Field test for cold bending of X70 high-strain steel pipe

To obtain desirable bending angles specified in design, common steel pipes are often used on site for fabrication of cold-bending pipes. In this research, in order to study the feasibility of making cold-bending pipes using high-strain steel pipes, 3 bending techniques were deployed in field test for cold bending of X70 high-strain steel pipe. Stretching test, Charpy impact test, drop-weight tear test (DWTT) and other tests were conducted to determine impacts of bending processes on geometric sizes and properties of X70 high-strain steel pipes. The research results show that bending processes have no great impacts on changes of wall thicknesses of pipes. Ovalities before and after bending demonstrate minor variations, and changes in horizontal properties are insignificant. Moreover, yielding strengths and yield ratios on external arc of the bending pipe increase dramatically, whereas vertical yield strengths and yield rations on inner arc of the bending pipe decrease with increase of radius of curvature. Cold-bending pipes bended by high-strain steel pipes have good performances and the research provides a new way for application of cold-bending pipes in complex environment.