Effect of Squeeze-out and Sizing Ratio to The Residual Circumferential Stress of HFW Pipe

Abstract

Residual circumferential stress originates from pipe forming process has a negative impact on the pressure carrying capacity; therefore it is necessary to keep the level of residual stress as low as possible and distributed uniformly around the pipe. Manufacturing of HFW (High-Frequency Welded) pipe involves pinching, bending, forming, welding, squeezing, sizing and straightening processes in several stages which produce both elastic and plastic deformation. Those processes produce residual stresses in the pipe wall in the circumferential and longitudinal directions. This paper presents the result of the trial test to investigate the effect of squeeze-out (SO) and the sizing ratio (SR) to the residual circumferential stress on HFW pipe. The trial was performed at PT INDAL STEEL PIPE (ISP) pipe mill, on pipe API 5L L360MO PSL2, nominal Outside Diameter (OD) 273 mm, wall thickness 12.7 mm. The SO was 0.7t and 0.9t, while the SR was set at 0.5 %, 0.8 %, and 1.0 %.