JP4151777B2 - Hot wire welding method and apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to hot wire welding, and more particularly to a hot wire welding method and apparatus suitable for performing high-efficiency welding by optimizing the hot-melt state of the hot wire.
[0002]
[Prior art]
FIG. 4 shows a configuration of a welding apparatus generally used conventionally as a hot wire TIG (Tungsten Inert Gas Arc) welding method. An arc power source 4 for direct current welding is connected to the tungsten electrode 2 and the base material 3 attached to the TIG welding torch 1, and an arc 5 is formed using the tungsten electrode 2 as a negative electrode in an argon shielding gas. The additive wire 6 for welding is led from the wire feeding device 7 through the conduit 8 and the wire torch 15 connected thereto to the arc forming portion and brought into contact with the base material 3. Although not shown in the drawing, the TIG welding torch 1 and the wire torch 15 are mechanically coupled by a connecting member and move together.
[0003]
A contact tip 9 and a ceramic guide 11 are arranged on the wire torch 15. A wire heating power source 10 is connected between the contact tip 9 and the base material 3, and direct current or alternating current is passed through the wire 6 to generate Joule heat. The melting speed of the wire 6 is increased. In the case of cold wire TIG welding in which the wire 6 is not energized and heated, the wire heating power source 10 is excluded from FIG.
[0004]
By the way, in hot wire TIG welding, it is known that if the energizing current of the wire 6 is increased, an electromagnetic force is generated between the wire and the arc current, and the arc 5 is disturbed by so-called magnetic blowing, making welding difficult. . Therefore, a method (Patent No. 2610819) in which a current having a pulse waveform as shown in FIG. FIG. 5A shows a method in which the arc current is constant and only the wire current is made into a pulse waveform current, and FIG. 5B is a case where both the arc current and the wire current are made into a pulse waveform current and the wire current is flowed. This is a method of reducing the current as much as possible. When the wire heating current is used as the pulse current and the period in which the arc 5 is continuously blown magnetically is shortened as much as possible, the arc 5 is blown instantaneously but immediately returns to the position immediately below the tungsten electrode 2. In addition, the rigidity of the arc 5 is maintained, and a decrease in workability due to magnetic blowing is not observed. As a result, workability of hot wire TIG welding has been remarkably improved, and practical application has progressed.
[0005]
The added wire 6 is energized and heated at the extension e portion between the contact tip 9 and the base material 3, and it is necessary to control the power applied to the added wire 6 and the amount of melted wire in a good balance. The optimum melting state of the additive wire 6 in hot wire TIG welding is that the tip of the additive wire 6 is brought into contact with the molten pool 12, but the wire 6 is already completely melted in the immediate vicinity of the contact interface. Furthermore, it is most desirable that the additive wire 6 is completely melted immediately before entering the molten pool 12, and the molten metal can be continuously melted down without being cut. However, the amount of heat input to the wire 6 is the heat generated by energizing the wire and the amount of heat from the arc 5, so the amount of heat from the arc 5 varies depending on the insertion position of the additional wire 6 into the arc 5, and The molten state will change.
[0006]
Thus, in hot wire TIG welding, it is necessary to adjust the heating power according to the wire feed speed to be added and the insertion position of the wire 6 into the arc 5, and when the heating power is insufficient, the wire 6 The wire torch 15 and the TIG welding torch 1 connected to the wire torch 15 are pushed up from the molten pool 12 or hit against the base material 3. As a result, the arc length becomes very long, so that welding cannot be continued. In addition, when the wire heating power is low, welding proceeds in a state where the additive wire 6 penetrates deeply into the molten pool 12 and is finally melted by receiving heat transfer from the molten pool 12. This is a less favorable situation. When the heating of the additive wire 6 is severe in such a state, the unmelted wire 24 remains in the weld metal 25 as it is, as shown in the sectional view of the weld bead shown in FIG. Will form. Conversely, when the heating power is excessive, the wire 6 is frequently melted by heating and spatters to adhere to the tungsten electrode 2 or form an arc 5 between the tip of the wire 6 and the tungsten electrode 2 for welding. The state becomes unstable and the welding operation is significantly impaired.
[0007]
Therefore, usually, the operator monitors the welded portion so that the wire 6 is in an appropriately melted state, that is, the tip of the wire 6 is in a melted state or just before melting, and is always in contact with the base material 3. However, the heating power is adjusted as a result by manually adjusting the heating current.
[0008]
Regarding the heating power adjustment, as described in Japanese Patent Publication No. 5-75512, the occurrence of fusing is detected from the wire voltage, and when the fusing occurs, the wire heating power is reduced slightly and the heating power is gradually increased from there. A control method has been proposed in which the wire heating power is automatically maintained in a state close to a proper melting state by repeatedly generating fusing again. The occurrence of fusing is preferably as small as possible. However, in this method, although the frequency is about once every 2 to 3 seconds, it is necessary to generate fusing, and some spatter is unavoidable.
[0009]
[Problems to be solved by the invention]
In the prior art, when the heating of the wire 6 is insufficient, the welding defect in which the unmelted wire 24 remains in the weld metal 25 as it is due to the lifting of the torch 15 due to the wire 6 being stretched or the heating of the wire 6 is insufficient. In order to prevent the occurrence of spatter and the occurrence of spatter due to heat fusing, the welding operator must constantly adjust the wire feeding speed and heating power while monitoring the melting state of the wire 6. Yes. Further, in the conventional automatic control method using the above-described fusing phenomenon, there is a problem that spatter is frequently generated, spatter accumulates on the tungsten electrode 2, and it is difficult to continuously operate for a long time.
[0010]
The present invention has been made on the basis of such a background, and the problem is that automatic adjustment of the wire heating current is performed so that the occurrence frequency of spatter in hot wire welding is reduced and an appropriate wire melting state is maintained. It is to provide a hot wire welding method and apparatus that can be performed.
[0011]
[Means for Solving the Problems]
A first aspect of the present invention is a hot wire welding method in which a voltage is supplied from a power source between a base material and an added wire, and welding is performed while controlling the heating of the wire. This is achieved by a hot wire welding method characterized by controlling electric power.
[0012]
As a method for setting the target value of the wire resistance value, a target wire resistance value is registered in advance, or the setting method is used, or the fusing phenomenon is generated by increasing the heating power at the start of welding, and the fusing phenomenon is detected by touch detection means. And the resistance value of the wire immediately before fusing measured by the wire resistance measuring means is set as a target value.
[0013]
There are the following methods for changing the target value of the wire resistance value.
(1) When the welding conditions are changed during welding, the heating power is increased to cause a fusing phenomenon, the fusing phenomenon is detected by, for example, touch detection means, and the resistance of the wire immediately before fusing measured by the wire resistance measuring means A method of registering and changing a value as a new target value.
[0014]
(2) The heating power is periodically increased to cause a fusing phenomenon, the fusing phenomenon is detected by, for example, touch detection means, and the resistance value of the wire immediately before fusing measured by the wire resistance measuring means is registered as a new target value. And how to change.
[0015]
(3) When a fusing phenomenon occurs during welding, the fusing phenomenon is detected by, for example, touch detection means, and the resistance value of the wire immediately before fusing measured by the wire resistance measuring means is compared with the previous target resistance value, A low resistance value is registered and changed as a new target value.
[0016]
According to a second aspect of the present invention, there is provided a wire heating power source for supplying a wire heating voltage between the base material and the added wire, a wire touch detection means for detecting whether or not the wire is in contact with the base material, and a wire Wire resistance measuring means for measuring the resistance value of the wire, and when the measured value of the wire resistance value has a deviation in the set target value, the wire heating for controlling the heating power of the wire so that the measured value becomes the set target value A hot wire welding apparatus including wire heating control means for adjusting heating power of a power source.
[0017]
The wire heating control means increases the heating power at the start of welding to generate a fusing phenomenon as the set target value, detects the fusing phenomenon by the touch detection means, and measures the resistance of the wire immediately before fusing measured by the wire resistance measuring means. A configuration in which a value is set as a target value can be adopted. The wire heating control means may be means capable of executing the methods (1) to (3) of the method of changing the target value of the wire resistance value described in the hot wire welding method according to the first invention.
[0018]
The present invention is not limited to the arc welding method in which an arc is generated between the base material and the torch, but can also be applied to a laser welding method.
[0019]
[Action]
FIG. 3A is a schematic diagram showing an optimum state of heating of the added wire and a graph of the temperature and electrical resistivity of the wire at that time, and FIG. 3B is a schematic diagram showing an excessive state of heating of the added wire and at that time. FIG. 3C is a schematic diagram showing a state in which heating of the added wire is insufficient, and a graph of the wire temperature and electrical resistivity at that time. The amount of heat QT input to melt the added wire 6 is determined by the electric heating amount QW and the arc by the hot wire current applied to the added wire 6 between the contact tip 9 and the base material 3 from the wire heating power source 10 (FIG. 1). The amount of heat QA applied from 5.
[0020]
QT = QW + QA (1)
QT is a value determined by the material of the additive wire 6 and the feed amount. For example, QT is 1.27 J / g in the case of mild steel. QA is a value that changes depending on the insertion position of the additive wire 6 into the arc 5 and the molten pool 12, and the additive wire 6 is inserted into the arc 5 and the molten pool 12 at a position close to the tungsten electrode 2 as shown in FIG. In this case, it increases as compared with the case where it is inserted at the end of the arc 5. That is, the QW needs to be changed according to the change of the QA. QW is expressed by the current I passed through the additive wire 6 and the resistance value R of the extension e part.
[0021]
QW = I ² × R (2)
The resistance value R of the extension e part is expressed by the length L of the extension e part, the cross-sectional area S of the added wire 6 and the electrical resistivity ρ.
[0022]
R = ρ × L ÷ S (3)
Here, since the cross-sectional area S of the additive wire 6 is constant and the length L of the extension e portion is an automatic welding machine, since the TIG welding torch 1 and the wire torch 15 are fixed integrally, there is a slight fluctuation during welding. There is almost constant. The electrical resistivity ρ varies depending on the temperature. Particularly, the rate of change of iron is very large. For example, it changes to 9.7 μΩ · cm at a temperature of 20 ° C. and 105.5 μΩ · cm at a temperature of 800 ° C.
[0023]
In addition, when the additive wire 6 is made of mild steel, the temperature of the additive wire 6 is heated to 1500 ° C. near the melting point near the melting point on the contact chip 9 side as shown in FIG. Ideal. And according to the temperature distribution of the added wire 6, the electrical resistivity ρ shows a similar distribution. Since the value obtained by integrating the electrical resistivity ρ from the contact tip 9 to the molten pool 12 becomes the resistance value R, the resistance value R may be considered to indicate the temperature of the additive wire 6, that is, the heating state. As shown in FIG. 3C, when the heating of the additive wire is insufficient, the temperature of the additive wire 6 does not rise to the melting point on the molten pool 12 side and becomes a low value. Similarly, the distribution of the electrical resistivity ρ is also lower than that in FIG. 3A, and the resistance value R is also low. On the contrary, as shown in FIG. 3B, when the heating of the additive wire 6 is excessive, it is necessary to reduce the energized heating amount when the heat input from the arc 5 increases. A fusing phenomenon occurs at the tip of the wire 6. FIG. 3B shows a state in which the tip of the additive wire 6 flows into the molten pool 12 while melting, and normal welding can be continued in this state. At this time, the temperature distribution of the additive wire 6 is slightly increased in the high temperature range on the molten pool 12 side, and the electric resistivity ρ also changes. However, if the additive wire 6 is not melted and connected to the molten pool 12, the temperature distribution of the additive wire 6 between the contact tip 9 and the arc 5 is lower than the state of FIG. The electrical resistivity ρ is also lower than that in the state of FIG. 3A, and the resistance value R is close to the value in the state of FIG.
[0024]
From the above, the heating state of the wire 6 can be determined based on the resistance value R of the added wire 6, and in particular, the resistance value R of the added wire 6 immediately before fusing flows into the molten pool 12 while melting the wire 6. It is a value in a state where the temperature distribution of the wire 6 is optimal. When the resistance value R immediately before fusing is set as a target value and the measured resistance value R is lower than the target value, heating is insufficient, and it can be determined that the temperature distribution of the wire 6 is lower than the optimum state. It is necessary to increase the heating power of the additive wire 6. Conversely, when the measured resistance value R is higher than the target value, it can be determined that the heating power is excessive. Therefore, the heating power of the additive wire 6 needs to be decreased. By measuring the energization resistance value of the additive wire 6 in this way, it becomes possible to automatically control the heating state of the additive wire 6 to an optimum state.
[0025]
There is a method in which the target value of the resistance value R of the additive wire 6 is determined by the operator measuring the resistance value R in the optimum heating state by judging the welding condition. Further, as a method for automatically determining the target value of the resistance value R of the additive wire 6, the heating power of the additive wire 6 is gradually increased to cause a fusing phenomenon, which is described in the above Japanese Patent Publication No. 5-75512. There is a method in which a fusing phenomenon is detected by touch detection means, and the resistance value R of the added wire 6 immediately before fusing is set to a target value.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a circuit configuration diagram of a control circuit of a hot wire welding apparatus according to an embodiment of the present invention. FIG. 2 is a circuit configuration diagram of the resistance measuring means of the added wire according to FIG.
[0027]
In FIG. 1, a TIG welding torch 1 holds a tungsten electrode 2, and the tungsten electrode 2 generates an arc 5 with a base material 3 of an object to be welded. A current from the wire heating power source 10 is contacted and supplied to the additive wire 6 by the contact tip 9, and the contact tip 9 has a ceramic guide for accurately and uniformly inserting the heated additive wire 6 into the molten pool 12. 11 is attached. When the molten pool 12 formed by melting the base material 3 by the arc heat solidifies, a weld bead 13 is formed.
[0028]
Further, the wire current value is measured by the current sensor 16, the touch detection means 17 for determining whether the added wire 6 is in contact with or separated from the base material 3 based on the wire voltage, and the wire resistance value from the wire current and the wire voltage. In order to determine the heating state of the added wire 6 based on signals from the wire resistance measuring means 18, the touch detecting means 17 and the wire resistance measuring means 18 for calculating R, and to adjust the heating power of the wire heating power supply 10 based on the determination result. The wire heating control means 19, the touch detection means 17, the wire resistance measurement means 18, the wire heating control means 19, and the like constitute a control device 20.
[0029]
Further, the wire heating power source 10 is controlled by the output (output value Ww) of the wire heating control means 19.
[0030]
As shown in FIG. 2, the dividing circuit (wire resistance measuring means 18) includes a wire current measuring circuit 21 for measuring the wire current value based on a signal from the current sensor 16, and a wire voltage for measuring the wire voltage value. Although a measurement circuit 22 is provided, a pull-up voltage is applied to the wire voltage in order to accurately perform touch detection by the touch detection means 17, and therefore, a substantial wire voltage obtained by subtracting the pull-up voltage is the wire voltage. The voltage measurement circuit 22 has a circuit configuration that can be measured. Further, a dividing circuit (wire resistance measuring means) 18 is provided for dividing the wire voltage Vw measured by the wire voltage measuring circuit 22 by the wire current Iw measured by the wire current measuring circuit 21 to calculate the resistance value Rw. Yes.
[0031]
Since the TIG arc welding, hot wire welding method, and welding procedure are the same as those of the conventional method, the description thereof will be omitted, and the hot wire welding control method and apparatus, which are the features of the present embodiment, will be described with reference to FIGS. .
[0032]
It is possible to determine the heating state of the wire 6 from the energization resistance value of the added wire 6 between the contact chip 9 and the base material 3. First, a method for measuring the energization resistance value will be described. The energization resistance Rw is represented by a voltage Vw and a current Iw applied to the additive wire 6 between the contact chip 9 and the base material 3.
Rw = Vw ÷ Iw (4)
[0033]
The resistance value is measured by the wire resistance measuring unit 18. Since the pull-up voltage is applied to the voltage Vw in order to accurately detect the touch by the touch detecting unit 17, the wire voltage measuring circuit 22 is connected to the pull-up voltage. The circuit configuration is such that a substantial wire voltage applied from the wire heating power supply 10 minus the above can be measured. The current Iw is measured by a wire current measuring circuit 21 based on a signal from a current sensor 16 such as a hall sensor, and the signals of the voltage Vw and the current Iw are input to a dividing circuit (wire resistance measuring means) 18 and a resistance value Rw is obtained. Can be sought.
[0034]
The target value of the resistance value Rw of the added wire 6 is determined by the operator determining the welding condition, measuring the resistance value Rw in the optimum heating state with the wire resistance measuring means 18, and supplying the value to the wire heating control means 19. There is a way to register.
[0035]
Next, a touch detection function (described in Japanese Patent Publication No. 5-75512) for detecting whether or not the added wire 6 is in contact with the base material 3 will be described. The wire voltage Vw when the additive wire 6 is not energized is close to 0 V when the additive wire 6 is in contact with the base material 3, and the tip of the additive wire 6 is separated from the base material 3, and When in contact with the plasma, the voltage of the plasma column is detected and becomes a negative voltage from -1V. Using this property, the touch detection means 17 for detecting whether the tip of the additive wire 6 is in contact with the base material 3 is configured. The output signal Tu from the touch detection means 17 is a voltage output signal of a high level signal H when the added wire 6 is in contact with the base material 3 and a low level signal L when the added wire 6 is away from the base material 3.
[0036]
As a method of automatically determining the target value of the resistance value of the added wire 6, the heating power of the added wire 6 is gradually increased to generate a fusing phenomenon, the fusing phenomenon is detected by the touch detection means 17, and immediately before fusing. There is a method in which the resistance value of the added wire 6 is measured by the wire resistance measuring means 18 and the value is registered in the wire heating control means 19. This additional wire resistance target value needs to be set once at the start of welding. When the welding conditions such as the welding current and the feeding of the wire 6 are changed, it is necessary to register again. Further, as welding progresses, the arc length fluctuates or the temperature of the base material 3 increases, so that the welding condition of the arc 5 and the molten pool 12 changes, and the heating condition of the additive wire 6 also changes somewhat. Come. Therefore, for example, if automatic re-registration of the resistance target value is performed periodically at a rate of once every several minutes, more accurate heating control can be performed.
[0037]
In the wire heating control means 19, when the resistance value measured by the wire resistance measuring means 18 during welding is lower than the target value with respect to the resistance target value set by the above method, the temperature distribution of the wire 6 is insufficient due to insufficient heating. Therefore, it is necessary to increase the heating power of the added wire 6, and a command to increase the heating power is issued to the wire heating power supply 10. On the contrary, when the measured resistance value is higher than the target value, it can be determined that the heating is excessive, so it is necessary to reduce the heating power of the added wire 6 and the wire heating power supply 10 is instructed to reduce the heating power. Put out. By measuring the energization resistance value of the additive wire 6 in this way, it becomes possible to automatically control the heating state of the additive wire 6 to an optimum state.
[0038]
Further, when the above control is performed during welding and the fusing phenomenon is detected by the touch detection means 17, it can be determined that the wire heating is excessive, so the wire 6 immediately before fusing measured by the wire resistance measuring means 18 is determined. It is necessary to compare the previous resistance value and the previous target resistance value, and re-register a low resistance value as a new target value.
[0039]
When the wire heating current uses a pulse current as shown in FIG. 5, the above control is naturally synchronized with the pulse current and operates only during the energization period of the wire current, and the non-energization period of the wire current. It needs to be activated.
[0040]
【The invention's effect】
According to the present invention, in hot wire welding, the torch is lifted by stretching the wire under insufficient heating of the wire, and the occurrence of welding defects in which the unmelted wire remains in the weld metal due to insufficient heating of the wire is prevented. By reducing the frequency of spattering due to heat fusing and maintaining an appropriate wire melting state, it is possible to perform automatic adjustment of the wire heating current, thereby promoting high efficiency by hot wire welding. It is possible to reduce the occurrence frequency of welding defects and contribute to labor saving.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a control circuit of a hot wire welding apparatus according to an embodiment of the present invention.
2 is a circuit configuration diagram of resistance measuring means for an added wire of the welding apparatus of FIG. 1;
FIG. 3 (A) is a schematic diagram showing the optimum heating state of the wire, and a graph of the temperature and electrical resistivity of the added wire at that time, and FIG. 3 (B) shows an excessive heating state of the wire. FIG. 3C is a schematic diagram illustrating a wire temperature and electrical resistivity at that time, and FIG. 3C is a schematic diagram illustrating a state in which the wire is insufficiently heated, and a wire temperature and electrical resistivity graph at that time.
FIG. 4 is a diagram showing a device configuration of a conventional hot wire TIG welding apparatus.
FIG. 5 shows a wire current waveform of a conventional wire heating power source. FIG. 5 (A) shows a method in which the arc current is constant and only the wire current is a pulse waveform current, and FIG. It is a figure which shows the method of making arc current as small as possible when making both wire current into the electric current of a pulse waveform, and flowing wire current.
FIG. 6 is a view showing a cross section of a weld bead.
[Name of code]
DESCRIPTION OF SYMBOLS 1 TIG welding torch 2 Tungsten electrode 3 Base material 4 Arc power supply 5 Arc 6 Addition wire 7 Wire feeding device 8 Conduit 9 Contact tip 10 Wire heating power supply 11 Ceramic guide 12 Weld pool 13 Weld bead 14 Wire reel 15 Wire torch 16 Current sensor 17 Touch detection means 18 Wire resistance measurement means (division circuit)
DESCRIPTION OF SYMBOLS 19 Wire heating control means 20 Control apparatus 21 Wire current measurement circuit 22 Wire voltage measurement circuit 24 Unmelted wire 25 Molten metal e Extension part I (Iw) Current L Length Tu Output signal R Resistance value Rw Current supply resistance Vw Voltage Ww Wire heating Output value to power supply

Claims (7)

In a hot wire welding method in which a voltage is supplied from a power source between a base material and an additive wire and welding is performed while heating the wire,
A hot wire welding method, wherein the heating power of a wire is controlled by a resistance measurement value of the wire. 2. A hot wire according to claim 1, wherein a target wire resistance value is registered in advance, and the heating power of the wire is controlled so that the measured resistance value of the wire becomes the registered target resistance value. Wire welding method. When the heating power is increased at the start of welding to generate a fusing phenomenon, and the fusing phenomenon is detected, the resistance value of the wire immediately before fusing is registered as a target value, and the heating power of the wire is controlled by the target value The hot wire welding method according to claim 1. When the welding conditions are changed during welding, the heating power is raised to cause a fusing phenomenon, and when the fusing phenomenon is detected, the resistance value of the wire immediately before fusing is re-registered as a target value, and becomes the registered target resistance value. The hot wire welding method according to claim 2, wherein the heating power of the wire is controlled. When the heating power is periodically raised to cause a fusing phenomenon, and the fusing phenomenon is detected, the resistance value of the wire is measured, the resistance value of the wire immediately before fusing is re-registered as a target value, and the registered target resistance value The hot wire welding method according to claim 2, wherein the heating power of the wire is controlled so that When a fusing phenomenon occurs during welding, the fusing phenomenon is detected, the resistance value of the wire just before fusing, which is measured for the wire resistance value, is compared with the previous target resistance value, and a lower resistance value is set as the new target value. The hot wire welding method according to claim 2, wherein the heating power of the wire is controlled by re-registering as. A wire heating power source for supplying a wire heating voltage between the base material and the additive wire;
Wire touch detection means for detecting whether or not the wire is in contact with the base material;
Wire resistance measuring means for measuring the resistance value of the wire;
When the measured value of the wire resistance measured by the wire resistance measuring means has a deviation in the set target value, the heating power of the wire heating power source that controls the heating power of the wire is adjusted so that the measured value becomes the set target value. A hot wire welding apparatus comprising: a wire heating control means for performing

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