JPS62203683A - High frequency electric seam welding method using laser beam as well - Google Patents

Abstract

PURPOSE:To prevent the generation of a welding defect by passing the high frequency current used together with a laser beam intermittently or high- loweringly at the specified time intervals. CONSTITUTION:The intermittently electrifying high frequency welding equipment 10 to heat the edge part 2 of a metal pipe 1 and laser beam projection device 5 are arranged. The whole welding range is uniformly heated by the Joule heat by the high frequency electric power fed via probes 4, 4 from the equipment 10 and the laser beam LB projected via an optical system 6 and beam guide 7 from the laser device 5. In this case, the high frequency current is passed intermittently periodically at the intervals of 0.1sec from 0.1msec. In this way, the plate thickness center part is heated over wide range and the press-fitting can be performed in the state of no discharging of the molten metal due to the electromagnetic force. Consequently the welding defect of a penetrator, etc., can be prevented.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a high frequency electric resistance welding method.

[Conventional technology]

In the field of manufacturing welded pipes, high-frequency electric resistance welding is generally used as a welding method for pipes called electric resistance welded pipes, which has a high welding speed, that is, has high productivity.

How to manufacture ERW pipes, for example conventional high frequency? ! ! An example of a welded pipe manufacturing process using the seam welding method will be explained with reference to FIG. First, the edge portion 2 of the strip 1 formed into a tubular shape by a group of forming rolls not shown in the drawings is abutted by a squeeze roll 3 and has a wedge shape with the abutting portion at the apex.

A high frequency voltage is applied to the contacts 4, 4 disposed upstream of the squeeze roll 3, and a high frequency current circuit from one contact 4 to the other contact 4 forms a wedge-shaped edge portion 2.
formed along the The edge portion 2 is heated by this high frequency current, and the apex of the wedge shape, that is, the welding point reaches the welding temperature and is welded under pressure by the squeeze roll 3.

Generally, the high frequency power used for ERW welding pipe production is 10
The frequency band of ~500 Hz is used, and the
Due to the synergistic effect of the two phenomena of "skin effect" and "proximity effect", the higher the frequency, the larger the electrical (electrical) proximity effect becomes. This is the reason why high frequency power is widely used in the construction of ERW 18 welded pipes.

However, this phenomenon peculiar to high frequencies causes non-uniform melting in the thickness direction of the edge portion as shown in FIG. That is, the high frequency current density in the corner portion 21 of the edge portion is higher than the high frequency current density in the thick central portion 22, resulting in non-uniform melting in the thickness direction.

This non-uniform melting in the wall thickness direction of the edge portion tends to become more pronounced as the wall thickness increases (eg, 6 mm or more in electric resistance welded pipes). If this non-uniform melting in the wall thickness direction is promoted, there will be a low heat input area where the welding temperature does not reach the welding point even when the welding point is reached, causing cold welding.

If the voltage applied to the contactor 4 is increased to increase the welding power in order to prevent the occurrence of cold welding, the corner portion 21 may become overmelted and weld defects such as repenerators may occur.

In order to suppress the occurrence of venetrators, in high-frequency electric resistance welding, a strong offset force is applied to the welded part by a squeeze roll 3, so that oxides are expelled to the surface of the strip together with the molten metal. However, a strong upset causes metal flow near the weld to rise and deteriorate the toughness of the weld.

As a result of various researches, the inventors of the present invention filed a patent application in 1986-2.
As disclosed in No. 444, it has been found that strong upsetting becomes unnecessary if the edge portion 2 is uniformly melted by irradiating a laser to the center of the plate thickness of the edge portion 2.

[Problem that the invention seeks to solve]

Uniform melting and low upset by combining lasers1
-Although welding is possible, most of the energy used to heat the butt surfaces is resistance heating using high-frequency current, and the welding phenomena during the heating, melting, and pressure welding processes are basically the same as electric resistance welding.

Therefore, even in high frequency type Ia welding using a combined laser, the occurrence of welding defects of about 0.05 to 0.5% in terms of the area occupied by the welded part is unavoidable, as in conventional high frequency electric resistance welding.

An object of the present invention is to prevent the occurrence of welding defects such as cold welding and springs 1 to 12 in laser compound high-frequency electric resistance welding.

[Means for solving problems]

The gist of the present invention is to supply a high-frequency current to a wedge-shaped workpiece whose abutting end faces asymptotically approach each other and have a welding point as its apex, and to supply a laser beam to the welding point from the open side of the wedge-shaped object. In the laser beam combined high frequency electric resistance welding method, in which the apex of the wedge shape is heated to the welding temperature by the generated Joule heat and laser beam energy: High frequency current is applied periodically from 0.1 m5ec to 0.1 sec at intervals of 1 sec. This is a high-frequency electric resistance welding method using a laser beam, which is characterized by applying current intermittently or at high and low pitches.

[Effect]

As a result of various studies regarding the relationship between welding conditions including welding heat input and welding characteristics, the inventors have obtained the following findings.

Strong ffi magnetic pressure is induced in the opposing edge portions 2 by high frequency currents flowing in opposite directions. , : When the edge portion 2 melts, the molten metal 1A23 is immediately discharged onto the surface of the strip, as shown in FIG. In this case, the edge portions 2 cannot meet at the V convergence point V where geometrical collision is expected, and a gap G is developed with a length commensurate with the molten metal discharged from the convergence point V (FIG. 7). This gap G expands as the strip l moves, but since the welding current 11 flows along the gap, as the gap becomes longer, the current path impedance increases, resulting in a decrease in welding current and melting amount.

Such a phenomenon accompanying the melting of the edge portion is a cause of a remarkable feature of the high frequency electric resistance welding phenomenon, that is, the periodicity represented by the periodic movement of the welding point W.

By the way, if this cycle exceeds 0.1 seconds, the edge gap G of the discharged molten metal a23 will increase during the periodic progress of welding.
Reflux may occur, and if oxides are involved at that time, welding defects called penetrators, which are unique to high-frequency electric resistance welding, will occur. On the other hand, if the edge portion 2 is not melted, a serious welding defect called cold welding will occur.

The above-mentioned welding defect generator (lη) is exactly the same even when a laser is used as a welding heat source.And this defect is caused by the magnetic force induced by the high frequency current.
This is due to the fact that the molten metal 23 is discharged from the edge portion 2 onto the surface of the strip.

Therefore, if the high-frequency current is cut off or reduced at regular intervals, the high-frequency current will only contribute to preheating the edge part 2 and melting the corner part 21, and the edge part 2 formed by the laser will
Most of the molten metal in the central part 22 of the plate thickness can be directly contributed to welding without being discharged. According to this energization method.

While the high-frequency current is cut off or reduced, the electromagnetic force is extinguished or becomes extremely weak, and the discharge of the molten metal is substantially stopped, and the molten metal remaining in the edge portion 2 performs molten pressure welding.

The intermittent energization cycle of the high frequency current is preferably 0.1 m5 ec or more and 0.1 sec or less. If it is less than 0.111 sec, it is the same as if the frequency of the high-frequency current exceeds 10 K I-1z, and the discharge of the molten metal cannot be prevented by electromagnetic force. When the intermittent energization period exceeds 0.1 sec, the energization cutoff period or the current reduction period becomes longer, resulting in pressure welding of the unmelted portion and generation of intermittent cold welding.

In this case, even if the current cutoff period or current reduction period is shortened, welding will continue to proceed at a cycle of 0.1 seconds, and spring 1 helators will occur frequently.

Note that within the scope of the present invention, the length of the energization cut-off period in the intermittent energization period is not particularly limited;
If it is in the range of 0% to 70%, the effect of preventing the occurrence of welding defects is particularly remarkable.

FIG. 1 shows an embodiment of the present invention in which the intermittent current high-frequency welding device 10 shown in FIG. 2 and the laser beam irradiation device 5 are used together. In this case, the etched portion 2 (wedge-shaped welding facing surface) of the metal body l receives Joule heat generated by high-frequency power supplied from an intermittent current high-frequency welding device 10 via contacts 4, 4, and a laser beam. From the irradiation device 5, the optical system 6. The laser beam LB irradiated via the beam guide 7 uniformly heats the entire thickness to the welding temperature.

The high-frequency current is periodically intermittent at intervals of 0.1 m5 ec to 0.1 sec, but the laser beam lxLB is continuously applied to 30% to 80% of the plate thickness including the center of the plate thickness of the butt end face.
% range. To explain this content, the laser beam LB is projected from the open side of the wedge shape toward the apex of the wedge shape at an angle θ. Laser beam LI'
3 is sufficient as long as it is a beam that converges on the welding point, and even if it is a beam that has a spread that does not necessarily converge to the welding point, the laser beam LB hits one of the opposing surfaces and is reflected there and directed to the other side. The light is reflected from the other side and hits the other side again, repeating the reflection and finally focusing on the welding point. That is, even if the laser beam LB does not directly irradiate the welding point, it reaches the welding point by reflection and convergence.

In this embodiment, during cessation of heating by high frequency current,
Even when the electromagnetic force is not working, the central part in the thickness direction of the plate with some of the corners of the welding point removed is heated over a wide range, and the molten part is pressure-welded without ejecting the molten metal due to the electromagnetic force. - reflux of molten metal between the abutting surfaces, which would lead to lamination, is largely prevented.

FIG. 2 shows that in order to carry out the present invention, the high frequency current is set to 0. I
An example of a configuration circuit of a high-frequency welding device IO that periodically conducts electricity intermittently at intervals of 0.1 sec from n+sac is shown.

In this example, a switching element 14 is inserted between the DC power supply and the anode of the oscillation tube 13 to control the positive tiA voltage E P +anode current Ip applied to the oscillation tube 13 on and off, or to high or low. are doing. As the switching element, for example, a silis inverter, an l-run risk inverter, etc. may be used. The intermittent energization period and the ratio of the on period to the off period can be set externally.

FIG. 3 shows another example of an intermittent energization high frequency welding device 10 used for carrying out the present invention. In this device, grid oscillation is utilized without using any switching elements or triplets. The grid circuit of the high frequency oscillator is a grid circuit with a 15. It consists of a grid capacitor + (3 (capacitance Cc)), etc. The resistance value Re of the resistor 15 is usually determined to provide the necessary grid bias and ensure continuous oscillation. If you double it,
This produces intermittent firing, the period of which is given by 2πR,C. Therefore, by appropriately selecting RQC5, 0.1m5
It is possible to obtain intermittent energization at intervals of 0.1 sec from ec.

Note that, similarly to the grid oscillation, a switching element may be connected to the grid, and the on/off of this element may be controlled at a predetermined cycle to perform oscillation and stop.

FIG. 4 schematically shows an example of the waveform of the high frequency current obtained by the apparatus shown in FIGS. 2 and 3.

〔Example〕

Figure 8 shows the results of investigating the relationship between the intermittent energization period and the appropriate heat input range by welding a plate of 101 mm thick mild steel at a speed of 30 m/in using the laser-combined high-frequency electric resistance welding device shown in Figure 1. Shown below. In the investigation of the same figure, the ratio of the energization period and the stop period of intermittent energization is l, that is, the energization period is 1 of the intermittent energization period.
/2. As is clear from Fig. 8, when the intermittent energization cycle is between 0.1 m5ec and 0.14 IOC, the incidence of welding defects is significantly reduced compared to the case of continuous energization. This was also confirmed when the plate thickness and welding speed were different.

In addition, although the above example shows a case where the current is periodically turned on and off, the present invention shows that even if the anode voltage EP is periodically reduced to 1/10 or less, the same effect as shown in FIG. 8 can be obtained.゛, etc. have been confirmed through experiments.

〔Effect of the invention〕

As explained above, according to the present invention, the laser beam
It is possible to prevent the occurrence of welding defects in high-frequency electric resistance welding for No. 1, and to obtain extremely high-quality welded parts.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a laser beam combined high frequency electric resistance welding apparatus that embodies one embodiment of the present invention. Figure 2 shows the intermittent current high-frequency welding equipment shown in Figure 1!
! FIG. 2 is a circuit diagram showing an outline of the configuration of IO. FIG. 3 is a circuit diagram schematically showing another configuration used as the intermittent energization high-frequency welding apparatus 10 in FIG. 1. FIG. 4 shows a schematic diagram of the high-frequency current waveform in the present invention. FIG. 2 is a perspective view showing a two-piece construction method. Fig. 6 is a schematic diagram showing the removal of molten metal on the edge surface by electromagnetic force to the plate surface.9 Fig. 7 is a schematic diagram showing the separation of the V convergence point V and the welding point W due to melting of the edge part. FIG. 8 is a graph showing that the occurrence of welding defects is significantly reduced by the present invention. 1, , IF Temporary 2: Edge portion 3;
Squeeze roll 4; Contact 5: Laser beam irradiation device 6: Optical system 7: Beam guide 1O: Intermittent energization high frequency welding device 11: High frequency welding power source 12: DC power source 13: Oscillator tube 14 Niswitching element 15: Grid brief resistor 16: Grid capacitor 21: Part of corner 22: Center of plate thickness 23: Molten metal EP: Oscillator tube anode voltage IP = Oscillation tube anode current RQ
Nigerid resistance value Cq Nigerid capacitor capacitance P; Electromagnetic force v; ■Convergence point.

Claims (1)

[Claims] Supplying a high-frequency current to a workpiece in the shape of a wedge whose abutting end faces that face each other asymptotically with the welding point as the apex, and projecting a laser beam from the open side of the wedge shape to the welding point, In the laser beam combined high frequency electric resistance welding method in which the apex of the wedge shape is heated to the welding temperature using the generated Joule heat and laser beam energy: The high frequency current is periodically intermittent or increased at intervals of 0.1 msec to 0.1 sec. A high-frequency electric resistance welding method using a laser beam, characterized in that electricity is applied using a laser beam.