Qingren Xiong

The Measurement and Control of Residual Stress in Spiral Sub-Merged Arc Welded Pipe

The problems related to the measurement and control of residual stress in the production of SSAW pipe are analyzed based on tests: (1) The relationship between circumferential opening in cut-ring test and residual stress from mechanical cutting stress releasing test; (2) The effects of severing position on the measured opening; (3) The effects of hydrostatic test on residual stress of SSAW pipe; (4) The supplementary specification of SSAW pipe. It is put forward that the circumferential opening varies with the severing position, and the normal hydrostatic test mainly bring about the redistribution of the residual stress as well as the decrease of that. The appropriate higher pressure can reduce residual stress considerably. Some suggestions about the supplementary specification related to residual stress of SSAW pipe were brought forward.Copyright

Effect of Different Cooling Rate on HAZ Microstructure of 2205 Duplex Stainless Steels

The effects of cooling rate ω8/5 and ω12/8 on the simulated HAZ microstructure transformation in 2205 duplex stainless steel are studied in this paper. The results indicate that 1200°C ∼ 800°C is the temperature range in which the microstructure transits the most violently for 2205 steel, and is also the cooling interval, that affects the phase proportion and microstructure morphology the most distinctly. Accordingly, It is more efficient to use ω12/8 as the parameter to investigate the microstructure transformation of welding HAZ microstructure of this material. The cooling rate in this interval will affect the microstructure transformation of HAZ microstructure of 2205 steel remarkably.Copyright

Effects of Axial and Radial Distortion on Residual Stress of HSAW Pipe

The complex distortion often occur when the pipe sections of HSAW pipe are cut along the axis. The residual stress caused by the axial and radial distortion in the cut-ring test of HSAW pipe is studied by elastic mechanics theory in this paper, and the effects of the axial and radial distortion on the residual stress of HSAW pipe are analyzed according to the results of the cut-ring test of HSAW pipe section and the mechanical status during the forming of HSAW pipe. The research indicates that the larger axial and radial displacement shows that the larger torsion and shearing stress exist during the strip forming, and which will result in the larger residual stress. It is suggested that the axial and radial displacement in the cut-ring test shall be limited in the technical specification of HSAW line pipe for pipeline project, especially for the key pipeline project.Copyright

Several Problems in Strength Testing of High Grade HSAW Pipe

Tensile property is the most important and basic property parameter, which is the base of pipeline design and safety assessment. This paper analyzes several issues such as the type of specimen and the test procedure, which occur during the strength testing of X80 HSAW pipe. It is presented that the yield strength value of base metal in transverse direction of X80 HSAW pipe from different kinds of specimen may be affected by many factors, such as Bauschinger effect, deformation strengthening effect and microstructure etc. It is suggested that the total elongation for high grade HSAW pipe in total extension under load method should be verified by ring expansion test.Copyright