JPH0475116B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a multi-electrode single-sided automatic welding method, and in particular maintains the back bead width constant against width fluctuations in the groove sheet gap, and maintains the front bead height. This is related to simultaneous control of the back bead and front bead to keep constant.

[Conventional technology] The single-sided automatic welding method performs arc welding from one side of the material to be welded, and has the advantage that a good weld bead can be formed on the back side of the material to be welded, and there is no need to turn the material to be welded. Therefore, it is widely used for welding structures that cannot be reversed, such as ships.

However, the shape of the weld bead depends on the accuracy of the root gap width of the groove. For example, in areas with a wide root gap, the penetration will be excessive,
In severe cases, bead erosion occurs. To prevent this, it is necessary to strictly control the accuracy of the root jump width, but the required accuracy is only about ±1 mm, and it is extremely difficult to achieve this in terms of processing accuracy. Therefore, in order to obtain an appropriate bead shape over the entire weld line, a control method that automatically corrects welding parameters in response to the constantly changing root gap width during welding is essential.

Conventionally, as this type of control method, for example, the applicant has disclosed Japanese Patent Application Laid-Open No. 61-56775, Japanese Patent Application Laid-Open No. 61-137676,
``Back bead control method in single-sided welding'' was proposed in JP-A-61-180677 and other publications. These methods form a constant back bead regardless of variations in root gap width. Note that this type of single-sided automatic welding method is generally carried out using multiple electrodes, ie, two or more electrodes, but multiple electrodes will also be used in the following description.

Figure 2 shows the principle diagram. In the single-sided welding shown in the figure, the electrode wires 4a and 4b are connected to the welding power source 5.
Power is supplied from and welding is performed in the direction of the arrow, but
The movement of the electrode wires 4a, 4b along the welding line is as follows:
It is assumed that this is automatically performed by a feeding mechanism (not shown).

Since there is no electrical connection between the back metal plate (eg, copper plate) 3 and the workpiece 1 at the start of welding, the voltage between the backing metal plate 3 and the workpiece 1 at the start of welding is zero. After welding starts, when the back bead is well projected, the arc emitted from the electrode wire 4a leaks between the welded materials 1, passes through the inorganic material 2 such as flux, and reaches the backing metal plate 3, and the welded materials 1 A voltage V is generated between the backing metal plate 3 and the backing metal plate 3.

The relationship between the voltage V (detected voltage V _d ) between the material to be welded 1 and the backing metal plate 3 and the back bead width is shown in the graph of FIG. This graph shows the detection voltage V _d on the vertical axis.
[V], the back bead width [mm] is plotted on the horizontal axis. The voltage V _d between the material to be welded 1 and the backing metal plate 3 shows a good correlation as shown in the graph of FIG. ₀ can be set, and the back bead width for single-sided automatic welding can be controlled online.

An example of a control circuit block used in this back bead control method in single-sided welding is shown in FIG. In the figure, a converter 7 converts the detected voltage V _d between the welded material 1 and the backing metal plate 3 detected by the voltmeter 6 into a DC signal. This converter 7 is necessary when an AC power source is used as the welding power source 5.
is not necessary if it is a DC power supply. The voltage signal output from the converter 7 has noise removed by a filter 8 and is input to a comparator 9. The voltage signal input to the comparator 9 is determined in advance according to a predetermined back bead width based on the correlation with the back bead width shown in FIG. 5 and the detected voltage V _d between the workpiece 1 and the backing metal plate 3. It is compared with a set reference voltage signal 10. Comparator 9 provides a deviation signal between the two voltage signals to welding power source 5 via integrator 11. The welding power source 5 outputs a welding current according to the input signal. That is, control is performed so that the voltage signal between the workpiece 1 and the backing metal plate 3 always matches the reference voltage signal 10.

In this example, the voltage V between the workpiece 1 and the backing metal plate 3 during welding was directly detected, but the voltage V between the electrode 4
Even if the voltage between a and the welded material 1, that is, the arc voltage, and the voltage between the electrode 4a and the backing metal plate 3 are measured, the difference between the two voltages is determined, and the difference between the two voltages is controlled to be constant, the above explanation will not occur. Similarly, the back bead width can also be controlled uniformly.

In addition, although voltage is used as the detection electric signal and reference signal in this example, current may also be used.
The welding parameters to be controlled may be arc voltage, welding current, welding speed, wire protrusion length, etc., as long as they are effective for forming the back bead and can control the detection signal. The source of the detection signal is not limited to the welding power source, and a special signal generator (having frequency, current, and voltage characteristics different from those of the welding power source) may be used.

The conventional single-sided automatic welding method is configured as described above, and by controlling the welding parameters so that the detection signal always matches the reference signal, it is possible to form a constant back bead width according to this reference signal. It's summery.

[Problems to be Solved by the Invention] In the conventional single-sided automatic welding as described above, the back bead width can be formed constant regardless of fluctuations in the groove root gap width, but for the front bead, due to fluctuations in the groove root gap width. As a result, the bead height becomes non-uniform, and especially when the groove root gap width becomes wide, there is a problem of insufficient reinforcement.

This invention has been made to solve these problems, and is capable of forming a constant width of the back bead regardless of fluctuations in the groove root gap width, as well as a constant height of the front bead. The purpose is to obtain an automatic welding method.

[Means for Solving the Problems] In the multi-electrode single-sided automatic welding method according to the present invention, a backing metal plate is applied to the back side of the material to be welded via an inorganic material, and a groove is formed from the front side of the material to be welded. When performing continuous arc welding while moving the welding electrode along the welding electrode, an electric signal between the base metal and the backing metal plate during welding is detected, and this detection signal matches a preset reference signal. In the multi-electrode single-sided automatic welding method that controls welding parameters including the welding current of the preceding welding electrode, (a) the controlled welding current I _L of the preceding electrode is detected, and the change in the detected welding current I _L is In contrast, the preceding wire feeding speed V _fL is calculated by the following formula: V _fL = AI _L + Bl _L I _L ² (I _L is the written value of the preceding welding current, l _L is the preceding wire protrusion length (constant), A, B are welding (a constant uniquely determined by the type of welding materials such as wire and shielding _gas ) _; The amount of welding by the leading electrode can be controlled by variable control using = v ₀ / I _L0 (v _{0 is} the initial value of the welding speed, v ₁ is the welding speed to be controlled, and I _L0 is the initial value of the welding current). (c) For the trailing wire protrusion length l _T , the trailing wire feeding speed V _fT is calculated using the following formula, V _fT = AI _T + Bl _T I _T ² (I _T is the trailing welding current, However, if I _T0 is the initial value of the trailing welding current, then I _T = I _T0 , A and B are variably controlled by the preceding wire feeding speed V (the same values as constants A and B in _{the fT} formula), (d) Find the change in root gap width △G using the following formula: △G = (I _L0 ~ I _L )/a (a is a constant uniquely determined by the type of welding materials such as welding wire and shielding gas), (e) Find the change △S in the groove cross-sectional area corresponding to the change △G in the root gap width using the following formula: △S=T・△G (T is the thickness of the base material), (f) The groove For the change in cross-sectional area △S, the following formula, △S=K {[V _fL /v ₁ )−(V _fL0 /v ₀ )] + [(V _fT
//v ₁ )−(V _fT0 /v ₀ )]} (V _fL0 is the initial value of the preceding wire feeding speed V _fL ,
(V _fT0 is the initial value of the trailing wire feeding speed V _fT , K is a constant uniquely determined by the type of welding materials such as welding wire and shielding gas) The wire protrusion length of the trailing electrode l _T This problem is solved by forming the weld bead at a constant height by variably controlling the height of the weld bead.

[Operation] According to the present invention, in order to form a back bead with a uniform width in multi-electrode single-sided automatic welding, the above-mentioned prior art back bead control method is performed. However, in the back bead control method used in the present invention, the welding current for the preceding electrode is taken as the control target.

Hereinafter, when carrying out the back bead control method of the prior art described above, the effect of forming the front bead at a uniform height will be explained. In the formulas described below, constants such as a, A, B, and K are constants that are uniquely determined by the types of welding materials such as welding wire and shielding gas. The values of these constants may be determined experimentally in advance, or data accumulated through experience may be used. In addition, the following description will describe two-electrode welding as an example of multi-electrode welding.

When performing the back bead control in which the welding current is controlled based on the detection signal between the workpiece to be welded and the backing metal plate in the prior art described above, the difference between the controlled preceding welding current I _L and the welding speed v during the back bead control is When the welding speed v is changed so that the ratio I _L /v remains constant, the heat input becomes constant, so the amount of welding by the preceding electrode becomes constant.

Therefore, the welding speed v ₁ that keeps the amount of welding by the preceding electrode constant against changes in the preceding welding current I _L is:
When the initial value of the welding current is I _L0 and the initial value of the welding speed setting is v ₀ , the welding speed control formula is obtained as v ₁ = v ₀ · I _L /I _L0 ().

In the present invention, the welding speed is variably controlled according to this equation (), but in this case, in response to the change in the controlled welding current _IL , the well-known relational equation is used to control the advance wire feeding speed. According to the formula V _fL = AI _L + Bl _L I _L ² ... (), the wire feeding speed V _fL of the leading electrode is variably controlled, and the wire protrusion length l _L of the leading electrode is maintained at a predetermined constant value. .

Variable control of the welding speed based on the above formula () is performed while the wire protrusion length l _L of the leading electrode is controlled to a constant value, as shown in formula (), and the amount of welding by the leading electrode is kept constant. .

Note that when the amount of welding is constant, the weld bead height may be excessive or insufficient due to changes in the groove root gap, but according to the present invention, the trailing electrode compensates for the amount of welding due to changes in the groove root gap. Control is performed to keep the weld bead height constant.

The wire feeding speed V _fT of the trailing electrode is calculated according to the wire protrusion length l _T of the trailing electrode, which is variably controlled as described below, using the well-known relational expression, trailing wire feeding speed control formula V _fT = AI _T + Bl Variable control is performed according to _T I _T ² ...(). Furthermore, in equation (), I _T
is the welding current of the trailing electrode, and this welding current I _T
is equal to its initial setting value I _T0 .

By controlling the equation (), the wire protrusion length l _T of the trailing electrode is maintained at a predetermined value (hereinafter referred to as the set value l _T0 ) when the root gap width is the set width. For example, when a change in the root gap width is detected, the wire protrusion length l _T takes a variable value in accordance with the change in the root gap width. That is, a change in the root gap width is detected, a change in the groove cross-sectional area corresponding to the change in the detected root gap width is determined, and the amount of welding required for this change in the groove cross-section is determined by the wire protrusion length of the trailing electrode. l Compensate by variable control of _T to keep the bead height formed by the leading and trailing electrodes constant.

Here, the controlled welding current I _L is used to detect a change in the root gap width. This controlled welding current I _L changes the root gap width by △G
It has been confirmed that it has a linear characteristic as follows: I _L =I _L0 -a△G, that is, the root gap width change calculation formula: △G=(I _L0 -I _L )/a...().

According to this equation (), the change ΔG in the root gap width is detected.

On the other hand, the change △S in the groove cross-sectional area corresponding to the change △G in the groove root gap width is calculated by the formula △S=T・△G, assuming that the groove angle can be ignored. ) as change in groove root gap width △G and plate thickness T
It can be expressed as the product of

Further, the increase ΔM in the amount of welding due to the control based on the formulas () to () above is the increase ΔM _L in the amount of welding of the preceding electrode according to the formulas () and () above, and the increase ΔM in the amount of welding of the preceding electrode according to the formulas () and () above, and The sum of the increase in the amount of welding of the trailing electrode ΔM _T according to the formula, ΔM=ΔM _L +ΔM _T.

Here, ΔM _L is ΔM _L = (V _fL /v ₁ )−(V _fL0 /v ₀ ) according to the above equations () and (), assuming that the initial setting value of V _fL is V _fL0 .

Similarly, ΔM _T is ΔM _T =(V _fT /v ₁ )−(V _fT0 /v ₀ ) according to the above equations () and (), assuming that the initial setting value of V _fT is V _fT0 .

Therefore, the increase △M in the welding amount due to the control based on the above formulas () to () is as follows: △M = △M _L + △M _T = {(V _fL /v ₁ ) − (V _fL0 / _v0 )
}+{(V _fT /v ₁ )−(V _fT0 /v ₀ )}...().

According to formulas () to (), the change in groove cross-sectional area △
The relational expression △S=T・△G=T・{(I _L0 −I _L )/a} =K・△M=K・{△M _L +△M _T }=K{[(V _fL /v ₁ )−(V _fLO /v ₀ )] + [(V _fT /v ₁ )−(V _fT0 /v ₀ )]} ...() is obtained.

By variably controlling the wire protrusion length l _T of the trailing electrode so as to satisfy this equation (), the amount of welding is compensated according to changes in the root gap width, and the bead formed by the leading and trailing electrodes is The height remains constant.

[Embodiments] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Note that the back bead control is the same as the above-mentioned prior art, so a description of the back bead control will be omitted.

FIG. 1 is a control block diagram according to an embodiment of the present invention, and shows an example in which the present invention is applied to two-electrode, single-sided automatic welding.

In the figure, a feed mechanism 19 integrally moves leading and trailing electrodes (not shown), which is controlled by a welding speed controller 17 via a drive motor 18. Further, the leading (trailing) wire feeding motors 21, (23) are controlled by the leading (trailing) motor controllers 20, (22), and further,
Trailing wire feed motor 23 is also controlled by trailing wire protrusion length controller 24 .

Control commands to each of these controllers 17, 20, 22, 24 are given from an arithmetic and control device 15 such as a microcomputer, for example.
are the constants (a, A, B, K, etc.) and initial setting values (vo, I _L0 ) set and inputted by the attached input device 16 and the detection signals described later in the above-mentioned () to
Arithmetic processing is performed according to equation () and a control signal is given to each controller.

Although the preceding welding current I _L fluctuates due to the back bead width constant control of the above-mentioned conventional technology, this controlled preceding welding current I _L is detected by the preceding current detector 12 and converted into a DC signal by the converter 13. However,
This converter 13 is unnecessary when a DC power source is used as the welding power source. The DC signal output from the converter 13 has noise removed by a filter 14 and is input to the arithmetic and control unit 15 . The arithmetic and control device 15 calculates the detected preceding welding current _IL , the initial speed v ₀ and the initial welding current I _L0 set and input to the input device 16 according to the above-mentioned welding speed control formula (),
Welding speed that keeps the amount of welding by the leading electrode constant
Find v ₁ . Furthermore, a speed control signal corresponding to this welding speed v ₁ is given to the welding speed controller 17 to control the drive of the feed mechanism drive motor 18 and to control the drive of the feed mechanism 19.
variable speed control. That is, the welding speed is variably controlled.

Further, the above-mentioned preceding wire feeding speed control formula (2) maintains the preceding wire protrusion length _{l L constant} against fluctuations in the detected preceding welding current IL. The arithmetic and control device 15 receives setting inputs from the input device 16 for constants A, B, and set values l _L and detects the detected preceding welding current I _L
is calculated according to formula (), and the detected preceding welding current I _L
A control signal for the preceding wire feeding speed _VfL in accordance with the fluctuation of is given to the preceding wire feeding speed controller 20. The leading wire feeding speed controller 20 controls the driving of the leading wire feeding motor 21 to maintain the leading wire protrusion length l _L constant.

By performing the above control at the same time, the amount of welding by the preceding electrode can be kept constant against fluctuations in the preceding welding current I _L while the preceding wire protrusion length l _L is constant.

Note that the trailing wire feeding speed V _fT of the trailing electrode is variably controlled in response to changes in the trailing wire protrusion length l _T , and the control formula for this is the aforementioned trailing wire feeding speed control formula () It is a formula. The arithmetic control device 15 of this equation () calculates the setting inputs from the input device 16 of constants A, B, I _T , and set value l _T0 according to the equation (), and controls the trailing wire feeding speed V _fT. A signal is given to the trailing wire feed speed controller 22 to control the drive of the trailing wire feed motor 23 to keep the given trailing wire protrusion length l _T0 constant and as long as there is no change in the root gap width. , this setting value l _T0 is held.

When controlling using the above formulas () to (),
A change in the size G of the root gap width is taken as a change ΔS in the groove cross-sectional area using the root gap width change calculation formula ( ) and the groove cross-sectional area change calculation formula ( ) described above. These calculation formulas () and () are also given to the arithmetic and control unit 15, and the initial value I _L0 , the setting input by the input device 16 of the constant a, and the detection signal I _L from the filter 14 are expressed in the formula (). Therefore, the magnitude G of the root gap width is calculated. The calculation result of this formula () and the setting input by the input device 16 of the plate thickness T of the material to be welded are calculated according to the formula (), and the change in the groove cross-sectional area △
S is required.

On the other hand, the increase in the amount of welding △M between the initial setting values V ₀ , V _fL0 , V _fT0 and the post-control values v ₁ , V _fL , v _fT due to control based on the above control formulas () to () The above-mentioned formula () for calculating the increase in welding amount captures this. The arithmetic and control unit 15 is also given an arithmetic expression for this purpose, and the initial values v ₀ , V _fL0 , V _fT0 are set by the input device 16 and the controlled v determined by the formulas () to () is ₁ , V _fL and V _fT are calculated according to the formula () to find the increase in the amount of welding ΔM.

Change in groove cross-sectional area △S and increase in welding amount △M calculated by these calculation formulas () to ()
The above-mentioned relational expression () shows the relationship between . The arithmetic and control unit 15 substitutes the calculation results of equations () to () into the relational expression (), and issues a control command for the trailing wire protrusion length l _T to the trailing wire protrusion length controller so that the equation () is satisfied. Give to 24. The trailing wire protrusion length controller 24 controls the trailing wire protrusion length via the trailing wire feed motor 23 so as to satisfy the equation ().
l Variably control _T. The arithmetic and control unit 15 resets the value of the trailing wire protrusion length l _T at this time as the initial value used in the control of equation (), and continues the subsequent control.
By controlling the trailing wire protrusion length l _T , the amount of welding is compensated for changes in the root gap width, and a surface bead is formed at a constant height over the entire weld area line.

In the multi-electrode single-sided automatic welding method configured as described above, the preceding welding current is controlled to form a back bead with a constant width, and the welding speed and the preceding wire are controlled based on this controlled preceding welding current. By controlling the feeding speed and the protruding length of the trailing wire, a surface bead can be formed at a constant height.

Incidentally, in the above embodiments, the case where the present invention is applied to two-electrode, single-sided automatic welding was explained.
It may also be applied to single-sided automatic welding using three or more electrodes.

[Effects of the Invention] As described above, according to the present invention, in multi-electrode single-sided automatic welding, a back bead with a uniform width and a uniform width can be achieved over the entire weld area line, regardless of variations in the groove root gap width. This has the effect that surface beads of a certain height can be formed at the same time.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the control circuit used in the present invention, Fig. 2 is a side view with a partial cross section showing a conventional bead control method, Fig. 3 is a characteristic diagram of detection voltage vs. back bead width, and Fig. 4 1 is a block diagram of a control system used in a conventional bead control method. In the figure, 12 is a leading current detector, 13 is a converter,
14 is a filter, 15 is an arithmetic control unit, 16 is an input device, 17 is a welding speed controller, 18 is a feed mechanism drive motor, 19 is a feed mechanism, 20 is a leading wire feeding speed controller, and 21 is a leading wire feeding motor,
22 is a trailing wire feeding speed controller, 23 is a trailing wire feeding motor, and 24 is a trailing wire protrusion length controller. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A backing metal plate is applied to the back side of the material to be welded via an inorganic material, and the leading and trailing welding electrodes are continuously moved from the front side of the material to be welded along the groove. When performing arc welding, the electric signal between the base metal and the backing metal plate during welding is detected, and the welding current including the welding current of the preceding welding electrode is adjusted so that this detection signal matches a preset reference signal. In a multi-electrode single-sided automatic welding method that controls parameters, (a) the controlled welding current I _L of the preceding electrode is detected, and the preceding wire feeding speed V _fL is decreased in response to a change in the detected welding electrode I _L ; Formula V _fL = AI _L + Bl _L I _L ² (I _L is the initial value of the preceding welding current, l _L is the preceding wire protrusion length (constant), A and B are depending on the type of welding materials used such as welding wire and shielding gas. (b) The welding speed is variably controlled by the following formula, v ₁ = v ₀ · _{I L /} I _L0 (v ₀ is the initial value of the welding speed, v ₁ is the welding speed to be controlled, I _L0 is the initial value of the welding current), the amount of welding by the leading electrode is kept constant, and (c) the trailing wire protrusion is The following formula is used to calculate the trailing wire feed speed V _fT for the length l _T , V _fT = AI _T + Bl _T I _T ² ( _IT is the trailing welding current, where I _T0 is the initial value of the trailing welding current. I _T = I _T0 , A and B are the same values as the constants A and B in the above-mentioned preceding wire feeding speed V _fT formula). G = (I _L0 - I _L )/a (a is a constant uniquely determined by the type of welding materials such as welding wire and shielding gas), and (e) the opening corresponding to the change in root gap width △G. The change in the cross-sectional area of the groove △S is determined by the following formula, △S=T・△G (T is the plate thickness of the base material). =K{[(V _fT /v ₁ )−(V _fL0 /v ₀ )] + [(V
_fT / v ₁ ) − (V _fT0 / v ₀ )]} (V _fL0 is the initial value of the preceding wire feeding speed V _fL ,
(V _fT0 is the initial value of the trailing wire feeding speed V _fT , K is a constant uniquely determined by the type of welding materials such as welding wire and shielding gas) The wire protrusion length of the trailing electrode l _T A multi-electrode single-sided automatic welding method that forms a weld bead at a constant height by variable control.