Spiral steel pipe submerged arc welding process
Automatic submerged arc welding was invented in 1940, a new kind of welding method, it adopts slag protection as manual welding, but is not coated electrode, the slag is specially welding flux smelting. This coating system is composed of a funnel with welding flux through a pipeline to the front of the welding. The second difference is it uses welding wire instead of the electrode because welding wire can continuously offer.
This kind of method make the fully automated come true and for the second reason is that it is under the submerged arc welding, so its stronger heat transfer and protection performance, the welding quality is higher; and the third advantage is that as a result of submerged arc automatic welding arc is buried under the fluxing agent, so it can be used in a large current, high welding efficiency. Recently, our country’s ongoing west-east gas pipeline project, steel pipe is a kind of high-strength steel, and the pipeline is firtly prefabricated into pieces in the factory, and then settled on the site and welding in the field. The welding technology of the pipeline in factory is using submerged arc welding, and submerged arc welding now has the double wire submerged arc welding and multi wire submerged arc welding, and the efficiency has further improved.
Spiral steel pipe process
(1)Raw materials that refers to the steel strip coil, wire spiral steel pipe, flux. Have to pass strict physical and chemical inspection before investment.
(2) Strip head to tail docking, use single or double wire submerged arc welding, after rolled to steel tube, adopts automatic submerged arc welding for repair welding.
(3) Before forming, strip steel should go through the process of flattening, cutting edge, edge planing, transmission and surface cleaning, flanging process.
(4) The electric contact pressure gauge to control the cylinder under pressure of two side of conveyor to ensure the smooth delivery of strip steel.
(5) The use of external control or internal control roll forming.
(6) the control unit to ensure weld spiral pipe weld space meets the demand of welding; the pipe diameter, quantity of the wrong side and weld gap are tightly controlled.
(7) External or internal welding are used the United States Lincoln welding machine for single or double wire submerged arc welding, to obtain the stable welding specification.
(8) After welding, the weld passes the online continuous ultrasonic automatic meter check, ensure the spiral weld nondestructive testing coverage of 100%. If there are defects, automatic alarm and spray tags, production workers to adjust process parameters, in a timely manner to eliminate defects.
(9) Using air plasma cutting machine to cut the steel tube into single.
(10) After cut into single, every batch of steel pipe in the first three must carry on the strict inspection, to check the weld mechanical properties, chemical composition and amalgamation. Steel tube surface quality and the nondestructive flaw detection to ensure that qualified pipe process and then can be formally put into production.
(11) There is a continuous acoustic detection on weld, after manual ultrasonic and X-ray check, if there are defects, after repair, again through the nondestructive inspection, until defects have been eliminated.
(12) Strip steel butt weld and fellowship with spiral weld “丁”joint in the tube, all pass X-ray films and television inspection.
(13) Each steel pipe after hydrostatic pressure test, radial sealing for the pressure. Test pressure and time are controlled strictly by steel pipe hydraulic microcomputer testing device.
(14) Pipe end machining to make the end vertical, and slope angle and the blunt edge to get accurate control.
