JPS598473B2 - Consumable electrode type arc welding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a consumable electrode type arc welding machine that performs welding by welding a welded part by welding the welded part with a gas mainly composed of an inert gas.

Electricity is supplied between the electrode wire and the base metal in a gas atmosphere mainly composed of an inert gas such as argon gas to generate an arc, and the arc heat melts the electrode wire and base metal to perform welding. The consumable electrode arc welding method (hereinafter referred to as
It's called MIG welding. ) is used for welding aluminum, stainless steel, etc. Generally, in this MIG welding, the electrode wire is fed at a constant speed, and a constant voltage characteristic type is used as the welding power source, and the welding current is automatically changed by the self-control action of the welding power source. A method is used that balances the melt consumption rate at different times.
Figure 1 shows a diameter of 1 mm in MIG welding of aluminum.
Approximately constant wire feeding speed Vf1 = 480, Vf2 = 640, Vf3 = 7 with preset electrode wire of 6 [ml]
Welding current Δ (horizontal axis) and arc voltage (vertical axis) when feeding at a constant speed of 90, Vf4 = 1000Cc1rL/mm and changing the arc voltage by changing the output voltage of the welding power source. This is a characteristic curve showing the relationship between

In the same figure, the wire feeding speed is set to Vf4=100, for example.
0C/mm], and gradually lower the output voltage of the welding power source from a high value to a low value to lower the arc voltage. On the dotted curve so far, even if the arc voltage value decreases, the welding current value remains at a substantially constant value of about 320. Further, when the output voltage of the welding power source is lowered, as shown by the solid line from point 4 on curve Vf4 to point 4e below, a so-called positive characteristic occurs in which the welding current value also decreases as the arc voltage value decreases. In such a positive characteristic region, that is, on the solid curve from point 4 to point 41, for example, if the arc length becomes shorter and the arc voltage decreases from point 4 to point 41, the welding current required at this time will decrease. The value also decreases from point 4 to point 41. In other words, the arc characteristics in this positive characteristic region are such that the welding current value decreases as the arc length shortens and the arc voltage decreases, but the welding current value is set by a welding power source with constant current characteristics. If the arc length can be maintained at a constant value, as the arc length becomes shorter, the wire melting rate will increase even though the wire feeding speed is constant, and the arc length will increase and return to its original value. It has a self-regulating effect. Self Fhl of this arc length
The cause of the m effect is as described in the 34th issue of ``Arc Phenomenon'' published by Takko Sangyo Tosho Co., Ltd. on July 7, 1960.
Various theories are explained in the sections 8, 5, 8, self-controlling action of arc length and 8, 5, 9, inherent self-controlling action of arc length on pages 3 to 349, but none have been established. When the arc voltage is further reduced, as shown by the dotted line below point 41 on the curve Vf4, at arc voltage values below 20 CV, the welding current value increases as the arc voltage value decreases, a so-called negative characteristic. becomes. These arc characteristics remain almost the same even when the wire feeding speed is reduced from Vf4 to Vfl, and also for electrode wires made of other materials such as iron, stainless steel, and copper. Next, the relationship between the arc characteristics and the welding power source characteristics shown by the curves Vfl to F4 will be discussed.

In MIG welding using a conventional constant voltage characteristic type welding power source, the output characteristics of the welding power source (hereinafter referred to as power source characteristics) are as shown by the straight line P in Figure 1, even if the welding current value changes, the output characteristics In so-called welding, the voltage value is almost constant, and even if the wire feeding speed or arc length changes, the welding current value changes greatly, and the arc length is maintained approximately constant by changing the wire welding speed. There is a self-control effect of the power supply, and the arc voltage is also kept at a constant value approximately equal to this output voltage. Therefore, as shown by the broken line in Figure 1, even in the high arc voltage range and the low arc voltage range, the arc is not stable because the arc characteristic curve Vf and the straight line P of the power supply characteristics are not parallel. The welding conditions can be easily adjusted while observing the arc condition. However, when using a constant voltage characteristic type welding power source in this way, the range indicated by the solid line in which good welding results can be obtained is due to the large change in welding current value even if the arc voltage value changes slightly.
The penetration depth of the base material also varies, making it impossible to obtain a uniform penetration depth of the base material. Furthermore, when using a constant voltage characteristic type welding power source, the short-circuit current is large, which increases the occurrence of spatter, especially large spatter, and the molten metal vibrates greatly, making it difficult to weld, especially when welding horizontally. It was difficult to perform welding or vertical welding. on the other hand,
If a welding power source with constant current characteristics is used, for example one with external characteristics such that the welding current value remains approximately constant even if the output voltage value changes, as shown by the straight line Q in Figure 1, constant voltage characteristics type welding will occur. Unlike a power source, a welding power source does not have a self-control function, but the arc can be stably maintained by the arc's self-control function as described above. In the case of a welding power source with constant current characteristics, there is almost no fluctuation in the welding current value, so the short circuit current is not so large, so the above-mentioned drawbacks when using a welding power source with constant voltage characteristics are eliminated. However, this method of welding using a welding power source with constant current characteristics has the following drawbacks because the arc length is maintained at a substantially constant value only by the self-control action of the arc. For example, if the wire feeding speed is too small for the set welding current value and exceeds the positive characteristic region, the dotted line above the arc characteristic curve Vf no longer intersects with the straight line Q of the power supply characteristic. The self-control effect of the arc is lost, the arc voltage becomes unstable and becomes too high, and the so-called parts pack phenomenon occurs, in which the electrode wire is welded to the contact tube. Conversely, even if the wire feeding speed is too high for the set welding current value and falls into the negative characteristic region of the dotted line below the arc characteristic curve f, the self-control action of the arc disappears. In other words, the arc characteristics in this negative characteristic region are such that as the arc length becomes shorter and the arc voltage decreases, the welding current value increases. Since it is maintained at a constant value, as the arc length becomes shorter, the wire melting rate decreases even though the wire feeding speed is constant, and the arc length becomes shorter and shorter, causing the wire to protrude into the base metal. As a result, the arc cannot be maintained stably. In this way, when using a constant current characteristic type welding power source, the arc is maintained at a preset approximately constant welding current value in order to maintain the stability of the arc only by the self-control action of the arc. The range of arc voltage in which the arc voltage can be stably maintained is limited only to the positive characteristic region, that is, the solid line portion of each curve in FIG.

For this reason, if you first set the appropriate welding current value determined by the type of base material, the range of wire feed speed suitable for that welding current value will be narrow, so set the wire feed speed carefully. The disadvantage is that it is difficult to find an appropriate value. Conversely, if you first set the appropriate arc voltage value determined by the type of base material, the range of welding current values suitable for that wire feed speed will be narrow, so you need to carefully set the welding current value. The disadvantage is that it is difficult to find an appropriate value. In other words, although workability is good and good welding results can be obtained if welding conditions such as welding current and wire feed speed are set to appropriate values, as mentioned above,
Since the appropriate range for both is narrow, it is difficult to set the welding conditions to appropriate values. It is an object of the present invention to enable one of the welding current and wire feed speed to be set to an appropriate value according to the base material, and the other to be automatically and centrally set to the appropriate welding conditions. An object of the present invention is to provide a consumable electrode type arc welding machine.

The present invention will be explained in detail below with reference to the illustrated embodiments.

Figure 2 shows welding current value (horizontal axis) and wire feed speed (vertical axis)
This is a diagram showing the relationship between the welding current value and the appropriate wire feeding speed for that current value, which is created by reading from the arc current-voltage characteristic diagram in Figure 1 the welding current value that provides the arc's self-destruction action, and the appropriate wire feeding speed for that current value. This is what I did.

The order in which straight lines R and S in FIGS. 1 and 2 are created will be explained below.

Wire feeding speed 1000 cCTn/Mm] and welding current value 32 at point 4h above curve Vf4 in FIG.
0CA) are taken as the vertical and horizontal axes of FIG. 2, parallel lines are drawn on each axis, and the intersection point is 4hr.

Similarly, the wire feeding speed at point 3h on curve F3 in Fig. 1 is 790 [CTL/Mm] and the welding current value is 250CA1.
From this, a point 3hr on FIG. 2 is obtained, and the wire feeding speed at point 2h on the curve F2 of FIG.
L/Mm] and the welding current value 200, point 2 is drawn on Fig. 2.
hr is obtained, and the wire feeding speed at point 1h on curve f1 in FIG. 1 is 480 [C! FL/Mvt] and the welding current value 150CX1, a point 1hr on FIG. 2 is obtained. Points 4hr, 3hr, 2hr obtained in this way
By connecting 1hr and 1hr, a substantially straight line R is obtained. Next, the first
Wire feeding speed 1000Ccm/Mm] and welding current value 260CA at the lower point 41 on curve F4 in the figure! 1, a point 41s on FIG. 2 is obtained, and the wire feeding speed of the curve Vf3 is 790 [C! RL/Mm] and welding current value 220
(Point 31s is obtained from Al, and the wire feeding speed of curve F2 is 640 CCW/Mm)] and point 21s on FIG. 2 is obtained from the welding current value of 180 CCWVmi! A point 11s on FIG. 2 can be obtained from the welding current value 130 (Al) and the welding current value 130 (Al).

By connecting the points 41s, 3'S, 2ls, and 11s obtained in this manner, a substantially straight line S is obtained. The line connecting these points can be approximated by a straight line for both R and S, and especially in the case of an electrode wire with a low resistance value such as aluminum, it can be regarded as an almost perfect straight line passing through the origin. In the same figure, below the straight line R, the arc length becomes too long, causing parts packs; conversely, above the straight line S, the arc length becomes too short, causing a short circuit;
The shaded area between and S has a self-control effect on the arc, which maintains the arc stably even when welding is performed by feeding the electrode wire at a constant speed using a constant current type welding power source. This is within the range that can be achieved. Therefore, if the welding current value is set to an appropriate value according to the base material, the wire feeding speed will automatically change to the appropriate value determined from the previously set welding current value, as shown by the shaded area in Figure 2. If unified control is performed so that the following conditions are achieved, it becomes extremely easy to set two or more welding conditions within appropriate ranges. The present invention is based on the results of the above studies, and FIG. 3 shows the basic configuration of the welding machine of the present invention.

In the figure, PS is a welding power supply unit with drooping characteristics, and this power supply unit includes an input terminal 1 and a welding power source control unit 2 that controls the input from the input terminal 1 to have drooping characteristics using a thyristor or magnetic amplifier. ing. The output controlled by this control section is output as welding current 1 from output terminal 3,
This welding current value is detected by a welding current detector 4.
Further, the welding power supply section PS includes a comparator 5 and an amplifier 6 that amplifies the output of the comparator 5 and applies it to the welding power supply control section 2. Output is supplied. Reference numeral 7 denotes a first output regulator connected to a setting voltage source a for setting the first output of the welding machine, and its output signal A is given to the other input terminal of the comparator 5.

Therefore, the comparator 5 compares the input signal A and the detected value of the welding current, and applies the difference between the two to the welding power source controller 2 via the amplifier 6. As a result, the welding current 1 is feedback-controlled, and the input signal A of the welding power source PS and the welding current 1 have a substantially linear relationship, and the following equation holds true. g here
and G are constants that define the relationship between input signal A and welding current 1.

8 is a second output regulator connected to the setting voltage source b;
This output regulator is mechanically interlocked with the first output regulator 7, and its output signal B is supplied to one input terminal of the comparator 9 of the welding wire feeder WF.

A wire feeding electric motor 10 is connected to the other input terminal of the comparison section 9.
The induced voltage of B, that is, a signal proportional to the wire feeding speed is inputted, and the difference between signal B and the signal proportional to this wire feeding speed is inputted to the feeding speed leg part 12 via the amplifier 11. The wire feeding electric motor 10 is controlled by the output of the feeding speed control section.
is driven. Therefore, the wire feeding speed f is subjected to feedback control, and a linear relationship as shown in equation (2) is established between the input signal B and the wire feeding speed f. Here, h and H are constants that determine the relationship between the input signal B and the wire feeding speed f.

As shown in Fig. 2, in MIG welding where the electrode wire is fed at a set approximately constant speed, there is an approximation between the welding current value 1 and the wire feeding speed f within the range of practical welding conditions. Generally speaking, a linear relationship as shown in equation (3) is established.

Here, K and K are constants determined by conditions such as the material and diameter of the electrode wire, and the composition of the insulating gas.

In particular, in the case of an electrode wire having a low resistance value such as aluminum, the relationship of equation (3) holds well, and the constant K has a value close to zero. Therefore, when the relationship between the setting signals A and B of the welding power source PS and the wire feeder WF is determined using equations 1), (2), and (3), KglB+--A+-
(KG+K-H) (4) Hh holds true.

here, If you put holds true.

In other words, if we obtain signal B proportional to signal A so as to satisfy equation (6), welding current value and wire feed speed under appropriate conditions can be obtained by adjusting only either signal A or B. is obtained.

In each of the above embodiments, if the amplification degrees of the amplification devices 6 and 11 of the welding power supply unit PS and wire feeder WF are appropriately increased, G+O and H
==O, and as mentioned above, with aluminum wire, the value of K in equation (3) can be made approximately zero.

Therefore, in this case, it becomes β+0 from equation (5), and (
6) Equation can be expressed as: The embodiment shown in FIG. 3 above is an embodiment in which β can be regarded as 0, and in the same figure, the first and second output regulators 7 and 8 are connected to two sets of potentiometers. If it is a yometer and its rotation rate is γ, then A=γVa and B=γVb.

Therefore, B=(Vb/a)A, and by selecting appropriate voltage values for A and b (if α in equation 5 is satisfied, the signal A can be adjusted by the first output regulator 7. An appropriate wire feeding speed can be obtained by simply adjusting the wire feed speed.Next, Figures 4 and 5 show examples of general cases in which β==o cannot be set. In the embodiment, potentiometers R are used as the first and second output regulators.
Two sets of potentiometers consisting of a and Rb are used.

In FIG. 4, if the rotation rate of the potentiometer is γ, then Va, where b/a=α, equation (6) can be satisfied by appropriately selecting Vb and Va so that b/a=α.

Therefore, by adjusting the rotation rate γ of the output regulator, the desired welding current can be obtained, and the distance (arc length) between the electrode wire tip and the base metal that is suitable for this welding current value can be automatically determined. You will be able to obtain Further, FIG. 5 shows the voltage V.

The voltage Vb is obtained by dividing the voltage, and resistors R1 and R2 are connected in series with the potentiometer Rb. In this case, the voltage Vb applied across the potentiometer Rb is as follows.

Also, from the formula 00) to (self), becomes.

Therefore α=Rb/(R1+Rb+R2), β=R2
Equation (6) can be satisfied by selecting each resistance value so that VO/(R1+Rb+R2). Since the constants α and β in equation (6) vary depending on the material, diameter, etc. of the electrode wire, one or both of them may be switched using a changeover switch to obtain a value suitable for each electrode wire. . For example, by switching the voltage value of Va or Vb in FIG. 4 or the resistance value of Rb in FIG. 5 using a changeover switch, the constant α can be changed, and the voltage value of B in FIG. R2 or voltage V. By switching the constant B using a changeover switch, the constant B can be changed. Also,
If either Va or Vb in Fig. 4 is made adjustable, α can be finely adjusted.Similarly, in Fig. 5, if R1 is made adjustable, α can be finely adjusted. can.

In this way, the welding conditions can be set at any part within the shaded area in FIG. 2, making it easier to set the optimum welding conditions.
Similarly, the value of β in FIG. 4, or the value of R2 in FIG. β may be adjusted by making the value of β adjustable. In addition, as shown in FIG. 2, in the case of melting characteristics that almost pass through the origin, fine adjustment of the welding conditions can be easily performed if α can be finely adjusted. In the above embodiment, the welding power source and the wire feeding device are controlled by feedback, but a nearly proportional relationship can be obtained between the setting signal and the welding current and between the setting signal and the wire feeding speed. Any welding power source and wire feeding device may be used.

In the above embodiment, the wire feeding device is electrically driven using a set voltage source, but pneumatic pressure or oil pressure can also be used as a driving source. In this case, a flow rate regulating valve is used as an output regulator. A hydraulic motor or an air motor may be used as the motor.

Further, in the above embodiments, a slider or a movable core transformer may be used as the output regulator, and each regulator may be interlocked with gears or a belt.

It is preferable that the welding power source used in the present invention has perfect constant current characteristics, but it may also have drooping characteristics, and generally any power source that has a voltage drop of 10 or more per 100 A is sufficient.

As described above, according to the present invention, an electrode wire is fed at a constant speed within a range where the voltage-current characteristics of the arc are in the positive characteristic region using a drooping characteristic type or constant current characteristic type welding power source. In the consumable electrode type arc welding method, the welding conditions can be set extremely easily, which eliminates the drawbacks such as poor bead shape and large amount of spatter that occur when using a constant voltage welding power source. This eliminates the hassle of adjusting the welding current and wire feeding speed separately, and even beginners can easily obtain good welding results.

Furthermore, since there is no need for trial welding to match the appropriate welding conditions, it is possible to reduce the waste of welding materials such as electrode wire and shielding gas, and to reduce dead time, resulting in improved welding quality, efficiency, and cost savings. Many effects can be obtained.

[Brief explanation of the drawings] Figure 1 is a welding current/arc voltage characteristic curve diagram when the electrode wire is fed at a constant speed. Figure 2 is a diagram showing the relationship between welding current and wire feeding speed. FIG. 3 is a block diagram showing an embodiment of the present invention, and FIGS. 4 and 5 are electrical connection diagrams showing main parts of a specific example of an output regulator.

Claims (1)

[Claims] 1. In a consumable electrode type arc welding machine that performs welding while feeding an electrode wire at a constant speed to a welding part, a first output regulator that outputs a signal A for setting a welding current, and the first output a signal B that is mechanically interlocked with the regulator and has a linear function relationship with the output signal A of the first output regulator;
a second output regulator that outputs a welding current approximately proportional to the signal A; a welding power source that receives the signal A and outputs a welding current that is approximately proportional to the signal A; A consumable electrode type arc welding machine equipped with a wire feeding device that feeds an electrode wire at a substantially proportional constant speed.