JPS5838250B2 - Bending method and device for metal tube with circular cross section - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a processing method and apparatus for bending a metal tube having a circular cross section (hereinafter referred to as a "circular tube") so that it does not become flat.

Here, "flat" refers to an oval shape in which the cross section of the tube has a long axis in a direction perpendicular to the bending plane, and "reverse flat" refers to an oval shape in which the direction of the long axis differs by 90 degrees from that of the flat tube.

When bending circular pipes, the requirements for the finished product are as follows:
■) Small change in wall thickness, 2) Accurate bending radius, and 3) No flattening. Among these, the change in wall thickness in 1) is determined by the bending radius, and 1)
In addition, the bending radius in 2) changes depending on the material and processing conditions, but there is no particular problem as it can be processed using the value multiplied by the correction coefficient, but bending to avoid flattening in 3) This is considered extremely difficult using conventional methods.

However, in the transportation of liquids by pipeline, which has become popular in recent years, when bending the circular pipes that make up the pipeline, special care must be taken to avoid flattening the pipes.
It is desirable that the surface be processed to have a perfect circular shape.

The reason for this is that if the cross section of the circular pipe is not a perfect circle, not only will it take time to join the circular pipes when forming the pipeline, but also impurities will adhere to the inner wall of the circular pipe while transporting the liquid. If a pig is used to clean a pipe, etc., the cleaning cannot be done satisfactorily, and if a pig is used as a partition to transport different types of liquids, a gap will be created between the pig and the inner wall, causing the different types of liquids to mix. It's because of that.

The present invention was made from the above-mentioned viewpoint with the purpose of bending a circular pipe so that it does not become flat.
When bending a metal tube with a circular cross section while heating it to a narrow width using induction heating, etc., before processing, the part to be bent is oriented 90 degrees different from the flatness that will occur after processing. It is characterized by bending by plastically deforming it into an inverted flat shape, and in the past, the equipment consisted of an annular heating device and a cooling device that heated the outer periphery of the circular tube Q to be bent, and a heating and cooling device. means for guiding the circular tube toward the heating device before passing through the device; means for pressurizing the circular tube in a vertical direction on its traveling plane; and pressing or guiding the circular tube in the bending direction after passing through the heating device and the cooling device. The invention is characterized in that it comprises a means for doing so.

In general, when a circular pipe is bent, the processed part inevitably becomes flattened, and the degree of flattening tends to be greatest at the position of 1/2 of the bending angle, that is, at the center.

The present invention utilizes this phenomenon in reverse, and before bending a circular pipe, it is deformed into an inverted flattened shape that is 90 degrees different from the flattened part that is about to occur during bending. This was done from the viewpoint that if the circular pipe is bent after being applied to the part to be bent, the cross section of the circular pipe after processing will be a perfect circle, and the material is STP.
G38, ※※Diameter 4 0 6. 4 tran, thickness 1
When a 2.7 mm circular tube was bent horizontally using the conventional method with a bending radius of 1219.2 m and a bending angle of 90 degrees, as shown in Table 1, the result was much flatter after the process than before. However, according to the method of the present invention, the circular tube was flattened before processing, plastically deformed into an inverted flat shape, and then bent using the same method as above. The cross section of the circular tube was almost completely circular.

Next, an example of implementation of the device of the present invention will be explained with reference to the drawings.

In the figure, 1 is a circular tube to be curved, and 2 is a heating device that heats the narrow outer circumference of the circular tube 1, using an annular inductor, an annular gas burner, or the like.

3 is a cooling device provided to inject cooling water to the delivery side of the circular tube 1 of the heating device 2; 4 and 5 are guide rolls that guide the circular tube 1 toward the heating device 2; and 6 and 1 are guide rolls that guide the circular tube 1 toward the heating device 2. With rolls that apply pressure perpendicular to the plane of movement, the circular tube 1 is guided to the heating device 2 by guide rolls 4 and 5, while being pressurized from above and below by rolls 6 and 7, plastically deformed into an inverted flat shape, and heated. It advances through the device 2, is evenly heated by the heating device 2, and is then cooled by the cooling device 3.

Reference numeral 8 denotes a support for receiving the tip of the circular tube 1, 9 is an arm, and 10 is a mounting shaft for the arm 9. The tip of the circular tube 1 is firmly tightened to the support 8 with a bolt 11, and the support 8 is attached to the arm. 9, and the arm 9 is configured to rotate around an axis 10.

That is, when bending the circular tube 1, the tip of the circular tube 1 is fixed to the receiver 8, and the circular tube 1 heated as described above is pulled and guided in the bending direction by the am 9. It is.

The guide rolls 4 and 5 are moved back at the same time as the pressure rolls 6 and 7 press the circular tube 1, so that there is no problem in deforming the circular tube 1 into an inverted flat shape. , 7, the cross-sectional shape of the starting end and end of the part to be bent is the same as that of the raw pipe, and gradually becomes inverted flat toward the center, with the center being the most inverted. The flatness shall be high.

In the apparatus of the above embodiment, the circular tube 1 that has passed through the heating device 2 and the cooling device 3 is pulled and guided in the bending direction by the arm 9, but the present invention is not limited to this. Instead, it may be guided by pressure using a push roll or the like.

When the above-mentioned circular tube was bent using the apparatus configured as described above, a circular tube whose cross section at the bent portion was almost perfectly circular was obtained, similar to the one after processing in Table 2. It was done.

The present invention is as described above, and when bending a circular pipe, in order to prevent the circular pipe from becoming flat after bending according to the conventional bending method, it is necessary to bend the circular pipe before bending. Since the section is bent after being given plastic deformation in an inverted flat shape that differs in direction by 90 degrees from the flat part, the cross section of the circular pipe after bending becomes almost a perfect circle. Suitable for bending circular pipes, etc. that are lined up, 1.
The device uses a circular tube that is placed in a bending device.
Before heating for bending, in order to plastically deform the portion of the circular tube to be bent into an inverted flat shape, it is equipped with means for pressurizing the circular tube in a direction perpendicular to its plane of movement.
It is possible to bend the circular tube so that it does not become flat while continuously deforming it into an inverted flat shape and bending it with good working efficiency.

[Brief explanation of the drawing]

The figures show an example of the implementation of the apparatus of the present invention, in which Fig. 1 is a plan view of the state in which a circular pipe to be bent is mounted, and Fig. 2 is a state before the apparatus is operated. 3 is a sectional view taken along the line A--A in FIG. 1 during operation. 1... Circular tube, 2... Heating device, 3...
... Cooling device, 4.5 ... Guide roll, 6
, 7...-Pressure 1'-le, 8... Receiver, 9... Arm, 10... Arm attachment shaft.

Claims (1)

[Scope of Claims] 1. When bending a metal tube with a circular cross section while heating it narrowly using induction heating, etc., the portion to be bent must be oriented at 90 degrees from the flattening that will occur after processing. A method for bending a metal tube with a circular cross section, which is characterized by plastically deforming and bending a metal tube into an inverted flat shape with different angles. 2. An annular heating device and cooling device that narrowly heats the outer periphery of a metal tube with a circular cross section to be bent, a means for guiding the tube before passing through the heating device within a bending plane toward the heating device, and the tube. A metal tube with a circular cross section, comprising means for pressurizing the tube in a direction perpendicular to its bending plane, and means for pressing or pulling the tube in the bending direction after passing through a heating device and a cooling device. Bending equipment.