24. Research on Metal Forming in the Pipe Ends Upsetting Process

Oil country tubular goods (OCTG) are widely used in the oil and gas industry. In order to increase joint efficiency of oil country tubular goods, the process for upsetting their ends is applied. However, the weakness of this upsetting technology is a frequent defect creation on the inner surface of the final product. These imperfections are surface breakings that reduce the effective pipe wall thickness; they are detected close to the upset ends of the pipe. Computer simulation and a full-scale experiment were used to study this defect nucleation. According to this research, the occurrence of defects is correlated with average pipe wall thickness, nonuniform wall thickness of the blank, heating mode, and friction conditions. The results of a full-scale experiment confirm the main conclusions made in the course of the finite element simulation. The research results define the interdependence of actual size of the blank and the operating tool calibration.