JPS6171178A - Optimum controlling method of arc welding - Google Patents

Abstract

PURPOSE:To set automatically optimum welding conditions even if a work condition and an environment are varied by calculating a weldability index from welding current and welding voltage waveform data, and controlling an output of an welding power source or a wire feed quantity so that the exponential value becomes minimum. CONSTITUTION:As current I0 and voltage waveform data in case of CO2 or MAG welding, an index W for grasping quantitatively the weldability from a short-circuit time TS, an arc time Ta, an average value Is.ave of a current of the short circuit period, an average value Ia.ave of a current of the arc period, etc. is calculated, and by its value, an output of a welding power source or a wire feed quantity is controlled. In this regard, the weldability index W can be derived from an expression I which has used the short circuit time, the arc time, sigmaTS, sigmaTa, sigmaIs-ave and sigmaIa-ave being standard deviations of an average value of the current of the short circuit period and an average value of the current of the arc period, a constant K being the product of those values in a reference welding condition, an average value Ra.ave of a resistance in the arc period, an electric power Pa in the arc period, Ra.ave in optimum conditions, and a regression expression Ri and Pi.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optimal control method for CO2 and MAG welding welding.

[Background of the invention]

In CO2 and MAG welding, the voltage value that allows good welding varies depending on the current value used. Furthermore, even if the voltage is set to an appropriate value, the arc condition will vary depending on the current value.

Therefore, in order to set an appropriate voltage value for each current value, a considerable amount of experience and skill of the operator is required.

However, the settings made by the worker tend to be qualitative and determined by the worker's own experience, skills, and preferences, and the better the worker is, the more accurate the setting is, but in general there are individual differences. , it is impossible to seek a uniform standard.

On the other hand, there is a method that displays all the adjustment knob positions that allow you to set the appropriate voltage for each current value, or you can preset the appropriate voltage Mk according to the current value in advance and turn on the lamp when it matches the voltage value set by the operator. Depending on the method of
Some machines allow even unskilled workers to set conditions. However, these appropriate voltage values are determined by skilled workers performing standard work under a certain working environment, and they are values that will satisfy all conditions under a wide variety of actual welding work conditions and environments. Not necessarily.

In other words, the voltage that is considered to be an appropriate value may deviate to the high direct voltage side or to the low voltage side in actual work.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, automatically set optimal welding conditions, and perform CO2 or MA
C-Determine to perform optimal control of welding.

[Summary of the invention]

The present invention provides an index for quantitatively understanding weldability from current/voltage waveform data (short circuit time, arc time, average value of current during short circuit period, average value of current during arc period, etc.) in CO2 or MAG # contact. This value is used to control the welding output or wire feed amount.

[Embodiments of the invention]

Generally, in OOZ and MAG welding, welding is performed by repeating short circuit and arc metal nine times. Figure 1 shows the welding voltage waveform and welding current waveform at that time, where Ts is the short circuit time, T& is the arc time, and ``ma'' is one period from one short circuit to the next short circuit.
x is the maximum current, engineering. ,. is the minimum current, Ill*1LY6
is the short circuit average current, 1e&V6 is the arc average current, Vj
indicates a worrying threshold voltage. In addition, engineering g-at. * Engineering a-oat. are the values obtained when the currents of short circuit time T8 and arc time Ta are converted into rectangular waves (ft), respectively. The switching between short circuit and arc occurs in a very short time, and usually
Ts has a value of about several ms, and Ta has a value of about 10 to 50 m5. Workability (weldability) during welding is determined by the uniformity of the arc condition, the degree of arc breakage, and arc flare-up9.
Judgment is made based on the overall degree.

(1) Uniformity of arc condition The power source used for C02 welding, etc. has constant voltage characteristics, and its output voltage is controlled, but the output current, short circuit, and arcing time are not control factors, but are This value is determined depending on the feed rate, power supply characteristics, and arc characteristics.

However, the output current, short circuit, and arcing time are very closely related to the arc condition, and fluctuations in these values have a large effect on the uniformity of the arc condition. That is, the uniformity of the arc state is determined by the short circuit time Ts, the arc time Ta, the average value of the current during the short circuit period, a, and the average value of the current during the arc period, 5 Y6 (19). It is related to the degree of variation in these factors, and can be simply expressed as the standard deviation σTs+σ7. σ, s8. . and σ
01. It can be expressed using a□.

If the amount of variation in any one of the above four factors increases, the uniformity of the arc state will be impaired, so the uniformity of the arc state "ara" can be expressed as follows.

'arc""σT8°σT＆'σX841) @°σXh
-hvo ”(“here σT8.σ7.σZ1)i&
1@' Ia*Lve are σ Ta, Ta, I, , respectively. ＋”I ave
is the standard deviation of Note that the distinction between a short circuit and an arc can be made by using a predetermined voltage Vj (generally 10
~20V], it can be determined whether the voltage value is higher or lower.

(1)) Degree of occurrence of arc breakage Welding is carried out by setting the voltage to the optimum voltage value for each current value, and the average value R1 of the resistance during the arcing period is determined as shown in Figure 2. , and can be regressed using the quadratic equation of welding and electric current as shown below.

R1-a-I +br+c (a, b, c are constants)
・+2) The values of constants a, b, and c are as shown in Table 1, and vary depending on the shielding gas composition. However, the model
These constants hardly change even if the wire diameter differs.

Resistance is to the west of voltage and current, so in CO□ welding, etc. using a constant voltage characteristic power supply that is controlled so that the output voltage is approximately constant, an increase in resistance means a decrease in current, and during the arc period during welding. The average resistance RIL-ILY@ is R shown in Figure 2.
The larger the value is than 1O, the lower the current is, indicating insufficient heating and melting of the wire, and the tendency to cause arc breakage.

Therefore, the degree of arc breakage WR can be expressed as follows.

WR zero R,,, v, / R1'...(3) Furthermore, wR
1, that is, %”&#& mallo is R in Figure 2.
If it is smaller than 1, there is no need to consider arc breakage, so the value of WR is set to the reference value of 1.

(ill As with the degree of arc flare-up R1, the sending power P during the arc period under optimal conditions
When we search for 1, it looks like Figure 3, which is natural! It is calculated by regression using the exponential function of '1 style I with 5 [6 seven bases.

Pi = hoe"x (g * h is a constant) - +4 The values of the constants g and h are shown in Table 2 and vary depending on the shielding gas composition. However, as in the case of R1, the Even if the diameter is different, the value of the constant y is constant.

The resulting force Pa during the arc period is a factor related to the generation and growth of droplets that transfer to the molten pool due to short circuit, and is equal to 1 of p and Pa.
The larger the value of Pl in FIG. 5, the more the wire is heated and melted, and the more easily the arc flares up. Therefore, the arc flare-up degree W can be expressed as follows: ℃1゜wP-Pa/P1...(5) If W<1, there is no need to consider the arc flare-up, so As in the case of WR, the value of W is set to the reference value of 1. The value of Waral "RS Wfl obtained as above is 5. Since workability deteriorates, the bath contactability index W can be expressed as follows.

W-(WfLr,)・(WR)β・(WP) −16
1 (α, β, γ are the weight constants of each factor) Roru standard welding conditions, for example, C using φ1.2 wire
Conditions that are said to show the best weldability in 02 general welding (
Cultivation is carried out at a welding current of 130 A and a welding voltage of about 19 V (5 L-). With the value of A"aro as a constant, - wo./K ... ()) Then, the constants α, β, and γ in equation (6) are simplified, and W can be expressed as follows.

W ・(W) ・W ... (8) ARP Since the difference between the maximum value and the minimum value of this W value is extremely large, it is more practical to convert the right side to a full logarithm and do the following. Become.

w-LN(WA)+2-L, N(WR)+LN(W,)
sw −k+LN(σTs'στ1σIm−*vm
Ia, ave)"- σ 2 misery N (R/R1) + LN (Pa/Pi)...
・(9) Tortoise・&v@ [However, k-LN(K)] Figures 4 to 7 show welding current t160^,
Installed in 200A, 250A and 300A, φ1.2
Weldability index W 'i when C02 welding of wire is performed and welding voltage is changed
This shows that the results are for a similar type of welding power source. However, k -7,95, R1-5,55X 1 0-'
・ I2- 3.1 3 X 1 0-5 ・
I+0.556, Pi=1.7941) 0°018I
And so. For any model or current value, the value of W forms a downwardly convex curve with a minimum value, and the voltage value showing the minimum value coincides with the voltage value at which the best weldability is obtained, that is, the optimum voltage.

FIG. 8 shows the value of W when the welding current was set to 1) 00 A and a φ0.9 wire was welded in a CO2 bath. φ1.2
As in the case of the wire, the reverse pressure value indicating the minimum value of W coincides with the optimum voltage.

Figures 9 and 10 show welding currents of 150 and 25 using a φ1.2 wire and varying shielding gas compositions.
This is the value of W when welding is performed at 0A. As in the case of CO2 bath contact, the voltage 1@ indicating the minimum value of W coincides with the optimum voltage.

As mentioned above, the weldability index W calculated by equation (9) is the same when the welding voltage is set to the optimal back pressure even if the welding flow, model, shielding gas composition, and wire diameter change. Minimum water supply. Therefore, if the value of the output 'Iw of the welding power source is controlled to be the minimum value, even if the working conditions and environment change,
Optimum conditions can be automatically set accordingly.

Figure 1) is a block diagram of an embodiment of the present invention. In the figure, a welding power source 1 applies a predetermined voltage between a wire 2 and a base material 4. The wire 2 is fed at a predetermined speed by the feed roller 3 in order to weld the base material 4t. The welding current is proportional to y to the feed speed of the wire 2. Although not shown in the figure, there is a torch 9 at the tip of the wire 2.
G02fMAG gas is ejected as the wire is fed. 5 is a shunt for measuring the welding current; 6 and 7 are for measuring the welding current and welding voltage, respectively;
These are a current detector and a voltage detector for amplifying to a predetermined level. The outputs of the current detector 6 and voltage detector 7 are sampled at predetermined intervals by an analog-to-digital converter (A/D converter) 8 and converted into digital signals.
The data are sequentially input to the central processing unit (CPU) 9. QPU
In step 9, the weldability index is totally calculated based on the input current data and voltage data, and it is determined whether or not the welding pressure 1 can be changed.
If a change is necessary, output the voltage data.

The voltage data output from GPtJ 9 is converted to analog (digital/analog converter 5 (D/A converter) 12
g, and the output control circuit 15 receives and receives the analog signal to increase or decrease the output voltage of the bath power source 1. 10 is a memory for storing processing programs of the CPU 9, input/output data, data in the middle of calculations, various constants, etc. 1) is an I
: A keyboard used to input various constants, initial data, etc. required for processing by the iPU 9.

The entire processing flow centered on the CPU 9 (l-) in FIG. 1) is shown in FIG.

First, an outline of yukatsuri'-ryuko. , welding voltage V. , number of data for sampling 7 N, sampling interval S of bath contact pressure
1 short circuit/arc judgment voltage vj, initial data n for welding index ↓ 1 output, input from keyboard 1) (step 101). Regarding the number of sampling data N, the thicker the data, the more accurate the data? However, sampling takes time and the memory capacity must be increased accordingly, so it is only necessary to increase the number to about 500 to 1000. The shorter the sampling interval S, the more accurate data can be obtained, but since it is also related to the memory capacity, it should be about 0.1 ms in a small current range and about 0.2 m8 in a large current range. If so, it will not be a problem in practice. The short-circuit/arc judgment voltage V] may be set to a value of about 10 V regardless of the current value, but since the short-circuit voltage and the shape of droplet transfer change depending on the current value, for example, when Case Vj-10V200A<1≦
In the case of 25OA, when Vj=15V, and when 250A<IO, better results can be obtained by slightly changing the current value, such as Vj=20v.

Next, welding is started (step 102), and nm
As n+1 (step 103), the calculation process of the bath contact index is executed as follows. Note that n represents the number of the calculated weldability index.

First, the welding current I and the bath contact pressure detected by the current detector 6 and voltage detector 7 are sampled at predetermined intervals S by the A/D converter 8, and then digitally converted to 'current data data'. (1), voltage data v(1) (1 indicates the sampling number) is obtained, and the current data I (il, voltage data V(1)'1cPU) is stored in the memory 10 through 9 times (to step 104). 106).

'w! of sampling point 1! Flow data (1), voltage data V (1-N each time il is stored in the memory 10)
is determined (step 107), and if it is not i-N, it is 1
-1+1 (step 108), step 104~
106 is repeated.

When sampling of a predetermined number (1-N) of welding current data e(1) and welding low pressure data v(1) is completed, lil'! is stored in the memory 10. il- is sequentially read out and compared with vj to obtain each short circuit starting point S (R1 and arc starting point T (RJk), and store the data number 1 in the memory 10 (step 109). Fig. 18 shows changes in welding voltage and Short circuit starting point,
This shows the relationship between arc starting points.

As shown in the 18th case, (1) is lower than Vj during the short circuit period and higher than Vj during the arc period. Therefore, by sequentially comparing the magnitude t of v(1) and Vj at each sampling point, the short circuit starting point 5 (R) is determined as the point where the illusion changes from V(phantom > Yj to V (1) < vj As, the arc starting point T (RJ is conversely v (1) is V (i)
It is found as the point where Vj changes from <Vj to V(il>vj).

Next, short circuit starting point S (river, arc starting point T (R), welding current data r (iJ and welding voltage data V (iJ
? ! - waveform data for each cycle, i.e., short circuit time (Ts in Figure 1), arc time (Ta in Figure 1), short circuit average current (Efia&Y@' in Figure 1, arc average current (Ta in Figure 1), The engineering a*ava's arc average resistance (formula (
31 R18. ) and arc power (Pa in equation (6)) (step 1)0), and calculate the average of these data (step 1)1). Furthermore, the standard deviation of the short circuit time, arc time, short circuit average current, and arc average current is also calculated (Step 1) 2)
.

When the calculation of the data necessary for calculating the weldability index Wn is completed, 1[1t - wn of wn is calculated and stored in the memory 10 (Step 1) 4).

In this way, when the welding instruction wn is determined, it is compared with the previously determined value 1, step 1) 5), w, 1 <
If wn-1, the fB contact voltage Vf predetermined: i (O9S V in the embodiment) increases (step 1) 6],
The processes after step 103 are executed to obtain the weldability index again. Moreover, if Wn<Wn-7, welding pressure v
After decreasing by 1 predetermined amount (in the example, the same <O, S V ) (step 1) 7), Kn f is determined the previous time.

Step 1) 8), Wn -Wn compared to "n-2"
If -2 is not found, the process from step 103 onwards is similarly executed to obtain the weldability index again.

The above process t-in-wn-2, that is, repeating until wn becomes the minimum value, changes the output voltage of the welding power source 1 through the path of the D/A converter 12 and the output control circuit 15 so that W becomes the minimum value. Increase or decrease.

When the minimum value of the weldability index Wn is determined, the welding voltage V is fixed at the value at that time, step 1) 9), and the weldability index Wn is
(Step 120), and if continuing, set it to m−n−1 (Step 12))
, the process returns to step 103, and if the calculation of Wn is to be stopped, welding is completely stopped and the process ends (step 122).

Note that the determination condition for Wn −Wn−2 k Wn −”n−
2+α5, and if the welding voltage V falls within the appropriate range, a method may be used in which the value of V is not changed even if it differs from the voltage value indicating the minimum value of wn. The operations from step 105 onward are repeated. - 10,000, if welding cannot be continued due to W calculation, stop welding and terminate the process (Step 1) 5).

FIG. 13 shows the details of the subroutine (SUBIJ) performed in the short circuit/arc determination process in step 109 in FIG. 12. In FIG. =mO1
After setting it to R-0 (steps 201 and 202), memory 1
0 to the first sampling point (1-0), read out the welding voltage data V (01t'' and compare it with V3 (step 205). Then, if v(01>Vj), step 2
Line 06 (but if v(0; ≦Vj, set it to 1-1 (step 204), read out t- and compare with Vj (step 204), V 1) at the next sampling point (1=1) Step 205]. While v(1)≦Vj, step 204.2
Repeat the process of 05. From Figure 18, ■(1)≦V3
means short circuit period. When V (1) > Vj, i(N'i is determined as i-1+1. Step 206
．． 207), i) If N, the subroutine process ends, but if i<H, read out to V(i)' and determine if Nil>Vjt (step 208).

Then, v (il > V2O, step 206 ~
Repeat the processing on the 20th. From Figure 18, V (1)
> vj means the entire arc period. Steps 206-2
When the process of 0B is repeated once, ■(1)≦Vj, that point means the short circuit starting point S (R) i. This 3(R)
The sampling point (1) corresponding to 7 is stored in a predetermined location in the memory 160 (step 209). Next, as i-1+1, i<Ni is determined. Step 2) 0, 2) 1), 1>
If N, the subroutine process ends, but if i<N, V (1) k R is extracted and V (1) ≦V
j i is determined (step 2) 2). And ■(1)
≦VjQ, repeat steps 2)0 to 2)2.

When this step 5 becomes 'I (1) ) Vj, that point is the arc starting point T (R1 - means this T (R1
The sampling point (1) corresponding to is stored in the memory 14 (step 2) 3). Thereafter, 5(R1, d(R)) are found one after another by repeating the process from step 206 onward as RR+1 (step 2) 4).Then, when 1>N, the subroutine Processing is completely completed.

FIG. 14 shows details of the subroutine (SUB2) for performing waveform data calculation processing in step 1)0 in FIG. 12. In FIG. 14, S (Pl, T (Pl has the same meaning as B (R1, T (RJ) in FIG. 13.

First, after setting P−〇 (step 501), the difference υ(S) between the arc starting point T (P) and the short circuit starting point s (p), the difference between the short circuit starting point s (p + 1) and the arc starting point T (PI U(A
) t- respectively (step 302.5a5). That is, UIS) is the sampling point of T (P) and s (p
), by taking the difference tone of the sampling point of U (
Al is determined by taking the difference between the sampling point of SLP+1) and the sampling point of T(Pi. Next, IJ
(81 multiplied by sampling interval s'6 short circuit time A (
Calculate the arc time B (PJ t
- Calculate (step s o s ) a This results in:
This means that A (Pi, 8 (P)) in the first period has been found. Next, the short circuit average current c (
p), arc average current D (PI, arc average resistance F,
(Pl, arc power F (P) t- is determined sequentially. That is, I (
kJ (C(P) using −x(i and u(s))
k calculation step 306], T (P) ~ S (P+1
) between I (kl (−I (tl ) and u (A
) to output D (Pl t 1!) (step 50
7) o Also, between T tPl and 3 (P+1) o
v(k) (-v(2) ) and I(k)(-1(il
) and U (Al' to calculate E(P) (step 308). Furthermore, T(PI SS (P+
1) between V (kl (-V ti) ) and I (Ic
) (−r (i) ) and sampling interval s'l
(Step 509).

After that, set P−P+1 (Step 510), and then proceed to determine P<H (Step 31)], and if P≧R! The processing of the routine ends, but if P<R, the processing from step 302 onward is repeated and A (Pi,
B (Pi, c(pH1D (PJ, E (P),
F(Find PJ.

FIG. 15 shows the details of the subroutine (SUB3) that performs the average value calculation process in step 1) 1 in FIG. 12.

The average value A1 of the short circuit time is the short circuit time A (r) of each cycle.
(-A (PJ)) and calculate it as the number of data P
(step 401).

Similarly, average constant Ab of arc time a(rJ (-5(Pi)), short circuit average current c (rl (-C(P))
average value Ac, arc average ゛1 current D(r) (-D(P
l ) average value Ad, arc average resistance IC(rl (-
Average value A6 of E(Pl), arc power F(rl (-
Sequentially calculate the average value kt of F(Pl) (step 4
02-406].

FIG. 16 shows a subroutine (SUB4) performed in the standard deviation calculation process of step 1)2 in FIG. That is, the standard deviations Ga (-σ, 8), G
b (-σ, ρ, Gc (-σrs, av+s', ca
(−σ 1. & 7°) is calculated (step 501
~504).

FIG. 17 is a subroutine (SUB5) that performs the weldability index calculation process of step 1)3 in FIG. 12. R1 and Pi in FIG. 17 are the previously mentioned Ra"ava,
The values of regression equations (2) and (4) of P& are TS. -Af, Ga
, Gb, Gc, G(1)
Find A (step 601), then use As and R1 to find the arc breakage occurrence rate wB'1 (step 602)
. Next, it is determined whether WR<0 (step 603)
, if WR<0, the process immediately goes to step 605, but if W
If R<0, IVR-1) (step 604
), go to step 605. In step 605, arc burn-up degree wp2 is determined using Af and Pi. Next W
p < o '2 determination step 606], Wp <
If it is O, it is set as Wp -0 (step 607). Using WA, WR, WP 2 thus obtained, a weldability index 1) is calculated (step 608).

In the above example, in order to obtain the minimum value of W, the output voltage of the bath-contact power source was increased and decreased, but instead of increasing the voltage, the wire feed amount was decreased and the voltage was decreased. It goes without saying that the same effect can be obtained even if the number of wire feeding lids is increased instead of 9.

〔Effect of the invention〕

As described above, according to the present invention, the following effects can be obtained.

(1) Even if the working conditions and environment change, it is possible to accurately set the optimal conditions according to the changes, and it is possible to perform good welding.

(2) Setting of optimal conditions is automated.

(3) The experience and skill of the operator, which was considered reliable, is no longer required to set the optimal conditions.

(4) There is no need to memorize welding conditions that differ slightly depending on shielding gas composition, wire diameter, etc.

(5) It is possible to unify the welding conditions, which were somewhat different depending on the preference of the operator, and improve the quality of welded joints.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of current and voltage waveforms in arc welding, Figure 2 is an explanatory diagram of arc average resistance, Figure 3 is an explanatory diagram of arc power, and Figures 4 to 10 are explanatory diagrams of weldability index. , 1st)
The figure is a block diagram of one embodiment of the present invention, and Fig. 12 is a block diagram of an embodiment of the present invention.
The entire 70-diagram explaining the operation of the diagram, FIG.
A flowchart of the arc determination process, FIG. 14 is a 70-diagram of the waveform data calculation process, FIG. 15 is a 70-diagram of the waveform data average value calculation process, and FIG. 16 is a 70-diagram of the waveform data standard deviation calculation process. 17 is a flowchart of the weldability index calculation process, and FIG. 18 is an explanatory diagram of the short circuit starting point and the arc starting point. DESCRIPTION OF SYMBOLS 1.° Welding power source, 2... Wire, 3... Feeding roller, 4... Base metal, 5... Shunt switch, 6... Welding current detector, 7... Welding voltage Detector, 8...A/D
Converter, 9...CPU. 10...Memory, 1)...Keyboard, 12...
D/A converter, 13...output control circuit. Fig. 1 Fig. 2; Climb I Fig. 3 Ii-tun Ar Ha dimension (') Figure 14 Closed light 17 Figure Convex

Claims (2)

[Claims] (1) In arc welding, where welding is repeatedly performed with short circuits and arcs, an index (weldability index) that quantitatively understands weldability is calculated from welding current and welding voltage waveform data,
An optimal control method for arc welding, comprising controlling the output of a welding power source or the amount of wire feed so that the weldability index is minimized. (2) The weldability index is σ_T_s, σ_T_a, σ_I_s_, which are the short circuit time, arc time, average value of current during short circuit period, and standard deviation of the average value of current during arc period.
・A constant K that is the product of _a_v_e and σ_I_a_・_a_v_e and their values under standard welding conditions, the average value of resistance during the arc period R_a_・_a_v_e, the power Pa during the arc period, and R_a_・_ under the optimal conditions
Using regression equations Ri and Pi of a_v_e and Pa, W=(σ_T_s・σ_T_a・σ_I_s_・_a_
v_e・σ_I_a_・_a_v_e/K)・(R_a
＿・＿a_v_e/Ri)^2・(Pa/Pi) or W=LN(σ_T_s・σ_T_a・σ_I_s_・＿
a_v_e・σ_I_a_・_a_v_e/K)+Z・
LN(R_a_・__a_v_e/Ri)+LN(Pa/
The optimal control method for arc welding according to claim 1, characterized in that the method is expressed as Pi).