JP2009183983A - Method of bending electric resistance welded steel tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of bending an electric resistance welded steel tube by which the life of a working tool of a rotating and pull-bending apparatus is prolonged in the working of the electric resistance welded steel tube having a stage for bending the electric resistance welded tube and a stage for expanding a tube end succeeding to the stage for bending. <P>SOLUTION: When bending the electric resistance welded tube p by a rotating and pull-bending apparatus, a rotating and pull-bending apparatus 8 on the surface of which relieving grooves 9 in which the bead part of the electric resistance welded steel tube p is housed are formed on the surface of the working tool 1 on the inside of bending and the surface of a ball mandrel 5 is used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of bending an electric resistance steel pipe by a rotary drawing bending apparatus in the processing of the electric resistance steel pipe having a step of bending the electric resistance steel pipe and a subsequent step of expanding the pipe end.

Pipe parts that have been subjected to minimal bending (for example, bending radius R = 1.5D or less, D: outer diameter) are widely used for automobile parts, air-conditioning parts, and the like. As a bending apparatus for bending a pipe, a rotary drawing bending apparatus as shown in FIG. 5 is widely used.
FIG. 5 (a) is a side view showing the configuration of a conventional rotary drawing and bending apparatus, and FIG. 5 (b) is a Y0-Y0 sectional view thereof.

  The rotary pull bending apparatus 8 includes a rotatable bending die 1 having a bending guide groove as a working tool corresponding to the cross-sectional dimension of the pipe p, and a clamp for fixing a part of the pipe p to the bending die 1. 2, a pressing die 3 that holds the bent outer peripheral surface of the pipe p, a wiper 4 that holds the inner peripheral surface of the pipe p, a ball mandrel 5 that is held in the pipe p, and a pipe p from the rear end of the pipe p. And a pipe booster 6 for urging the shaft in the axial direction.

The pressing die 3 is supported by a holder 7 so as to be movable in the axial direction of the pipe p, and the holder 7 can be adjusted in the radial position of the bending die 1 by a position adjusting screw 7a. In general, the position of the pressing die 3 is often fixed when the pipe p is processed.
The method of bending the pipe p by the rotary pull bending apparatus is as follows.
A part of the pipe p is fixed to the bending die 1 by the clamp 2, and the pressing die 3 is moved to a desired position by the position adjusting screw 7 a, and the bending die 1, the wiper 4, the ball mandrel 5 and the pressing die 3 are used for the pipe. By rotating the bending die 1 while pinching p, the pipe p is bent into a shape following the groove shape of the bending die 1. Further, if necessary, the pipe p is urged by the pipe booster 6 in contact with the rear end of the pipe p.

  In the bending method using the above-described rotary pulling bending apparatus, as shown in FIG. 6, it is known that the bending behavior differs between the inside and the outside with a neutral axis as a boundary. That is, since the locus length of the outer portion of the bend from the neutral axis is longer than the locus length of the bending radius R, the thickness after the bending is longer than the original thickness t at the time of bending. Also become thinner. On the other hand, the portion inside the bend is contracted in the axial direction at the time of bending, and the thickness after bending becomes thicker than the original thickness t.

Due to this, at the time of bending, cracks are likely to occur at the outer portion of the pipe p, and buckling is likely to occur at the inner portion of the bend. Therefore, conventionally, in order to prevent the buckling of the pipe p, the ball mandrel 5 is disposed inside the pipe p, and the bending inner wall of the pipe p is held by the bending die 1 and the wiper 4 to perform the bending process. It was.
JP-A-8-117801

When the pipe p is a seamless steel pipe, there was not much problem in processing due to the cross-sectional shape, but when the pipe p was an electric resistance steel pipe, the problem in processing due to the shape of the bead portion extending in the pipe axis direction. was there.
That is, when bending the ERW steel pipe with the rotary pull bending apparatus, if the thickness of the bead portion extending in the pipe axis direction is the same as the thickness of the ERW steel pipe, there will be no problem in the bending process. In the pipe end expansion process, it occurs at a probability of cracking from the bead part of the ERW steel pipe.

Therefore, in order to efficiently process the ERW steel pipe, the ERW steel pipe is manufactured by cutting the bead portion so that the bead portion protrudes by a predetermined amount on the inner surface side and the outer surface side. When such an electric-welded steel pipe is bent by a rotary pull bending apparatus, the wear of the working tool that comes into contact with the bead portion proceeds, and the tool life is shortened due to the progress of cracking and wear of the working tool. .
In view of the above prior art, the present invention provides an electric machine capable of extending the tool life of a rotary draw bending apparatus in the machining of an ERW steel pipe having a process of bending an ERW steel pipe and a process of expanding a pipe end following the process. It aims at providing the bending method of a sewn steel pipe.

The present inventor has intensively studied, and when bending an ERW steel pipe by a rotary drawing bending apparatus, the tool life is shortened because the working tool inside the bending where the surface pressure is remarkably increased, that is, as shown in FIG. It was found that they were a bending die 1 (hereinafter referred to as a formed die 1), a wiper 4 and a ball mandrel 5.
Therefore, a relief groove that can accommodate the bead portion of the ERW steel pipe is formed on the surface of the bending inner working tool (formed die 1, wiper 4) and the ball mandrel 5, and the bead portion of the ERW steel pipe is It was found that the above-mentioned problem can be effectively solved by making the machining tool non-contact, and the present invention was made.

  That is, according to the present invention, in the machining of the ERW steel pipe having the process of bending the ERW steel pipe and the subsequent pipe end expanding process, when bending the ERW steel pipe by the rotary pull bending machine, A method of bending an ERW steel pipe, characterized by using a rotary drawing bending apparatus in which a relief groove capable of accommodating the bead portion of the ERW steel pipe is formed on the surface of a tool and the surface of a ball mandrel.

  According to the present invention, when bending an ERW steel pipe with a rotary pull bending apparatus, the surface pressure is increased by contact with the inner working bead and the inner bead part where the surface pressure is significantly increased by contacting the outer bead part. Since the escape groove that can accommodate the bead portion of the ERW pipe is formed on the surface of the ball mandrel 5 that is remarkably high, it is possible to extend the tool life of the rotary bending machine compared to the case without the escape groove. is there.

  The method for bending an ERW steel pipe according to the present invention includes a bending inner working tool, that is, a formed die 1 and a wiper 4 in machining an ERW steel pipe having a step of bending the ERW steel tube and a step of expanding the tube end. (Refer to FIG. 1 and FIG. 5) and a rotary pull bending apparatus in which a relief groove 9 capable of accommodating the bead portion of the electric resistance steel pipe is formed on the surface of the ball mandrel 5, the electric resistance steel pipe is bent. Other than that, it is the same as the bending method using the conventional rotary drawing bending apparatus in which the escape groove 9 is not formed.

FIG. 1 is a cross-sectional view of an essential part showing an embodiment of a rotary drawing and bending apparatus used in the present invention, and FIG. 5 (a) is a side view showing the configuration of a conventional rotary drawing and bending apparatus. b) is a sectional view taken along the line Y0-Y0.
An example of a part obtained by the present invention is shown in FIG.
2 is a cross-sectional view showing a part processed in two bending steps using the rotary pull bending apparatus shown in FIG. 1, FIG. 3 is a Y1-Y1 cross-sectional view of FIG. 2, and FIG. 4 is Y2 of FIG. It is -Y2 sectional drawing. b schematically shows a bead portion of the electric resistance welded steel pipe p. The two bent portions were formed by using a rotary drawing and bending apparatus in which a clearance groove capable of accommodating the bead portion b of the ERW steel pipe p was formed.

  Parts having a pipe portion that is inclined with respect to the straight pipe before bending (in the case of FIG. 2, an intermediate portion that is inclined by 90 degrees with respect to the axial direction of the straight pipe before bending) is an exhaust pipe of an automobile with limited piping. Applicable to parts and useful. A part having such a pipe portion uses a rotary pull bending apparatus in which a clearance groove capable of accommodating the bead part b of the electric resistance welded steel pipe p is used, and the bending direction is mutually changed at two different positions in the pipe axis direction before processing. It can be easily obtained by bending in the opposite direction. At that time, the bending process at one place is located on the inner side of the bending of the rotary pulling bending apparatus (bent portion shown by the Y1-Y1 cross section in FIG. 2), so that compared with the conventional case without the escape groove 9. The tool life of the rotary bending machine can be greatly extended.

  A relief groove 9 that can accommodate the bead portion b of the electric resistance welded steel pipe p is formed on the surface of the bending die of the rotary drawing bending apparatus, that is, the formed die 1, the wiper 4, and the ball mandrel 5, and during bending, A test was conducted to bend the ERW steel pipe while the bead portion b of the ERW steel pipe p was housed in the escape groove 9. In the test, the bending radius R of the bending portion shown in FIG. 2 is 1.5D (D: outer diameter of pipe = 38.1 to 42.7 mm, standard: JIS 430M, 429), and the thickness t of the electric resistance welded steel pipe = 1.5 mm.

Note that the width a and the depth of the relief groove shown in FIG. 1 were as follows. That is, the width a of the relief groove of the formed die 1 and the wiper 4 which are the inner working tools of the bending is the width of the outer surface bead portion + (2 to 5) mm, and that of the ball mandrel 5 is the width of the inner surface bead portion + (2 To 5) mm.
Further, the depth of the relief groove of the formed die 1 and the wiper 4 is the height of the outer bead portion + (0.2 to 0.5) mm, and that of the ball mandrel 5 is the height of the inner bead portion + (0 .2 to 0.5) mm.

  As a result of this test, when the relief groove 9 was formed on the surface of the formed die 1, the wiper 4 and the ball mandrel 5, the tool life of the rotary bending machine could be greatly extended compared to the conventional machining tool. .

It is principal part sectional drawing which shows one Example of the rotation drawing bending apparatus used for this invention. FIG. 2 is a cross-sectional view showing a part obtained by two bending processes using the rotary pull bending apparatus shown in FIG. FIG. 3 is a Y1-Y1 cross-sectional view of FIG. 2. FIG. 3 is a Y2-Y2 cross-sectional view of FIG. 2. (A) is the side view which showed the structure of the conventional rotation drawing bending apparatus, (b) is the Y0-Y0 sectional drawing. It is sectional drawing which shows the neutral axis | shaft in a bending process.

Explanation of symbols

p Pipe (steel pipe)
a Width of relief groove b Bead part t Thickness D Outer diameter R Bending radius o Bending center of rotation (rotating axis)
1 Bending mold (formed die)
2 Clamp 3 Push type (pressure die)
4 Wiper 5 Ball mandrel 6 Pipe booster 7 Holder 7a Position adjusting screw 8 Rotating draw bending device 9 Relief groove

Claims (1)

In the machining of an ERW steel pipe having the process of bending the ERW steel pipe and the subsequent pipe end expanding process, when the ERW steel pipe is bent by the rotary pull bending machine, the surface of the inner working tool and the ball mandrel are bent. A method for bending an ERW steel pipe, characterized in that a rotary pulling bending apparatus in which a relief groove capable of accommodating the bead portion of the ERW steel pipe is formed on the surface of the ERW steel pipe is used.

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