JPH07112628B2 - Keyhole type single-sided welding method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a keyhole-type single-sided welding method to which a high-speed rotary arc welding method is applied, and more specifically, to a backside bead shape in a grooved single-sided welding with intermittent tacky beads. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a keyhole-type single-sided welding method in which stable control is performed based on a sensor, that is, information from a welding current and an arc voltage.

[0002]

2. Description of the Related Art In the conventional arc welding method in which a single-sided welding is performed while forming a keyhole directly under the arc, a backing method is generally used to control the shape of the back bead. An optical sensor for detection is attached to control welding conditions such as welding current, voltage, and welding speed (Japanese Patent Publication No. 62-36787). Further, in the case where such a sensor is not provided, there is also a method of previously obtaining a certain correlation between the arc voltage or welding current and the width of the back bead and controlling the back bead width based on this correlation. (JP-A-61-137676, JP-A-61-180677)
issue).

[0003]

However, the above-described control method using the optical sensor requires a backing device that moves the backing material and the optical sensor in synchronization with the welding torch, and such a backing device is complicated. Moreover, the installation may be difficult.

On the other hand, in the method of controlling the back bead width from the correlation with the arc voltage or the welding current, it is necessary to grasp all the correlations according to various conditions such as welding conditions, groove shape, plate thickness and the like. However, when it is difficult to determine these fluctuation factors, and when the groove state fluctuates (a groove state, such as root gap or root face fluctuation can often occur in actual single-sided welding), a stable back Controlling the bead shape becomes more difficult.

Generally, in order to obtain a good back bead, it is necessary to keep the groove state uniform, but in reality, the root gap and the root face often change. Therefore, the groove is usually tack welded at predetermined intervals before the main welding.

[0006] However, since the groove with such temporary tack welding mixes a section with a tack bead and a section without a tack bead, welding conditions naturally change for each section. In all of the above-mentioned conventional methods, it is a natural precondition that a uniform groove shape without a temporary bead is formed.

Therefore, the present inventors sought to develop a technique capable of controlling the shape of the back bead without using a special sensor even for a groove where an intermittent temporary bead exists. . As a result, it was found that the problem can be solved by further developing the techniques of Japanese Patent Application Laid-Open No. 64-15287 and Japanese Patent Application Laid-Open No. 62-248571 related to the applicant's patent application. That is, these patent publications show a high-speed rotating arc welding method in which the arc itself that rotates at a high speed is used as a sensor, and the groove tracing control is performed by this arc sensor. When welding is performed, the arc voltage at the front point C _f of the arc rotation position changes at the position of the temporary bead, and the change in arc length at the rear point C _r of the arc rotation position depends on the change in the groove state. It was found to be compatible with changes in the back bead shape.

The present invention has been made on the basis of such knowledge, and for a groove having an intermittent temporary bead, it is stable based on only the information of the arc sensor without using a special sensor. An object of the present invention is to provide a keyhole type single-sided welding method capable of controlling the back bead shape.

[0009]

In order to achieve the above-mentioned object, a keyhole type single-sided welding method according to the present invention is a single-sided groove with intermittent tacky beads while forming a keyhole directly under the arc. In the arc welding method for welding, a high-speed rotating arc welding method is used, in which the torch height (sum of wire protrusion length and arc length) is known by the ACC control method (torch height is set so that the welding current becomes constant. Method for controlling the arc) while keeping it constant, the rear point C of the rotational position of the arc
The arc length at _r is calculated from the detected values of the arc voltage and the welding current at the point C _r , and the welding current is controlled so that the obtained arc length becomes equal to the set value.
The starting end position of the temporary bead is the front point C _f of the arc rotation position.
Detected by a decrease in the arc voltage at, from about that time, preferably the welding current is increased from the time when the center of the arc reaches the start end of the temporary bead, and the welding current is changed from when the arc voltage returns to the original value. The welding current was increased so as to keep the torch height constant while lowering it.

Further, as a detection value of the arc voltage and the welding current in the C _r point will be referred to with the integrated averaged value for the C _r predetermined phase angle around the point phi, further arcs in C _r point When the welding current is changed so that the length becomes equal to the set value, the wire feed speed is also changed so that the torch height (sum of wire protrusion length and arc length) is constant, and at the same time, the welding cross section is constant. So that the welding speed is also changed.

[0011]

The operation of the present invention will be described with reference to FIGS. 1 is a sectional side view showing a keyhole type single-sided welding method of the present invention, FIG. 2 is a plan view thereof, and FIGS. 3 and 4 are sectional views taken along the lines AA and BB of FIG. 1, respectively. . In the figure, 1 is a welding torch, 2 is a welding wire, 3 is an arc,
4 and 5 are members to be welded, 6 is a groove, 7 is a molten pool, 8 is a keyhole, 9 is a weld bead, 10 is a back bead, and 11 is a temporary bead.

As shown in the figure, when single-sided welding is performed while forming the keyhole 8 using the high-speed rotary arc welding method,
The arc 3 is always in front of the molten pool 7 and rotates at high speed.
Then, the arc 3 exhibits a vibration phenomenon such that the front point C _f of the rotational position swings to the groove 6 side as shown by a broken line, and the rear point C _r swings to the molten pool 7 side. At this time, in the section without the temporary bead 11, the shape of the back bead 10 is affected by the state of the groove 6 as described above, and the back bead 10 is affected by the size of the root gap a and the root face b.
Shape changes. That is, the molten pool 7 causes the keyhole 8 to narrow or widen due to the change in the state of the groove 6. For example, when the root gap a small or root face b is, is large, the molten pool 7 as shown by the broken line 12 in FIG. 1 is advanced in the direction of narrowing the keyhole 8, the arc length in the order C _r point Becomes shorter. Then, the back bead width is reduced or is not formed. Since the arc length is shortened in this way, the welding current at the _Cr point increases and the arc voltage decreases. On the other hand, if the root gap a is large or the root face b is small, the molten pool 7 retreats in the direction of expanding the keyhole 8 as shown by the broken line 13 in FIG. It becomes a phenomenon.

Therefore, the state of the back bead can be detected by detecting the arc voltage E (voltage between the welding tip and the base metal) and the welding current I at the point C _r .

FIG. 5 shows the definition of the arc rotation position (C _f , R, C _r , L) with respect to the welding progress direction, and FIG. 6 shows the relationship between the arc rotation position and the arc voltage E due to the change in the groove state. Indicates. In the figure, A indicates a proper groove state, B indicates a small root gap or a large root face, and thus C indicates a large root gap or a small root face when the back bead is insufficient. For this reason, the back bead is too large or too large. That is, when the back bead shortage B occurs in the proper state A, the arc voltage E at the point C _r decreases, and conversely when the back bead excess C occurs, the arc voltage E at the point C _r rises.

Next, as the control method of the present invention, first, C
The arc voltage E and welding current I at point _r are detected. However, in this case, in order to detect the change in the arc length, it is necessary to carry out while controlling the height of the welding torch 1 (the sum of the wire protrusion length and the arc length) to be constant by the ACC control method. This is to prevent the members to be welded from being affected by the unevenness and undulations. The arc voltage E and the welding current I are detected by integrating (for removing noise components) and averaging during a predetermined phase angle φ as shown in FIG. Phase angle φ is 5 ° or more 90
° or less. Next, the arc length is calculated from those detected values, the welding current is changed so that the calculated value becomes equal to the set value, and the torch height (sum of wire protrusion length and arc length) becomes constant. The wire feeding speed is also changed so that the welding cross section becomes constant at the same time, that is,
The welding speed is also changed so that the ratio of the wire feeding speed and the welding speed becomes constant.

Further, since the welding conditions are different in the section with the temporary bead 11 and the section without the temporary bead 11, it is necessary to detect the location of the temporary bead 11. Therefore, when the arc voltage at the point C _f shown in FIG. 5 is monitored, the arc 3 shows the temporary bead 1
When approaching 1, the arc voltage at point C _f drops. The arc voltage returns to the original level at the end of the temporary bead 11. Figure 7
Shows the arc voltage waveform at the arc rotation position. That is, in the section where the temporary bead 11 is absent, the arc voltage at the point C _f is slightly higher as shown by the solid line 14, but the end 17 after the point C _f approaches the starting end 16 of the temporary bead 11. Until then, the arc voltage at the C _f point decreases as indicated by the broken line 15.

Therefore, the position of the temporary bead 11 can be detected by the change in the arc voltage at the point C _f. Following this detection, the temporary bead 11 is melted, and the back bead 1 is melted as described above.
The shape of 0 must be controlled. Therefore, first, the timing of increasing the welding current is set at a time point when the C _f point almost reaches the starting end 16 of the temporary bead 11, preferably the arc 3
When the center of the arc reaches the starting end 16 (this timing can be obtained from the rotating diameter of the arc 3 and the welding speed), the timing of lowering the welding current is the arc voltage waveform of FIG. Suppose it changes to 14. The amount of increase in the welding current during that period is ACC.
The torch height by the control method increases so that it becomes constant.

Further, the present invention can be carried out without using the conventional backing method. Since the conventional arc sensor is for the purpose of groove tracking control, it is controlled only based on the information on the C _f point.

[0019]

FIG. 8 is a block diagram showing an embodiment of an apparatus for carrying out the keyhole type single-sided welding method of the present invention.

To rotate the arc 3 at the tip of the welding wire 2, an eccentric tip method (Japanese Patent Publication No. 63-39346) is used.
And an eccentric rotation mechanism type (Japanese Patent Laid-Open No. 62-104684), which is shown by the latter eccentric rotation mechanism type.
That is, the upper portion of the welding torch 1 is supported by the self-aligning ball bearing 21, the eccentric rotation mechanism (gear mechanism) 22 is provided in the middle portion through the self-aligning ball bearing (not shown), and the lower end of the welding torch 1 is driven by the motor 23. Is to rotate at high speed so as to make a circular motion. As a result, the tip of the welding wire 2 fed to the center of the welding torch 1 makes a circular motion, and the arc 3 rotates at a high speed. The rotational position of the welding wire 2, that is, the arc 3 (see FIG. 5) is detected by the encoder 24 attached to the motor 23.

The welding power source 25 is connected between the welding torch 1 and one member 4 to be welded. The arc voltage E and the welding current I of the arc 3 are detected by the arc voltage detector 26 and the welding current detector 27, respectively, and input to the CPU 30 via the differential amplifiers 28 and 29, respectively. Reference numerals 31 and 32 are a setter for the arc voltage reference value and a setter for the welding current reference value, respectively. The arc voltage detector 26 and the differential amplifier 28, and the arc from the welding current detector 27 and the differential amplifier 29, respectively. The voltage / welding current waveform signal and the rotational position signal from the encoder 24 are obtained, and the CPU 30 performs the groove tracing control 33 by a known arc sensor and the torch height control 34 by the ACC control. The control circuit and the torch height control circuit for this groove copying are not shown. However, here, in order to detect the change of the arc length at the point C _r , that is, the members to be welded 4, 5
Since it is necessary to control the height of the tip of the welding wire 2 to be constant due to unevenness, waviness, etc., the torch height is controlled to be constant by the ACC control method.

Under such torch height control, when the rotational position signal from the encoder 24 is input to the CPU 30, the arc voltage E and the welding current I are detected according to the rotational position signal, and E _cf The determiner 35 first determines whether the arc voltage E _cf at the point C _f is larger than a predetermined threshold value x. As described above, when the arc 3 approaches the starting end 16 of the temporary bead 11, the arc voltage E _cf at the point C _f.
Will fall. In addition, the arc 3 is the end 17 of the temporary bead 11.
When it deviates further, the arc voltage E _cf at the point C _f returns to the original value.
Therefore, by monitoring the arc voltage E _cf at the point C _f , the presence and position of the temporary bead 11 can be detected when the change occurs. The threshold value x is set as an index of the existence and position of the temporary bead 11, and if E _cf ≧ x, the temporary bead 11 does not exist, so the set value of the welding current setter 32 is set by the welding current controller 36. C without changing
The arc length l _cr at the _r point is controlled to be constant as described later. Further, when E _cf <x, the temporary bead 11 is present, so the set value of the welding current setting device 32 is increased so that the torch height becomes constant until the next E _cf ≧ x again. Changed and also C _r under this increased welding current
The arc length l _cr at the point is controlled to be constant. The timing of raising and lowering the welding current is as described above.

The control of the arc length (1) _cr at the point C _r is performed as follows. That is, the arc voltage / welding current waveform signal is output from the E _cr integrator 37 and the I _cr integrator 38 as shown in FIG.
In the range of the phase angle φ centered on the point C _r as shown in FIG.
_Ecr and the integral value S _Icr of welding current are calculated. Then, the respective average values of the integrated values S _Ecr and S _Icr , that is, E _cr and I _cr are input to the l _cr calculator 39, and l _cr is obtained by solving the following six equations.

Referring to FIG. 9, the arc length l at the point C _{r is} determined by the detected values of E _cr and I _cr , the wire feeding speed V _f , and the wire feeding speed v _f detected by the control circuit 43. _cr can be calculated by the following formula.

E _cr = V _a + V _L (1) V _L = aLI _a −bv _f / I _a (2) V _a = V _o + _X l _cr (3) V _o = cI _cr + d (4) _{X = eI cr + f ... (} 5) v f = gI a + hLI a 2 ... (6) here, V _L: welding wire protrusion voltage drop V _a across: the voltage drop in the arc column L: wire Protrusion length I _a : average value of welding current (average value of welding current detected by ammeter 27) v _f : wire feeding speed X: arc potential gradient a to h: all constant, wire, shield It is determined experimentally depending on the type of gas.

The welding current I _a is changed so that the arc length l _cr obtained from the above six equations becomes equal to the preset reference arc length l _cro in the proper state A.
That is, when l _cr > l _cro , the welding current I _a is decreased until l _cr = l _cro, and when l _cr <l _cro ,
The welding current _Ia is increased until l _cr = l _cro .
For this purpose, a comparator 40 and an l _cro setting device 41 are provided. The output of the comparator 40 is fed back to the CPU 30, and the welding current I _a (36) and the wire feeding speed v
_{The f} (43) and the welding speed v (42) are controlled respectively. Here, when changing the welding current I _a ,
In the equation (6), the wire feeding speed v _f is also changed so that the wire protrusion length L becomes constant, and the current reference value in the ACC torch height control is always constant at the torch height using this I _a. Control it. Further, when the welding current I _a is changed, the welding speed v is also changed so that the welding cross section (S = v _f / v) becomes constant.

[0027]

As described above, according to the present invention, the high-speed rotating arc welding method is applied to the keyhole type single-sided welding for the groove having the intermittent temporary bead, and based on only the information of the arc sensor. The arc length at the rear point C _r of the rotating position of the arc is controlled to be constant, and the position of the temporary bead is detected by the change of the arc voltage at the front point C _f , and the torch height is detected at the position of the temporary bead. By increasing the welding current so as to keep constant, there is an effect that the shape of the back bead can be stably controlled without using any special sensor.

[Brief description of drawings]

FIG. 1 is a sectional side view showing a keyhole type single-sided welding method of the present invention.

FIG. 2 is a plan view of FIG.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a sectional view taken along line BB in FIG.

FIG. 5 is an explanatory diagram showing a rotational position of an arc with respect to a welding advancing direction.

FIG. 6 is an arc voltage waveform diagram showing a relationship between an arc rotation position and an arc voltage due to a change in a groove state.

FIG. 7 is an arc voltage waveform diagram showing a change in arc voltage at point C _f depending on the presence or absence of a temporary bead.

FIG. 8 is a block diagram showing an embodiment of an apparatus for carrying out the method of the present invention.

FIG. 9 is an explanatory diagram used to calculate an arc length.

[Explanation of symbols]

1 Welding torch 2 Welding wire 3 Arc 4 Welded member 5 Welded member 6 Bevel 7 Molten pool 8 Keyhole 9 Weld bead 10 Back bead 11 Temporary bead 23 Motor 24 Encoder 26 Arc voltage detector 27 Welding current detector 28 Differential amplifier 29 Differential amplifier 30 CPU 35 E _cf decision device 36 Welding current controller 37 E _cr integrator 38 I _cr integrator 39 l _cr calculator 40 comparator 41 l _cro setting device

Claims (5)

[Claims] 1. An arc welding method for forming a keyhole directly under an arc and performing one-sided welding of a groove having an intermittent tack bead, wherein a high-speed rotating arc welding method is used, and a torch height is increased by an ACC control method. is to control (wire sum of projection length and arc length) constant, while at the same time performs an included automatic scanning control by arc sensor, the arc length in the rear point C _r of the rotational position of the arc, the arc in the C _r point The temporary current is calculated by calculating the detected value of the voltage and the welding current, controlling the welding current so that the obtained arc length becomes equal to the set value, and detecting the arc voltage at the forward point C _f of the arc rotation position. detecting the position of the biasing bead, wherein increased welding current substantially since that time when the arc voltage drops at C _f point, or when the arc voltage in the C _f point is returned again to the original Lowering the welding current, keyhole type single-sided welding method characterized by increasing the welding current to maintain a constant during the torch height. As wherein detected values of the arc voltage and the welding current in the C _r point when calculating the arc length of the C _r points were integrated and averaged for the C _r predetermined phase angle around the point φ A value is used, The value is used.
Keyhole type single-sided welding method described. 3. The torch height (sum of wire protrusion length and arc length) is constant when controlling the welding current so that the arc length at the point C _r obtained by the calculation becomes equal to the set value. The wire feeding speed is also changed so that the single-sided keyhole welding method according to claim 1 or 2. 4. The welding speed is changed so that the welding cross-section is constant when the welding current is changed so as to be equal to the set value at the point C _r. Keyhole type single-sided welding method described. 5. The keyhole type single-sided welding method according to claim 1, wherein the arc length welding current is increased at a timing when the center of the high-speed rotating arc reaches the starting end of the temporary bead.