JP2006035299A - Method for efficiently and consistently manufacturing tube of high dimensional accuracy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently and consistently manufacturing a tube of high dimensional accuracy capable of efficiently and consistenty manufacturing the tube of high dimensional accuracy. <P>SOLUTION: When manufacturing a tube of high dimensional accuracy by extrusion in which a plug 1 is inserted in a tube 4 and the tube is pressed into and extruded from the hole of a die 2, the taper angle θ1 of the plug to be used is set to be not more than the taper angle θ2 of the die, and the outermost diameter d0 of the plug is set to be below the inside diameter D0 of the tube on the inlet side of the die. The bearing diameter d1 of the plug is preferably set to be not less than (the die outlet side hole diameter d2-2 × the wall thickness t of the tube on the inlet side of the die). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-efficiency and stable manufacturing method for high-dimensional accuracy pipes, and more specifically, a high-efficiency and stable production of pipes that require high dimensional accuracy, such as automobile drive system parts. The present invention relates to a highly efficient and stable manufacturing method of a dimensional accuracy tube.

  Metal pipes, such as steel pipes, are generally roughly classified into welded pipes and seamless pipes. Welded pipes are manufactured by rounding the width of the strip and welding by welding both ends of the rounded width, such as ERW steel pipes, while seamless pipes are used to drill a mass of material at high temperatures. It is manufactured by a method of rolling with a mandrel mill afterwards. In the case of a welded pipe, the bulge of the welded part is ground after welding to improve the dimensional accuracy of the pipe, but the thickness deviation is 3.0%, although efforts are made to reduce it in a later process. Exceed. In the case of a seamless pipe, it is easy to be eccentric in the drilling process, and a large thickness deviation is likely to occur due to the eccentricity. Although efforts have been made to reduce this thickness deviation in a later process, it cannot be sufficiently reduced, and remains at 8.0% or more at the product stage.

  Recently, due to environmental problems, the weight reduction of automobiles has been accelerated, and drive system parts such as drive shafts are being replaced from solid metal rods to hollow metal tubes. The metal pipes of these automobile drive system parts are required to have a high dimensional accuracy of 3.0% or less, more strictly 1.0% or less, as deviations in thickness, inner diameter, and outer diameter.

Therefore, as a means for improving the accuracy of the thickness, inner diameter, and outer diameter of the metal pipe, conventionally, as shown in FIG. 3, after forming the pipe 4 (both welded pipe and seamless pipe), the die 6 and the plug 5 are inserted. A manufacturing method (so-called cold check method) that is used and pulled out cold is used (for example, Patent Document 1).
Japanese Patent No. 2812151

  However, in the conventional cold check method, when the restrictions on equipment and the thickness and diameter of the tube are large and sufficient pulling stress cannot be obtained and the diameter reduction rate must be lowered, etc., a machining tool (plug and plug) Because the stress of the tube within the gap between the die hole inner surface is a tensile stress, the contact between the die and the outer surface of the tube and the plug and the inner surface of the tube is insufficient, and the smoothness of the inner and outer surfaces of the tube is insufficient. Unevenness is likely to remain. Therefore, in the cold check method, the reduction ratio of the tube is increased to improve the contact between the inner and outer surfaces of the tube and the plug and die in the machining tool. However, when the diameter reduction ratio of the pipe is increased in the cold check method, unevenness is generated on the inner surface of the pipe, and the roughness due to the unevenness increases as the diameter reduction ratio of the pipe increases. As a result, the cold check method has a problem that it is difficult to stably obtain a pipe with high dimensional accuracy.

  Also, in the manufacture of high dimensional accuracy pipes made of steel pipes, if the frictional force between the plug surface, the die surface and the steel pipe surface in contact with them is not reduced as much as possible, seizure such as seizure will occur on the steel pipe surface during processing. Occurs, the surface quality of the steel pipe after processing deteriorates and the steel pipe does not become a product, but the processing load may increase significantly and processing itself may become impossible, resulting in high dimensional accuracy. There was also a problem that the production efficiency of the tube was significantly reduced.

  An object of the present invention is to solve the above problems and to provide a high-efficiency and stable manufacturing method for a high-dimensional accuracy tube that can stably manufacture a high-dimensional accuracy tube with high efficiency.

  As a result of intensive studies to achieve the above object, the inventors have adopted a punching method in which a plug is inserted into a tube and the tube is pushed through a hole of a die and the plug and die to be used are optimized. Thus, it has been found that a high dimensional accuracy tube that could not be achieved by the cold check method can be stably manufactured, and the present invention has been made.

  That is, in the present invention, in manufacturing a high dimensional accuracy tube by punching through which a plug is inserted into the tube and the tube is pushed through the hole of the die, the taper angle of the plug to be used is equal to or less than the taper angle of the die. In addition, the present invention provides a highly efficient and stable production method of a high dimensional accuracy pipe, characterized in that the outermost diameter of the plug is less than the inner diameter of the pipe on the die entry side.

  In the present invention, it is preferable that the bearing diameter of the plug is equal to or greater than (die outlet side hole diameter−die inlet side pipe thickness × 2). In the present invention, it is preferable that the die to be used is an integrated die. In the present invention, the plug is preferably floated in the pipe.

  According to the present invention, since the punching process is adopted and the plug and the die to be used are optimized, the high dimensional accuracy tube can be manufactured efficiently and stably.

  Conventionally, when a pipe is pulled out using a die and a plug, it is difficult to improve the dimensional accuracy of the pipe. This is due to the fact that is insufficient. That is, as shown in FIG. 3, by inserting the plug 5 into the tube 4 and pulling the tube 4 out of the die 6, the cutting tool 10 is pulled by the pulling force 10 applied by the tube drawing machine 7 on the exit side of the die 6. A tension (tensile stress) is generated inside. Since the inner surface of the tube deforms along the plug 5 on the entry side in the machining bite, the outer surface of the tube does not contact the die 6 or only slightly, and on the exit side in the machining bite, the die 6 Since the outer surface of the tube contacts and deforms, the inner surface of the tube does not contact the plug 5 or only slightly contacts. For this reason, both the outer surface of the tube and the inner surface of the tube have free deformation portions in the working bite, and the unevenness cannot be sufficiently smoothed, and only a tube with insufficient dimensional accuracy has been obtained after drawing.

  In contrast, in the punching process used in the present invention, as shown in FIG. 2, the plug 1 is inserted into the tube 4, and the pushing force is applied to the tube 4 by the tube pusher 3 from the entry side of the die 2. 11 is added and the tube 4 is fed into the hole of the die 2. Therefore, a compressive stress acts on the whole area of the tube 4 in the machining tool. As a result, the tube 4 can sufficiently contact the plug 1 and the die 2 regardless of the entry side or the exit side in the machining tool. In addition, even in the case of a small diameter reduction ratio, since the inside of the working bite is in a compressive stress state, the tube 4 and the plug 1 and the tube 4 and the die 2 are more easily contacted than the drawing, and the tube is smoothed. This makes it easy to obtain a tube with high dimensional accuracy.

  However, in the punching, if both the inclined portion 1T of the plug 1 and the bearing portion 1B are brought into contact with the inner surface of the tube 4 as shown in FIG. 2, the friction area between the tube 4 and the plug 1 increases and the punching load is increased. Will increase. As a result, depending on the material, seizure may occur and punching may become impossible.In this case, in order to enable punching, the shape of the die and plug is modified to reduce the diameter reduction rate or lubrication. It was necessary to change the agent.

  Accordingly, the present inventors have focused on the contact between the tube and the plug, and have studied a method that enables highly efficient punching without causing seizure. In this study, the lubricant was changed for each of the plug and tube, and the die and tube, and punching was performed. As a result, it was understood that the friction between the plug and the pipe was so large that seizure was likely to occur and sufficient lubrication was necessary. Therefore, if the contact between the plug and the tube can be relaxed, the frictional force can be reduced, the punching load is reduced, and seizure can be prevented.

  On the other hand, since the outer diameter and thickness of the pipe on the die exit side need to be finished to a predetermined size, the diameter of the bearing portion of the plug needs to correspond to the predetermined size.

  Therefore, in the present invention, paying attention to the taper portion of the plug, as shown in FIG. The inner diameter D0 of the tube 4 was set to be less than that. Here, the taper angle θ1 of the plug 1 is an angle formed by the peripheral surface of the inclined portion 1T connected to the bearing portion 1B with respect to the processing center axis 8, and the taper angle θ2 of the die 2 is the processing center on the inner surface of the inclined hole. An angle formed with respect to the axis 8. Thereby, the contact between the plug 1 and the tube 4 can be relaxed.

  However, if the contact between the tapered portion 1T of the plug 1 and the tube 4 is relaxed, it may be difficult to keep the dimensional accuracy of the tube 4 high. In that case, it is preferable that the bearing diameter d1 of the plug 1 is equal to or greater than (die exit side hole diameter d2—thickness t × 2 of the pipe on the die entrance side). Thereby, the bearing diameter d1 can be made larger than the inner diameter of the pipe when passing through the die outlet side hole when there is no plug, and sufficient contact between the bearing portion 1B and the pipe 4 becomes possible.

  In addition to the integrated die, the die includes a split die. However, it is preferable to use the integrated die from the viewpoint of avoiding a dimensional defect due to the joint of the die. Further, it is preferable to float the plug in the pipe because the pipe can be continuously pushed in and can be further processed with high efficiency.

(Invention Examples 1 and 2)
Using an ERW steel pipe having an outer diameter D0 = 40 mm and a wall thickness t = 6 mm as a raw material, a punching process was performed in the form shown in FIG. 1 using a mirror surface plug and an integrated die. The plug and die shape conditions used are shown in Table 1. The plug was floated in the tube.
(Comparative Example 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 punching process was performed in the form shown in FIG. 2 using a mirror surface plug and an integrated die. The plug and die shape conditions used are shown in Table 1. The plug was floated in the tube.
(Comparative Examples 2 and 3)
A steel pipe of the same lot as that of the example of the present invention was used as a base pipe, and a drawing process was performed in the form shown in FIG. 3 using a mirror surface plug and an integrated die. The plug and die shape conditions used are shown in Table 1. The plug was floated in the tube.

  Table 1 shows the presence or absence of seizure during processing, the processing efficiency, and the dimensional accuracy (thickness deviation, outer diameter deviation) of the pipe after processing for each of the above examples. Here, the machining efficiency is shown as a relative value where the number of pieces processed within a predetermined time is set to 1 in the case of Comparative Example 3. The outer diameter deviation is obtained by image analysis of the circumferential section of the tube and calculating the maximum deviation from the perfect circle (that is, (maximum diameter−minimum diameter) / true circle diameter × 100%) in the circumferential direction. It was. Further, the thickness deviation is obtained by image analysis of the circumferential cross section of the tube, and the maximum deviation with respect to the average thickness from the image of the thickness cross section (that is, (maximum thickness−minimum thickness) / average thickness × 100%). As measured directly.

  From Table 1, in the example of the present invention, it was possible to stably perform the punching process with high efficiency, and the dimensional accuracy of the steel pipe after the punching was remarkably good. On the other hand, in Comparative Example 1, seizure occurred in about 1% of the number of steel pipes being processed, and the plug and the die were exchanged, so that the processing efficiency was slightly lowered. In Comparative Example 2, the dimensional accuracy after drawing after drawing was significantly reduced. In Comparative Example 3, seizure occurred during drawing and the plug and the die were exchanged, so that the processing efficiency was slightly lowered and the dimensional accuracy was remarkably lowered.

It is a longitudinal cross-sectional view which shows embodiment of this invention. It is a longitudinal cross-sectional view which shows the outline | summary of the punching process used by this invention. It is a longitudinal cross-sectional view which shows the outline | summary of the conventional cold check method.

Explanation of symbols

1 Plug 1B Bearing part 1T Taper part 2 Dies (integrated die)
3 Tube pusher 4 Tube (metal tube, steel tube)
5 Plug 6 Die 7 Pipe puller 8 Machining center axis 10 Pulling force 11 Pushing force

Claims (4)

  When manufacturing a high dimensional accuracy tube by inserting a plug into the tube and pushing the tube through the hole of the die and passing it through, the taper angle of the plug to be used is less than the taper angle of the die and the outermost of the plug A high-efficiency and stable production method for high-dimensional accuracy pipes, characterized in that the diameter is less than the inner diameter of the pipe on the die entry side.   The high-efficiency and stable production method for a high-dimensional accuracy pipe according to claim 1, wherein a bearing diameter of the plug is equal to or larger than (die outlet side hole diameter-die inlet side pipe thickness x 2).   3. A highly efficient and stable method for producing a high dimensional accuracy tube according to claim 1, wherein the die used is an integrated die.   The high-efficiency stable manufacturing method for a high-dimensional accuracy pipe according to any one of claims 1 to 3, wherein the plug is floated in the pipe.

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