CN109848524B - Narrow-gap gas metal arc vertical welding seam tracking method - Google Patents
Narrow-gap gas metal arc vertical welding seam tracking method Download PDFInfo
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Abstract
The invention discloses a narrow-gap gas metal arc vertical welding seam tracking method, belongs to the technical field of intelligent welding, and aims to solve the problems that an existing mechanical stylus type sensor is easily subjected to thermal deformation and cannot avoid interference caused by metal particles adhered to the side wall of a groove, and a laser vision sensor cannot extend into the groove to detect the root gap of a large thick plate or a wall member due to the limitation of geometric dimension and depth of field. The method comprises the steps of obtaining the average value of initial current at the left side, the right side and the stay position of a central welding torch of the groove as the datum data of welding seam tracking, starting the welding seam tracking in a new welding period, obtaining the position of the welding torch by a PLC after welding is stable, obtaining real-time welding current when the welding torch stays at the left side of the groove, obtaining the average value of the current according to a distinguished welding mode, removing a special point, comparing the average value with the datum data, and respectively tracking the height of the welding torch and the level of the welding torch until the welding seam is finished. The invention is used for tracking the welding seam.
Description
Technical Field
The invention relates to a welding seam tracking method, and belongs to the technical field of intelligent welding.
Background
With the rapid popularization of modern industrial equipment and national major projects to high capacity and high parameters, the large-scale, heavy-duty, high-strength and thick-plate type industrial equipment and steel structures become the most important characteristics of the current manufacturing industry, the quantity of welding projects is increased in geometric series, and the contradiction between the welding production efficiency and the manufacturing period as well as the manufacturing cost is increasingly prominent. The high-efficiency, high-quality and low-cost welding of large thick plates and extra thick plates has become the leading-edge field of the development of the current manufacturing technology.
The Gas Metal Arc Welding (GMAW) has the comprehensive technical advantages of small groove filling area, high deposition efficiency, low Welding heat input, full-position Welding and the like, and is an optimal technical approach for solving the contradiction between production efficiency, manufacturing period and manufacturing cost. Because the groove gap is narrow (generally within 20 mm), the repair difficulty is high, and how to ensure low splashing in the welding process and stable fusion of the two side walls of the groove are the key points of narrow gap GMAW. The current development of a digital power supply and a waveform control technology can basically meet the welding requirement of narrow-gap GMAW low spattering. However, good stable fusion of the groove side walls requires reliable and accurate weld tracking techniques.
In order to solve the problems of fusion quality monitoring or weld tracking of the side wall of a narrow-gap GMAW groove, the prior art mainly comprises the following 5 types: (1) a mechanical probe is adopted, a rotary potentiometer is used as an angular displacement sensor, the position deviation of the welding torch is amplified and converted into electric quantity through mechanical detection (a probe or a guide wheel), and whether the welding torch is strictly centered or not is judged; (2) extracting a longitudinal deviation signal and a transverse deviation signal of the welding torch by adopting a capacitive sensor and sequentially performing capacitive voltage conversion, filtering, amplification, A/D conversion and the like; (3) collecting images of a groove and an electric arc by adopting a laser vision sensor, and guiding a welding torch to be centered by key point data through image processing such as noise reduction, feature extraction, mode matching and the like; (4) collecting arc acoustic signals under different arc-side wall distances by adopting an acoustic signal sensor, extracting characteristic quantities representing the arc-side wall distances through signal noise reduction and processing, and indirectly judging the welding torch centering condition; (5) the height and horizontal deviation of the welding torch are judged by adopting an arc sensor and through current sampling and comparison based on the change rule of the electric signal of the arc. The mechanical probe or guide wheel adopted by the technology (1) is easy to deform due to radiation of a molten pool and electric arc, cannot avoid interference caused by metal particles adhered to the side wall of the groove, and is mainly used for seam tracking of narrow-gap submerged arc welding; technologies (2) and (3) relate to installation of sensors and accessories, are interfered by arc light, electromagnetism, splashing, smoke dust and the like in an arc welding process, and are limited in accessibility of a welding torch and a detection range method; the technology (4) is easily polluted by the environmental noise of a production field, is difficult to control data, is basically invalid when being used alone, and cannot realize accurate quantitative description; technique (5) works well for typical sheet butt or angle joints, but requires bevel angles substantially above 45 ° and is dominated by horizontal position welding arc tracking applications, which limits its application in narrow gap GMAW. In recent years, research on narrow-gap GMAW arc tracking strategies, precision, stability, real-time performance and the like has been carried out in domestic scientific research institutes, and certain results are obtained, but the narrow-gap GMAW arc tracking strategies are basically in the laboratory stage. Particularly, for narrow-gap GMA vertical welding seam tracking which is not reported, technical breakthrough and industrial application are urgently awaited.
Disclosure of Invention
The invention aims to solve the problems that the existing mechanical contact pin type sensor is easy to be subjected to thermal deformation and cannot avoid interference caused by metal particles adhered to the side wall of a groove, and a laser vision sensor cannot extend into the groove to detect the root gap of a large thick plate or a wall member due to the limitation of geometric dimension and depth of field, and provides a narrow-gap consumable electrode gas shielded vertical welding seam tracking method.
The invention relates to a narrow-gap gas metal arc vertical welding seam tracking method, which comprises the following specific processes:
s1, inputting welding parameters and tracking parameters on a human-computer interaction interface, and adjusting the welding parameters and the tracking parameters to meet the welding seam forming requirements by observing the stability of the electric arc and the fusion quality of the side walls of the two sides of the groove;
s2, starting the welding torch, obtaining an initial current mean value at the left side of the groove at the position where the welding torch stays, an initial current mean value at the right side of the groove at the position where the welding torch stays and an initial current mean value at the center of the groove at the position where the welding torch stays, and taking the three initial current mean values as datum data for welding seam tracking;
s3, starting weld joint tracking in a new welding period;
s4, the PLC acquires the position of the welding torch, and when the welding torch stops at the left side of the groove, the signal acquisition module senses the welding current value through the current sensor and sends the welding current value to the ARM processor;
s5, the ARM processor converts the current signal into a digital signal and judges the welding mode according to the current change rule;
s6, obtaining the current mean value I of the left welding torch of the groove at the stop position according to the welding mode judged by S5LMean value of current I at the position where welding torch stays on the right side of grooveRAnd the mean value I of the current at the stay position of the welding torch at the center of the grooveC；
S7, obtaining three current mean values I obtained in S6L、IRAnd ICConverting into actual current value, and calculating three current average values I in sampling periodL、IRAnd ICStandard deviation of (d);
s8, removing the specific points of the current mean value from the standard deviation obtained in S7, and recalculating the three current mean values I after the specific points are removedL'、IR' and IC'；
S9, the signal acquisition module removes three current mean values I of the special points through the serial portL'、IR' and IC' send to PLC;
s10, comparing the current mean value obtained in the S9 after the special points are removed with the reference data obtained in the S2, and tracking the height and the level of the welding torch respectively;
and S11, repeatedly executing S3-S10 until the welding of the welding seam is finished.
Preferably, the welding parameters of S1 include welding current, arc voltage, welding speed and swing parameters.
Preferably, the tracking parameters of S1 include an allowable fluctuation range of the current comparison quantity and a deviation correction displacement quantity;
wherein the allowable fluctuation range of the current comparison quantity comprises: tracking the allowable fluctuation range sigma of the process current comparison quantity for the height of the welding torch and tracking the allowable fluctuation range sigma' of the process current comparison quantity for the level of the welding torch;
the deviation correcting displacement comprises the following steps: and (3) tracking the deviation correcting displacement of the welding torch in the height tracking process and tracking the deviation correcting displacement of the welding torch in the horizontal tracking process.
Preferably, the specific process of S2 is:
s2-1, acquiring the position of the welding torch after the welding is stable by the PLC, sensing the welding current value by the signal acquisition module through the current sensor when the welding torch stops at the left side of the groove, and sending the welding current value to the ARM processor;
s2-2, the ARM processor converts the current signal into a digital signal, judges whether welding starts or not according to a current change rule, and judges a welding mode if the welding starts;
s2-3, obtaining the initial current mean value I at the position where the welding torch at the left side of the groove stays according to the welding mode judged by S2-2L0Initial current mean value I at the position where welding torch stays on the right side of grooveR0And the mean value I of the initial current at the stay position of the welding torch at the center of the grooveC0；
S2-4, obtaining three initial current mean values I from S2-3L0、IR0And IC0Converting into actual current value, and calculating three initial current average values I in sampling periodL0、IR0And IC0Standard deviation of (d);
s2-5, removing the specific points of the initial current mean value from the standard deviation obtained in the step S2-4, and recalculating the three initial current mean values I after the specific points are removedL0'、IR0' and IC0'；
S2-6, the signal acquisition module removes the three initial current mean values I of the special points through the serial portL0'、IR0' and IC0' send to PLC;
s2-7, PLC will IL0'、IR0' and IC0' make first backup, with first backup IL0'、IR0' and IC0' as reference data for seam tracking.
Preferably, the step of obtaining three current mean values I according to the welding mode in S6L、IRAnd ICThe basis of (A) is as follows:
when the welding mode is a pulse mode, respectively obtaining the current average value I at the staying position of the welding torch on the left side of the groove according to the pulse periodLMean value of current I at the position where welding torch stays on the right side of grooveRAnd the mean value I of the current at the stay position of the welding torch at the center of the grooveC；
When the welding mode is a non-pulse mode, grooves are respectively obtained according to 10ms as one periodAverage current I at left torch dwell positionLMean value of current I at the position where welding torch stays on the right side of grooveRAnd the mean value I of the current at the stay position of the welding torch at the center of the grooveC。
Preferably, the specific process of tracking the height of the welding torch in S10 is as follows:
the PLC receives the current mean value I at the staying position of the welding torch at the center of the groove with the specific point removedC', mean value of initial current I at position where the central torch of the groove stops with the specific point removedC0' making a difference IC'-IC0'；
Will be different from the difference value IC'-IC0' comparison with the allowable fluctuation range σ of the current comparison amount:
IC'-IC0if the height is higher than sigma, the current welding torch is low, and the PLC controls the welding torch to be lifted according to the deviation correcting displacement;
IC'-IC0' less than-sigma, it indicates that the current welding torch is higher in height, and the PLC controls the welding torch to be lowered according to the deviation correcting displacement.
Preferably, only one torch height tracking comparison is made per arc travel cycle.
Preferably, the specific process of tracking the torch level in S10 is:
the PLC receives the current mean value I at the stay position of the welding torch at the left side of the groove with the special point removedL' and mean value of current I at the position where welding torch stays on the right side of grooveR', do not make a difference IL'-IR'＝A；
The mean value I of the initial current at the stay position of the welding torch at the left side of the groove with the special point removedL0' and initial current mean value I at the torch stopping position on the right side of grooveR0' making a difference IL0'-IR0'＝B；
And (3) comparing the difference between A and B with the allowable fluctuation range sigma' of the current comparison quantity:
(IL'-IR')-(IL0'-IR0') is greater than sigma', indicating that the current welding torch is horizontally deviated to the left, and the PLC controls the welding torch to move to the right according to the deviation-rectifying displacement;
(IL'-IR')-(IL0'-IR0') < -sigma', indicating that the current welding torch is horizontally deviated to the right, and the PLC controls the welding torch to move to the left according to the deviation correcting displacement.
Preferably, only one torch level tracking comparison is made per arc movement cycle.
The invention has the advantages that: the invention relates to a method for welding torch self-adaptive groove tracking in a narrow-gap consumable electrode gas shielded welding process of a thick plate/thick-wall structural member. The automatic tracking and deviation correction in the height and horizontal direction of the welding torch is realized by collecting and calculating the current mean values of the left and right side stopping positions and the groove center position of each arc moving period in the stable welding state, and the automatic tracking and deviation correction method has the advantages that:
1. the welding torch does not need to be provided with a sensor and an additional module, and the accessibility is not influenced;
2. the welding seam tracking method is suitable for various arc moving modes such as swing arc, rotating arc, swinging arc and the like, and is also suitable for different welding positions such as horizontal welding, vertical welding and the like;
3. the singular point of the current mean value is removed by adopting the standard deviation, the fluctuation of the welding process caused by the adhesion of metal particles on the side wall is effectively avoided, and the tracking reliability is high;
4. the tracking method is suitable for welding torches with 0-2.5-degree deviation in the height direction and 0-3.0-degree deviation in the horizontal direction, and under the condition of reasonable parameter setting, the horizontal tracking precision can reach +/-0.2 mm, and the height tracking precision can reach +/-0.5 mm;
5. the tracking method is convenient to integrate with an automatic special machine and a robot, and meets the welding production requirements of high-efficiency, high-quality and low-cost narrow-gap gas metal arc vertical welding of thick plate/thick-wall structural members.
Drawings
FIG. 1 is a schematic block diagram of a narrow gap gas metal arc vertical welding seam tracking method according to the present invention;
FIG. 2 is a block flow diagram of a narrow gap gas metal arc vertical welding seam tracking method according to the present invention;
FIG. 3 is a graph comparing the weld tracking accuracy according to the third embodiment;
fig. 4 is a schematic view of a groove form of gas metal arc vertical welding with narrow gaps on both sides of the high-strength steel extra-thick plate according to the fourth specific embodiment.
Detailed Description
The first embodiment is as follows: the following describes the present embodiment with reference to fig. 1 and fig. 2, and the narrow gap gas metal arc vertical welding seam tracking method of the present embodiment includes the following specific processes:
s1, inputting welding parameters and tracking parameters on a human-computer interaction interface, and adjusting the welding parameters and the tracking parameters to meet the welding seam forming requirements by observing the stability of the electric arc and the fusion quality of the side walls of the two sides of the groove;
the welding parameters include welding current, arc voltage, welding speed, and swing parameters.
The tracking parameters comprise an allowable fluctuation range of the current comparison quantity and a deviation correction displacement quantity;
wherein the allowable fluctuation range of the current comparison quantity comprises: tracking the allowable fluctuation range sigma of the process current comparison quantity for the height of the welding torch and tracking the allowable fluctuation range sigma' of the process current comparison quantity for the level of the welding torch;
the deviation correcting displacement comprises the following steps: and (3) tracking the deviation correcting displacement of the welding torch in the height tracking process and tracking the deviation correcting displacement of the welding torch in the horizontal tracking process.
S2, starting the welding torch, obtaining an initial current mean value at the left side of the groove at the position where the welding torch stays, an initial current mean value at the right side of the groove at the position where the welding torch stays and an initial current mean value at the center of the groove at the position where the welding torch stays, and taking the three initial current mean values as datum data for welding seam tracking;
the specific process is as follows:
s2-1, acquiring the position of the welding torch after the welding is stable by the PLC, sensing the welding current value by the signal acquisition module through the current sensor when the welding torch stops at the left side of the groove, and sending the welding current value to the ARM processor;
s2-2, the ARM processor converts the current signal into a digital signal, judges whether welding starts or not according to a current change rule, and judges a welding mode if the welding starts;
s2-3, determined according to S2-2In a welding mode, obtaining an initial current mean value I at the staying position of a welding torch on the left side of the grooveL0Initial current mean value I at the position where welding torch stays on the right side of grooveR0And the mean value I of the initial current at the stay position of the welding torch at the center of the grooveC0；
S2-4, obtaining three initial current mean values I from S2-3L0、IR0And IC0Converting into actual current value, and calculating three initial current average values I in sampling periodL0、IR0And IC0Standard deviation of (d);
s2-5, removing the specific points of the initial current mean value from the standard deviation obtained in the step S2-4, and recalculating the three initial current mean values I after the specific points are removedL0'、IR0' and IC0'；
S2-6, the signal acquisition module removes the three initial current mean values I of the special points through the serial portL0'、IR0' and IC0' send to PLC;
s2-7, PLC will IL0'、IR0' and IC0' make first backup, with first backup IL0'、IR0' and IC0' as reference data for seam tracking.
S2-3, acquiring the initial current mean value I at the stay position of the welding torch on the left side of the groove according to the welding modeL0Initial current mean value I at the position where welding torch stays on the right side of grooveR0And the mean value I of the initial current at the stay position of the welding torch at the center of the grooveC0The basis of (A) is as follows:
when the welding mode is a pulse mode, respectively obtaining the initial current mean value I at the staying position of the welding torch on the left side of the groove according to the pulse periodL0Initial current mean value I at the position where welding torch stays on the right side of grooveR0And the mean value I of the initial current at the stay position of the welding torch at the center of the grooveC0；
When the welding mode is a non-pulse mode, respectively obtaining the initial current mean value I at the stay position of the welding torch on the left side of the groove according to a period of 10msL0Initial current mean value I at the position where welding torch stays on the right side of grooveR0And the mean value I of the initial current at the stay position of the welding torch at the center of the grooveC0。
S3, starting weld joint tracking in a new welding period;
s4, the PLC acquires the position of the welding torch, and when the welding torch stops at the left side of the groove, the signal acquisition module senses the welding current value through the current sensor and sends the welding current value to the ARM processor;
s5, the ARM processor converts the current signal into a digital signal and judges the welding mode according to the current change rule;
s6, obtaining the current mean value I of the left welding torch of the groove at the stop position according to the welding mode judged by S5LMean value of current I at the position where welding torch stays on the right side of grooveRAnd the mean value I of the current at the stay position of the welding torch at the center of the grooveC；
S7, obtaining three current mean values I obtained in S6L、IRAnd ICConverting into actual current value, and calculating three current average values I in sampling periodL、IRAnd ICStandard deviation of (d);
s8, removing the specific points of the current mean value from the standard deviation obtained in S7, and recalculating the three current mean values I after the specific points are removedL'、IR' and IC'；
S9, the signal acquisition module removes three current mean values I of the special points through the serial portL'、IR' and IC' send to PLC;
s10, comparing the current mean value obtained in the S9 after the special points are removed with the reference data obtained in the S2, and tracking the height and the level of the welding torch respectively;
the specific process of tracking the height of the welding torch comprises the following steps:
the PLC receives the current mean value I at the staying position of the welding torch at the center of the groove with the specific point removedC', mean value of initial current I at position where the central torch of the groove stops with the specific point removedC0' making a difference IC'-IC0'；
Will be different from the difference value IC'-IC0' comparison with the allowable fluctuation range σ of the current comparison amount:
IC'-IC0if the height is higher than sigma, the current welding torch is low, and the PLC controls the welding torch to be lifted according to the deviation correcting displacement;
IC'-IC0' less than-sigma, it indicates that the current welding torch is higher in height, and the PLC controls the welding torch to be lowered according to the deviation correcting displacement.
The specific process of tracking the welding torch level is as follows:
the PLC receives the current mean value I at the stay position of the welding torch at the left side of the groove with the special point removedL' and mean value of current I at the position where welding torch stays on the right side of grooveR', do not make a difference IL'-IR'＝A；
The mean value I of the initial current at the stay position of the welding torch at the left side of the groove with the special point removedL0' and initial current mean value I at the torch stopping position on the right side of grooveR0' making a difference IL0'-IR0'＝B；
And (3) comparing the difference between A and B with the allowable fluctuation range sigma' of the current comparison quantity:
(IL'-IR')-(IL0'-IR0') is greater than sigma', indicating that the current welding torch is horizontally deviated to the left, and the PLC controls the welding torch to move to the right according to the deviation-rectifying displacement;
(IL'-IR')-(IL0'-IR0') < -sigma', indicating that the current welding torch is horizontally deviated to the right, and the PLC controls the welding torch to move to the left according to the deviation correcting displacement.
And S11, repeatedly executing S3-S10 until the welding of the welding seam is finished.
The second embodiment is as follows: in this embodiment, the first embodiment is further explained, in which the torch height tracking comparison is performed only once per arc moving period; only one torch level tracking comparison is made per arc movement cycle.
The third concrete implementation mode: the present embodiment will be described with reference to FIG. 3, and the first embodiment will be further described, in which A709-50-2 having a plate thickness of 50mm is placed on a milling machine to form a simulated groove having a width of 20X 8.5mm, and the bottom of the test plate is tilted by a spacer block by 5mm (1.6 ℃ tilt) in the horizontal direction and by 6mm (1.6 ℃ tilt) in the height direction of the welding torch. Selecting a diameter of 12mm MG-S88A welding wire, loose YD-500GS4 as welding power source, 85% Ar + 15% CO as protective gas2The protective gas flow is 15-20L/min (gun) + 30-40L/min (cover). During welding, the robot carries the narrow-gap GMA welding torch to make translational motion along the length direction of the groove and the depth direction of the groove, and the motion in the width direction of the groove is realized by a rotation and swing mechanism of the narrow-gap welding torch. The following implementation process of the tracking effect of the narrow-gap swinging arc GMA vertical welding seam is as follows:
on the human-computer interface of the weld tracking system, manually adjusting welding parameters (including welding current, arc voltage, welding speed and swing parameters) and tracking parameters (including allowable fluctuation range sigma/sigma 'of current comparison amount and deviation correction displacement/') as shown in tables 1 and 2:
TABLE 1
TABLE 2
And observing the stability of the narrow-gap consumable electrode gas-shielded vertical welding arc and the fusion quality of the side walls on two sides of the groove until the requirement of welding seam formation is met.
The narrow-gap gas metal arc vertical welding arc tracking actual measurement effect is good, the surface of a welding line is formed to be slightly concave, the side walls on two sides are fused well, and the fusion depth is close. Meanwhile, in the welding tracking process, a welding line deviation straight line (theory) is drawn according to position measurement, the tracking center position is read after tracking is started, the actual center line position deviation is calculated, and the value is taken once in each arc moving period. The weld tracking accuracy is calculated by comparing the theoretical weld deviation straight line with the actual center line position, as shown in fig. 3. Therefore, the horizontal tracking precision of the system can reach +/-0.2 mm, the height tracking precision can reach +/-0.5 mm, and the requirements of the narrow-gap gas metal arc vertical welding process are met.
The fourth concrete implementation mode: the following describes the embodiment with reference to fig. 4, and the embodiment further describes the first embodiment, and the self-elevating platform pile leg uses an 177.8mm thick high-quality advanced quenched and tempered high-strength steel elongation process assessment test as an application target, and adopts a double-sided single-filament narrow-gap gas metal arc vertical welding process. The high-quality ocean engineering super-thick plate is 177.8mm thick rack steel DILLIMAX690E produced by Germany Dilingge iron and steel company, the groove design is as shown in figure 4, the single-side groove angle alpha is 1.0 degrees, the pairing gap is 18mm, the root chamfer R is 3.0mm, and the root blunt edge b is 3 mm. According to the principle of equal-strength matching, MG-S88A welding wires with the diameter of 1.2mm are selected, the shielding gas is 85% Ar + 15% CO2, and the shielding gas flow is 15-20L/min (gun) + 30-40L/min (cover). During welding, the robot carries the narrow-gap gas metal arc vertical welding torch to make translational motion along the length direction and the depth direction of the groove, and the motion in the width direction of the groove is realized by a rotation and swing mechanism of the narrow-gap welding torch. The welding sequence is as follows: preheating before welding (the preheating temperature is 160 +/-10 ℃) → front welding 3-4 layers (the thickness of an accumulated welding layer is about 15mm, the interlayer temperature is 180 +/-10 ℃) → back gouging (the back gouging depth reaches a front bottom layer) → back welding until the thicknesses of the welding layers on the two sides of the groove are basically the same → bilateral symmetrical welding till the end → dehydrogenation treatment (the heating temperature is 250 +/-50 ℃, and the heat preservation time is 2 h). The implementation process of the tracking effect of the narrow-gap consumable electrode gas metal vertical welding seam of the high-strength steel extra-thick plate is as follows:
on the human-computer interface of the weld tracking system, manually adjusting welding parameters (including welding current, arc voltage, welding speed and swing parameters) and tracking parameters (including allowable fluctuation range sigma/sigma 'of current comparison amount and deviation correction displacement/') as shown in tables 3 and 4:
TABLE 3
TABLE 4
And observing the stability of the narrow-gap GMA vertical welding arc and the fusion quality of the side walls of the two sides of the groove until the welding seam forming requirement is met.
50 layers, a front surface 24 layer and a back surface 26 layer are welded together. And carrying out ultrasonic and magnetic powder inspection 72h after welding, wherein the detection result shows that the welded joint has no internal welding defects and surface welding cracks. Meanwhile, the cut multiple groups of joint macroscopic samples are planed, polished and eroded for macroscopic inspection, and no defect is found on all the sections. The welding layer is clear, the width and the thickness of the welding layer are uniform, and the side wall fusion is good.
According to the invention, the current mean values of the left and right side staying positions and the groove center position of each arc moving period in a stable welding state are collected and calculated, and the difference value comparison is carried out to realize automatic tracking and deviation correction of the height and the horizontal direction of the welding torch, under the condition of reasonable parameter setting, the horizontal tracking precision of the system can reach +/-0.2 mm, the height tracking precision can reach +/-0.5 mm, and the welding production requirements of high-efficiency, high-quality and low-cost narrow-gap metal-arc vertical welding of thick plate/thick-wall structural parts are met.
In the present invention, the principle of torch height (arc length) tracking is: when the dry elongation of the welding wire is increased, the welding current is reduced; when the dry elongation of the wire is reduced, the welding current is increased. Under ideal conditions, when the height of the welding torch is not changed, the real-time current average value I of the central position of the welding seamC' with reference value IC0Within the permitted range of fluctuation, i.e. IC'-IC0' is less than or equal to sigma; and when the welding torch is lifted or lowered, the real-time current average value I of the welding seam center positionC' with reference value IC0The difference will be outside the allowable range, i.e. IC'-IC0' > σ, the arc length tracking mechanism is initiated. If IC'-IC0' > sigma, indicating that the height of the welding torch is lower and controlling the welding torch to lift; otherwise, IC'-IC0' < -sigma, indicating that the torch is high and the torch is controlled to lower.
In the invention, the welding torch horizontal (centering) tracking principle is the same as the arc length tracking phaseSimilarly, under ideal conditions, when the welding torch is centered on the center of the welding seam, the difference I between the real-time current mean values of the stay positions on the two horizontal sides of the grooveL'-IR' with reference value IL0'-IR0Within the allowable fluctuation range, i.e. (I)L'-IR')-(IL0'-IR0') is less than or equal to sigma'; when the welding torch deviates to the left or the right, the difference I of the real-time current mean values of the stopping positions at the two horizontal sides of the grooveL'-IR' Difference from reference IL0'-IR0The difference will be outside the allowable range, i.e., (I)L'-IR')-(IL0'-IR0') > σ', initiates a centering tracking mechanism. If (I)L'-IR')-(IL0'-IR0') > σ', indicating that the welding torch is horizontally deviated to the left and controlling the welding torch to move to the right; otherwise, (I)L'-IR')-(IL0'-IR0') < - σ', indicating that the welding torch is horizontally deviated to the right and the welding torch is controlled to move to the left.
Before controlling a welding torch deviation rectifying execution motor, firstly adjusting parameters through a human-computer interaction interface until welding requirements are met, then sensing a current signal in the narrow-gap gas metal arc vertical welding process through a current sensor by a tracking system, acquiring and solving a current mean value of a left side stopping position, a right side stopping position and a groove center position of each arc moving period by utilizing an ARM processor, and then sending the current mean value to a PLC (programmable logic controller) through a serial port; after the PLC receives the data, current mean values of three positions are backed up to be used as a tracking reference, series operation is carried out on the current mean values and real-time welding current mean values obtained later, and a servo driving unit in the height direction and the horizontal direction of the welding torch is controlled to carry out deviation rectification adjustment according to a comparison result.
Claims (9)
1. The method for tracking the welding seam of the narrow-gap gas metal arc vertical welding is characterized by comprising the following specific processes:
s1, inputting welding parameters and tracking parameters on a human-computer interaction interface, and adjusting the welding parameters and the tracking parameters to meet the welding seam forming requirements by observing the stability of the electric arc and the fusion quality of the side walls of the two sides of the groove;
s2, starting the welding torch, obtaining an initial current mean value at the left side of the groove at the position where the welding torch stays, an initial current mean value at the right side of the groove at the position where the welding torch stays and an initial current mean value at the center of the groove at the position where the welding torch stays, and taking the three initial current mean values as datum data for welding seam tracking;
s3, starting weld joint tracking in a new welding period;
s4, the PLC acquires the position of the welding torch, and when the welding torch stops at the left side of the groove, the signal acquisition module senses the welding current value through the current sensor and sends the welding current value to the ARM processor;
s5, the ARM processor converts the current signal into a digital signal and judges the welding mode according to the current change rule;
s6, obtaining the current mean value I of the left welding torch of the groove at the stop position according to the welding mode judged by S5LMean value of current I at the position where welding torch stays on the right side of grooveRAnd the mean value I of the current at the stay position of the welding torch at the center of the grooveC；
S7, obtaining three current mean values I obtained in S6L、IRAnd ICConverting into actual current value, and calculating three current average values I in sampling periodL、IRAnd ICStandard deviation of (d);
s8, removing the specific points of the current mean value from the standard deviation obtained in S7, and recalculating the three current mean values I after the specific points are removedL'、IR' and IC'；
S9, the signal acquisition module removes three current mean values I of the special points through the serial portL'、IR' and IC' send to PLC;
s10, comparing the current mean value obtained in the S9 after the special points are removed with the reference data obtained in the S2, and tracking the height and the level of the welding torch respectively;
and S11, repeatedly executing S3-S10 until the welding of the welding seam is finished.
2. The narrow gap gas metal arc vertical welding seam tracking method according to claim 1, wherein the welding parameters of S1 include welding current, arc voltage, welding speed and swing parameters.
3. The narrow-gap gas metal arc vertical welding seam tracking method according to claim 1 or 2, wherein the tracking parameters of S1 comprise allowable fluctuation range of current comparison quantity and deviation correction displacement quantity;
wherein the allowable fluctuation range of the current comparison quantity comprises: tracking the allowable fluctuation range sigma of the process current comparison quantity for the height of the welding torch and tracking the allowable fluctuation range sigma' of the process current comparison quantity for the level of the welding torch;
the deviation correcting displacement comprises the following steps: and (3) tracking the deviation correcting displacement of the welding torch in the height tracking process and tracking the deviation correcting displacement of the welding torch in the horizontal tracking process.
4. The narrow-gap gas metal arc vertical welding seam tracking method according to claim 3, characterized in that the specific process of S2 is as follows:
s2-1, acquiring the position of the welding torch after the welding is stable by the PLC, sensing the welding current value by the signal acquisition module through the current sensor when the welding torch stops at the left side of the groove, and sending the welding current value to the ARM processor;
s2-2, the ARM processor converts the current signal into a digital signal, judges whether welding starts or not according to a current change rule, and judges a welding mode if the welding starts;
s2-3, obtaining the initial current mean value I at the position where the welding torch at the left side of the groove stays according to the welding mode judged by S2-2L0Initial current mean value I at the position where welding torch stays on the right side of grooveR0And the mean value I of the initial current at the stay position of the welding torch at the center of the grooveC0；
S2-4, obtaining three initial current mean values I from S2-3L0、IR0And IC0Converting into actual current value, and calculating three initial current average values I in sampling periodL0、IR0And IC0Standard deviation of (d);
s2-5, removing the specific points of the initial current mean value from the standard deviation obtained in the step S2-4, and recalculating the three initial current mean values I after the specific points are removedL0'、IR0' and IC0'；
S2-6, the signal acquisition module removes the three initial current mean values I of the special points through the serial portL0'、IR0' and IC0' send to PLC;
s2-7, PLC will IL0'、IR0' and IC0' make first backup, with first backup IL0'、IR0' and IC0' as reference data for seam tracking.
5. The narrow gap gas metal arc vertical welding seam tracking method according to claim 1, wherein the welding mode determined according to the step S5 of S6 is used for obtaining three current mean values IL、IRAnd ICThe basis of (A) is as follows:
when the welding mode is a pulse mode, respectively obtaining the current average value I at the staying position of the welding torch on the left side of the groove according to the pulse periodLMean value of current I at the position where welding torch stays on the right side of grooveRAnd the mean value I of the current at the stay position of the welding torch at the center of the grooveC；
When the welding mode is a non-pulse mode, respectively obtaining the current average value I at the stay position of the welding torch on the left side of the groove according to a period of 10msLMean value of current I at the position where welding torch stays on the right side of grooveRAnd the mean value I of the current at the stay position of the welding torch at the center of the grooveC。
6. The narrow gap gas metal arc vertical welding seam tracking method according to claim 4, wherein the specific process of tracking the welding torch height in S10 is as follows:
the PLC receives the current mean value I at the staying position of the welding torch at the center of the groove with the specific point removedC', mean value of initial current I at position where the central torch of the groove stops with the specific point removedC0' making a difference IC'-IC0'；
Will be different from the difference value IC'-IC0' comparison with the allowable fluctuation range σ of the current comparison amount:
IC'-IC0' > σ indicates that the current torch is low in height, PThe LC controls the welding torch to rise according to the deviation correcting displacement;
IC'-IC0' less than-sigma, it indicates that the current welding torch is higher in height, and the PLC controls the welding torch to be lowered according to the deviation correcting displacement.
7. The narrow gap gas metal arc vertical weld tracking method of claim 6, wherein only one torch height tracking comparison is performed per arc travel cycle.
8. The narrow gap gas metal arc vertical welding seam tracking method according to claim 4, wherein the specific process of tracking the welding torch level in S10 is as follows:
the PLC receives the current mean value I at the stay position of the welding torch at the left side of the groove with the special point removedL' and mean value of current I at the position where welding torch stays on the right side of grooveR', do not make a difference IL'-IR'＝A；
The mean value I of the initial current at the stay position of the welding torch at the left side of the groove with the special point removedL0' and initial current mean value I at the torch stopping position on the right side of grooveR0' making a difference IL0'-IR0'＝B；
And (3) comparing the difference between A and B with the allowable fluctuation range sigma' of the current comparison quantity:
(IL'-IR')-(IL0'-IR0') is greater than sigma', indicating that the current welding torch is horizontally deviated to the left, and the PLC controls the welding torch to move to the right according to the deviation-rectifying displacement;
(IL'-IR')-(IL0'-IR0') < -sigma', indicating that the current welding torch is horizontally deviated to the right, and the PLC controls the welding torch to move to the left according to the deviation correcting displacement.
9. The narrow gap gas metal arc vertical weld tracking method of claim 8, wherein only one torch level tracking comparison is performed per arc movement cycle.
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