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Advances in Homopolar Welding of API Line Pipe for Deepwater Applications

1999; Volume: 14; Issue: 02 Linguagem: Inglês

10.2118/56086-pa

1945-1547

R.S. Hudson, R.W. Carnes, Steven P. Nichols,

Non-Destructive Testing Techniques

Summary The University of Texas at Austin Center for Electromechanics is conducting a research program, funded by six oil companies, two industrial contractors, and two government agencies, to study homopolar welding of line pipe for J-Lay applications. In 1995, the third year of the five year research program, the set of weld parameters, those input variables used to control weld performance and quality, was expanded to include joint geometry, with dramatic improvement in the mechanical properties of two HSLA nominal 3-in. line pipe materials: X60 and X65. These improvements increased the Charpy V-Notch impact toughness properties to near parent metal values, while maintaining acceptable strength. After demonstrating repeatable performance with the new parameters, new research focused on real world effects including tolerancing the parameters and evaluating the effect of poor fit up resulting from misalignment and rough and wavy interfaces. During the final year of the research program, the pipe welding program has scaled up to 12-in. nominal line pipe, a seven-fold increase in the cross-sectional area. The paper will cover the basics of homopolar welding (HPW), weld parameters and modifications, the effects of these changes on real time process data, mechanical properties, weld upset profile, HPW metallurgy, and the studies of real world effects. Results from HPW of 12-in. pipe will also be presented.