JPH0453620B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a welding device, and more particularly to a control device for controlling a hot wire TIG welding device that performs good welding.

A type of arc welding is TIG welding, which is performed under an inert gas shield using a less consumable metal such as tungsten as an electrode. Although this welding can form a good weld bead, the welding speed is slow, and improvements in this point are desired. As a method for increasing the welding speed in TIG welding, hot wire TIG welding is attracting attention in which the welding wire is heated to a predetermined temperature before welding.

Figure 1 shows the configuration of equipment commonly used in hot wire TIG welding.

The tungsten electrode 1 and base material 2 of the TIG torch 4 are connected by an arc power source with DC drooping characteristics, and an arc 5 is formed by the arc power source 3 in a shielding gas such as argon with the tungsten electrode 1 as a negative electrode and the base material 2 as a positive electrode. If the wire 6 sent out from the reel 11 is added directly to this arc 5, it is normal TIG welding, but in the hot wire TIG welding method, the contact tip 7 and the base metal 2 are connected by a DC or AC wire power source 9. Then, direct current or alternating current is passed through the wire 6 sent from the wire feeding device 10 to the arc generating part to generate Joule heat, and by heating the wire 6 before welding, the melting speed of the wire 6 is improved. There is. The problem with this method is that the wire current causes a magnetic blowing phenomenon in the arc. That is, the magnetic field generated near the wire due to the wire current and the magnetic field due to the arc current interfere, and an attractive force or force is generated between the two, causing the arc to swing and making it impossible to perform stable welding. For this reason, the wire current is limited to about one-half of the arc current, and the wire melting speed that can be welded while reducing the influence of magnetic blowing is limited to about 20 g/min, making it impossible to significantly increase the welding speed. For this reason, the hot wire switching TIG welding method has been implemented as a method to eliminate the magnetic interference of the arc caused by the wire current and further increase the amount of wire melting. In this method, as shown in Figure 2, the arc current is made into a pulsed square wave, and the period T ₁ when the arc current is at its peak AP is
At this time, the wire is not energized, and the wire current WP is passed only during the period _T2 of the base current AB when the arc current is low, thereby eliminating magnetic blow and obtaining a high welding amount. As a result, melting rates of over 100 g/min can now be obtained with almost no influence from magnetic blowing. FIG. 3 shows the principle of the configuration circuit of a conventionally used hot wire switching TIG power supply, which is an application of a chopper type power supply using a large capacity transistor 20.
This method requires a large power transformer 21, a large number of large capacity transistors, and a complex control circuit, resulting in a large and expensive welding machine.

For this reason, the inventors have separately proposed a device shown in FIG. That is, this device performs switching by connecting two gate turn-off thyristors (hereinafter referred to as "GTO") 23 and 25 in parallel to each other in parallel with the arc 5 for the arc power supply circuit 24. This is the configured device. In addition, the code 12 is an auxiliary power source, and the arc 5
It is intended to maintain the In this device, when both GTO1 and GTO2 are in the OFF state, an arc current flows between the electrode 1 and the base material 2 as shown in FIG. Turn on GTO1 and 23 at time t ₁
Then, the arc current is short-circuited to the wire 6, and the wire current WP is caused to flow, thereby heating the wire. more time
Turn on GTO2 and 25 and turn off GTO1 and 23 at t ₂
If the current is shorted to the power side the wire current,
Arc current no longer flows. then at time t ₃
If GTO2 and 25 are turned off, an arc will occur again and arc current will flow. In other words, the electric power applied to the wire is adjusted by changing the time during which the wire is energized, and the melting rate of the wire is controlled separately from the arc current. Detect the wire current Iw and wire voltage Vw in the wire and calculate the wire current force Pw = Iw × Vw
×(t ₂ −t ₁ )/T is calculated, and the rotational speed of the feeding motor 10a is controlled so as to obtain a wire feeding speed VF corresponding to this value. Conversely, control can also be performed by changing the time (t ₂ −t ₁ ) so as to obtain electric power commensurate with the wire feeding speed VF. This device has high performance as described above, but on the other hand, it has two
In reality, the control mechanism to synchronize the operations of both is complex and expensive.

In addition, GTO1 and 23 are turned ON for the period t ₁ to _{t 3} , and the GTO
The same function can be achieved by turning on the switches 2 and 25 for the period t ₂ to _{t 3} .

An object of the present invention is to provide a control device for controlling a hot wire switching TIG welding apparatus that eliminates the above-mentioned problems and allows easy control of the power applied to the wire.

In short, this invention turns on and off a large current switching element provided in a circuit parallel to the arc circuit.
In a hot wire switching TIG welding control device that controls welding by periodically shunting the arc current to the additive wire and controlling the amount of power supplied to the electrode and wire to heat the wire,
A circuit that controls the wire applied power supply time so as to control the energization of the arc current and the wire current so that they do not overlap and supply the appropriate wire applied power in accordance with the wire feeding speed, and the variation of this control time Controls three circuits: a circuit that compares and calculates the average arc current fluctuated by the set average arc current and a set average arc current, and a circuit that controls the average arc current to be equal to the set average arc current based on the calculation results of this circuit. This is a hot wire switching TIG welding control device characterized by having a device for

Examples of the present invention will be described below.

FIG. 6 shows a hot wire switching TIG having a device for controlling the above three circuits according to the present invention.
It is a welding device. This welding equipment itself is the equipment shown in Figure 4 with GTO2 and 25 removed.
In other words, one GTO 23 is connected to the arc power supply circuit 24 in parallel with the arc 5. Reference numeral 15 in the figure is a control device according to the present invention, which constantly controls the wire heating current necessary for the feed speed of the wire 6 and the electric power necessary for arc formation even if the wire feed speed changes. This is a control device that controls the supply of the appropriate amount.

Next, the control state of the control device that controls the hot wire switching TIG welding apparatus described above will be explained.

In FIG. 8, first, the average arc current Ias is set 30 and the wire feeding speed VF is set 31, and welding is started 32 based on these set values.
In this case, the applied power Pw actually supplied to the wire is detected 33, and on the other hand, a comparison calculation 34 is performed with the appropriate applied power P _VF calculated based on the speed VF. Note that Pw=Iw・Vw・Dw (Iw: wire peak current, Vw: wire peak voltage,
Dw: (described later). In this case, if Pw=P _VF , it means that a predetermined power is applied to the wire, so a comparison operation 34 of △P=Pw−P _VF is performed, and a judgment 35 of the value of △P is performed. When P<0, control 36 is performed to increase Dw, and when ΔP>0, control 37 is performed to decrease Dw, so that ΔP=0. Here, Dw is
Tw/T in FIG. 9 is shown. In other words, the time T from when the arc current reaches the base current AB until it reaches the peak current AP ₁ and the next base current.
In contrast, the time Tw during which the wire current is ON
This is the ratio of In other words, the configuration is such that the amount of wire current required for the speed _VF is obtained by changing this time Tw. In this case, supplying both wire current and arc current at the same time causes magnetic blowing, which is not allowed, so the wire current is ON.
If the time changes, the arc current conduction time T
-Tw changes, resulting in excess or deficiency of arc current. It should be noted that changing the time T makes the control considerably complicated, so it is not very appropriate.

Next, the average arc current Ia actually supplied when △P=0 is detected 38, and compared 40 with the average arc current Ias set in 30, but this comparison is based on △I=Ia −Ias is calculated, △
If I<0, control 41 to increase Ia, △I>
If it is 0, control 42 is performed to reduce Ia, and finally the appropriate condition 43 is achieved. For example, △P<0,
If it becomes necessary to increase Dw and the wire current supply time is increased from Tw to Tw', the arc current conduction time will decrease and △I<0, but the peak current will be increased from AP ₁ to AP ₂ . By doing so, Ia is increased and ΔI is set to 0. FIG. 7 shows the relationship between the wire applied power and the wire melting rate, showing that the two are proportional.

By implementing this invention, even in a hot wire switching TIG welding device with one switching element, it is possible to supply appropriate wire applied power and arc power regardless of changes in wire feed rate.
In addition, since there is no possibility of unstable arc fluctuations due to magnetic blowing of the arc by the wire current, a stable arc can be created and good welding can be performed.

[Brief explanation of the drawing]

Figure 1 is a basic configuration diagram of commonly used hot wire switching TIG welding equipment, Figure 2 is an explanatory diagram of the arc and current flowing through the wire in hot wire switching TIG welding, and Figure 3 is a large capacity A diagram of the circuit principle of a hot wire switching TIG welding device that uses transistors, Figure 4 is a circuit diagram of a hot wire switching TIG welding device that connects two gate turn-off thyristors, and Figure 5 shows the current of the device shown in Figure 4. 6 is a circuit diagram of a hot wire switching TIG welding device having a control device according to the present invention, FIG. 7 is a diagram showing the relationship between wire current and wire melting rate, and FIG. Flow chart showing the operation of the device of the invention, No. 9
The figure is an explanatory diagram showing an example of current control. 1...Tungsten electrode, 3...Arc current,
5... Arc, 6... Wire, 15... Control device.

Claims (1)

[Claims] 1 By turning on and off a large current switching element installed in a circuit parallel to the arc circuit, the arc current is periodically shunted to the additive wire, and the amount of power supplied to the electrode and wire is controlled to heat the wire and weld. In a hot wire switching TIG welding control device, the arc current and wire current are controlled so that they do not overlap, and the wire is applied so that the appropriate wire applied power is supplied in accordance with the wire feeding speed. A circuit that controls the power supply time, a circuit that compares and calculates the average arc current that fluctuates due to fluctuations in the control time and the set average arc current, and a circuit that calculates the average arc current based on the calculation results of this circuit and the set average arc current. A hot wire switching device characterized in that it has a device for controlling three circuits, and a circuit for controlling the circuits to be equal.
Control device for TIG welding.