Welding technology has been widely applied in the oil industry and piling pipe and played an increasingly important role. For coiled tubing drilling, the weakest of the bottom hole assembly (BHA) that is dangerous section of the welds. In recent years, with the development of welding technology, coiled tubing manufacturer application of new technologies to improve the welding process, and improve the pipeline performance. Coiled tubing from the past "pipe on the tube end butt spiral submerged arc welded technology alternative. The immediate advantage of the spiral submerged arc welding is to weld the spiral-shaped distribution, greatly increase the axial strength of the tubing, coiled tubing reliability has also been significantly improved.
Submerged arc welding principle and characteristics - submerged arc welding arc as a heat source. The submerged arc welding when the arc is burning in the granular layer to melt the solder under the coverage of the arc is not exposed, and thus called the submerged arc welding. Welding arc burning between the wire and the workpiece. Arc hot wire end and the arc near the base metal and flux melting. Molten metal formed in the weld pool, molten flux as slag. The arc to move forward, the arc force in the bath of liquid metal into the weld pool behind the. In the subsequent cooling process, this part of the liquid metal solidified into a weld. The slag is solidified into a slag shell covering on the weld surface. Slag in addition to the mechanical protection role of the weld pool and weld metal from the welding process, the molten metal, the metallurgical reaction, thus affecting the chemical composition of the weld metal. Submerged arc welding, the welder parts and wires were connected to the welding power poles. Wire by sliding contact with the contact tip and power connections. Welding circuit including the welding power source, connection cable, tip, wire arc, molten pool, work and other sectors. Continue to melt the wire end in the electric arc thermal effect, which wire should be sent in a continuous manner, in order to maintain the stability of the welding process is continuous. Wire feeding speed wire melting rate to the balance.
In addition, spiral submerged arc welded in the oil industry and piling is also reflected in the drilling of casing (surface casing, intermediate casing, etc.)
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