1. Flash butt welding: Two welded steel bars are contacted by a butt welding machine. The steel bar is heated to a certain temperature, softened by low voltage and strong current, and then axially pressurized and upset to form a butt joint, and the steel bar is elongated along the axial direction. According to butt welding technology, flash butt welding is divided into continuous flash welding and flash-preheating-flash welding, the latter is used to weld large diameter steel bars. This welding is used for prestressed steel bars.
2. Arc welding: The arc welding machine generates a high-temperature arc between the covered electrode and the weldment, so that the covered electrode within the arc combustion range and the weldment melt and solidify to form a joint or weld. The joint forms of steel arc welding are: lap joint (single-sided welding or double-sided welding), adhesive joint (single-sided welding or double-sided welding) and split joint (flat welding or vertical welding).
3. Electroslag pressure welding: put a small piece of conductive agent (steel ball, covered electrode, etc.). ) Put a medicine box between the upper and lower welded steel bars, fill it with flux, turn on the circuit and ignite it with an AC welder. When a slag pool is formed and the steel bars are melted and arc stabilized for a certain period of time, at the same time of power failure, use a manual pressurizing mechanism to pressurize and upset, eliminate slag inclusion and bubbles, and form a joint. This kind of welding is mostly used for the extension of vertical steel bars in cast-in-place reinforced concrete structural members.
4. Resistance spot welding: the upper and lower electrodes of the spot welding machine contact the intersecting steel bars and connect the current. The contact point resistance of the intersecting steel bars is large, the heat generated by the current melts the steel bars, and at the same time, the electrodes are welded under pressure. Used for welding the cross connection of steel bars such as steel mesh and steel skeleton.
5. Pneumatic welding of steel bar: use a certain proportion of oxygen (purity ≥98.5%, bottled working pressure less than 5 ~ 10 kg/cm2) flame to heat the end of steel bar to a plastic state (the temperature is about 1320 ~ 1340℃), and apply pressure while heating, and finally apply 3000 kg.
Welding equipment includes heater (composed of mixing gas pipe and nozzle), pressurizing oil pump (composed of oil cylinder and pedal hydraulic pump) and crimping device (used for clamping, adjusting eccentricity and crimping steel bar). When cutting steel bars, it is not advisable to use a cutting machine to avoid the horseshoe joint being crimped, and it is advisable to use a toothless saw to cut it off.
The robot used to weld the workpiece to be welded must have the same assembly quality and accuracy. The application of welding robot should strictly control the preparation quality of parts and improve the assembly accuracy of weldments. The surface quality, groove size and assembly accuracy of parts will affect the weld tracking effect. The quality of parts preparation and the assembly accuracy of weldments can be improved from the following aspects.
1. Make special welding process for welding robot, and strictly stipulate the process of part size, weld groove and assembly size. Generally, the dimensional tolerance of parts and grooves is controlled within 0.8 mm, and the assembly dimensional error is controlled within 65438±0.5mm, which can greatly reduce the probability of welding defects such as blowholes and undercut.
2. Adopt high-precision welding fixture to improve the assembly accuracy of weldments.
3, weld should be clean, no oil, rust, welding slag, slag and other sundry. Otherwise, the success rate of arc striking will be affected. The tack welding was changed from covered electrode welding to gas shielded welding. At the same time, the spot welding parts are polished to avoid slag shells or pores left by spot welding, thus avoiding arc instability or even splashing.
Extended data:
In addition, the welding robot's requirements for welding wire: the robot can choose barreled or coiled welding wire as needed. In order to reduce the frequency of changing welding wires, robots should choose barreled welding wires. However, due to the use of barreled welding wire, the wire feeding hose is very long and has great resistance, which requires high quality such as welding wire hardness.
When welding wire with poor copper plating quality is used, the copper plating on the surface of welding wire will reduce the internal volume of the conduit due to friction, and the resistance will increase during high-speed wire feeding, which will make the welding wire unable to feed smoothly, produce jitter, make the arc unstable and affect the weld quality. In severe cases, the robot will stop because it is stuck, so it is necessary to clean the welding wire conduit in time. Programming skills:
Choose a reasonable welding sequence. In order to reduce the welding deformation and the walking path length of the welding torch, the welding sequence is formulated.
2. The spatial transition of welding torch requires short, stable and safe motion trajectory.
3. Optimize welding parameters. In order to obtain the best welding parameters, a specimen was made for welding test and process evaluation.
4. Reasonable locator position, welding torch posture and welding torch relative joint position. After the workpiece is fixed on the positioner, if the weld is not at the ideal position and angle, it is necessary to constantly adjust the positioner during programming to make the welded weld reach the horizontal position one by one according to the welding sequence.
At the same time, it is necessary to constantly adjust the position of each axis of the robot, and reasonably determine the position and angle of the welding gun relative to the joint and the extension length of the welding wire. After the position of the workpiece is determined, it is difficult to observe the position of the welding torch relative to the joint through the programmer's eyes. This requires programmers to be good at summing up accumulated experience.
5. Insert the gun cleaning program in time. After a certain length of welding program is written, the gun cleaning program should be inserted in time, which can prevent welding spatter from blocking the welding nozzle and the conductive nozzle, ensure the cleanliness of the welding gun, improve the nozzle life, ensure reliable arc striking and reduce welding spatter.
6. General programming cannot be completed in one step. In the process of robot welding, it is necessary to constantly check and modify the program, adjust the welding parameters and torch posture, and then form a good program.
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