SAW(Submerged Arc Welding)
Submerged arc welding is an arc welding under flux layer combustion method. Welding arc between the wire and the weldment burning heat of the arc and arc welding wire ends near the base metal and solder melted wire continuously fed, and proceeds along a certain trajectory, an arc weld pool solidified metal is removed to weld the molten solder is solidified into a shell covering the surface of the weld slag, slag of molten pool and weld metal for protection against arcing and the pool by the outside air intrusion.
For the submerged arc welding equipment, there are two. One is the constant wire submerged arc welding machine, wire feed speed according to the set speed constant, maintaining a relatively stable arc arc is to rely on self-regulation. Another is the shift wire submerged arc welding machine, which is the use of arc voltage as a feedback signal, after changing the wire feed speed control system, so as to maintain a relatively stable arc. Further, in order to ensure that the most suitable welding process in a stable position and reliable welding process, SAW also need more complex auxiliary equipment compatible with the welder, commonly used auxiliary equipment: weldments displacement equipment, welding machine operator (ie welding head displacement device), welding jig and weld equipment.
Since the SAW current, deep penetration, the groove form and size requirements are: a thickness of not less than 12mm plate beveling, in 12 ~ 20mm thickness can be used between the side welding, welding opposite gouging, more than when asked to open groove 20mm, but its blunt edge requires 5 ~ 6mm. Welding current based on the wire diameter, the thickness of the weldment, and the flux model is selected. Because of the large submerged arc welding current, welding the first layer prone to burn, often using the following welding process: SMAW welding back permanently submerged plate, lock bottom butt joint submerged arc welding, flux pad SAW.
HFW(High-frequency Welding)
In high-frequency current heating of the workpiece, and then applying pressure welding joints (see figure) is formed. A high-frequency current is concentrated along the surface of a conductor and flow along the path of least inductance over principle, the current will be concentrated heating of the workpiece surface to be welded, the thermoplastic state is reached or a partially molten state, extruding the molten metal on the workpiece and pressing the metal oxide, they form a welded joint. High-frequency welding common frequency range of 60 to 500 kHz. High frequency resistance welding high frequency welding points welding two kinds of high-frequency induction.
① High Frequency Resistance Welding: the contact with the wheel or as a sub-electrode high-frequency currents in the workpiece, suitable for continuous longitudinal seam welded pipe and spiral lap seam welding, boiler tube and fin heat exchanger spiral welded fin, can pipe external diameter of 1200 mm and a wall thickness of 16 mm, beam welding abdominal electrode thickness 9.5 mm, high productivity.
② High-frequency induction welding: a small diameter tube and the wall thickness of the workpiece by the induction heating coil can be welded to an outer diameter of 9 mm and 1 mm thin-walled tube. Commonly used in small diameter longitudinal pipe and brass seam welding, girth welding can also be used, but the power consumption is greater than the high-frequency resistance welding. The main parameters affecting the high-frequency welding quality is high-frequency power frequency, power, workpiece forming angle, welding speed and pressure from the squeeze, the electrode (or induction coil) and squeeze rollers. Major equipment has a high-frequency power supply, the workpiece forming apparatus and extrusion machinery. Stable high-frequency welding quality, high productivity and low cost. For high-efficiency automatic production line, the production of advanced methods slit tube.
