JP2002321054A - Device for determination of welding stability of pulsed arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device to accurately and quickly determine the welding stability of a pulsed arc welding, by quantitatively and accurately assessing a phenomenon of welding instability at the time of steady state welding of a consumable electrode pulsed arc welding. SOLUTION: At least one numeric value out of a welding voltage between a welding electrode 2 and a material to be welded 5, a welding current between the electrode 2 and the material 5, and an energization time of a pulse period or a base period is detected by a detecting device 11-13. The degree of distortion of the detected value is computed by a computing device 14. The welding stability at the time of steady state welding of the pulsed arc welding is determined based on the deviance between the computed degree of distortion and the degree of distortion at the time of steady state welding of a normal pulsed arc welding. For example, each pulse cycle of a product of each standard deviation of a pulse current integral value and a base current integral value and the like is computed as the degree of distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for judging the welding stability during steady-state welding of pulse arc welding among consumable electrode type gas shielded arc welding.

2. Description of the Related Art In a consumable electrode type gas shield pulse arc welding method, as shown in a schematic diagram of FIG. 8, a pulse current of a fixed period is applied to a welding wire to form a gap between the welding wire and a portion to be welded. The tip of the welding wire is melted by the heat input of the arc discharge, and the molten portion is squeezed out by the electromagnetic pinch force by the pulse current to release the droplet from the tip of the welding wire and transfer the droplet to the portion to be welded. Things,
In a stable welding state under optimum welding conditions, a droplet transfer form of one pulse → one drop is taken.

In the pulse arc welding method, recently, the progress of the inverter welding power supply has made it possible to carry out high-speed control of the output current and finely control the output voltage, thereby making it possible to shift the droplet from one pulse to one drop. As a result, it has become possible to reduce welding spatter, improve the regular reproducibility of the welding state, and improve the high-speed weldability.

[0003] Incidentally, at the time of steady welding of pulse arc welding, a change in the relative distance between the welding torch and the material to be welded, a rapid change in the groove shape, a change in the wire feeding speed, and the like may occur unexpectedly. Often there. In such a case, a short-circuit phenomenon or the like occurs, the droplet transfer state changes, and the arc length greatly changes, so that the arc phenomenon becomes unstable. And the uniformity and aesthetics of the weld bead cannot be maintained,
It becomes difficult to obtain stable welding quality.

Conventionally, the stability of welding phenomena at the time of steady welding has been determined mainly by visually observing the uniformity, shape and spatter adhesion amount of the weld bead by an operator or a technician. However, since both are qualitative judgments by visual observation, individual differences are inevitable in the judgment of minor abnormalities, and it has been difficult to obtain a uniform standard for in-line judgment.

Further, as a quantitative determination method, for example, Japanese Patent Application Laid-Open No. H11-123547 (first conventional technology) and Japanese Patent Application Laid-Open No. H10-314940 (second conventional technology) have been proposed. The first prior art is a determination method for quantitatively displaying an arc instability phenomenon during steady welding with a welding stability determination index, and the second prior art is a welding current and a welding current output from a welding power source. This is a monitoring method that measures at least one of the voltages and displays a measured value in a stable region excluding an unstable measured value at the time of a pulse rise of a pulse welding power supply.

[0006]

The first prior art is directed to consumable electrode type gas shielded arc welding in which welding is performed while alternately repeating a short circuit and an arc. In this short-circuit arc welding method, as shown in the schematic diagram of FIG. 7, the tip of a consumable electrode (hereinafter, referred to as a welding wire) is melted by the heat input of arc discharge, and the melted portion is electromagnetically pinched by a high current density. The wire is detached from the tip of the welding wire as a droplet and short-circuited to the portion to be welded, and takes the form of “contact transfer” of the droplet due to the short-circuit phenomenon. Therefore, the index of weldability is very effective because it is easy to extract and judge the index because the index with periodicity in the originally non-periodic arc phenomena is used as a measure of welding stability. It can be said that it is a method.

However, when a short circuit phenomenon does not basically occur and a welding waveform inherently includes a periodicity as in pulse arc welding, an index having a periodicity as in the first prior art is used to determine the welding stability. In the method of determining the index as a scale, it is difficult to extract the index itself, and it is difficult to quantitatively determine the stability of the arc phenomenon. There is.

Therefore, although the phenomenon at the time of occurrence of a welding defect is the same in both welding methods, as described above, the droplet transfer mode is completely different, and thus the process leading to the welding defect is also different, and the evaluation of welding stability during steady welding is performed. It turned out that a common judgment index cannot be used because of the following.

Incidentally, even if the method for determining the welding stability at the time of steady welding in the short-circuit arc welding method described in Japanese Patent Application Laid-Open No. 11-23547 is applied to the similar determination in the pulse arc welding method, the periodic It is difficult to quantitatively detect the instantaneous arc unstable phenomenon from the pulse waveform, and accurate determination cannot be made.

On the other hand, in the case of the second prior art, it can be said that it is an effective method for determining welding conditions (welding voltage and welding current) necessary for desired welding quality because only the measured value in the stable region is determined. However, it is difficult to quantitatively determine the instability of the arc phenomenon, and there is a risk of erroneous determination when determining the welding quality of a steady-state weld.

As described above, the method for judging the welding stability at the time of steady welding in the short-circuit arc welding method cannot be used for the same judgment in the pulse arc welding method. This has been a major problem in preventing outflow of poor welding quality caused by an unstable state of the welding phenomenon during steady welding in a welding line.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has a quantitative and accurate understanding of a welding instability phenomenon during steady-state welding in consumable electrode type pulse arc welding. It is an object of the present invention to provide a determination device for accurately and quickly determining quality.

According to a first aspect of the present invention, there is provided an apparatus for determining a welding stability of pulse arc welding, comprising the steps of: applying a welding voltage between a welding electrode and a workpiece; In a consumable electrode type gas shielded pulse arc welding in which a pulse-base current is alternately and repeatedly supplied, and a droplet is dropped from the welding electrode on the material to be welded every pulse, the welding electrode and the welding electrode are welded. Welding voltage between materials,
Detecting means for detecting at least one of a welding current and an energizing time between the welding electrode and the material to be welded; calculating means for calculating a degree of disturbance of a detection value of the detecting means; And judge means for judging the welding stability at the time of steady welding of pulse arc welding from the degree of divergence between the two and the degree of turbulence at the time of steady welding.
According to the above welding stability determination device, the degree of turbulence is calculated by the calculation means based on the detection value from the detection means for determining whether the welding stability is good at the time of steady welding of pulse arc welding, Since the pass / fail is judged by the judging means, an accurate judgment of the welding stability in the steady welding of the pulse arc welding is made.

According to a second aspect of the present invention, there is provided the welding stability determining apparatus for pulse arc welding, wherein the calculating means disturbs a product of each standard deviation of a pulse current integral and a base current integral for each pulse period. It is characterized in that it is calculated as a degree.
In this welding stability determination device, the product of each standard deviation of the pulse current integral value and the base current integral value for each pulse cycle is taken as an index of welding stability during steady welding of pulse arc welding. This index evaluates both the uniformity of the pulse current and the base current and the uniformity of the pulse time and the base time at the same time. This indicates that the droplet transfer phenomenon is stable.

According to a third aspect of the present invention, in the apparatus for determining welding stability of pulse arc welding, the calculating means disturbs a product of each standard deviation between a pulse period energizing time and a base period energizing time for each pulse cycle. It is characterized in that it is calculated as a degree.
According to the welding stability determination device described above, the product of each standard deviation of the pulse period energizing time and the base period energizing time for each pulse cycle is taken as an index of welding stability during steady welding of pulse arc welding. I have. This index evaluates the uniformity of the pulse time and the base time, and the smaller the value of this index, the more stable the droplet transfer phenomenon during steady welding of pulse arc welding as described above. It shows that.

According to a fourth aspect of the present invention, in the pulse arc welding welding stability judging apparatus, the calculating means disturbs the product of the pulse voltage integral and the standard deviation of the base voltage integral for each pulse period. It is characterized in that it is calculated as a degree.
According to the above welding stability determination device, the uniformity of the pulse and the base voltage and the uniformity of the pulse and the base time can be simultaneously evaluated. In particular, the product of this voltage integral standard deviation is
Since the voltage waveform changes greatly with momentary arc interruption, it is effective in determining arc interruption failure, and the arc phenomenon is more stable as the product of each standard deviation of the pulse voltage integral value and the base voltage integral value is lower. It can be said that.

According to a fifth aspect of the present invention, in the apparatus for determining welding stability of pulse arc welding, the arithmetic means includes a pulse current integrated value for each pulse cycle and a standard deviation of a pulse current integrated value for normal welding. The ratio is calculated as the degree of turbulence. According to the welding stability determination device described above, as an index of welding stability at the time of steady welding of pulse arc welding, the ratio of each standard deviation between the pulse current integrated value for each pulse cycle and the pulse current integrated value during normal welding is used. Has been picked up. This index evaluates the degree to which the current dropping state of the droplet is deviated from the optimal dropping state. This indicates that the dropping state of the droplets is good.

According to a sixth aspect of the present invention, in the pulse arc welding welding stability judging apparatus, the calculating means may be configured such that the pulse current integral value obtained by dividing the pulse current integral value for each pulse period by the pulse period energizing time. The ratio of the average value of the normal pulse current integral value obtained by dividing the integral value of the pulse current during normal welding for each pulse period by the pulse period conduction time is calculated as the degree of disturbance. This index evaluates how much the current heat input state to the welding wire deviates from the optimal heat input state, and determines the stability of the arc phenomenon from excess or deficiency of the heat input. is there.

Since the five types of indices described in claims 2 to 6 are important in order to determine the welding stability at the time of steady welding of pulse arc welding as described above, these five indices are used. It is desirable to calculate the values of all the indices and determine whether the welding stability is good by comparing the values with the respective reference values. In some cases, one or two of these five indices are used. An index may be calculated, and the index may be compared with a corresponding reference value to determine whether welding stability is good.

Further, a product obtained by multiplying two or more of the above-mentioned five indices by each other is calculated as a degree of turbulence, and this is compared with the degree of turbulence of the same index during normal welding of normal pulse arc welding.
The welding stability at the time of steady welding of pulse arc welding may be determined from the degree of deviation between the two.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as an embodiment of the present invention,
The case of performing the pulse MIG welding will be described with reference to FIGS. 1 to 7.

FIG. 1 shows a schematic configuration of a consumable electrode type gas shield pulse arc welding apparatus (hereinafter simply referred to as an arc welding apparatus) according to an embodiment of the present invention. In FIG. 1, 1 is a welding power source, 2 is a welding wire, 3 is a feed roller, 4 is a contact tip, 5 is a material to be welded, 6 is a shunt for measuring welding current, 31 is a welding current detection circuit, 32 Is a welding voltage detection circuit. A current / voltage supplied from the welding power source 1 is applied between the welding wire 2 and the workpiece 5. The welding wire 2 is sent out at a predetermined speed by the feed roller 3 and passes through the contact tip 4 to the material 5 to be welded.
It is supplied to. The ground side of the welding power source 1 is connected to the welding current detection circuit 31 via the shunt 6, while being directly connected to the welding voltage detection circuit 32 and the conduction time detection circuit (not shown). .

FIG. 2 is a block diagram showing a basic configuration of the pulse arc welding determination device 10 of the present invention. The welding stability determination device 10 includes a welding current detecting means 11 for a pulse period or a base period, a pulse period or a base period. Period welding voltage detecting means 12, pulse period or base period energizing time detecting means 13,
It has welding stability calculation means 14, welding stability determination means 15, and alarm means 16. And three detecting means 11, 1
The turbulence degree of each detection value is individually calculated by the welding stability calculation means 14 based on the detection values detected from 2, 13 and
The degree of turbulence is compared with the degree of turbulence of the same detection value during normal welding of normal pulse arc welding by the welding stability judging means 15, and based on the divergence between the two, the welding stability during steady welding of pulse arc welding is determined. If the overall deviation is determined to be beyond the reference value and it is determined that there is no welding stability, a warning is issued by the warning means 16.

Next, a pulse arc welding stability determination device 1
The basic circuit of 0 will be described with reference to the block diagram of FIG.
In the figure, 20 is a processing unit (CPU), 21 is a memory (ROM), 22 is a memory (RAM), 23 is an input interface, 24 is an output interface,
Reference numeral 5 denotes a peripheral device such as a keyboard, display, or printer, 26 denotes a controller containing the above elements, 30 denotes an A / D converter (signal conversion means), 31 denotes a welding current detection circuit, 32 denotes a welding voltage detection circuit, and 33 denotes a welding voltage detection circuit. An energization time detection circuit 34 is a drive circuit for driving the alarm unit 16.

The memory (ROM) 21 stores programs (judgment programs) for various processes including a flowchart described later for judging weldability, and while the processing unit (CPU) 20 is activated. The determination program is executed. The memory (RAM) 22 temporarily stores variable data necessary for executing the determination program.

The output signals of the detection circuits 31 to 33 are A /
The respective turbulences related to the welding current, welding voltage, and energization time, which are input to the processing unit (CPU) 20 from the input interface 23 via the D converter 30 and calculated by the processing unit (CPU) 20, are compared with respective reference values. When the value deviates from the reference value, the drive circuit 34 is driven via the output interface 24, and an alarm is issued from the alarm means 16.

Next, a flowchart for determining the weldability will be described with reference to FIGS. FIG. 4 shows a schematic flowchart, and FIGS. 5 and 6 show detailed flowcharts. As described above, the determination program for executing these flowcharts is stored in the memory (ROM) 21 in FIG. As can be seen from FIG. 4, sampling is started by the start of welding (steps 101, 10).
2) Sampling is completed by the end of welding (steps 103 and 104). Thereafter, the pulse-base current integral value standard deviation product, pulse-base time standard deviation product, pulse The base voltage integrated value standard deviation product, the pulse base current integrated value standard deviation ratio, and the pulse base current integrated value average value ratio are sequentially calculated (steps 105 to 109), and these indexes are compared with the same kind index at the time of normal welding. Then, the quality of weldability is determined based on the degree of deviation between the two (step 110), and if the degree of deviation is greater than the reference value, an abnormal signal is output (step 11).
1).

Next, a flow chart from the start of sampling to the calculation of the pulse-base current integral value standard deviation product, the pulse-base time standard deviation product, and the pulse-base voltage integral value standard deviation product will be described with reference to FIG. Referring to FIG. 9 described above, the pulse-base current integrated value standard deviation product = σ (∫IP _(n) dt) × σ (∫IB _(n) dt), the pulse-base time standard deviation product = σT _{P (n)} × σT _{B (n)} , standard deviation product of pulse-base voltage integrated value = σ (∫V _{P (n)} dt) × σ (∫V
_{B (n)} dt). As can be seen from FIG. 5, sampling of the welding current and welding voltage is first started (step 20).
1) It is determined whether energization has been started (step 2)
02) If started, measurement of the welding current and welding voltage during the steady welding period is started (step 203).

After step 203, it is determined whether the welding current is equal to or greater than the pulse determination current Iw1 (see FIG. 9) (step 204). If the conditions are satisfied, the pulse welding current, pulse welding voltage, The measurement of the pulse time is started (Step 205). If the current is equal to or less than the pulse determination current Iw1, measurement of the base welding current, the base welding voltage, and the base time is started (step 20).
8). Next, it is determined whether the welding current is equal to or less than the pulse determination current Iw1 (step 206). When the conditions are satisfied, the measurement of the pulse welding current, the pulse welding voltage, and the pulse time is completed (step 207). It is determined whether the pulse determination current is equal to or greater than Iw1 (step 2).
09) When the conditions are satisfied, the measurement of the base welding current, the base welding voltage, and the base time is completed (Step 210).

Next, it is determined whether or not the time is up (step 211). If the time is up, the pulse current integral, the pulse voltage integral, the pulse time, the base current integral, the base current integral during the steady welding period are determined. The voltage integration value and the base time are calculated (steps 212, 213, 214),
Next, the respective standard deviations of the pulse current integral, the pulse voltage integral and the pulse time, and the standard deviations of the base current integral, the base voltage integral and the base time are calculated (steps 215, 216 and 217). The respective standard deviation products are calculated (steps 218, 219, 22).
0).

FIG. 6 shows the standard deviation ratio (σ (∫
I _{P (n)} dt) / S _σ ) and the pulse current integral average value ratio (Ave (∫I
_{In the} flowchart relating to _{p (n)} dt) / _Save ), sampling of the welding current and welding voltage is first started (step 30).
1) It is determined whether energization has been started (step 30).
2) If started, measurement of the welding current and welding voltage during the steady welding period is started (step 303). Next, it is determined whether or not the welding current is equal to or greater than the pulse determination current Iw1 (step 304). If the conditions are satisfied, measurement of the pulse welding current and the pulse conduction time is started (step 305). Next, it is determined whether the welding current is equal to or less than the pulse determination current Iw1 (step 306). When the conditions are satisfied, the measurement of the pulse welding current and the pulse time is terminated (step 307). Next, it is determined whether or not the time is up (Step 308). If the time is up, the pulse current integral value during the steady welding period is calculated (Step 309), and then the standard deviation and average value of the pulse current integral value are calculated. Calculate (steps 310 and 311), and then, when the pulse current integral standard deviation is welded at an appropriate voltage, the pulse welding current integral standard deviation appropriate value “S _σ : σ (∫I
_{P (n)} dt) "to calculate the pulse current integral standard deviation ratio (step 312). Moreover, the pulse current integral average proper value _{"S ave: Ave (∫I p (} n) dt) " is divided by, for calculating the pulse current integral value average ratio (Step 31
3).

The value of each important characteristic calculated according to the above-described procedure is compared with the respective reference value to determine whether the welding stability is good or not. If it is determined that the welding stability is not good, an alarm is issued as described above. In this case, the operation of the welding line is immediately stopped so that defective welding does not flow in the subsequent process, and the inspection and adjustment of abnormal parts of the welding equipment are performed. Will be restarted.

The embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and various modifications can be made. The product of each standard deviation of the current integral value and the base current integral value, the product of each standard deviation of the pulse period conduction time and the base period conduction time, the product of each standard deviation of the pulse voltage integral value and the base voltage integral value, and the pulse current integral Although five indices of the ratio of the standard deviation to the standard deviation during normal welding and the ratio between the average value of the pulse current integrated value and the same average during normal welding have been exemplified, the present invention is not limited to these five indices. It is also possible to calculate the index as the degree of turbulence. For example, (pulse current integral standard deviation) × (base current integral standard deviation) × (pulse period conduction time standard deviation) × (base period conduction time standard deviation) The degree of disturbance It may be used as the target.

[0032]

As described above, according to the present invention, the welding current in the pulse period and the base period in the steady welding of the pulse arc welding,
Since the welding voltage and the welding time were each detected and the degree of turbulence of these detection values was calculated, and the degree of turbulence was compared with the same kind of index during normal welding to determine the welding stability from the degree of divergence between the two. The quality of welding stability can be accurately determined in real time, and outflow of defective welding products can be prevented. In addition, since the result of a countermeasure in the event of poor welding is immediately known, early countermeasures such as feedback control of a power supply control signal in automatic recovery processing in the event of a welding error can be easily performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a pulse arc welding device incorporating a welding stability determination device of the present invention.

FIG. 2 is a block diagram showing a basic configuration of a welding stability determination device.

FIG. 3 is a block diagram showing a basic circuit of the welding stability determination device.

FIG. 4 is a schematic flowchart of a determination program.

FIG. 5 is a detailed flowchart of a determination program.

FIG. 6 is a detailed flowchart of a determination program.

FIG. 7 is a schematic diagram showing a known droplet transfer mode in a short-circuit arc welding method.

FIG. 8 is a schematic view showing a known droplet transfer mode in the pulse arc welding method.

FIG. 9 is a schematic diagram showing a relationship between transfer of a pulsed arc droplet and welding voltage / current.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 welding power source 2 welding electrode (welding wire) 5 material to be welded 11 welding current detecting means 12 welding voltage detecting means 13 conduction time detecting means 14 welding stability calculating means 15 welding stability determining means 30 A / D converter (signal converting means) )

Claims (6)

[Claims] 1. A pulse-base current is alternately and repeatedly supplied by applying a welding voltage between a welding electrode and a workpiece.
In a consumable electrode type gas shield pulse arc welding in which a droplet is dropped from a welding electrode onto a material to be welded every pulse, a welding voltage between the welding electrode and the material to be welded, a welding voltage between the welding electrode and the material to be welded, Detecting means for detecting at least one of a welding current and an energizing time between welding materials; calculating means for calculating a degree of turbulence of a detection value of the detecting means; Determining means for determining welding stability during steady-state welding of pulse arc welding based on a degree of deviation between the two and a degree of turbulence, the welding stability determining apparatus for pulse arc welding. 2. The pulse arc welding according to claim 1, wherein the calculating means calculates a product of a standard deviation of a pulse current integral value and a base current integral value for each pulse period as a degree of turbulence. Stability determination device. 3. The welding of pulse arc welding according to claim 1, wherein said calculating means calculates a product of each standard deviation between a pulse period energizing time and a base period energizing time for each pulse cycle as a degree of turbulence. Stability determination device. 4. The welding of pulse arc welding according to claim 1, wherein said calculating means calculates a product of a standard deviation of a pulse voltage integral value and a base voltage integral value for each pulse period as a degree of turbulence. Stability determination device. 5. The apparatus according to claim 1, wherein said calculating means calculates a ratio of a standard deviation between a pulse current integral value for each pulse period and a pulse current integral value during normal welding as a degree of turbulence.
A welding stability determination device for pulse arc welding according to the above. 6. The pulse current integration value obtained by dividing the pulse current integration value for each pulse period by the pulse period conduction time, and the pulse current integration value during normal welding for each pulse period. The welding stability determination apparatus for pulse arc welding according to claim 1, wherein the ratio of the average value of the integral values of the normal pulse currents divided by (1) is calculated as the degree of turbulence.