JP2006175486A - Method and apparatus for highly efficiently manufacturing pipe having high dimensional accuracy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for highly efficiently manufacturing a pipe having high dimensional accuracy by which the pipe having the high dimensional accuracy is efficiently manufactured by preventing the buckling of the pipe which is pushed. <P>SOLUTION: In the manufacturing method of the pipe having the high dimensional accuracy by which pushing is performed by feeding the pipe continuously and forcing it into a die 2 while charging a plug 1 into the pipe 3 and floating the pipe, the unworked part of the pipe is pressed with a press roller 5 during working the pipe. It is preferable that a pair and/or a plurality of the press rollers are provided in the feeding direction of the pipe. It is preferable that the press rollers are arranged in a position where buckling critical load is not smaller than pushing load. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-efficiency manufacturing method and apparatus for high-dimensional accuracy pipes, and more particularly to a method and apparatus for high-efficiency manufacturing of pipes requiring high dimensional accuracy, such as automobile drive system component pipes.

  For example, metal pipes such as steel pipes (hereinafter also simply referred to as pipes) are 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 drill a mass of material at high temperatures. It is manufactured by a method of rolling with a post mandrel mill or the like. In the case of a welded pipe, the bulge of the welded portion is ground after welding to improve the dimensional accuracy of the pipe, but the thickness deviation exceeds 3.0%. 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.

  Pipes used for automobile drive system parts and the like 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 wall thickness, inner diameter, and outer diameter of the pipe, conventionally, a metal pipe (both welded pipe and seamless pipe) is generally made by cold drawing using a die and a plug after pipe making ( A so-called cold check method is employed (see, for example, Patent Document 1).

  However, with the cold check method, when the drawing stress cannot be sufficiently obtained due to restrictions on the equipment or the pipe thickness / diameter is large, etc., it is necessary to reduce the diameter reduction rate. Since the stress field in the gap between the inner surface of the hole) is a tensile field, the contact between the die and the outer surface of the tube, and between the drawing plug and the inner surface of the tube is insufficient, and the inner surface of the tube and the outer surface are not smoothed, resulting in unevenness. It tends to remain. For this reason, in the cold check method, it is attempted to increase the diameter reduction ratio of the pipe so that the contact between the inner and outer faces of the pipe and the plug and the die is sufficient in the machining tool. However, when the tube is pulled out using a die, unevenness is generated on the inner surface of the tube, and the roughness due to the unevenness increases as the diameter reduction ratio of the tube increases. As a result, it has been difficult to obtain a tube with high dimensional accuracy by the cold check method, and a tube with better dimensional accuracy has been strongly demanded.

Further, since it is necessary to apply tension by strongly pinching the tip of the tube in the drawing, it is necessary to narrow the tip of the tube and pull out the tube in a single shot, and the processing efficiency is extremely low.
On the other hand, recently, a manufacturing method of a high dimensional accuracy pipe by a punching process in which a plug is inserted into a pipe and the pipe is pushed through a die is proposed (see Patent Document 2). According to this punching process, the tube with the plug inserted therein is pushed into the die, so that the entire area inside the machining tool becomes a compression field. As a result, the pipe is plugged regardless of the entry side or exit side in the machining tool. And can fully contact the die. Moreover, even if the diameter reduction is slight, the inside of the working bite becomes a compression field, so the tube and plug, and the tube and the die are more easily in contact with each other than withdrawing, and the tube is easy to smooth and has high dimensional accuracy. A tube is obtained. In addition, since the tube is pushed from the die entry side in the punching, it is not necessary to squeeze the tip of the tube, and the preceding tube and the succeeding tube can be continuously fed into the die one after another and processed efficiently. Can do.
Japanese Patent No. 2812151 JP 2004-314083 A

However, in the punching process, buckling is a problem because the tube is pushed in its longitudinal direction (= tube feeding direction). When a thin and long tube is pushed in the longitudinal direction with a large force, the tube buckles and cannot be bent and processed, and a great load is applied to force the bent tube straightly. Therefore, a means that can advantageously prevent the buckling of the tube and efficiently perform the punching process is desired.
In response to this demand, an object of the present invention is to provide a high-efficiency manufacturing method and apparatus for a high dimensional accuracy tube that can efficiently manufacture a tube with high dimensional accuracy by preventing buckling of the tube to be punched. .

The present invention that has achieved the above object is as follows.
(1) In a manufacturing method of a high dimensional accuracy pipe in which a pipe is continuously inserted into a pipe and floated, and the pipe is continuously sent and pushed into a die to be punched out. A high-efficiency manufacturing method for high-dimensional accuracy pipes, characterized in that the pipe is pressed by a pressing roller.
(2) The high-efficiency manufacturing method for a high-dimensional accuracy tube according to (1), wherein the pressing roller is a pair.
(3) The high-efficiency manufacturing method for a high-dimensional accuracy pipe according to (1) or (2), wherein a plurality of the pressing rollers are provided in the pipe feeding direction.
(4) The pressing roller is provided at a position where the buckling limit load is equal to or greater than the punching load. The high dimensional accuracy tube according to any one of (1) to (3), Efficiency manufacturing method.
(5) In a high dimensional accuracy pipe manufacturing apparatus having a die through which a pipe with a plug inserted is passed and a pipe pusher for continuously feeding the pipe into the die, the pipe being pushed into the die A high-efficiency manufacturing apparatus for high-dimensional accuracy tubes, comprising a pressing roller that presses the die at the entrance side of the die.
(6) The high-efficiency manufacturing apparatus for high-dimensional accuracy tubes according to (5), wherein the pressing roller is a pair.
(7) The high-efficiency manufacturing apparatus for high-dimensional accuracy pipes according to (5) or (6), wherein a plurality of the pressing rollers are provided in the pipe feeding direction.
(8) The pressing roller is provided at a position where the buckling limit load is equal to or greater than the punching load. The high dimensional accuracy tube according to any one of (5) to (7), Efficiency manufacturing equipment.

  According to the present invention, it is possible to stably produce a pipe with high efficiency while obtaining remarkably good dimensional accuracy.

When the tube is punched, if the load for reducing the diameter of the tube with a die is low, stable processing is possible if the outer diameter of the tube is large and the wall thickness is large.
However, when the friction between the die and the tube or the plug and the tube increases and the punching load is large, or when the outer diameter of the tube is small and the wall thickness is small, the tube is likely to buckle. Once buckling occurs, processing must be stopped to remove the tube, and the peripheral device may be damaged by the buckled tube, and the buckled and bent tube may be reused. However, it is necessary to add correction, which increases costs and processing time, and becomes a big problem.

  Therefore, the present inventors have paid attention to a method of pressing down a tube being processed in order to prevent buckling. That is, in order to prevent buckling during the punching of the tube, a pressing roller is installed on the entry side of the die, and the tube is pressed by this pressing roller. Thereby, the buckling length becomes the distance from the pressing portion to the die. If a plurality of pressing rollers are installed in the tube feeding direction and the tube is pressed down, the distance between the pressing rollers becomes the buckling length. Therefore, the buckling limit length is remarkably shortened and buckling can be prevented.

However, since the direction of buckling and bending is not always constant, buckling can be prevented without being affected by the direction if the pipe is pressed by a pair of pressing rollers. In addition, when the length of the tube is long, by installing the pressing rollers at a plurality of points in the tube feeding direction, the length between the pressing rollers can be shortened, and buckling can be advantageously prevented.
In addition, the punching load greatly affects the buckling of the pipe. Therefore, buckling can be prevented if the buckling limit load can be increased beyond the punching load (= the load required for punching = processing load). Therefore, the distance from the die to the pressing roller or between the pressing rollers is reduced. Therefore, the buckling limit load should be improved.

Specifically, using the following formulas (I) and (II), replace the buckling limit load with the load required for punching out, and back-calculate the buckling limit pipe length in the formula. It is preferable to determine the position where the pressing roller is installed so that the distance between the pressing roller and the die or the distance between the pressing rollers does not exceed the shorter pipe length.
σ _k = YS × (1−a × λ), λ = (L / √n) / K, n = 1, a = 0.0185 (I)
σ _k = n × π ² × E ₀ × (K / L) ² (II)
YS: Yield stress of pipe, L: Pipe length, K: Secondary radius of cross section, E ₀ : Young's modulus In addition, when punching, a lubricant is applied to the pipe to reduce the frictional force with the die and / or plug Then, the punching load can be reduced, which is preferable.

  FIG. 1 is a longitudinal sectional view showing an example of the device of the present invention. In this example, a pair of pressing rollers 5 and 5 are disposed on the entry side of the die 2. The tube 3 is inserted into the die 2 by the tube pusher 4 with the plug 1 inserted therein, and is being punched. The pressing roller 5 presses the unprocessed portion of the tube 3 to prevent buckling due to the compressive force of the tube pusher 4.

(Condition 1) Manufacture of 10 tubes of φ3.5 mm × 6 mmt by punching using a steel tube of size = φ40 mm × 6.0 mmt × 5.5 mmL and yield stress = 490 MPa as a material. Tried. The distance between the tube pusher 4 and the die 2 was 500 mm, and the distance between the die 2 and the pressing roller 5 was 250 mm. A dry lubricant film was sufficiently adhered to the tube before processing, and the tube was continuously fed to be processed.
(Condition 2) Using the same steel pipe as in Condition 1, the production of 10 tubes of the same size as in Condition 1 was attempted by punching using the apparatus shown in FIG. The distance between the tube pusher 4 and the die 2 was 500 mm. While supplying the liquid lubricant to the tube 3 between the tube pusher 4 and the die 2, the tube was continuously fed and processed.
(Condition 3) Using the same steel pipe as in Condition 1, the production of 10 tubes of the same size as in Condition 1 was attempted by drawing using the apparatus shown in FIG. A dry lubricant film was sufficiently adhered to the tube before processing. Since it is necessary to squeeze the tip of the tube 3 in order to force the tube drawing machine 6 to grip it, the tubes were processed one by one.

  Table 1 shows the results of investigating the presence or absence of buckling, the processing load of punching or drawing, processing efficiency, and dimensional accuracy (represented by wall thickness accuracy and outer diameter accuracy) for steel pipes manufactured under each condition. The wall thickness accuracy is obtained by image analysis of the circumferential section of the tube, and from the image of the wall section, the maximum deviation from the average wall thickness (that is, wall thickness deviation = (maximum wall thickness−minimum wall thickness) / average wall thickness × 100%. ) Was measured and evaluated. The outer diameter accuracy is evaluated by image analysis of the circumferential section of the tube and measuring the maximum deviation from the average outer diameter (ie, outer diameter deviation = (maximum outer diameter-minimum outer diameter) / average outer diameter x 100%). did. The machining efficiency is shown as a relative ratio where the number of machining per unit time in the conventional example is 1 (reference).

  From Table 1, the comparative example (Condition 2) has much better dimensional accuracy and machining efficiency than the conventional example (Condition 3), but has the disadvantage that the machining load is high and buckling occurs. On the other hand, in the example (condition 1) of the present invention, the machining load is reduced and the machining efficiency is improved while maintaining the dimensional accuracy at the same level.

It is a longitudinal cross-sectional view which shows an example of embodiment of this invention. It is a longitudinal cross-sectional view which shows a comparative example. It is a longitudinal cross-sectional view which shows a prior art example.

Explanation of symbols

1 Plug 2 Die 3 Tube 4 Tube Pusher 5 Pressing Roller 6 Tube Puller

Claims (8)

  In a manufacturing method of a high dimensional accuracy pipe, in which a plug is inserted into a pipe and floated, and the pipe is continuously sent and pushed into a die to perform punching processing. A high-efficiency manufacturing method for high-dimensional accuracy pipes, characterized in that it is held in place.   The high-efficiency manufacturing method for a high-dimensional accuracy tube according to claim 1, wherein the pressing rollers are a pair.   The high-efficiency manufacturing method for a high-dimensional accuracy pipe according to claim 1 or 2, wherein a plurality of the pressing rollers are provided in the pipe feeding direction.   The high-efficiency manufacturing method for a high-dimensional accuracy pipe according to any one of claims 1 to 3, wherein the pressing roller is provided at a position where a buckling limit load is equal to or greater than a punching load.   In a manufacturing apparatus for a high dimensional accuracy pipe having a die for passing a pipe having a plug inserted therein and a pipe pusher for continuously feeding the pipe and pushing the pipe into the die, the pipe being pushed into the die is moved to the die. A high-efficiency manufacturing apparatus for high-dimensional accuracy pipes, comprising a pressing roller for pressing on the inlet side of the tube.   6. The high-efficiency manufacturing apparatus for high-dimensional accuracy tubes according to claim 5, wherein the pressing roller is a pair.   The high-efficiency manufacturing apparatus for high-dimensional accuracy pipes according to claim 5 or 6, wherein a plurality of the pressing rollers are provided in the pipe feeding direction.   The high-efficiency manufacturing apparatus for high-dimensional accuracy tubes according to any one of claims 5 to 7, wherein the pressing roller is provided at a position where a buckling limit load is equal to or greater than a punching load.