JP2003326361A - Method for discriminating arc start property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically discriminate normal/defective condition of arc start property in consumable electrode gas shielded arc welding. <P>SOLUTION: The normal/defective condition of arc start property in consumable electrode gas shielded arc welding is discriminated by calculating the number of times of long period short circuit Ts for which timewise short circuit not less than a reference value continues, the number of times of long period arc cutting Tn for which timewise arc-cutting not less than a reference value continues, and the variance Wpp, Tvr of moving average value in a welding voltage, during a predetermined discriminating period Tj from the arc starting time t1, by inputting these calculation results and by using a prescribed discrimination standard. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the quality of arc startability in consumable electrode gas shielded arc welding, and more particularly to a method for automatically determining arc startability based on a welding voltage / current waveform.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a consumable electrode gas shielded arc welding apparatus including an arc monitoring apparatus for monitoring a welding state in the prior art. Hereinafter, description will be given with reference to FIG.

The welding power source PS outputs a welding voltage Vw and a welding current Iw suitable for welding, and also outputs a feed control signal Fc for controlling the feeding of the welding wire 1 to the wire feeding motor WM. . The welding wire 1 is rotated by the feed roll 5 directly connected to the wire feed motor WM.
While being fed through the welding torch 4, the power feeding tip 5
Power is supplied from a, and an arc 3 is generated between the base material 2 and the base material 2.

The voltage detector VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The current detector ID detects the welding current Iw and outputs a current detection signal Id. The arc monitor AM receives the above voltage detection signal Vd and current detection signal Id as input, monitors the welding state by the following circuit, and issues an alarm when an abnormal state occurs. The voltage average value calculation circuit VDA receives the above voltage detection signal Vd as an input and averages it with a time constant of about several hundred ms to several s and outputs a welding voltage average value signal Vda. The current average value calculation circuit IDA receives the above current detection signal Id as an input and averages it with a time constant of about several hundred ms to several s and outputs a welding current average value signal Ida. The welding state determination circuit AJ inputs the above-mentioned welding voltage average value signal Vda and welding current average value signal Ida, determines the quality of the welding state by the determination method described later with reference to FIG. 6, and issues an alarm in the case of an abnormal state. .

FIG. 6 is a voltage / current waveform diagram showing the above-described welding state determination method. The welding voltage Vw is shown in FIG.
The time change of the welding current Iw is shown in the same figure (B), the time change of the welding voltage average value signal Vda is shown in the same figure (C), and the welding current average value signal is shown in the same figure (D). The time change of Ida is shown. The figure illustrates the case of short-circuit transfer welding, which is a typical welding method of consumable electrode gas shield arc welding, and the same applies to other cases such as globule transfer welding and pulse arc welding. Hereinafter, description will be given with reference to FIG.

Period before Time t1 (Good Welding State) Since the period before time t1 is the good welding state, the welding state is the welding voltage Vw as shown in FIG.
And the arc period in which the arc voltage value is high are periodically repeated. Similarly, the welding current Iw repeats the operation of increasing during the short circuit period and decreasing during the arc period. In the welding state determination method of the prior art, such abruptly changing voltage / current waveform is measured for several hundred ms to several s.
Generally, the welding voltage average value and the welding current average value are calculated by smoothing with a large time constant, and the welding state is generally determined by determining whether these values are within a predetermined appropriate range.
Therefore, as shown in FIG. 7C, the welding voltage average value signal Vda in a good welding state is substantially linear, and the value is within the voltage proper range Wv. Similarly, as shown in FIG. 3D, the welding current average value signal Ida is also a substantially straight line, and its value is within the proper current range Wi.

Period after Time t1 (Abnormal Welding State) Immediately before time t1, the welding state is caused by various disturbances such as fluctuations in the wire feed rate, fluctuations in the wire protrusion length, and irregular movements of the molten pool and droplets. Becomes unstable and an arc break occurs, the welding voltage Vw becomes the maximum no-load voltage as shown in FIG. 4A, and the welding current Iw does not flow as shown in FIG. As a result, as shown in FIG. 7C, the welding voltage average value signal Vda gradually increases due to the time constant and becomes outside the voltage proper range Wv at time t2. Further, as shown in FIG. 4D, the welding current average value signal Ida gradually decreases due to the time constant and becomes outside the proper current range Wi at time t2. By discriminating this, the abnormal state of the welding state is determined. Although the case of arc breakage has been described above, other abnormal conditions in which the short circuit period and the arc period become extremely long or short are also determined. When an abnormal state as described above occurs, there is a high possibility that welding defects such as a change in melting and a defective bead appearance will occur. Therefore, it is important for quality control to determine an abnormal state and issue an alarm. .

[0008]

In welding, it is not during welding but during arc start that welding failure is most likely to occur. This is because an unstable state is likely to occur due to various factors in the transient state in which the arc is called from the state where no arc is generated to lead to a more stable arc generation state. Hereinafter, problems that occur when the above-described welding state determination method of the prior art is used to determine the quality at the time of arc start will be described.

FIG. 7 is a voltage waveform diagram at the time of arc start in the prior art. The welding voltage Vw in the same figure (A) and the welding voltage average value signal Vda in the same figure (B) show good waveforms at the time of arc start, and the welding voltage Vw in the same figure (C) and the welding in the same figure (D) The voltage average value signal Vda shows a waveform at the time of a bad arc start. Hereinafter, description will be given with reference to FIG.

At the time of good arc start As shown in the same figure (A), when the welding wire contacts the base metal at time t1, the welding voltage Vw is a steady state in which the short-circuit voltage and the arc voltage repeat from the maximum no-load voltage. Smoothly transition to. Since FIG. 9A shows a case of a good arc start, this transition is performed immediately and smoothly.
The welding voltage average value signal Vda at this time gradually decreases with time constant and converges to a steady value, as shown in FIG.

At the time of a bad arc start As shown in FIG. 6C, when the welding wire contacts the base metal at time t1, from the no-load state to the long-term short-circuit state indicated by X1 and X2 and the long-term state indicated by Y1 and Y2. A poor arc start occurs after the arc breaks and then the steady state is entered. For this reason, the welding voltage Vw fluctuates greatly due to long low short circuit voltage or high unloaded voltage due to arc breakage. The above-mentioned long-term short circuit is a short circuit whose short-circuit time is longer than the reference value, and long-term arc break is an arc break whose time is longer than the reference value, and its reference value is a dozen ms. ~ It is about several tens of ms.
At this time, the welding voltage average value signal Vda gradually decreases from the no-load voltage due to the individual constant, as shown in FIG. Fluctuates. However, since it is smoothed by a large time constant, its fluctuation range is small and does not fall outside the voltage proper range Wv. As a result, even if the arc start is defective, it is often not possible to determine it as defective. That is, with the welding state determination method of the prior art, it was not possible to accurately determine the quality of the arc startability.

Therefore, the present invention provides a method capable of accurately determining a defective arc start caused by the occurrence of a long-term short circuit, a long-term arc break, or the like.

[0013]

According to a first aspect of the present invention, there is provided a method of determining the quality of arc startability in consumable electrode gas shielded arc welding, wherein a long-term short-circuit is detected during a predetermined determination period Tj from the start of arc start. The number of times Ns, the number of long-term arc breaks Nn, and the variation value Bd of the welding voltage moving average value Vra during the determination period Tj by the moving average period Tra shorter than the determination period Tj are calculated, and the number Ns of long-term short circuits and the above Number of long-term arc breaks Nn
And a method of automatically determining whether the arc startability is good or not based on the variation value Bd of the moving average value of the welding voltage.

According to a second aspect of the present invention, the variation value Bd of the welding voltage moving average value described in the first aspect is a time Tvr during which the welding voltage moving average value Vra during the determination period Tj is outside the predetermined proper range Wvr. This is the arc start determination method that is the sum value Stv of.

According to a third aspect of the present invention, the number Ns of long-term short circuits is greater than or equal to a predetermined reference number Nst, the number Nn of long-term arc breaks is greater than or equal to a predetermined reference number Nnt, and the welding voltage moving average value is appropriate. Stv, which is the total time out of range
Is equal to or longer than the predetermined first reference time Tt1
If the arc startability is judged to be somewhat poor when the time is less than the reference time Tt2 of the above, and the sum value Stv of the time when the moving average value of the welding voltage is out of the proper range is the second reference time Tt2 or more, the arc is started. 3. The startability is determined to be bad, and the arc startability is determined to be good otherwise.
It is the described arc start determination method.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a voltage waveform diagram at the time of a defective arc start corresponding to FIG. 7C described above in the embodiment of the present invention. FIG. 7A shows the change over time of the welding voltage Vw and has the same waveform as that of FIG. 7C described above. Further, FIG. 6B shows a moving average value V of the welding voltage.
The time change of ra is shown. Hereinafter, description will be given with reference to FIG.

As shown in FIG. 3A, at the time of a bad arc start, a long-term short circuit and a long-term arc break occur as described above. Then, the quality of the arc startability is determined by the number of occurrences of long-term short circuit and long-term arc breakage, the total time, a combination of these, and the like. Therefore, it is possible to automatically determine the arc startability by calculating and quantifying these factors that determine the arc startability. In the present invention, the following three items are used as judgment items.

Number of Long-Term Short Circuits Ns As shown in FIG. 4A, the welding voltage Vw is compared with a predetermined short circuit determination value Vt1, and when Vw ≦ Vt1 is determined as the short circuit period Ts. Then, when the short-circuit period Ts is longer than a predetermined long-term short-circuit discrimination value Tst, it is discriminated as a long-term short circuit. The number Ns of occurrences of the above-mentioned long-term short circuit is counted during a predetermined determination period Tj from the start of the arc start at time t1. The determination period Tj is set to about several seconds, which is the time required for the arc start to converge to a steady state.

Number of long-term arc breaks Nn As shown in FIG. 7A, the welding voltage Vw is compared with a predetermined arc break judgment value Vt2, and when Vw ≧ Vt2, it is judged as the arc break period Tn. . Then, this arc break period Tn is a predetermined long-term arc break determination value Tnt.
When it is longer than the above, it is determined as a long-term arc break, and the number Nn of long-term arc breaks occurring during the above-described determination period Tj is counted.

Variation value Bd of welding voltage moving average value Vra The welding voltage moving average value Vra shown in FIG. 7B is a calculated moving average value of the welding voltage Vw shown in FIG. The moving average period corresponding to the time constant during smoothing is shorter than the determination period Tj (several s), and the time constant for averaging in the above-described conventional technique (several hundred ms to several s).
Shorter than this, set to about 10 ms to 200 ms. This is to quantify the irregularity of the short circuit period and the arc period. That is, if the moving average period is too long, it becomes smooth and it becomes impossible to discriminate irregularities. Conversely, if the moving average period is too short, the irregularity is still discriminated because the fluctuation range is large even if it is not irregular. Can't do it.

Therefore, the irregularity between the short circuit period and the arc period can be discriminated by the variation value Bd of the welding voltage moving average value Vra. As this variation value Bd, the maximum fluctuation width Wpp of the welding voltage moving average value can be used as shown in FIG. Further, it is also possible to use the out-of-range time sum value Stv obtained by adding the out-of-range time Tvr during which the welding voltage moving average value Vra is outside the predetermined moving average value proper range Wvr during the determination period Tj.

The arc startability can be determined by the number of long-term short-circuits Ns, the number of long-term arc breaks Nn, and the variation value Bd of the welding voltage moving average value. Although the determination criteria vary depending on various welding conditions, for example, when Ns ≧ 3 and Nn ≧ 2 and Wpp ≧ 4V in the determination period Tj = 3s, it can be determined that the arc start is defective.

FIG. 2 is a block diagram of arc monitor apparatus AM in the embodiment of the present invention. The structure of the welding device including this device is the same as that of FIG. 5 described above. Hereinafter, each circuit block will be described with reference to FIG.

The determination period timer circuit TJ receives the current detection signal Id as an input, and becomes a high level for a predetermined time from the arc start start time when the welding wire comes into contact with the base metal and the current starts energizing. The signal Tj is output. The first comparison circuit CP1 has a voltage detection signal Vd.
Is compared with a predetermined short circuit determination value Vt1, and Vd ≦ Vt1
At this time, the short-circuit period signal Ts which becomes High level is output. The second comparison circuit CP2 has the above-mentioned short-circuit period signal T
s is compared with a predetermined long-term short-circuit discrimination value Tst, and Ts
When ≧ Tst, the long-term short-circuit period signal LTs which becomes High level is output. The long-term short-circuit number counting circuit NS counts the number of times the above-mentioned long-term short-circuit period signal LTs changes from the Low level to the High level while the above-mentioned determination period signal Tj is at the High level, and outputs the long-term short-circuit number signal Ns. . The third comparison circuit CP3 compares the voltage detection signal Vd with a predetermined arc break determination value Vt2, and Vd ≧
An arc cut-off period signal Tn which becomes High level when Vt2 is output. The fourth comparison circuit CP4 compares the above arc break duration signal Tn with a predetermined long-term arc break determination value Tnt, and outputs a long arc break duration signal LTn that becomes High level when Tn ≧ Tnt. . The long-term arc breakage frequency counting circuit NN uses the determination period signal T described above.
While j is at the high level, the number of times the above-described long-term arc break period signal LTn changes from the low level to the high level is counted and the long-term arc break number signal Nn is output.

The welding voltage moving average value calculation circuit VRA receives the above voltage detection signal Vd, calculates a moving average value during a predetermined moving average period Tra, and outputs a welding voltage moving average value signal Vra. Variation value calculation circuit BD
Is the input of the welding voltage moving average value signal Vra,
As described above with reference to FIG. 1, the variation value signal Bd such as the maximum fluctuation width Wpp and the out-of-range time sum value Stv is output. The arc start determination circuit ASJ uses the above-mentioned long-term short circuit count signal N
s, long-term arc breakage frequency signal Nn and variation value signal B
With d as an input, the arc startability is determined according to a predetermined determination criterion exemplified in FIG. 4 described later.

FIG. 3 is a block diagram of the variation value calculation circuit BD for calculating the above-mentioned out-of-range time total value Stv. The fifth comparison circuit CP5 compares the welding voltage moving average value signal Vra with a predetermined moving average value appropriate range Wvr, and outputs an out-of-range time signal Tvr that is at a high level when it is out of the range. The summing circuit SUM uses the determination period signal T
The above-mentioned out-of-range time signal Tvr is added while j is at the high level, and the out-of-range time combined value signal Stv is output as the variation value signal Bd.

FIG. 4 is a flowchart showing the arc startability determination processing by the arc startability determination circuit ASJ described above. The figure is an example of a determination process. Hereinafter, description will be given with reference to FIG.

In step ST1, the number of long-term short-circuits N
s is greater than or equal to the predetermined reference number Nst, the out-of-range time sum value Stv is greater than or equal to the predetermined first reference time Tt1 and less than the predetermined second reference time Tt2, and the long-term arc breaks. It is determined whether the number of times Nn is equal to or greater than a predetermined reference number Nnt. If YES, the process proceeds to step ST2, where the arc startability is determined to be "slightly defective", and if NO, the process proceeds to step ST3.

In step ST3, it is determined whether the summed time value Stv out of the range is equal to or longer than the second reference time Tt2. If YES, the process proceeds to step ST4 to determine that the arc startability is "poor", and NO. If so, it is determined to be “good”.

[0030]

According to the arc startability determination method of the present invention, it is possible to accurately and automatically determine the quality of arc startability based on the number of long-term short circuits, the number of long-term arc breaks, and the variation value of the welding voltage moving average value. Therefore, the quality of the arc start portion can be strictly controlled.

[Brief description of drawings]

FIG. 1 is a voltage waveform diagram showing an arc startability determination method according to the present invention.

FIG. 2 is a block diagram of an arc monitor apparatus AM according to the present invention.

FIG. 3 is a block diagram of a variation value calculation circuit BD according to the present invention.

FIG. 4 is a flowchart showing an arc startability determination process according to the present invention.

FIG. 5 is a configuration diagram of a welding device including an arc monitor device in a conventional technique.

FIG. 6 is a voltage / current waveform diagram showing a welding state determination method in the prior art.

FIG. 7 is a voltage waveform diagram at the time of arc start for explaining the problems of the conventional technique.

[Explanation of symbols]

1 welding wire 2 base material 3 arc 4 welding torch 5 feeding rolls 5a Power supply chip AJ Welding condition judgment circuit AM arc monitor ASJ arc start judgment circuit BD variation value calculation circuit Bd Variation value of welding voltage moving average value Vra (signal) CP1 First comparison circuit CP2 Second comparison circuit CP3 Third comparison circuit CP4 Fourth comparison circuit CP5 Fifth comparison circuit Fc feed control signal ID current detector Id current detection signal IDA current average value calculation circuit Ida Welding current average value signal Iw welding current LTn Long-term arc break period signal LTs Long-term short circuit signal NN Long-term arc break count circuit Nn Number of long-term arc breaks (signal) Nnt, Nst reference number of times NS long-term short circuit counter Ns Number of long-term short circuit (signal) PS welding power supply ST1-5 steps SUM summing circuit Stv Out-of-range time total value (signal) TJ judgment period timer circuit Tj judgment period (signal) Tn arc break period (signal) Tnt Long-term arc break judgment value Tra moving average period Ts Short circuit period (signal) Tst Long-term short circuit judgment value Tst Long-term short circuit judgment value Tt1 First reference time Tt2 Second reference time Tvr out-of-range time (signal) VD voltage detector Vd voltage detection signal VDA voltage average value calculation circuit Vda Welding voltage average value signal VRA Welding voltage moving average value calculation circuit Vra Welding voltage moving average value (signal) Vt1 short circuit judgment value Vt2 Arc break judgment value Vw welding voltage Wi current proper range WM wire feeding motor Wpp Maximum fluctuation range of welding voltage moving average Wv voltage proper range Wvr Moving average value proper range

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Claims (3)

[Claims] 1. A method for judging the quality of arc startability in consumable electrode gas shielded arc welding, comprising the steps of:
The number of long-term short circuits and the number of long-term arc breaks, and the variation value of the welding voltage moving average value during the determination period by the moving average period shorter than the determination period are calculated, and the number of long-term short circuits and the number of long-term arc breaks are calculated. And a method for judging the arc startability, which is characterized by automatically judging the quality of the arc startability based on the variation value of the moving average value of the welding voltage. 2. The arc startability determination method, wherein the variation value of the welding voltage moving average value according to claim 1 is a total value of times during which the welding voltage moving average value is outside a predetermined appropriate range during the determination period. . 3. The total value of the times in which the number of long-term short-circuits is a predetermined reference number or more, the number of long-term arc breaks is a predetermined reference number or more, and the welding voltage moving average value is out of the appropriate range. When the predetermined first reference time or more and the predetermined second reference time or less, the arc startability is determined to be somewhat defective, and the total value of the times when the welding voltage moving average value is outside the appropriate range is The arc startability determination method according to claim 2, wherein the arc startability is determined to be poor when the second reference time is longer than the second reference time, and the arc startability is determined to be good otherwise.