JPS6142389B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating device for heating the end of a forge-welded pipe material bent into a tubular shape.

1 and 2 show a conventional induction heating device. In the figure, reference numeral 1 denotes a pair of current-carrying parts between which an insulating plate 2 is fixed, one end of which extends in a direction away from the other. 3 has both ends 1
The heating parts 4 are connected to one end of each of the heating parts 1, and 4 are a pair of terminals provided at the other ends of both current-carrying parts 1.

FIGS. 3 and 4 show a state in which a forge-welded pipe is manufactured using a conventional induction heating device. In FIGS. 3 and 4, reference numeral 5 denotes a forge-welded pipe material that is heated entirely with heavy oil or the like and then bent so that the ends 5a to be welded face each other with a space between them.
It is moving in the direction shown by arrow A. 6 to 8 are rolls arranged to press the forge-welded pipe material 5 from both sides, the distance between the rolls 7 is smaller than the distance between the rolls 6, and the distance between the rolls 8 is smaller than the distance between the rolls 7. is smaller than the interval.

When the heating section 3 is inserted between the forge-welded ends 5a while the forge-welded tube material 5 is moving, the current flowing through the heating section 3 heats the forge-welded ends 5a to a temperature at which the forge-weld ends 5a can be forged-welded. Then, the ends 5a to be welded, which have been heated to a temperature that allows forge welding, are pressed against each other by rolls 6, 7, and 8 and forge welded, thereby producing a forge welded pipe.

By the way, when the forge-welded pipe material 5 is bent into a tubular shape so that the ends 5a to be forged welded face each other with an interval, the shape of the interval between the ends 5a to be forge-welded is the center of the forge-welded pipe material 5 as shown in FIG. It gets narrower as you get closer to the end.

In the conventional induction heating device, the forged end 5 of the heating section 3
Since the cross section facing a is rectangular, the distance between the outer surface side of the welded end 5a and the heating part 3 is larger than that on the inner surface side, and in FIG. 5, the isotemperature curve θ ₁ ~
As shown by θ ₄ , the temperature on the outer surface side of the forge-welded end 5a was lower than the temperature on the inner surface side, resulting in a disadvantage that the quality of the forge-welded pipe deteriorated.

This invention was made in order to eliminate the above-mentioned drawbacks, and by inserting the workpiece between the ends of the workpiece and configuring it so that the cross section facing the workpiece end expands from the center of the pipe, the workpiece can be welded. To provide an induction heating device capable of heating an end so that there is no temperature difference between the outer surface side and the inner surface side.

The figures will be explained below. In FIGS. 6 to 8, numerals 1, 2, 4, and 5 are the same as the conventional induction heating apparatus shown in FIGS. 1 to 4. In one embodiment of the present invention, the heating part 9 has a triangular cross section, that is, the cross section facing the welded end 5a expands from the center of the tubular shape, so that the heating part 9 and the forged end 5a The distance between the forged and welded ends 5a is equal on the outer surface and the inner surface of the welded end 5a.

When a high frequency current is passed through the induction heating coil, a magnetic flux (not shown) is generated around the outer periphery of the heating section 9. Therefore, this magnetic flux interlinks with the end 5a at right angles, and as shown by the isotemperature curves θ ₁ to θ ₄ in FIG. temperature difference disappears.

As described above, according to the present invention, by configuring the cross section that is inserted between the ends to be welded and faces the stepped contact end to expand from the center of the tubular shape, the end to be welded is connected to the outer surface side. Heating can be performed so that there is no temperature difference on the inner surface, making it possible to manufacture a forge-welded tube of good quality.

[Brief explanation of the drawing]

Fig. 1 is a front view of a conventional induction heating device, Fig. 2 is a side view thereof, Fig. 3 is a plan view showing how the conventional induction heating device is used, and Fig. 4 is a cross section taken along the - line in Fig. 3. Figure 5 is an explanatory diagram showing the temperature distribution of the welded end heated by a conventional induction heating device, Figure 6
FIG. 7 is a front view of an embodiment of the present invention, FIG. 7 is a side view thereof, and FIG. 8 is an explanatory diagram showing the temperature distribution of the welded end heated by the induction heating device of the embodiment of the present invention. In the figure, 3 and 9 are heating parts, 5 is a forge-welded tube material, and 5a is an end to be forge-welded. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A flat plate-shaped tube to be welded whose end surfaces are cut parallel to each other is bent into a tubular shape, and a heating section is inserted between the opposed ends to be welded so as to spread out from the center of the tubular shape, and each of the above-mentioned ends to be forged to be welded is heated. The induction heating device is characterized in that the heating section is configured such that a cross section facing the end to be forged to be welded widens from the center of the tubular shape.