Measures to improve the quality of pipeline steel pipe welding

1 outside dc welding with welding current display device

1.1 with welding current display control for outside welding welding units of Lincoln NA a 5 control box, the welding control characteristic is CV (constant pressure control), and can preset including welding voltage, welding speed and wire feed speed welding parameters. On the control box panel welding voltage and wire feed speed display, no display of welding current, as shown in figure 1. Due to not have accurate display of welding current when the supervisor and the owner to know figure 1 NA - 5 control box appearance figure of the welding current size, can only use digital clip-on ammeter measure 5 ~ 6 times, take the average, the time is long and great error in the measurement process. Therefore, decided to install ammeter to display welding current.

1.2 implement methods there are three methods to choose from: (1) use a pointer type current meter; (2) using digital ammeter; (3) using the original current sensor design digital display device. Pointer type current meter is economical and practical, easy installation, ewei repair, and the characteristics of small affected by environment, combining the reality of the scene of the workshop Conditions, and with reference to a 3 s and NA NA a 4 control box, decided to adopt a pointer type current meter and shunt outside welding dc display device. Choose magnetoelectric ammeter, models for 63 c18, range 1 500 A. Specific method is: after the ammeter and shunt in parallel, in series to the holder line again, as shown in figure 2. With this set of device, the operator can be adjusted accurately and visually outside welding welding current, so as to realize the effective monitoring of butt welding by electric current.

2 weld automatic tracking system

2.1 the improved scheme

The original weld automatic tracking device low accuracy, real-time, response time is long, still need to operating personnel can't meet the requirements of the production of the welding process. So, decide, and outside welding respectively with British Meta Vista automatic weld seam tracking system.

2.2 system

Vista automatic Weld seam tracking system by sensor components, servo motor actuators, industrial computer image processing part, control components, etc. The system with laser stripe as working medium, when the camera after laser stripe images collected, into the computer image processing, the results after the executing agency to complete the action. The device has high reliability, stable work, the advantages of simple structure, convenient installation and maintenance. System structure diagram as shown in figure 3.

2.3 working principle

Laser structure light vision sensing principle as shown in figure 4, here only draw a laser stripe, the other two the same. This system belongs to the use of structured light laser as light source visual sensing of weld tracking system. Laser tube a point light source by the cylindrical lens into a strip light source, projected onto the workpiece weld groove, the deformation of the laser stripe have corresponding to diffuse over artifacts. CCD camera to receive from the workpiece shape on the diffuse reflection of slope mouth shape of laser stripe, through image acquisition and image processing link, that is the laser stripe deformation in the center position, namely the weld centerline. CCD camera to the computer for image processing, laser stripe image and compared with the center of the set, when there is deviation, send out the correction instruction system, device and controlled by the PLC control servo motor movements, complete correction tracking process. The junction structure light method can not only detect the center of the weld, and also can get the weld cross section shape and characteristic parameters such as size, suitable for different weld and all kinds of welding methods. The production actual use prove that the automatic tracking system Can be corrected in the welding process of small deviation, greatly reducing the welding welding defects such as partial, incomplete fusion, improve the welding quality. Compared with the conventional tracking equipment and manual operation, the system has high tracking precision, response speed, the advantages of simple operation, friendly man-machine interface, fully meet the requirements of welded with steel tube forming. The laser tracking system field application photos as shown in figure 5. Figure 5 field application of laser tracking system

2.4 the problems

If the working environment of dust is bigger, especially when dust contains large amounts of ferromagnetic particles, will lead to a touch screen display is disabled, touch function failure. If the monitor installation position close distance from the tube, also will be affected by electromagnetic interference, easy, graphic distortion of the display resolution. Sometimes, because of the plate rolling, which leads to the adversary to trace before and after the result is bad, then would like to hand control box to play to the "manual adjustments" state, with a manual to adjust the tracking system.

3 improve welding in dc electric welding machine output ability

3.1 the improved scheme

The pipeline steel pipe specifications for l 219 mm x 17.2 mm in diameter, material for X70 grade pipeline steel, the normal production of welding in the dc welding current can reach 1350 ~ l400A, is close to the maximum output current welding machine. Production beginning with 1 electric welding machine, dc welding when need the output welding current is larger, adjusting knob has been transferred to the limit, the rise of temperature of the electric welding machine and the failure rate increased significantly at the same time, led to the decrease of the quality of the welding in welding. Will, therefore, the welding current is changed to by two parallel output, electric welding machine to increase output current, improve the quality of welding.

3.2 implementation method

The two Lincoln welder one 1500 (DC) in parallel, connect into the form of a main and auxiliary. Internal control as specified in the relevant principle of wiring, Lincoln welding machine. The host of the line no. 4 and no. 31 and corresponding auxiliary line no. 4 and no. 31 Pick up, the host of 75, 76 and 77 lines with Lincoln welding machine control box NA a 3 s connected to external connect in parallel output, as shown in figure 6. Field use shows that the two parallel welding machine, welding in the straight flow of the current output capacity increased significantly, the increased range to adjust current, slag inclusion, incomplete fusion welding defects such as decreased significantly, improve the welding quality. After put into operation, welding machine work stable and reliable, temperature rise is normal, no failure occurs.

Within 4 to improve welding wire feeding mechanism

Within the original welding wire feeding mechanism is fixed on the frame 2 root wire rod, no Angle on the calibration, every time the operator adjust the Angle of welding wire degree, time is long, and it is difficult to adjust Angle control. Sometimes wire rod for fixed with rickety bridge oscillation, which occur welding point offset, therefore, a new wire feeding mechanism is designed. New wire feeding mechanism are connected by a fan-shaped plate, wire rod, bar, etc, the fan has four arc wall plate, connecting Angle connected with arc wall, side connected with wire rod, as shown in figure 7. After the modification of the wire feed mechanism, wire rod fixation is firm and reliable, deviation in the welding points are no longer, also made a standard template. When replacement of wire feeding mouth, if the wire produces deviation Angle, Angle is available standard template control measure, which can be faster and more accurate to adjust the Angle of welding wire, welding wire spacing, deviation of wire around and around several refs. Using this device is easy to operate, greatly improving the welding stability qualitative. The specification of pipeline steel pipe during normal continuous production, wire feeding mechanism parameter is set to: 1 silk from the upper edge is 25 mm, 1 ý wire from the lower edge of 38 mm; 2 wire from the upper edge of 28 mm, 16 mm 2 wire from the lower plate edge; Two wire Angle 27 degrees.

5 conclusion

The above several improved, through field use card, not only improves the welding quality, and reduce staff labor intensity, improve equipment utilization, reduce the operating error, etc., all got good effect, meet the requirements of the supervisor and the owner, the successful completion of the production tasks of the submerged arc welding steel pipe.