JPH09267183A - Device for controlling flash butt welder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the welded strength of a joined part by obtaining power supply voltage having comparatively high voltage instantaneously at the time of shifting to an upset process. SOLUTION: A series circuit of a phase control switch 6 and an autotransformer 8 are interposed in a connecting wire 3a between a power supplying transformer 2 and a welding transformer 4, and a phase control switch 7 is parallel connected with the phase control switch 6 between a voltage dropping reference position 2a on the secondary winding of a power supplying transformer 2 and the connecting wire 3a. A phase control switch 9 is parallel connected with the autotransformer 8 between a voltage rising reference position 4a on the primary winding of the welding transformer 4 and the connecting wire 3a. The comparatively low welding voltage is supplied by reducing the number of the secondary winding under switch-on condition only to the phase control switch 6 at the time of a front period flash process and under switch-on condition only to the phase control switch 7 at the time of a latter period flash process. The comparatively high welding voltage instantaneously risen is supplied by reducing the number of the primary winding under switch-on condition further to the phase control switch 9 at the time of upset process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a flash butt welding machine for controlling welding electric power supplied between welding electrodes of a flash butt welding machine, and more particularly, to provide a non-energization time from a flash process to an upset process. It was made possible to migrate without.

[0002]

2. Description of the Related Art In various continuous processing lines such as a continuous pickling line for steel strips and a continuous tandem rolling line, in order to continuously treat steel strips for the purpose of improving the operating rate, a flash is usually used on the line-entry side. A butt welder welds steel strip.

In this flash butt welding, an arc between the ends of the steel strip and a local short circuit are repeated, and the contact portion of the steel strip (due to minute unevenness on the end face) is heated and melted by the short circuit, and the steel strip burns off. The droplets are splashed by the arc as a flash. In this way, when the unevenness of the end faces disappears and the ends of the steel strips are sufficiently melted, a strong pressure is applied between the ends of the steel strips to push out the oxide or the like in the molten state of the end faces for pressure welding. That is, flash butt welding includes a flash process and an upset process, and the flash process is further divided into a first period in which preheating of a welded part is dominant and a second period in which flashing becomes intense. Therefore, it is necessary to control the welding power applied to the welding electrode in each of the first flash process, the second flash process, and the upset process.

As a control device for a conventional flash butt welding machine, a structure shown in FIG. 4 has been proposed. In this conventional example, the primary side of the power transformer 2 is connected to the AC power source 1, and the primary side of the welding transformer 4 is connected to the secondary side of the welding transformer 4 via the connecting wires 3a and 3b, respectively, and the secondary side of the welding transformer 4 is welded. The electrodes 5a and 5b are connected. Then, a phase control switch 6 for controlling the current during the first flush process is inserted in the connection line 3a between the power supply transformer 2 and the welding transformer 4, and the connection line 3a and the power supply transformer 2
A phase control switch 7 for controlling the currents in the latter flush process and the upset process is inserted in parallel with the secondary side winding of the first phase control switch 6.

Then, in the first flash process, only the phase control switch 6 is turned on to apply the power supply voltage adjusted to a predetermined pressure by the power transformer 2 to the primary side of the welding transformer 4, and in the second flash process, the phase control is performed. Switch 7
Only turn on. At this time, the phase control switch 7
Is connected in the middle of the secondary winding of the power transformer 2, and the number of secondary windings of the power transformer 2 decreases, so that the secondary voltage of the power transformer 2 is the secondary winding during the previous flash process. It becomes smaller than the side voltage, and the power supply voltage applied to the primary side of the welding transformer 4 becomes lower than that in the previous flash process. At the time of upset, the secondary side voltage of the power supply transformer 2 is controlled by controlling the firing angle of the phase control switch 7 while keeping the phase control switch 6 in the off state, and this power supply voltage is welded. 4 is applied to the primary side.

FIG. 5 shows the power supply voltage applied to the primary side of the welding transformer 4 in the latter flash process and the upset process.
Since the phase control switch 7 is turned on, the AC voltage shown in FIG. 5 (a) is applied. However, during the upsetting process, the phase control switch 7 is controlled by the firing angle.
As shown in (b), the applied period becomes shorter, and the power supply voltage applied to the primary side becomes smaller than that in the latter flash process.

[0007]

However, in the control device for the conventional flash butt welding machine described above, during the upsetting process, the phase control switch 7 is controlled to ignite the ignition angle so that a predetermined power supply voltage is applied to the primary of the welding transformer 4. Since the voltage is applied to the side, it is possible to lower the voltage than the applied voltage in the latter flash process, but it is not possible to raise the voltage.

Therefore, in order to obtain good welding quality, a relatively high welding voltage is applied to the welding electrodes 5a and 5b during the first flashing step, a relatively low voltage is applied during the second flashing step, and a comparison is made during upset. It is known that it is preferable to apply a static high voltage to control the upset current to a high current value, but in the conventional control device, it is not possible to boost the power supply voltage during the latter flash process, There is a problem that the welding quality cannot be improved.

In order to avoid this, immediately after the end of the latter flash process, the phase control switch 7 is turned off and the phase control switch 6 is turned on, and a relatively high voltage is applied again to the primary of the welding transformer 4. It is conceivable to apply the voltage to the side, but in this case, the phase control switches 6 and 7 are turned on at the same time, and a closed circuit composed of the phase control switch 6, the power supply transformer 2 and the phase control switch 7 is formed and short-circuited. In order to prevent the current from flowing, first the phase control switch 7 is turned off, then the phase control switch 6 is turned on,
At this time, in order to protect the equipment from the short-circuit current, after the phase control switch 7 is turned off, a de-energized time of about 1 to several cycles is required.

Therefore, the temperature of the welded joint is lowered, and air bubbles and oxides remain and the weld strength is lowered.
There is a problem that the welded portion is likely to be broken and the processing efficiency or the operation stability is reduced in various continuous processing lines.

Therefore, the present invention has been made by paying attention to the above-mentioned conventional problems, and at the time of shifting to the upset process, a relatively high power supply voltage is instantaneously obtained without providing a non-energization time, and the bonding is performed. An object of the present invention is to provide a control device for a flashback welder capable of obtaining a welded portion having a high welding strength.

[0012]

In order to achieve the above object, a control device for a flash butt welding machine according to the present invention uses a power transformer and a power transformer control means interposed between the welding transformers to transform the power transformer. A control device for a flash butt welding machine, wherein the ratio is controlled, and the welding power supplied between the welding electrodes of the flash butt welding machine connected to the secondary side of the welding transformer is controlled. It is characterized in that welding transformer control means for controlling the transformation ratio of the welding transformer is provided between the welding transformer and in series with the power transformer control means.

Therefore, at the time of shifting from the first flash process to the second flash process, by controlling the transformation ratio of the power transformer in the step-down direction by the power transformer control means, a relatively low voltage is applied to the welding transformer, and When shifting from the flash process to the upset process, a higher voltage is applied to the welding transformer by controlling the transformation ratio of the welding transformer in the step-up direction by the welding transformer control means. Therefore, during the transition from the late flash process to the upset process, the secondary voltage of the welding transformer is lower than the secondary voltage during the late flash process by operating only the welding transformer control means without operating the power transformer control means. Is also boosted, and since the welding transformer control means is provided in series with the power supply transformer control means, there is no possibility that a short-circuit current will occur. Instead, the transition from the latter flash process to the upset process is performed instantaneously.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 shows an example of an embodiment of the present invention, and is a circuit diagram showing a schematic configuration of a control device of a flash butt welding machine.

In the figure, 1 is an AC power source, 2 is a power transformer,
3a and 3b are connecting wires, 4 is a welding transformer, 5a and 5b
Is a welding electrode, and the configuration thereof is the same as that of the conventional example, and therefore its detailed description is omitted.

Reference numeral 6 is a phase control switch for setting current in the first flash process, and 7 is a phase control switch for setting current in the second flash process. These phase control switches are formed by, for example, two thyristors. Has been done. And
Similar to the above-mentioned conventional example, the phase control switch 6 is connected to the connection line 3a between the power transformer 2 and the welding transformer 4, and the phase control switch 7 is the step-down reference position 2a on the secondary winding of the power transformer 2. And the welding transformer 4 are connected in parallel with the phase control switch 6.

A single winding transformer 8 is inserted between the parallel circuit of the phase control switches 6 and 7 and the welding transformer 4, and the parallel circuit of the phase control switches 6 and 7 and the single winding transformer 8 are inserted. A phase control switch 9 is connected in parallel with the single-winding transformer 8 between the space and the boosting reference position 4a on the primary winding of the welding transformer 4.

The autotransformer 8 is provided so that a short circuit current does not flow in the phase control switch 9 during the upsetting process. The phase control switch 9 is for controlling the current value during the upset process, and is formed similarly to the phase control switches 6 and 7.

The phase control switches 6 and 7 correspond to the power transformer control means, and the phase control switch 9 corresponds to the welding transformer control means. Next, the operation of the above embodiment will be described.

The welding electrode 5a is fixed to one of the members to be welded, and the welding electrode 5b is fixed to the other. In this state, a gate signal is supplied to the thyristor of the phase control switch 6 while lightly contacting the welding end surfaces of the members to be welded with each other, thereby controlling the ON state. As a result, a closed circuit including the power transformer 2, the phase control switch 6, the single-turn transformer 8 and the welding transformer 4 is formed, and the welding voltage V of a relatively high voltage adjusted by the closed circuit is formed.
_FB is induced on the secondary side of the welding transformer 4, and this is applied to the welding end surface of the member to be welded via the welding electrodes 5a and 5b, and the previous flash state is achieved.

At this time, the distance between the welding end faces of the member to be welded is light.
Since it is in contact, it is in conduction and current is applied at that time.
Preheating between the weld end faces is caused by Joule heat generated by electric power.
You. Then, preheating between the weld ends is completed and
Late flash state when flash (electrical spark) occurs
Then, the phase control switch 6 is turned off and
Therefore, the phase control switch 7 is controlled to the ON state. This
Power transformer 2, phase control switch 7, single winding transformer
8. A closed circuit consisting of the welding transformer 4 is formed.
Welding voltage V adjusted by the circuit_FAWelding transformer 4
Is induced on the secondary side of. At this time, the phase control switch 7
Connect to the step-down reference position 2a on the secondary winding of the power transformer 2.
Since it is continued, for example, the secondary winding of the power transformer 2
The number n _TwoThen, the power supply transformer during the previous flash process
Number of secondary windings n_2BIs n _2B= N_TwoBut in the second half
Number of secondary windings n of power transformer 2 during flash process_2A
Is the original number of windings n_TwoWill be a smaller value. Therefore,
Since the secondary voltage of the power transformer 2 becomes smaller,
Welding voltage V during rush process_FBLower than, relatively low power
Welding voltage V_FAIs induced on the secondary side of the welding transformer 4.
Will be.

Therefore, at this time, the step-down reference position 2a
Is set according to the welding voltage V _FB ′ required in the latter flash process, the power source voltage of the AC power source 1 is adjusted by the power source transformer 2, the single winding transformer 8 and the welding transformer 4, and The desired welding voltage V _FB ′ on the secondary side
Will be induced.

Then, the welding voltage V _FB is the welding electrodes 5a, 5
When applied to the welding end face of the member to be welded via b, in this case, the welding voltage V _FB is a relatively low voltage, so that a short circuit occurs as compared with the period in which an arc is generated and the molten portion is scattered as a flash. The welding end face can be heated well by Joule heat during a short circuit, and the craters generated on the welding end face due to flash can be reduced, and uniform upset can be performed during the subsequent upset. It becomes possible.

Then, at an appropriate time when the welding end face is covered with the metal vapor and the molten metal, a strong pressure is applied to one of the members to be welded to press-weld the welding end faces of both members to be welded,
At the same time, the up-setting phase control switch 9 is controlled to the ON state.

As a result, the phase control switch 9 is turned on.
Since it is in a state, it is difficult for current to flow to the autotransformer 8 side.
Power transformer 2, phase control switch 7, phase control
A closed circuit consisting of the switch 9 and the welding transformer 4 is formed,
Welding voltage V adjusted by this closed circuit_APIs welded
It is induced on the secondary side of the lance 4. At this time, open the phase control
Since the closing device 7 remains in the ON state,
The transformation ratio is the same as in the latter flash process, but the phase control
The switch 9 is a booster base on the primary winding of the welding transformer 4.
Since it is connected to the sub-position 4a,
The number of secondary windings is n ₁Then, the melting during the latter flash process
Number of primary windings of contact transformer 4 n_1FIs n _1F= N₁Becomes
Is the number of primary windings of the welding transformer 4 during the upset process
n_1APIs the original number of windings n₁Will be a smaller value. Yo
Therefore, the transformation ratio of the welding transformer 4 is set during the latter flash process.
Since the voltage rises above the transformation ratio of the
Welding voltage V during the welding process_FARelatively higher voltage than
Contact voltage V_APAre induced on the secondary side of the welding transformer 4.

Therefore, at this time, the boosting reference position 4a
Is set in accordance with the welding voltage V _AP ′ required during the upset process, the power source voltage of the AC power source 1 is adjusted mainly by the power source transformer 2 and the welding transformer 4, and the secondary side of the welding transformer 4 is adjusted. The desired welding voltage V _AP ′ will be induced.

At this time, in order to shift from the latter flash process to the upset process, it is sufficient to control the phase control switch 9 in the off state to the on state, and the phase control switch 9
Is connected in series with the other phase control switches 6 and 7, the ON / OFF control of the phase control switch 9 can be performed regardless of the ON / OFF state of the other phase control switches 6 and 7. Therefore, it is not necessary to provide the non-energization time, and the welding voltage can be instantly increased.

As a result, a high voltage welding voltage V _AP is instantly induced on the secondary side of the welding transformer 4 after the end of the latter flushing step, and the welding end faces are instantly melted.
This molten metal is extruded from the welding surface by the strong pressure at the time of pressure welding, and a clean weld is obtained.

Therefore, since it is possible to instantaneously shift from the latter flash process to the upset process without providing a non-energized time, bubbles or the like may be generated in the welded joint, or oxide may remain. It is possible to obtain a high quality welded joint having high welding strength.
Therefore, in various continuous continuous processing lines, breakage at the welded portion of the steel sheet is prevented, so that processing efficiency can be improved and operational stability can be improved.

Further, since the welding strength can be improved, it is possible to constantly improve the welding strength even for a member to be welded having a large cross-sectional area and to improve the quality of the welding material.

Further, since the single-winding transformer 8 is provided in parallel with the welding transformer 4, even when the phase control switch 9 is turned on, it is possible to surely prevent the short circuit current from flowing through the phase control switch 9. be able to.

In the above embodiment, the case where the thyristor is used as the phase control switch has been described, but the present invention is not limited to this, and other power control elements such as ignitron can be applied. Is.

Further, in the above embodiment, the case where the phase control switch is controlled to be turned on and off has been described. However, by controlling the firing angle, for example, the voltage can be controlled with higher accuracy, and the welding portion The quality can be improved.

Further, in the above embodiment, the case where the phase control switches 7 and 9 are directly connected to the power supply transformer 2 and the welding transformer 4 has been described, but the present invention is not limited to this, and for example, a tap changer or the like is provided, It goes without saying that the tap position can be changed according to the welding voltage in the latter flushing process and the welding voltage in the upsetting process, so that it can be selected according to the member to be welded.

[0035]

Embodiments of the present invention will be described below. A base material for a 45K steel cold-rolled steel sheet having a thickness of 4.5 [mm] and a width of 1500 [mm] was used as a member to be welded, and was welded using the controller of the flash butt welding machine shown in FIG. Then, with respect to the welded member welded by the control device of FIG. 1 and the welded member welded by using the control device of the conventional flash butt welding machine, the number of repeated bendings until the welded portion was broken was measured.

In the conventional controller, the voltage of the welding transformer 4 when the secondary side is unloaded is 17.9 [V] for 8 seconds in the first flash process, and 10.2 [V] in the second flash process. For 8 seconds during the upsetting process,
Subsequently, each was energized at 10.2 [V] for 1 second (FIG. 2A). Further, in the control device of the present invention, 17.9 [V] is used for 8 seconds in the first flash process, 10.2 [V] is used for 8 seconds in the second flash process, and 17.9 [V] is used in the upset process. Each was energized for 1 second (FIG. 2 (b)).

In each transformer, assuming that the number of primary windings is n ₁ and the number of secondary windings is n ₂ , the winding number ratio of the power transformer 2 is n ₁ : n ₂ = 6.6: 1, rated output is 15
00 [kVA], the winding number ratio of the welding transformer 4 is n ₁ :
n ₂ = 28: 1, the rated output was 250 [kVA] × 4, and the rated output of the single-winding transformer was 500 [kVA].

As a result, as shown in FIG. 3, the welded member by the conventional control device broke about 2 to 8 times and broke on average about 5 times. For example, it broke 12 to 30 times and broke 24 times on average. Therefore, it was confirmed that the welding strength of the joint portion of the welded member was significantly improved.

[0039]

As described above, the controller of the flashback welding machine according to the present invention controls the transformer ratio of the welding transformer in series with the power transformer control means for controlling the transformer ratio of the power transformer. Since the means is provided, the secondary voltage of the welding transformer can be changed to the secondary voltage during the latter flashing step by operating only the welding transformer control means without the operation of the power transformer control means when shifting from the latter flashing step to the upset step. It is possible to boost the voltage higher than the side voltage, and since the operation of the welding transformer control means can be performed regardless of the operating state of the power transformer control means, it is possible to boost the voltage instantaneously without providing a non-energized time. It is possible to obtain a high-quality welded member having high welding strength by preventing a decrease in welding temperature at the time of shifting to the process.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a control device of a flashback welding machine according to the present invention.

FIG. 2 is a graph showing the number of repeated bendings until the joint member by the conventional control device and the joint member by the control device of the present invention are broken.

FIG. 3 is an explanatory diagram showing a change state of a welding voltage when the number of repeated bendings in FIG. 2 is measured.

FIG. 4 is a circuit diagram showing an example of a control device of a conventional flashback welding machine.

FIG. 5 is an explanatory diagram for explaining a welding voltage control method in a conventional controller for a flashback welding machine.

[Explanation of symbols]

 1 AC power supply 2 Power supply transformer 4 Welding transformer 5a, 5b Welding electrode 6 Phase control switch for early flash 7 Phase control switch for late flash 8 Single-winding transformer 9 Phase control switch for upset

Claims (1)

[Claims] 1. A power transformer control means inserted between a power transformer and a welding transformer controls a transformation ratio of the power transformer, and between welding electrodes of a flash butt welding machine connected to a secondary side of the welding transformer. In a controller for a flash butt welding machine configured to control welding power to be supplied, a transformer ratio of the welding transformer is controlled between the power transformer control means and the welding transformer and in series with the power transformer control means. A control device for a flash butt welding machine, which is provided with a welding transformer control means.