JPS6146327A - Hot bend work method of pipe - Google Patents

Abstract

PURPOSE:To check the thickness decrease of a bend work part by providing an annular heating coil where the coil width varies in peripheral direction and by working with arranging so that the wider part of the coil width comes to the outside of bend and the narrower part to the inside of bend. CONSTITUTION:The setting of a coil 2 is made on the outer periphery of the bend work part of a pipe 1. The wider coil width 2a part of a heating coil 2 is made to come to the outside of the bend and the narrower coil width 2n part to the inside of the bend. When a high frequency oscillator 3 is electridied the bend work part of the pipe 1 is heated. A working force 4 is loaded via a pusher 7 by a hydraulic cylinder 8 in the axial direction of the pipe 1 with heated condition. The pipe 1 is worked with a hot bend with being conducted at the prescribed radius of curvature (r) around a pivot 6. In this case the sectional area of the heating coil 2 of the bend inside is smaller and the high frequency current density is made higher and the inside 1b becomes higher in temp. against the outside 1a. The thickness decrease of the outside 1b is thus checked.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for hot whitening of pipes, which utilizes high-frequency induction heating and is particularly aimed at preventing thinning of the whitened portion of the pipe. The present invention relates to a hot-mortar processing method.

[Background of the invention]

As a method for suppressing the thinning of the processed part during the machining process of pipes, for example, the method shown in Japanese Patent Application Laid-open No. 159424/1980 is to cut and machine the inner pipe in advance. There is a method of using it as a raw pipe.

This is because the material pipe is thickened in advance on the thinning side (the outside of the bend), and this prevents thinning after the bending process.

However, this method has a problem in that it requires the use of expensive raw tubes manufactured by mechanical Roe. .

[Purpose of the invention]

The present invention solves the above-mentioned problems of the prior art and makes it possible to prevent the thinning of the machining section A without using expensive blank pipes. This is the purpose of providing this information.

[Summary of the invention]

The structure of the pipe hot bending method according to the present invention is as follows.

An annular heating coil whose coil width changes in the circumferential direction is placed around the outer circumference of the bent part of the pipe, so that the wide part of the coil is on the outside and the narrow part of the coil is on the same side. The heating coil is used to perform high-frequency induction heating of the bending blade part while the vibrating blade is being bent.

For more details, change the width of the heating coil in the circumferential direction.
It is advantageous to arrange the T part, which has a large coil width, that is, the part with a large cross-sectional area, on the side with reduced thickness (the outside part of the bend), and the part with the small width of the coil, with the increased thickness @ (the inside part of the bend). By giving a temperature distribution in the circumferential direction of the pipe and creating a gradient in the deformation resistance, it is possible to create a gradient during bending! Reduce the thickness of the shaft @ (move to the outside of the bend,
This is the next step to prevent wall thinning.

[Embodiments of the invention]

The following is an explanation using examples.

FIG. 1 relates to one embodiment of the present invention. FIG. 2 shows an example of the apparatus used for carrying out the hot machining method for pipes, and the plan view of the pipes to be machined by this method. FIG. 3 is a plan view showing details 7 of the coil width and heating temperature diagram showing the relationship between the coil width and the heating temperature.

In Fig. 1, numeral 1 indicates the besa pipe at the agglomerated part.

5 is a rotary arm that clamps one end of this pipe 1 and can freely rotate around the pipotron, 7 is a prisha connected to the other end of the pipe 1, and 8 is a pusher 9 that connects the pipe to A hydraulic cylinder 9 for applying an axial machining force 4 to the pipe 1 is a guide roll that holds the pipe 1yt and regulates the moving direction of the pipe 1 in the advancing direction. 2 is
It is an annular heating coil with different cross-sectional areas (different coil widths) in the circumferential direction, the details of which are shown in FIG. A portion having a narrow coil width 2b is arranged on the outer periphery of the bent portion of the pipe 1 so as to go all the way around the inside of the bend. This heating coil 2 has a radius of 1 m on the outside of the pipe 1 and a bending circle of 1 m! A two-color thermometer (not shown) is installed that can detect the temperature t of the lit cell without contact. 3 is a high-frequency oscillator that supplies a high-frequency current to the heating coil 2.

According to the device according to the first factor, which is configured as shown in FIG.

Explain the Loe method of hot bending pipes.

First, a pipe 1 (a carbon steel pipe with an outer diameter of 21,011φ, a plate thickness of 9.5 mm, and a width of 5.51 m) is placed between the guide rolls 9, one end of which is clamped to the rotating arm 5, and the other end is clamped to the prisha 7. Join. A heating coil 2 is installed around the outer periphery of the whitening section of the pipe 1. This heating coil 2 is 2
The coil width 2a on the outside of the bend is 50 mm, the coil on the inside of the bend -
2b is 201J and the vicinity of the two axes is approximately 3511).

When the high-frequency generator 3 is energized, a high-frequency current with a frequency of 2500 Hz flows through the heating coil 2, and an induced current flows through the machining part of the pipe 1, causing heat generation due to ohmic loss.

When the detected value of the two-color thermometer (not shown) rises to a predetermined temperature, a machining force 4 is applied to the hydraulic cylinder/8 in the axial direction of the pipe 1 through the L cupshaft 7χ while the pipe is heated. Ru. Since one end is clamped to the rotating arm 5, the pipe 1 bends around the pivot 9 with a predetermined bending radius r (=32
5WM). The bending moment generated as a result of this causes the pipe 1 to be bent with a hot bending knife. During this hot bending process, the coil width 2a on the outside of the S bevel is 5011, and the coil width 2b [2Qjll
Therefore, the cross-sectional area of the heating coil 2 on the inside of the bend is small, the high frequency current density is high, and the bend circle 1 of the pipe 1 is
1Nb has a high temperature relative to the bending outer side 1aK. In this embodiment, as shown in FIG. 3, the outside bend #1a (coil! 50 m! 1) of the pipe 1 is 600°C, and the inside bend 1b (coil! 20 m!) t! At 900℃, the deformation resistance of the crack is 114f/II, 51Pf/gll.
Bending! The axis moves outward from the center of the pipe 1.

Therefore, the thinning of the outside bend 1b is suppressed, and the thinning wind of the outside bend 111j1a of the pipe 1 subjected to hot whitening is 7% in the X embodiment, which is the JIS standard value 12. s
There is a gap below XX.

If the above-described embodiments are followed, high-frequency induction heating can be used to prevent thinning of the nage 7711 section.
It is possible to provide a method for hot bending of pipes, and there is no need to use expensive raw pipes such as thick-walled pipes and thin-walled pipes, which has the effect of reducing material costs by about 10%.

〔Effect of the invention〕

To provide a method for hot bending a pipe, which is described in detail above and can prevent thinning of the bending jaw section without using an expensive blank pipe, if implemented according to the present invention. I can do it.

[Brief explanation of drawings]

The first example is an example of a device used to carry out a hot bending method for pipes according to an embodiment of the present invention. Figure 2 is a plane view showing details of the vicinity of the heating coil in the first cause, and Figure 3 is a plane view showing the details of the vicinity of the heating coil in the first cause. It is a T coil width-skin heat temperature diagram showing the relationship. 1...Pipe, 1a...Bending outside of the pipe, 10.
・Inside bending of pipe, 2...Blade heating coil, 2a・
... Coil width on the outer side of the grinding, 2b... Coil width on the same side of the whitening, 3... High frequency dust generator.

Claims (1)

[Claims] 1. An annular heating coil whose coil width changes in the circumferential direction is placed around the outer circumference of the bent portion of the pipe so that the wide part of the coil is on the outside of the bend and the narrow part of the coil is on the inside of the bend. A method for hot bending a pipe, characterized in that the pipe is bent while the bending portion is heated by high frequency induction using the heating coil.