JPS61132281A - High frequency welder - Google Patents

Abstract

PURPOSE:To elevate a heating efficiency without eddycurrent loss by providing the coil winding a work coil so that the flowing direction of the current is made same on the inner side of an open pipe and tube and by feeding thereto the current that the current value and phase are adjusted. CONSTITUTION:The current Ic', Ib' in the same direction with both sides edge part Ia and in the reverse direction with Ia is flowed on the pipe outer face and inner face respectively, when the current value and phase are set adequately and the current is flowed on a coil 5. The induced current to pass the inner face side of open pipe 1 and tube 4 to be generated by a work coil 2 can be thus made smaller. Consequently a welding current Iw' can be made larger. With the above the induced current which does not contribute to the welding of the inner face of the open pipe 1 is controlled and the eddycurrent loss is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high frequency welding machine used for manufacturing electric resistance welding pipes.
Specifically, we propose a high-frequency welding machine that can increase heating efficiency compared to conventional welding machines.

[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 an 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 While heating and melting with high frequency current, butt welding is performed using squeeze rolls placed opposite each other to form a tube.
Manufactured with other finishing treatments.

When manufacturing an electric resistance welded pipe in this way, a part of the current flowing through the open pipe does not flow to the welding points (7 points), but instead flows to the inner surface of the open pipe, refluxing and becoming a reactive current that does not contribute to welding. . In order to suppress this reactive current, the impedance on the inner surface of the open pipe is increased by loosely fitting an impeder into the open pipe near the welding point from the upstream side of the work coil arrangement position. It is configured to reduce reactive current.

[Problems to be Solved by the Invention] Now, when the thickness of the skeleton is thick or when the welding speed is increased, it is necessary to increase the current flowing through the work coil 22. Magnetic flux density increases. For this reason, for pipes with small diameters, it is not possible to increase the diameter of the impeder 20, so the impeder 20 becomes saturated with magnetic flux, and the current flowing on the inner surface of the oven pipe 21 is no longer sufficiently suppressed by the impeder 20, so that the inner current increases. There is a problem that the welding current flowing through the fJ contact (point v) becomes small, and the heating efficiency of both edge portions of the open pipe 21 is reduced.

This will be explained in more detail as follows.

That is, when energized as shown by the white arrow in FIG. 2, magnetic fluxes 21a and 20a are formed in the open pipe 21 and impeder 20, respectively, due to the action of the work coil 22, and as a result, the open pipe is opened due to the induction action of the magnetic flux 21a. An induced current 1a is generated in the pipe 21, and an induced current rb inside the open pipe and an induced current 1c on the outer surface of the open pipe are generated by the induction effect of the magnetic flux 20a.

However, when magnetic flux saturation occurs in the impeder 20, Ib.

Ic decreases together. On the inner surface of the tube or open pipe, Ia and Ib are in opposite directions, and on the outer surface, Ia and Ic are in the same direction, so the combined currents on the inner and outer surfaces are Ia - rb and Ia + re, respectively. Naru, Ib
, The former increases and the latter decreases as rc decreases, so the welding current 1w-(Ia+Ic)-(I
a-Ib) will decrease.

[Means for solving problems]

The present invention has been made in order to solve such problems, and a coil wound so as to cancel the current 1a flowing through the inner surface of the open pipe is provided inside the open pipe and the required amount of current 1a is provided inside the open pipe. An object of the present invention is to provide a high-frequency welding machine that can increase welding current and improve heating efficiency by passing current.

A high-frequency welding machine according to the present invention is a high-frequency welding machine that applies a high-frequency current to a work coil and heats and welds the edges of both sides of the open pipe using the induced current generated in the open pipe passing through the work coil to manufacture a pipe. An open pipe located in the area covered by the magnetic field of the work coil, an inner-side induced current canceling coil provided inside the pipe so that the direction of current flow is the same as that of the work coil;
In order to cancel the induced current flowing through the inner surface of the open pipe or tube by the inner side induced current canceling coil, a current phase adjuster is provided to adjust and supply the current phase to the inner side induced current canceling coil. It is characterized by

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a perspective view showing an embodiment of a high frequency welding machine according to the present invention.

1 in the figure is an open pipe, and the skeleton is passed through a group of forming rolls (not shown) from the U-shaped cross section to the edge portions 1 on both sides.
a (only one side is shown in the drawing) is bent to have an approximately 0-shaped cross section facing each other, and this open pipe (■) is then formed into an annular shape in appearance of the present invention machine A, which is an edge heating means. The high-frequency current passed through the work coil 2 induces an induced current in the open pipe 1, heating the edge portions 1a on both sides, and moving the pipe toward the squeeze roll 3. At the same time as it is melted, it is butt-welded by the lateral pressure of the squeeze roll 3 (only one side is shown) to form the tube 4, and is ready for finishing processes such as cutting the inner bead (not shown) and the outer bead 4a. is to be transported in the direction of the white arrow.

Inside the open pipe 1 and tube 4 in the area covered by the magnetic field of the work coil 2, the inner-side induced current canceling coil 5 of the present invention taA is arranged. The coil 5 is an open pipe 1. where the magnetic field of the work coil 2 extends. It is wound a plurality of times to have a length corresponding to the range of the tube 4, and is provided so that the length direction and the tube axis direction coincide,
One end thereof is connected to a portion of the work coil 2 outside the annular portion via a current value/phase adjuster 6.

The current value/phase adjuster 6 is a coil having a movable core, and the current value/phase of the current flowing through the coil 5 can be changed by changing the insertion dimension of the movable core within the coil. .

Therefore, by appropriately setting the current value and phase and passing the current through the coil 5, a current 1c' corresponding to 1c and Ib in iii. , Ib' flows. This makes it possible to reduce the induced current that would otherwise occur in the work coil 2 and pass through the inner surface of the open pipe 1 and tube 4. As a result, welding current 1w' can be increased.

In this way, in the case of the present invention machine A, the open pipe l
Induced current that does not contribute to welding of the inner surface is suppressed, and therefore eddy current loss, which was a bottleneck in improving heating efficiency in conventional machines, can be reduced. In addition, since Ia is canceled by energizing the coil 5, magnetic flux saturation is not involved as in the case of an impeder, and the machine A of the present invention is suitable for manufacturing small diameter pipes because the diameter of conventional impeders is limited, and the eddy current loss can be reduced to a sufficient level. This makes it possible to efficiently heat small-diameter pipes.

In the above embodiment, the coil 5 is connected to the work coil 2 and the current flowing through the work coil 2 is applied to the coil 5, but the present invention is not limited to this case.
Different currents may be passed through the coil 5 and the work coil 2.

In addition, although the impeder is not included in the above embodiment,
Of course, the present invention can be implemented by inserting an impeder into the inner side induced current canceling coil 5.

〔effect〕

As detailed above, the high frequency welding machine according to the present invention includes an open pipe located within the area covered by the magnetic field of the work coil, and a coil wound inside the pipe so that the direction of current flow is the same as that of the work coil. Since the structure is configured to supply a current with adjusted current value and phase, there is no eddy current loss due to the generation of induced current that does not contribute to welding, and the heating efficiency per unit of power consumption is significantly improved. The present invention exhibits excellent effects, such as being able to achieve high efficiency and efficiently manufacturing small-diameter pipes.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a perspective view showing an induced current generated in an oven pipe when a conventional device is used. 1... Oven pipe 2... Work coil 5...
・Inner side induced current cancellation coil 6...Current value/phase adjuster

Claims (1)

[Scope of Claims] 1. A high-frequency welding machine that manufactures a pipe by applying a high-frequency current to a work coil and heating and welding the edges of both sides of the open pipe using the induced current generated in an open pipe passing through the work coil. An open pipe in the area covered by the magnetic field of the coil, an inner-side induced current canceling coil installed inside the pipe so that the direction of current flow is the same as that of the work coil, and the inner-side induced current. In order to cancel the induced current flowing through the inner surface of the open pipe or tube by the canceling coil, the present invention is characterized by comprising a current phase adjuster that adjusts and supplies the current phase to the inner side induced current canceling coil. High frequency welding machine.