Fabrication of high strength seam welded steel tubes and quality indicator testing

Abstract

The selection of steel, the dimensions and methods of fabricating seam welded steel tubes are closely connected to the function of tube as a whole structure in specific working conditions, for a calculated service life. The quality of welded joints in the fabrication process of seam welded tubes is defined by properties the tubes must possess in order to satisfy defined requirements, and can be achieved by choosing appropriate procedures and welding parameters, by following control programmes in all fabricating operations, and through mechanical and technology stress and strain tests of base metal and seam welded joints. In the paper are described quality indicator research results of seam welded tubes made of high strength steels X60 and J55, dedicated for producing oil and gas pipelines and in oil wells. Spiral welded tubes are produced by submerged arc welding (SAW), and the longitudinal welded pipes by high frequency welding technique. .

Izbor čelika, dimenzija i načina proizvodnje šavnih cevi je deo procesa konstruisanja, jer je u uskoj vezi sa funkcijom cevi kao konstrukcijske celine u određenim uslovima eksploatacije za predviđeni vek trajanja. Kvalitet zavarenih spojeva u procesu proizvodnje šavnih cevi definiše se karakteristikama koje cevi moraju imati da bi zadovoljile određene zahteve, što se postiže izborom odgovarajućih postupaka i parametara zavarivanja, sprovođenjem programa kontrole svih tehnoloških operacija u njihovoj izradi i mehaničkim i tehnološkim ispitivanjima otpornosti i deformacije osnovnog materijala i zavarenih spojeva cevi. U radu su prikazani rezultati istraživanja pokazatelja kvaliteta šavnih cevi izrađenih od čelika povišene čvrstoće X60 i J55, namenjenih za izradu cevi za naftovode, gasovode i bušotine. Spiralno zavarene cevi izrađuju se zavarivanjem pod praškom (EPP), a uzdužno zavarene, visoko-frekventnim postupkom zavarivanja (VF). .