JPH054187B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a high-frequency welding machine used for manufacturing ERW pipes, and specifically relates to a high-frequency welding machine that can increase heating efficiency compared to conventional welding machines. This is a proposal.

[Prior art]

In general, electric resistance welding pipes that undergo high-frequency induction welding are made by passing a skeleton through a group of forming rolls and bending it into a roughly O-shaped cross section so that the edges on both sides face each other.An open pipe is passed through the work coil, and the edges on both sides are It is manufactured by heating and melting with high frequency current and butt welding using squeeze rolls facing each other to form a tube, which is then subjected to cutting of the inner and outer beads and other finishing treatments.

When manufacturing ERW pipes in this way, part of the current flowing through the open pipe is at the welding point (point V).
Instead of flowing to the inner surface of the open pipe, it flows back and becomes a reactive current that does not contribute to welding. In order to suppress this reactive current, conventionally, an impeder is loosely fitted into the open pipe from the upstream side of the work coil installation position to the vicinity of the welding point, thereby increasing the impedance on the inner surface of the open pipe. It is configured to reduce reactive current.

However, in the case of a conventional machine with such a configuration, when energized as shown by the white arrow in FIG.
and magnetic fluxes 21a and 20a in the impeder 20, respectively.
As a result, an eddy current Ia is generated in the open pipe 21 due to the magnetic flux 21a, and the magnetic flux 20
Due to a, an eddy current Ib on the inner surface of the open pipe and an eddy current Ic on the outer surface of the open pipe are generated.

A total outer current Io and a total inner current Ii generated on the outer and inner surfaces of the open pipe 21 due to these eddy currents are expressed by the following equation (1), respectively.

Io=Ia+Ic Ii=Ia−Ib……(1) And the welding current, that is, the current flowing to the welding point V
Iw is expressed as the difference between the outer surface current Io and the inner surface current Ii, as shown in equation (2) below.

Iw=Io−Ii=Ib+Ic……(2) As is clear from the above equation (2), the welding current Iw is the sum of the inner surface eddy current Ib and the outer surface eddy current Ic due to the magnetic flux 20a of the impeder 20. Current other than
That is, the eddy current Ia due to the magnetic flux 21a of the open pipe 21 is a reactive current that does not contribute to welding in any way,
Eddy current loss reduces heating efficiency per unit of power consumption, and in conventional machines, there was a limit to the improvement of heating efficiency due to eddy current loss.

〔the purpose〕

The present invention was made in view of the above circumstances, and an impeder is placed inside an open pipe in which a work coil for heating the open pipe is located, and the magnetic flux generated in the open pipe by the work coil is generated in the opposite direction. A magnetic flux canceling coil that generates magnetic flux is provided upstream of the work coil in the open pipe transfer direction, and the distance between the work coil and the magnetic flux canceling coil is such that the magnetic flux of the magnetic flux canceling coil is generated by the work coil. By setting the distance at least so that it does not affect the magnetic flux of the impeder,
An object of the present invention is to provide a high-frequency welding machine that can reduce eddy current loss and significantly improve heating efficiency.

[Structure of the invention]

The high-frequency welding machine according to the present invention applies a high-frequency current to a work coil to heat both edge portions of an open pipe that passes through the work coil, and also installs an impeder in the open pipe to increase heating efficiency. In the high-frequency welding machine for manufacturing pipes, the impeder is arranged at a position corresponding to the work coil, and is used to cancel magnetic flux that generates a magnetic flux in the opposite direction to the magnetic flux generated in the open pipe by the work coil. The coil is installed upstream of the work coil in the open pipe transfer direction, and the distance between the work coil and the magnetic flux canceling coil is such that the magnetic flux of the magnetic flux canceling coil does not affect the impeder magnetic flux generated by the work coil. It is characterized by being greater than or equal to the distance.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 2 is a perspective view showing an embodiment of the high frequency welding machine according to the present invention.

In the figure, reference numeral 1 is an open pipe, and the skeleton is passed through a group of forming rolls (not shown) so that the cross section changes from a U-shape to an O-shape in which both edge portions 1a (only one side is shown in the diagram) face each other. It becomes curved,
This open pipe 1 is then passed through a work coil 2 which is formed into an annular external appearance of the proposed device A, which is an edge heating means, and an induced current is induced in the open pipe 1 by the high frequency current passed through the work coil 2. The edge portions 1a on both sides are heated and moved toward the squeeze roll 3 side, and at the same time, the edge portions 1a on both sides are melted and are butt-welded by the lateral pressure of the squeeze roll 3 (only one side is shown) to form the tube 4. formed, its inner surface bead (not shown);
It is arranged to be transported in the direction of the white arrow toward the finishing process such as cutting of the outer surface bead 4a. 11 is tube 4
The mandrel is a mandrel for supporting a cutting tool (not shown) for cutting the inner surface bead of the mandrel, and is disposed substantially parallel to the open pipe 1 and the pipe 4 inside the open pipe 1 and the pipe 4 so as to span both of the pipes. The tip thereof is located inside the tube 4, and a header (not shown) for supporting a cutting tool is provided here. Further, the base end portion is led out to the outside through between the edge portions 1a on both sides of the open pipe 1 on the upstream side, and is fixed to a forming roll stand (not shown) (an appropriate stand between the breakdown roll and the fin pass roll). There is. The mandrel 11 has a cylindrical shape, and on its outer periphery from the position where the work coil 2 is disposed to the center of the squeeze roll 3, an impeder 10 made of laminated ferrite and formed into a cylindrical shape is used to conduct high-frequency current at the edge portions 1a on both sides. It is mounted so that it faces the position.

The impeder 1 is placed on the upstream side in the transfer direction of the open pipe where the work coil 2 is disposed, and so as not to affect the magnetic flux of the impeder 10.
A magnetic flux canceling coil 5 of the present invention machine A is arranged at a position sufficiently separated from zero. The magnetic flux canceling coil 5 has an annular appearance like the work coil 2, and one end of each of the work coil 2 and the coil 5 is connected to each other, and each other end is connected to a high frequency power source (not shown). The direction of current flow is, for example, as shown by the arrow in FIG.
is selected so that it is the opposite of that of .

In the case of the machine A of the present invention having such a configuration, a magnetic flux is generated in the impeder 10 by the action of the work coil 2, and this magnetic flux causes an outer surface side eddy current to be generated in the open pipe 1, which contributes to welding. . Further, although magnetic flux is generated in the open pipe 1, this magnetic flux is canceled by the magnetic flux in the opposite direction generated in the open pipe 1 by the coil 5. Therefore, in the case of the machine A of the present invention, the eddy current that does not contribute to welding due to the magnetic flux formed in the open pipe 1 is reduced, and the eddy current loss, which was a problem in achieving heating efficiency in the conventional machine, is reduced. can. Note that the present invention does not simply provide an impeder in an open pipe at a position corresponding to the work coil, and a coil that cancels the magnetic flux generated by the work coil at a position separated from the work coil. An impeder is placed in the open pipe at a position, and a magnetic flux canceling coil that generates magnetic flux in the opposite direction to the magnetic flux generated in the open pipe by the work coil is installed on the upstream side of the open pipe transfer direction by the work coil. The distance between the magnetic flux canceling coil and the magnetic flux canceling coil is such that the magnetic flux of the magnetic flux canceling coil does not affect the impeder magnetic flux generated by the work coil. It is possible to further improve heating efficiency by suppressing eddy currents that do not contribute to welding due to the generated magnetic flux.

Next, the effects of the present invention will be explained based on Examples.

However, the number of turns of the work coil: 1 The number of turns of the magnetic flux canceling coil: 1 The frequency of high-frequency current: 330KHz Specifications of the ERW tube: 101.6 mm outside diameter x 4.2 mm wall thickness JIS SGP This example is compared to the conventional machine. We were able to improve heating efficiency by 20%.

〔effect〕

As detailed above, the high frequency welding machine according to the present invention includes an impeder provided in the open pipe in which the work coil is located, and the work coil cancels the magnetic flux that generates the magnetic flux in the opposite direction to the magnetic flux generated in the open pipe. The magnetic flux canceling coil is installed upstream of the work coil in the open pipe transfer direction, and the distance between the work coil and the magnetic flux canceling coil is set so that the magnetic flux of the magnetic flux canceling coil does not affect the impeder magnetic flux generated by the work coil. The present invention has excellent advantages such as suppressing the generation of eddy currents that do not contribute to welding, reducing eddy current loss, and greatly improving heating efficiency per unit of power consumption. be effective.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing eddy currents generated in an open pipe when a conventional device is used, and FIG. 2 is a perspective view showing an embodiment of the present invention. 1...Open pipe, 2...Work coil,
5... Coil for magnetic flux cancellation, 10... Impeder.

Claims (1)

[Claims] 1 High-frequency current is passed through a work coil to heat both edges of an open pipe that passes through the work coil, and an impeder is placed inside the open pipe to increase heating efficiency. In the welding machine, the impeder is
A magnetic flux canceling coil is disposed at a position corresponding to the work coil and generates a magnetic flux in the opposite direction to the magnetic flux generated in the open pipe by the work coil, and is provided on the upstream side of the work coil in the open pipe transfer direction, A high-frequency welding machine characterized in that the distance between the work coil and the magnetic flux canceling coil is set to be at least a distance at which the magnetic flux of the magnetic flux canceling coil does not affect the magnetic flux of the impeder generated by the work coil.