JPH11123547A - Method for judging stability of welding at stational part of arc welding and device for judging stability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the flowing of welded defective developed caused by the unstability of arc discharging state, in the state welding part of a consumable electrode type gas shielded arc welding. SOLUTION: This device transmits analog signals by detecting the welding current and the welding voltage with detecting means 7, 8. Even analog signal is made to a digital signal by sampling with an A/D converter 9. Based on these digital signals, one or more items among four items of welding current integral value standard deviation during arc in each one period, welding current integral value standard deviation during short circuit in one period, arc/short circuit time ratio standard deviation in each one period and short circuit frequency with a CPU 10 are calculated. When the difference between the calculated value of any item and the corresponding reference value exceeds the permissible range, it is judged that the welding is unstable or defective and the result is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to consumable electrode type gas shielded arc welding, in which a steady welding portion is welded for preventing outflow of poor welding quality caused by instability of a welding phenomenon in the steady welding portion. The present invention relates to a stability determination method and a determination device.

[0002]

2. Description of the Related Art In consumable electrode type gas shielded arc welding, the output control of a welding power source is changed from a thyristor type to an inverter type due to the progress of control elements, and the control speed is 30%.
The speed is increased about 50 to 200 times from 0 Hz to 15 to 60 kHz, and the waveform of the welding current can be controlled, improving the arc start performance, improving the stability of the welding state in high-speed welding, and reducing the amount of spatter generated. And the stability of the welding phenomenon is being improved.

[0003] However, the welding quality of the steady-state welding portion is liable to cause various abnormal phenomena because the welding condition is constantly changing due to processing distortion or thermal distortion, etc., which is a major problem of an automatic welding line by a welding robot or the like. Had become.

[0004] Generally, a worker or a technician visually checks the uniformity of the appearance of a weld bead to determine whether or not the stability of the welding state of the steady weld portion is good. However, in the qualitative judgment by visual observation, there is an individual difference in the judgment in the case of a minute abnormality, and it is difficult to obtain a unified standard for the judgment in-line.

[0005] There is also a method of measuring the welding phenomena of the steady welding portion by measuring the welding current and voltage with a measuring device, but it takes time for analysis, and it is difficult to make a determination in real time. Furthermore, these data are not necessarily quantitative data, and it has been difficult to evaluate the stability of welding phenomena in steady-state welds.

[0006] For example, Japanese Patent Publication No. 2-62017 (hereinafter referred to as the first prior art) discloses that a short circuit period and an arc period are determined by measuring a welding voltage, and a welding current and a welding current in each period are determined. A technique is disclosed in which the observation result of the voltage waveform is calculated by a predetermined function, and the quality of the weldability is determined based on the degree of uniformity of the welding state, the degree of arc breakage, and the degree of burning of the arc.

In Japanese Patent Publication No. 7-2275 (hereinafter referred to as a second prior art), a moving average of each is calculated by using a monitoring section setting means for a welding current and a welding voltage.
A technique for determining a welding situation and a welding result is disclosed.

[0008]

However, in the case of the first prior art, since a measurement section is not set, erroneous determination may be caused if data is determined from immediately after an arc start to a steady portion. There is a disadvantage that there is.
This is because the welding phenomenon immediately after the arc start is unstable and is not directly involved in welding in a steady portion.
The average current (I) during the arc period is determined by the degree of arc break.
The average resistance (R = V / I) according to the voltage (V) is used.
XV), the average current during the arc period is liable to change depending on the arc time. If the average current is used to determine the degree of arc breakage and the degree of arc burn-up, an erroneous determination is caused. It has the drawback of being afraid.

In the case of the second prior art, it is necessary to accurately evaluate fluctuations in arc time and short-circuit time (long-term arc, instantaneous arc, long-term short-circuit, instantaneous short-circuit phenomenon, etc.), that is, the degree of stability of the welding phenomenon. It has the drawbacks to say.

As described above, the conventional determination of the stability of the welding phenomena in a steady welding portion is qualitative, requires a long time for analysis, and requires a long time in an automatic welding line and a semi-automatic welding line by an arc welding robot or the like. This is still a major problem in preventing outflow of poor welding quality caused by instability of the welding phenomenon at the welded portion.

At present, there is no method for real time and quantitatively monitoring the stability of the welding phenomena of the steady welding portion in real time, and there is no method for monitoring all the steady welding portions. These countermeasures have been taken after replacing a wire conduit cable, replacing a contact tip, or an abnormal welding quality.

The present invention has been made in view of the above-mentioned problems of the prior art, and accurately captures the welding phenomena of a steady welding portion.
It is an object of the present invention to provide a method and an apparatus for quickly determining the stability of a welding state.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to claim 1 is to provide a consumable electrode type gas shielded arc welding in which welding is performed while alternately repeating a short circuit and an arc. A determination method, comprising: voltage detection means for detecting a welding voltage between a welding electrode (hereinafter referred to as a welding wire) and a workpiece; and current detection means for detecting a welding current flowing between the welding wire and the workpiece. Is converted into a digital signal at a predetermined sampling frequency, and the degree of stability of the steady welding portion is determined by the following four items (a) to (d), Standard deviation σ (∫I _An dt) of the welding current integral value during the period (b) Standard deviation σ (∫I _Sn dt) of the welding current integral value during the short circuit period every cycle (c) Arc / short circuit every cycle Standard deviation of the time ratio σ ( _An / T _Sn) (d) calculating a least inner any one or two items of shorting frequency f _S, as compared to the reference values corresponding to the difference between any one even reference value preset This is a method for determining welding stability in a steady part of arc welding, characterized in that it is determined that welding is unstable or defective when exceeding an allowable range.

According to a second aspect of the present invention, there is provided the method for determining the stability of a steady part of arc welding according to the first aspect, wherein a section for monitoring arc welding is set, and the section is arbitrarily divided according to the welding time. It is characterized by doing.

A third aspect of the present invention is an apparatus for determining the stability of arc welding stability in a consumable electrode type gas shielded arc welding in which welding is performed while alternately repeating a short circuit and an arc. Voltage detecting means for detecting a welding voltage between the two, current detecting means for detecting a welding current flowing between a welding wire and a workpiece, an A / D converter for converting an analog output signal from both means into a digital signal, Based on the digital signal from the converter, (a) the standard deviation of the welding current integral during the arc period every cycle σ (∫I _An dt) (b) the standard deviation of the welding current integral during the short circuit period every cycle Deviation σ (∫I _Sn dt) (c) Standard deviation of arc / short circuit time ratio for each cycle σ (T _An / T _Sn ) (d) Short circuit frequency f _S Any one or more of four items Computing means for computing A comparator for comparing the calculation result from the calculating means with a preset reference value to determine whether the difference from the reference value is within an allowable range, and a display for displaying the output of the comparator. This is a device for judging the welding stability of the steady part of arc welding, which is a feature.

According to a fourth aspect of the present invention, there is provided the apparatus for judging the stability of an arc welding steady portion according to the third aspect, wherein a section for monitoring the arc welding is set, and the section is arbitrarily divided according to the welding time. Means are provided.

[0017]

The degree of stability of the welding phenomena caused by the unstable formation of the arc discharge in the steady welding portion is determined by the standard deviation of the arc period welding current integral value and the short-circuit period welding current integral value for each cycle. And the standard deviation of the arc / short time ratio per cycle, and the short circuit frequency of 4
Arbitrary one or two or more of the items are calculated and displayed as quantitative values, and compared with the corresponding reference values,
It is determined that the welding phenomenon is unstable when the difference between any one of the quantitative values and the reference value exceeds a predetermined allowable range. By doing so, abnormal welding quality due to welding phenomenon instability due to poor power supply to the welding wire, increased feed resistance, and fluctuations in wire extension can be accurately and reliably detected.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention. Reference numeral 1 in the figure denotes a welding power source that applies a predetermined current and voltage between the welding wire 2 and the workpiece 5.
The welding wire 2 is fed at a predetermined speed by a feed roller 3 to weld the workpiece 5. 4 is a contact tip, 6 is a shunt for measuring a welding current, 7 is a current detection circuit for detecting a welding current flowing through a welding wire and a workpiece, and 8 is a welding voltage between the welding wire and the workpiece. 9 is an A / D converter for converting each analog output signal from both detection circuits 7 and 8 into a digital signal at a predetermined sampling frequency, and 17 is an arithmetic and output device for both detection circuits 7, 8 and A / D converter 9 is included.

This device 17 measures and converts the welding voltage and welding current into digital values, and converts the standard deviation of the welding current integral value of the arc period and the standard deviation of the welding current integral value of the short-circuit period for each cycle.
In addition, various calculations are performed to calculate the standard deviation of the arc / short-circuit time ratio for each cycle, the short-circuit frequency and the average value, and the calculation results are compared with a preset reference value. CPU1 for comparing whether the difference is within an allowable range
0, CRT 11 for displaying and printing their operation data
(Display) and a printer 15, a memory (ROM 1) for storing programs and various data necessary for arithmetic operations.
2, RAM 13) and a keyboard 14 for inputting constants and other data necessary for measurement, and a display 16 for displaying an abnormal signal such as an abnormal welding current integrated value, an abnormal arc / short-circuit time ratio, or an abnormal short-circuit frequency. You.

Next, the method for determining the stability of welding phenomena in a steady-state weld according to the present invention will be described. First, FIG. 2 shows a schematic processing flow of executing a welding phenomenon analysis of a steady welding portion. First, a sampling speed, a trigger level, and an arc / short circuit determination voltage are input from the keyboard 14 and set in the CPU 10 to start welding. In this embodiment, the setting of the sampling speed is set to 27 KHz which is higher than the control speed of the welding power supply 1 so that the control waveform of the welding power supply 1 can be determined in this embodiment, but the setting can be changed.

When the welding voltage reaches the trigger level, the input of the welding voltage and current is started, and the data of the welding voltage and current at each sampling point is converted to R until the number of measurements reaches the set number.
Store it in AM13. When a predetermined number of samplings are completed, various calculations are performed by executing a program stored in the ROM 12.

Here, for various calculations, the setting of the calculation section can be input from the keyboard 14 in order to prevent erroneous determination of the calculation data. That is, the welding phenomenon unstable region at the time of arc start can be excluded from the calculation section.

When the calculation is completed, the various calculation results are compared with the corresponding reference values, and when any one of the results exceeds the predetermined allowable range, the welding phenomenon becomes unstable. It is considered that there are abnormal welding current integrated values, arc /
An abnormal signal such as an abnormal short-circuit time ratio or an abnormal short-circuit frequency is output to judge an abnormal welding quality such as a humping bead, undercut, burn-through, or insufficient bead length. When the arc discharge is formed stably, an OK signal is output.

Next, the calculation of the arc period welding current integral value in subroutine 1 in FIG. 2 will be described. FIG. 3 shows the details of the subroutine for performing the arc period welding current integral standard deviation calculation processing. Calculation of arc period welding current integral value standard deviation, after T ₁ times timeout of the steady welding measurement start time, a welding current flowing between the welding wire and material to be welded up to the set time T ₂ of the steady welding measurement end time The welding voltage is sampled, and the measurement of the welding current is started from the time when the welding voltage V (n) in the n-th cycle has reached the arc / short circuit judgment voltage Va or more, and the welding current during the arc period from the time when the voltage has dropped to Va or less. The integrated value is calculated, and then the standard deviation of the integrated value is calculated. The judgment voltage Va and T ₁ , T ₂
The time setting can be changed arbitrarily.

As shown in FIG. 6, the arc period welding current integral value represents the arc period welding current waveform for each cycle and the area ∫I _An dt surrounded by the arc time, and its standard deviation σ (∫I _Sn dt) simultaneously represents variations in welding current and arc time during the arc period.

The fact that the standard deviation of the welding current integral becomes large means that the droplet transfer phenomenon is unstable due to the occurrence of an instantaneous arc in which a short circuit phenomenon almost continues or a long-term arc phenomenon that does not lead to a short circuit. The lower the standard deviation, the more stable the droplet transfer phenomenon.

Here, in order to reduce the change of the standard deviation due to sampling noise and chattering, an arc phenomenon within 1 msec is calculated as a short circuit time. This arc period welding current integral standard deviation is compared with a reference value, and when the difference from the reference value exceeds a predetermined allowable range, an abnormal signal is output as an arc period welding current integral value abnormality.

Next, the calculation of the short-circuit period welding current integral value in subroutine 2 in FIG. 2 will be described. FIG. 4 shows the details of the subroutine for performing the welding current integral standard deviation calculation processing during the short-circuit period. The operation of the short circuit period welding current integral value standard deviation, flows from time T ₁ after the time-up is a steady welding measurement start time, between the welding wire and material to be welded set up time T ₂ is a steady welding measurement end time welding The current and the welding voltage are sampled, and the measurement of the welding current is started from the time when the welding voltage V (n) in the n-th cycle has reached the arc / short circuit determination voltage Va or less, and the short-circuit period from the time when the welding voltage V (n) has risen to Va or more The integrated value of the welding current is calculated, and then the standard deviation of the integrated value is calculated. The setting of the judgment voltage Va and the times T ₁ and T ₂ can be arbitrarily changed.

The short-circuit time welding current integral value represents the welding current waveform of the short-circuit period for each cycle and the area ΔI _Sn dt surrounded by the short-circuit time as shown in FIG. _Sn dt) simultaneously represents the welding current during the short circuit period and the variation in the short circuit time.

The fact that this standard deviation becomes large means that
The short-circuit phenomenon is unstable due to the occurrence of an instantaneous short-circuit or a short-circuit phenomenon where the droplet transfer hardly occurs, and the short-circuit phenomenon is not released.The lower the standard deviation, the more stable the short-circuit phenomenon and the periodic transfer of the droplet Indicates what is happening.

Here, in order to reduce the change of the standard deviation due to sampling noise and chattering, a short circuit phenomenon within 1 msec is calculated as an arc time. This short-circuit period welding current integral standard deviation is compared with a reference value, and when the difference from the reference value exceeds a preset allowable range, an abnormal signal is output as a short-circuit period welding current standard deviation abnormality.

Next, the calculation of the standard deviation of the arc / short circuit time ratio in subroutine 3 in FIG. 2 will be described. FIG. 5 shows the details of the subroutine for performing the standard deviation calculation processing of the arc / short circuit time ratio. The calculation of the standard deviation of the arc / short-circuit time ratio is performed after a time-up time of T ₁ , and a set time T _2.
The welding current and the welding voltage flowing between the welding wire and the material to be welded are sampled, and the arc time T _An is measured from the time when the welding voltage V (n) in the n-th cycle reaches the arc / short circuit judgment voltage Va or more. The arc time from the start to the time when the voltage drops to Va or less and the welding voltage V (n) in the n-th cycle are Va.
The measurement of the short circuit time T _Sn is started from the time when the following is reached,
The short circuit time up to the time when the voltage exceeds Va is measured, the arc / short time ratio is calculated, and then the standard deviation σ (T _An / T _Sn ) of the arc / short time ratio for each cycle is calculated.

The fact that the standard deviation of the arc / short-circuit time ratio becomes large means that the droplet transfer phenomenon due to the occurrence of an instantaneous arc, a long-term arc, an instantaneous short-circuit, a long-term short-circuit, etc. is unstable, and the standard deviation is low. It shows that the droplet transfer phenomenon is more stable. The standard deviation of the arc / short circuit time ratio is compared with a reference value, and when the difference from the reference value exceeds a predetermined allowable range, an abnormal signal is output as an arc / short circuit time ratio abnormality.

Next, the short-circuit frequency of subroutine 4 in FIG.
The operation will be described. FIG. 6 shows the calculation processing of the short-circuit frequency.
It is a detail of the subroutine which performs processing. Calculation of short circuit frequency
Is T ₁After the time is up, set time T_TwoUp to melting
The welding current and welding voltage flowing between the contact wire and the workpiece are supported.
The welding voltage V (n) in the n-th cycle
When the voltage drops below the short circuit judgment voltage Va, the voltage rises above Va
Calculate the short-circuit frequency with the short-circuit time until the time when
You. Here, sampling noise and chattering
Short circuit within 1 msec to reduce the change of short circuit frequency
The phenomenon is calculated as an arc time. Based on this short circuit frequency
Compared to the reference value, the difference between the reference value and the
When it exceeds, an abnormal signal is output as a short circuit frequency abnormality.

As described above, the monitoring of abnormal welding quality is performed only for the steady welding portion excluding the arc start portion and the termination processing portion. Various abnormal phenomena are likely to occur due to the state of contact, and if the unstable state of the welding phenomenon that appears only at the start part is included in the calculation range, even though the welding phenomenon of the steady welding part is stable, This is because a calculation result indicating that the welding phenomenon is unstable is output. Also, the termination processing unit is not included in the calculation range for the same reason.

Furthermore, it is better to make a determination by calculating the entire section of the steady welding portion, but the determination may be made using data of only a part of the section. Therefore, according to the present embodiment, when the welding phenomenon is stably formed in the steady welding portion, the abnormal signal is not output.
Therefore, in the automatic and semi-automatic arc welding equipment, the unstable state of the welding phenomenon in the steady welding part can be easily detected by an operator or a technician by outputting an abnormal signal. Outflow of good products can be reliably prevented.

FIG. 7 shows steps (a) to (d) during arc welding.
It is a figure explaining the transfer phenomenon of the droplet in (h), a welding voltage waveform, and a welding current waveform.

[0038]

As described above, according to the method for judging the welding stability of a steady welding portion according to the first aspect, the welding current and the welding voltage are calculated for one or more of four items over a predetermined period of time, and each is calculated. If the difference between the reference value and any one of the quantitative values exceeds the preset allowable range, the welding phenomenon of the steady welding part is said to be unstable or defective. Can be determined in real time. Also, there is an effect that these data can be effectively used as an index for outputting a power supply control signal for an automatic recovery process when a welding abnormality occurs.

Further, according to the welding stability judgment method of the present invention, since the section for monitoring arc welding is set arbitrarily and all the steady-state welds are monitored, there is an advantage that highly reliable monitoring can be performed. .

Further, according to the welding stability judgment apparatus of the third and fourth aspects, the welding stability of the steady welding portion can be arbitrarily divided according to the welding time during welding, and all the steady welding portions can be accurately and quantitatively determined in real time. This has the advantage that the outflow of defective welding quality can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of a steady welding portion welding stability determination device of the present invention.

FIG. 2 is an analysis execution flowchart of the present invention.

FIG. 3 is a subroutine for performing an arc period welding current integral standard deviation calculation process;

FIG. 4 is a subroutine for performing a short-term welding current integral standard deviation calculation process.

FIG. 5 is a subroutine for performing an arc / short circuit time ratio standard deviation calculation process.

FIG. 6 is a subroutine for performing a short-circuit frequency calculation process.

FIG. 7 is an explanatory diagram of a droplet transfer phenomenon, a welding voltage waveform, and a welding current waveform during arc welding.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 welding power supply 2 welding wire 4 contact tip 5 workpiece 6 shunt 7 welding current detection circuit 8 welding voltage detection circuit 9 A / D converter 10 CPU 16 display 17 calculation and output device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Taro Kamiya 3-126-1, Kosakahonmachi, Toyota-shi, Aichi Prefecture Safinia MI602

Claims (4)

[Claims] 1. A method for determining the stability of arc welding stability of a consumable electrode type gas shielded arc welding in which welding is performed while alternately repeating a short circuit and an arc, comprising a welding electrode (hereinafter referred to as a welding wire) and a material to be welded. An analog output signal output by using a voltage detecting means for detecting a welding voltage between the electrodes and a current detecting means for detecting a welding current flowing between a welding wire and a workpiece is converted into a digital signal at a predetermined sampling frequency. And the degree of welding stability of the steady-state
Items (a) to (d), (a) the standard deviation of the welding current integral during the arc period per cycle σ (∫I _An dt) (b) the standard deviation of the welding current integral during the short circuit period per cycle σ (∫I _Sn dt) (c) Standard deviation of arc / short time ratio for each cycle σ (T _An / T _Sn ) (d) Calculate any one or more of the short circuit frequency f _S , Arc welding steady state characterized in that it is determined that welding is unstable or defective when any one of the differences from the reference value exceeds a predetermined allowable range, as compared with corresponding reference values. Method for determining the welding stability of the part. 2. The method according to claim 1, wherein a section for monitoring arc welding is set, and the section is arbitrarily divided and determined according to welding time. 3. An apparatus for determining the stability of arc welding stability in a consumable electrode type gas shielded arc welding in which welding is performed while alternately repeating a short circuit and an arc, wherein a welding voltage between a welding wire and a workpiece is detected. Voltage detecting means, current detecting means for detecting a welding current flowing between a welding wire and a workpiece, an A / D converter for converting an analog output signal from both means into a digital signal, and a digital signal from the converter. (A) Standard deviation σ (∫I _An dt) of the welding current integral during the arc period for each cycle (b) Standard deviation σ (∫I _Sn dt) of the welding current integral during the short circuit period every cycle (C) a standard deviation σ (T _An / T _Sn ) of the arc / short time ratio for each cycle (d) calculating means for calculating any one or more of the four items of the short circuit frequency f _S , Calculation result from calculation means A comparator for comparing with a preset reference value to determine whether the difference from the reference value is within an allowable range, and a display for displaying the output of the comparator; Welding stability judgment device. 4. The welding stability judging apparatus according to claim 3, further comprising means for setting a section for monitoring arc welding and arbitrarily dividing the section in accordance with the welding time.