JP3532067B2 - Arc sensor copying control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic welding method for welding a structural member such as a steel pipe or a thick plate in which a groove is copied in real time by an arc sensor.

[0002]

2. Description of the Related Art FIG. 7 shows a welding wire swing state in a general groove. In the figure, a swing center control shaft 18 for copying the groove center as a copy control shaft, a torch height control shaft 19 for keeping the welding wire protrusion length constant, and a swing according to the groove width variation. The swing amplitude control shaft 20 for performing is shown.

In many cases, the conventional arc sensor copying is intended for the groove center copying. For example, Japanese Patent Laid-Open No. 58-112661, which copies the groove center line in weaving welding, and the groove center in high-speed rotary arc welding, are known. Kaisho 57-
91877 can be mentioned.

However, the groove shape often changes due to the assembling condition of the members to be welded and the thermal deformation during welding, and if the groove center tracking control is performed while keeping the swing amplitude or the turning radius constant, As the groove width becomes wider than the specified width, deviation of the bead due to delay in copying occurs,
Further, when the groove width becomes narrower than a predetermined width, the welding arc scrapes the groove wall surface to cause welding defects such as undercut. Therefore, it is essential to control the swing amplitude according to the variation of the groove width.

As a countermeasure against the groove width variation, Japanese Patent Application Laid-Open No. 5-2
As disclosed in Japanese Patent No. 3856, there is one that performs a swing amplitude scanning control by detecting the sum of arc voltages at the left and right sides of the groove and comparing it with a preset value. However, the arc voltage changes its setting depending on the welding attitude and the change of the shield gas type, and also greatly changes depending on the fluctuation of the primary power supply voltage and the short circuit condition of the welding wire. That is, in the swing amplitude control, it is necessary to change the set value each time according to various welding conditions. In particular, it is very difficult to change the set value when continuously changing a number of welding conditions such as all-position welding of a steel pipe or the like.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an arc that makes it possible to perform groove tracking control even with various changes in welding conditions only by a predetermined setting. An object is to provide a sensor scanning control method.

[0007]

That is, the gist of the present invention is as follows: (1) In an arc sensor scanning control method, an average welding current value or an average welding current value when the welding wire swing position is in a predetermined region on the right side. The difference between the voltage value and the average welding current value or the average welding voltage value when the swing position is in the central predetermined region is S _R , and the average welding current value or the average welding voltage value when the swing position is in the left predetermined region. Let S _L be the difference between the average welding current value and the average welding voltage value when the swing position is in the central predetermined region, and set S _R and S _L in advance.
The converted at step function F (V), each of the sum F
_{(S R) + F (S} L) is arc sensor tracking controlling method which is characterized in that the oscillation amplitude control of the welding wire to be equal to the reference value V ₁ which is set in advance, and the S _R (2) The arc sensor tracking control method according to the above 1, wherein the swing center control of the welding wire is performed so that the difference in S _L becomes zero. ( 3 ) The average current value of one swing cycle is preset. 3. The arc sensor copying control method according to claim 1, wherein the torch height is controlled so as to be equal to the reference value I ₁ .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1A shows the relationship between the welding wire swing position and the welding current and welding voltage when the groove width is wide.
(B) shows the relationship between the welding wire swing position, the welding current, and the welding voltage when the groove width is narrowed without changing the swing amplitude. Regarding the symbols shown on the horizontal axis, R indicates the wire swing right end, L indicates the wire swing left end, C1 indicates the swing center position on the way to the right end of the wire, and C2 indicates the swing center position on the way to the left end of the wire. .

When the changes in the current and voltage waveforms due to the wire swing are examined, the welding current increases and the welding voltage drops at the swing end R or L. Further, at the swing center C1 or C2, the welding current drops and the welding voltage increases.

Therefore, the respective predetermined regions in R, L, C1 and C2 (the predetermined regions are ranges for removing the noise components of the welding current and welding voltage and are not particularly limited,
Centering around R, L, C1, or C2 1 / of one oscillation cycle
The width of the groove is preferably 4 or less) and the average current value or the average voltage value is obtained to estimate the groove width. For example, the average welding voltages 6 and 8 at the swing center and the average welding voltage 5 at the swing end
Comparing the differences (6-5) and (8-7) with 7 and 7 by the size of the groove width, (6-5) and (8-7) are small when the groove width is wide, When the tip width is narrow, (6-5) and (8-7) become large.

That is, if (6-5) is S _R and (8-7) is S _L , the respective sum S _R + S _L is compared with a preset reference value V ₁ , and S _R + S _L is when greater than V ₁ was to reduce the oscillation amplitude is regarded as the groove width is narrow, S _R
+ S _L is allow oscillation amplitude control corresponding to the groove width variation by widening the oscillation amplitude is regarded as the groove width is wide is smaller than V _1.

However, generally, the welding conditions are not constant. For example, the welding voltage is set to a high value in the large current welding in the downward position, and the welding voltage is set to a low value in the low current welding in the upward position. Under such welding conditions, if S _R + S _L is obtained by changing the groove width while keeping the swing amplitude constant, as shown in FIG. 2, even if the groove width is the same, different values result in good swing amplitude control. Cannot be done.

[0013] Therefore S _R and S _L converted in FIG. 4 shows a step function F (V) a, S _R + S instead F (S of _L
FIG. 3 shows _R ) + F (S _L ), which is shown similarly to FIG. Unlike FIG. 2, F (S _R ) + F (S _L ) shows a constant value regardless of welding conditions, and good swing amplitude control can be performed even when welding conditions are different. The above F
Although the step function is used for (V), a non-linear function such as a sigmoid function may be used.

On the other hand, in the present invention, the swing center scanning control and the torch height scanning control are simultaneously performed. In the swing center scanning control, center axis control is performed so that the difference S _R −S _L between S _R and S _L described above is used as a center shift detection amount and the value becomes zero. Further, in the torch height control, the torch height is controlled so that the average current value I _avg in one oscillation cycle is used as the height shift detection amount and the value becomes equal to the preset reference value I ₁ .

[0015]

EXAMPLE FIG. 5 shows an arc sensor control system. After passing the welding voltage and welding current signals through the DC amplifier 9, they are taken into the A / D converter 10 in synchronization with the encoder pulse 15 output from the welding wire swing shaft, and the control amount is obtained by the personal computer 11. , To each of the control devices 12, 13, and 14. FIG. 6 shows a block diagram for obtaining the control amount.

In step 1, S _R and S _L for rocking amplitude control and S _R -S for rocking center control are provided for each one cycle of rocking.
_L and _Iavg for torch height control are obtained. In step 2, the nonlinear function conversion of S _R and S _L is performed and the sum F
Calculate (S _R ) + F (S _L ). If the welding conditions are always constant and it is not necessary to perform function conversion, S _R + S _L may be obtained without performing non-linear function conversion.

In step 3, in order to stabilize the control amount, the average value of the oscillation frequency cycles is calculated for each axis. The average count can be set independently for each axis.

In step 4, the average value obtained for each axis and a preset reference value V ₁ (reference value for oscillation amplitude control), zero (reference value for oscillation center control), and I ₁ (torch height). (Reference value for control) is obtained, and the value is output to each of the control devices 12, 13, 14 as a control amount. By repeating this series of operations, arc welding can be performed while performing online copying control.

The downward butt welding of the thick plate was actually carried out, the copying control thereof was carried out, and the effect thereof was investigated. The base material is SM400 steel with a plate thickness of 20 mm, and the groove has a root gap of 4
It is an I-shaped groove that linearly changes from mm to 8 mm.
A mixed gas of Ar (80%)-CO ₂ (20%) was used as the shield gas.

Table 1 shows the copying results when the swing center control and the torch height control are performed without performing the swing amplitude control, and when the swing amplitude control, the swing center control, and the torch height control are all performed. Indicates. Welding conditions are condition 1 (current 300A, voltage 2).
8 V, welding speed 72 cm / min) as a basic condition, and welding voltage was raised under condition 2 (current 300 A, voltage 30 V,
Welding speed 72 cm / min) and Condition 3 with low welding current (current 250 A, voltage 24 V, welding speed 45 c)
m / min). The control conditions were all the same.

[0021]

[Table 1]

In the case of no swing amplitude control, poor fusion occurred at the bottom of the groove where the groove width was narrow, and uneven beading occurred where the groove width was wide. On the other hand, in the case where the swing amplitude control is performed, it is different even though the control conditions are the same.
We were able to maintain good quality with no defects for various welding conditions.

[0023]

As described above, according to the present invention, it is possible to perform a highly accurate groove tracking control in welding a structure such as a steel pipe or a thick plate. Further, since it shows a good copying result under various welding conditions, it is possible to improve the reliability of the quality of the welded portion and to save labor and improve efficiency by automated welding.

[Brief description of drawings]

FIG. 1A is a diagram showing the relationship between welding current and welding voltage when the groove width is wide and the wire swing position, and FIG. 1B is welding current when the groove width is narrow, welding voltage and wire swing position. Diagram showing the relationship between

FIG. 2 is a diagram showing S _R + S _L when the groove width changes.

FIG. 3 is a diagram showing F (S _R ) + F (S _L ) when the groove width changes.

FIG. 4 is a diagram showing a step function as an example of a non-linear function.

FIG. 5 is a diagram showing an arc sensor control system.

FIG. 6 is a block diagram for calculating a controlled variable according to the present invention.

FIG. 7 is a view showing a wire swing state in a general groove.

[Explanation of symbols]

1 Right-side swing end Average welding current value in predetermined region 2 Swing center midway toward left-side swing end Average welding current value in predetermined region 3 Left-side swing end Average welding current value in predetermined region 4 Right-side swing end On the way to the center of swinging, the average welding current value 5 in a predetermined area on the right side swinging end 6 The average value of welding voltage on a predetermined area of the right side swinging edge 6 The average welding voltage value on a predetermined area of swinging center on the way to the left side swinging edge 7 Average welding voltage value of the area 8 Swing center on the way to the right swing end Average welding voltage value of a predetermined area 9 DC amplifier 10 A / D converter 11 Personal computer 12 Oscillation amplitude control device 13 Oscillation center control device 14 Torch height control device 15 Encoder pulse of wire swing motor 16 Groove 17 Groove width 18 Swing center control shaft 19 Torch height control shaft 20 Swing amplitude control shaft 21 Welding wire S _R 1-2 or 6-5 S _L 3-4 or 8-7

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Norimitsu Baba 2-6-3 Otemachi, Chiyoda-ku, Tokyo Within Nippon Steel Corporation (56) Reference JP-A-2-59179 (JP, A) JP 60-174268 (JP, A) JP 59-156577 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 9/127 507 B23K 9/12 350

Claims (3)

(57) [Claims] 1. An arc sensor copying control method, comprising:
Average when the swing position of the welding wire is in the predetermined area on the right side
The welding current value or average welding voltage value and the swing position are set to the center.
Average welding current value or average welding voltage value when in area
The difference of S_R Average melting when the rocking position is in the predetermined area on the left side
The contact current value or average welding voltage value and the swing position are in the center
Of the average welding current value or average welding voltage value in the range
The difference is S_L age, Said S _R And S _L The preset
Convert by the Tep function F (V),Sum of eachF (S
_R ) + F (S _L )Is a preset reference value V₁ Is equal to
To control the swing amplitude of the welding wire so that
Arc sensor copying control method to be considered. 2. The arc sensor copying control method according to claim 1, wherein the swing center control of the welding wire is performed so that the difference between S _R and S _L becomes zero. 3. The arc sensor scanning control method according to claim 1, wherein the torch height control is performed so that the average current value of one oscillation cycle becomes equal to a preset reference value I _1. .