The high dimensional accuracy pipe of the present invention has excellent effects of remarkably improving dimensional accuracy, having excellent fatigue strength, and being manufacturable at low cost, and therefore, remarkably contributing to the promotion of weight reduction of automotive drive components and the like. Further, according to the manufacturing method of the present invention, there is an excellent effect that a metal pipe having a remarkably excellent dimensional accuracy in a wide range of required pipe dimensions can be manufactured at low cost.

TABLE 1

	Mode of processing	Die set	Core rod	Diameter reduction ratio (％)	Outlet side wall thickness	Deviation of outer diameter ^* (％)	Deviation of inner diameter ^* (％)	In the circumferential direction Deviation of wall thickness ^* (％)	Fatigue test Endurance limit number of times (times)
	Mode of processing	Die set	Core rod	Diameter reduction ratio (％)	Outlet side wall thickness	Deviation of outer diameter ^* (％)	Deviation of inner diameter ^* (％)		Fatigue test Endurance limit number of times (times)	Example 1.1	Stamping	Integrated fixing	Fixing	10	Same inlet side	0.5	0.5	0.5	500×10 ³
Example 1.2	Stamping	Integrated fixing	Fixing	5	Same inlet side	0.7	2.5	0.7	500×10 ³	Example 1.1	Stamping	Integrated fixing	Fixing	10	Same inlet side	0.5	0.5	0.5	500×10 ³
Example 1.2	Stamping	Integrated fixing	Fixing	5	Same inlet side	0.7	2.5	0.7	500×10 ³	Example 1.3	Stamping	Integrated fixing	Float	5	Same inlet side	0.3	0.5	0.5	500×10 ³
Comparative example 1.1	Drawing	Integrated fixing	Fixing	5	Reducing the thickness	4.0	4.0	5.0	100×10 ³	Example 1.3	Stamping	Integrated fixing	Float	5	Same inlet side	0.3	0.5	0.5	500×10 ³
Comparative example 1.1	Drawing	Integrated fixing	Fixing	5	Reducing the thickness	4.0	4.0	5.0	100×10 ³	Comparative example 1.2	Pressed in	Combined rotation	Fixing the device	5	Same inlet side	3.3	3.5	4.2	200×10 ³
Comparative example 1.3	Pressed in	Combined rotation	Fixing	5	Increase in thickness	3.5	4.0	4.5	200×10 ³	Comparative example 1.2	Pressed in	Combined rotation	Fixing the device	5	Same inlet side	3.3	3.5	4.2	200×10 ³

^* Deviation from target value

TABLE 2

	Method of working	Outlet side wall thickness	Deviation of outer diameter (％)	Deviation of inner diameter (％)	In the circumferential direction Deviation of wall thickness (％)	Processing efficiency: number of processed pieces per 1 hour (root)
	Method of working	Outlet side wall thickness	Deviation of outer diameter (％)	Deviation of inner diameter (％)			Examples of the invention	Stamping	Same inlet side	0.5	0.5	0.5	130
Comparative example 2.1	Drawing	Reducing the thickness	4.0	4.6	5.0	40	Examples of the invention	Stamping	Same inlet side	0.5	0.5	0.5	130
Comparative example 2.1	Drawing	Reducing the thickness	4.0	4.6	5.0	40	Comparative example 2.2	Rotary forging press	Thickness increase	3.8	4.0	4.5	60

TABLE 3

	Method of working	Presence or absence of Lubricating film	Lubricant agent	Presence or absence of Defect of	Deviation of wall thickness (％)	Deviation of inner diameter (％)	Deviation of outer diameter (％)
	Method of working	Presence or absence of Lubricating film	Lubricant agent	Presence or absence of Defect of	Deviation of wall thickness (％)	Deviation of inner diameter (％)	Deviation of outer diameter (％)	Comparative example 3.1	Stamping	Is free of	Is free of	Is provided with	2.0	2.0	1.0
Inventive example 3.1	Stamping	Is provided with	Liquid lubricant	Is composed of	0.5	0.5	0.5	Comparative example 3.1	Stamping	Is free of	Is free of	Is provided with	2.0	2.0	1.0
Inventive example 3.1	Stamping	Is provided with	Liquid lubricant	Is composed of	0.5	0.5	0.5	Inventive example 3.2	Stamping	Is provided with	Lubricant-based lubricant	Is free of	0.5	0.5	0.5
Inventive example 3.3	Stamping	Is provided with	Drying resin	Is composed of	0.3	0.3	0.3	Inventive example 3.2	Stamping	Is provided with	Lubricant-based lubricant	Is free of	0.5	0.5	0.5
Inventive example 3.3	Stamping	Is provided with	Drying resin	Is composed of	0.3	0.3	0.3	Inventive example 3.4	Stamping	Is provided with	Solvent dilution of drying resins	Is free of	0.3	0.3	0.3
Inventive example 3.5	Stamping	Is provided with	Latex of drying resin	Is free of	0.3	0.3	0.3	Inventive example 3.4	Stamping	Is provided with	Solvent dilution of drying resins	Is free of	0.3	0.3	0.3
Inventive example 3.5	Stamping	Is provided with	Latex of drying resin	Is free of	0.3	0.3	0.3	Comparative example 3.2	Drawing	Is provided with	Liquid lubricant	Is free of	4.5	3.5	3.5
Comparative example 3.3	Pressed in ^*	Is provided with	Liquid lubricant	Is composed of	4.5	4.0	3.5	Comparative example 3.2	Drawing	Is provided with	Liquid lubricant	Is free of	4.5	3.5	3.5

^* Rotary forging press-in method

TABLE 4

	Method of working	Expansion ratio ％	Diameter reduction ratio ％	θA °	θB °	Target outer diameter ^* 2 mm	Deviation of wall thickness ％	Deviation of inner diameter ％	Deviation of outer diameter ％	Cross section of Hardness of Hv	After processing Outer diameter mm	After processing Wall thickness mm	Remarks for note
	Method of working	Expansion ratio ％	Diameter reduction ratio ％	θA °	θB °	Target outer diameter ^* 2 mm	Deviation of wall thickness ％	Deviation of inner diameter ％	Deviation of outer diameter ％	Cross section of Hardness of Hv	After processing Outer diameter mm	After processing Wall thickness mm	Remarks for note	1	Stamping	8	8	4.95	4.97	40	0.3	0.3	0.3	320	40	6.0	Examples of the invention
2	Stamping	6	8	3.64	4.85	39	0.25	0.3	0.3	320	39	6.0	Examples of the invention	1	Stamping	8	8	4.95	4.97	40	0.3	0.3	0.3	320	40	6.0	Examples of the invention
2	Stamping	6	8	3.64	4.85	39	0.25	0.3	0.3	320	39	6.0	Examples of the invention	3	Stamping	1	17	0.59	9.88	34	0.15	0.2	0.2	320	34	6.0	Examples of the invention
4	Drawing	-	8	0	4.85	39	5.0	4.0	4.0	200	39	5.8	Comparative example A	3	Stamping	1	17	0.59	9.88	34	0.15	0.2	0.2	320	34	6.0	Examples of the invention
4	Drawing	-	8	0	4.85	39	5.0	4.0	4.0	200	39	5.8	Comparative example A	5	Drawing	-	16	0	9.20	34	4.5	3.5	3.5	320	34	5.1	Comparative example A
6	Pressed in ^* 1	-	8	0	4.85	39	4.5	4.0	3.5	200	39	6.2	Comparative example B	5	Drawing	-	16	0	9.20	34	4.5	3.5	3.5	320	34	5.1	Comparative example A

^* 1: rotary forging press-in method

^* 2: target outside diameter of pipe on die outlet side

TABLE 5

		Shape conditions of core rod and die				Whether or not to manufacture	Dimensional accuracy
		Shape conditions of core rod and die					Dimensional accuracy				Method of processing	Core rod reducing Angle of the part (°)	Core rod reducing Length of the part (mm)	Mandrel support Length of the part (mm)	Die set Angle of rotation (°)	Deviation of wall thickness (％)	Deviation of inner diameter (％)	Deviation of outer diameter (％)
Inventive example 5.1	Stamping	21	11	20	21		Can be used for	0.5	0.5		Method of processing	Core rod reducing Angle of the part (°)	Core rod reducing Length of the part (mm)	Mandrel support Length of the part (mm)	Die set Angle of rotation (°)	Deviation of wall thickness (％)	Deviation of inner diameter (％)	Deviation of outer diameter (％)	0.5
Inventive example 5.1	Stamping	21	11	20	21	Inventive example 5.2	Can be used for	0.5	0.5	Stamping	11	20	15	13	Can be prepared by	0.5	0.5	0.5	0.5
Inventive example 5.3	Stamping	5	90	4	5	Inventive example 5.2	Can be prepared by	0.8	0.8	Stamping	11	20	15	13	Can be prepared by	0.5	0.5	0.5	0.7
Inventive example 5.3	Stamping	5	90	4	5	Inventive example 5.4	Can be prepared by	0.8	0.8	Stamping	40	5	35	40	Can be used for	0.3	0.4	0.3	0.7
Comparative example 5.1	Stamping	4	11	4	4.5	Inventive example 5.4	Whether or not	-	-	Stamping	40	5	35	40	Can be used for	0.3	0.4	0.3	-
Comparative example 5.1	Stamping	4	11	4	4.5	Comparative example 5.2	Whether or not	-	-	Stamping	45	11	210	45	Whether or not	-	-	-	-
Comparative example 5.3	Stamping	21	4	4.5	21	Comparative example 5.2	Whether or not	-	-	Stamping	45	11	210	45	Whether or not	-	-	-	-
Comparative example 5.3	Stamping	21	4	4.5	21	Comparative example 5.4	Whether or not	-	-	Stamping	5	105	210	5	Whether or not	-	-	-	-
Conventional example 5.1	Drawing	21	11	20	21	Comparative example 5.4	Can be used for	4.5	3.5	Stamping	5	105	210	5	Whether or not	-	-	-	3.5
Conventional example 5.1	Drawing	21	11	20	21	Conventional example 5.2	Can be used for	4.5	3.5	Rotary forging Make the pressure in	21	11	20	21	Can be used for	4.5	4.0	3.5	3.5

TABLE 6

	Method of processing	Changing conditions during processing	Relative machining Time	Loss at machining	Deviation of wall thickness (％)	Deviation of outer diameter (％)
	Method of processing	Changing conditions during processing	Relative machining Time	Loss at machining	Deviation of wall thickness (％)	Deviation of outer diameter (％)	Example 6.1	Stamping	Shape of die and core rod	0.2	Is free of	0.5	0.6
Comparative example 6.1	Stamping	Kind of lubricant Shape of die and mandrel	1	Breakage of mold	0.5	0.6	Example 6.1	Stamping	Shape of die and core rod	0.2	Is free of	0.5	0.6
Comparative example 6.1	Stamping	Kind of lubricant Shape of die and mandrel	1	Breakage of mold	0.5	0.6	Comparative example 6.2	Drawing	Shape of die and mandrel	2	Breakage of mold	3.5	3.2

TABLE 7

	Mode of processing	Die set	Core rod	Outlet side wall thickness	In the circumferential direction Deviation of wall thickness (％)	Deviation of inner diameter (％)	Deviation of outer diameter (％)
	Mode of processing	Die set	Core rod	Outlet side wall thickness		Deviation of inner diameter (％)	Deviation of outer diameter (％)	Example 7.1	Punching (intermittent)	Integrated fixing	Fixing	Same inlet side	0.5	0.5	0.5
Example 7.2	Punching (intermittence)	Integrated fixing	Float	Same inlet side	0.4	0.5	0.3	Example 7.1	Punching (intermittent)	Integrated fixing	Fixing	Same inlet side	0.5	0.5	0.5
Example 7.2	Punching (intermittence)	Integrated fixing	Float	Same inlet side	0.4	0.5	0.3	Example 7.3	Punching (continuous)	Integrated fixing	Float	Same inlet side	0.3	0.3	0.3
Comparative example 7.1	Drawing (continuous)	Integrated fixing	Fixing the device	Reducing the thickness	5.0	4.0	4.0	Example 7.3	Punching (continuous)	Integrated fixing	Float	Same inlet side	0.3	0.3	0.3
Comparative example 7.1	Drawing (continuous)	Integrated fixing	Fixing the device	Reducing the thickness	5.0	4.0	4.0	Comparative example 7.2	Press-in (intermittent)	Combined rotation	Fixing	Increase in thickness	4.5	4.0	3.5

TABLE 8

	Efficiency of processing	Wall thickness deviation (%)	Outer diameter deviation (%)
	Efficiency of processing	Wall thickness deviation (%)	Outer diameter deviation (%)	Inventive example 8.1	10	0.5	0.5
Inventive example 8.1	10	0.5	0.5	Inventive example 8.1	10	0.5	0.5
Inventive example 8.1	10	0.5	0.5	Comparative example 8.1	1.2	0.8	0.7
Comparative example 8.2	1	0.8	0.7	Comparative example 8.1	1.2	0.8	0.7

TABLE 9

	Processing method	Bending prevention device	Bend (mm)	Wall thickness deviation (%)	Outer diameter deviation (%)
	Processing method	Bending prevention device	Bend (mm)	Wall thickness deviation (%)	Outer diameter deviation (%)	Example 9.1	Stamping	Against the exit side of the mould Pipe bending micro-adjusting device	0.1	0.5	0.6
Example 9.2	Stamping	Bending of tubes against the exit side of the mould Micro-adjusting device + inlet and outlet side guide cylinder	0.2	0.5	0.6	Example 9.1	Stamping		0.1	0.5	0.6
Example 9.2	Stamping		0.2	0.5	0.6	Comparative example 9.1	Stamping	Inlet and outlet side guide cylinder	0.7	0.5	0.6
Comparative example 9.2	Stamping	Is free of	1.8	0.5	0.6	Comparative example 9.1	Stamping	Inlet and outlet side guide cylinder	0.7	0.5	0.6
Comparative example 9.2	Stamping	Is free of	1.8	0.5	0.6	Comparative example 9.3	Drawing	Pulling force in the drawing direction at the outlet side	0.3	3.5	3.0

Watch 10

	Method of working	Time required for manufacture (ratio)	Wall thickness deviation (%)	Outer diameter deviation (%)
	Method of working	Time required for manufacture (ratio)	Wall thickness deviation (%)	Outer diameter deviation (%)	Examples	Stamping	0.1	0.5	0.6
Comparison column	Drawing		1	3.5	Examples	Stamping	0.1	0.5	0.6	3.2

Claims

1. A high dimensional accuracy pipe in a pressed state, characterized in that the pipe is obtained by performing cold press in which a metal pipe is pressed into a die hole and passed through in a state in which a core rod is incorporated into the metal pipe, and that any one or two or more of an outer diameter variation, an inner diameter variation, and a circumferential wall thickness variation is 3.0% or less.

2. The high dimensional accuracy tube in a pressed state according to claim 1, wherein it is produced by performing cold pressing in which the metal tube is pressed into and passed through a die hole in a state in which a core rod is fitted into the metal tube and setting the thickness of the metal tube on the outlet side of the die to be equal to or less than the thickness of the metal tube on the inlet side; and any one or two or more of the outer diameter variation, the inner diameter variation and the circumferential wall thickness variation is 3.0% or less.

3. The high dimensional accuracy tube according to any one of claims 1 to 2, wherein the mold is an integral type and/or fixed type mold.

4. A method for efficiently manufacturing a high-dimensional-precision pipe, characterized by performing cold stamping in which a metal pipe is pressed into a die hole and passed through the die hole with a mandrel bar inserted therein, and when the high-dimensional-precision pipe is formed by improving one or more of the outer diameter variation, inner diameter variation, and circumferential wall thickness variation of the pipe by stamping, the mandrel bar is inserted into the pipe so as to float, and the pipe is continuously fed into the die by a pipe feeding device on the inlet side of the die.

5. A high efficiency method of manufacturing high dimensional accuracy pipe according to claim 4, wherein said pipe feeding means is a crawler which grips the pipe before processing.

6. A high efficiency manufacturing method of high dimensional accuracy tubes as claimed in claim 4 wherein said tube feeding means is an endless belt compressing the tube before machining.

7. A high-efficiency manufacturing method of a high dimensional accuracy tube according to claim 4, wherein said tube feeding means is an intermittent conveyor which grips the tube before processing and alternately intermittently conveys the tube.

8. A high-efficiency manufacturing method of a high dimensional accuracy pipe according to claim 4, wherein said pipe feeding means is a press machine which sequentially presses the pipe before processing.

9. A high-efficiency production method of a high-dimensional accuracy pipe according to claim 4, wherein said pipe feeding means is a hole roll for nipping a pipe before processing.

10. A method for manufacturing a high dimensional accuracy pipe having a good surface quality, characterized by performing cold stamping in which a metal pipe is pressed into a die hole and passed through the hole with a mandrel bar inserted therein, thereby forming a lubricating film on the inner surface and/or outer surface of the pipe, then inserting the mandrel bar into the pipe, and cold stamping the pipe with a die.

11. The method of producing a high dimensional accuracy pipe having a good surface quality as set forth in claim 10, wherein the pipe on which the lubricating film is formed is a steel pipe in a state of scale.

12. The method of producing a high dimensional accuracy pipe having a good surface quality as set forth in claim 10 or 11, wherein the lubricating film is formed of a drying resin.

13. A method for manufacturing a high dimensional accuracy pipe, characterized by performing cold stamping in which a metal pipe is pressed into a die hole and passed through with a mandrel bar, which is a mandrel bar having a tapered angle at an expanded portion smaller than that at a reduced diameter portion, being fitted into the metal pipe.

14. A method for stably manufacturing a high dimensional precision pipe, characterized in that, in a cold press process for pressing and passing a metal pipe into a die hole with a mandrel bar inserted therein, when manufacturing the high dimensional precision pipe by a press process for pressing and passing the pipe into which the mandrel bar is inserted, the mandrel bar is used with a table of a reduced diameter portion and a machining center axis forming an angle of 5 to 40 DEG and a length of the same reduced diameter portion of 5 to 100mm, and the die is used with an inner surface of the hole on the inlet side and the machining center axis forming an angle of 5 to 40 DEG.

15. A stable manufacturing method of a high dimensional accuracy tube as set forth in claim 14, wherein the length of the supporting portion of the mandrel bar is 5 to 200mm.

16. An apparatus for manufacturing a high dimensional accuracy pipe, comprising: a mandrel contactable with the inner surface of the metal pipe in a full circumference, a die having a hole contactable with the outer surface of the pipe in a full circumference, and a pipe extruding machine for extruding the same pipe; and cold stamping may be performed by pressing a metal tube into the die hole and passing the metal tube through the die hole by the tube extruding machine in a state where the mandrel bar is fitted into the tube.

17. The apparatus for manufacturing a high-dimensional accuracy pipe according to claim 16, wherein the mold is an integral type and/or a fixed type mold.

18. An apparatus for manufacturing a high dimensional accuracy pipe as defined in claim 16 or 17, wherein said mandrel is a traveling mandrel.

19. The apparatus for manufacturing a high dimensional accuracy tube according to any one of claims 16 to 17, wherein said tube extruder continuously extrudes said tube.

20. The apparatus for manufacturing a high dimensional accuracy tube as defined in claim 18, wherein said tube extruder continuously extrudes said tube.

21. The apparatus for manufacturing a high dimensional accuracy tube as set forth in any one of claims 16 to 17, wherein said tube extruder intermittently extrudes said tube.

22. A high dimensional accuracy tube manufacturing apparatus as recited in claim 18, wherein said tube extruder intermittently extrudes said tube.

23. A high dimensional accuracy tube manufacturing apparatus as defined in claim 16 having a die through which the tube passes and an extruder for pressing the tube into the die, wherein a tube bending fine adjustment device having a hole pattern through which the tube passes, a support base plate for supporting the hole pattern movably in a plane perpendicular to a tube passing direction, and a hole pattern moving mechanism for moving the hole pattern supported on the support base plate is provided in the vicinity of the exit side of the die.

24. A manufacturing facility set of high dimensional accuracy pipes comprising the manufacturing apparatus of high dimensional accuracy pipes according to claim 16, characterized in that a pipe end surface grinding means capable of grinding an end surface of a pipe to be perpendicular to a pipe axial direction, a lubricant dip coating tank for dip coating a lubricant on the pipe, a drying means for drying the pipe coated with the lubricant, and the manufacturing apparatus of high dimensional accuracy pipes are arranged in this order.

25. The set of high-dimensional-accuracy pipe manufacturing equipment according to claim 24, wherein a lubricant spray coating device for spraying a lubricant onto a pipe or a lubricant spray drying device for spraying a lubricant onto a pipe and then drying it is disposed on the die inlet side of the high-dimensional-accuracy pipe manufacturing apparatus, instead of the lubricant dip coating tank and the drying device.