Papers by Keyword: Line Pipe

Abstract: The strain-hardening performance and characteristics of pipeline steel material have an important influence on the deformation behavior and arrest behavior of the line pipe. In this paper X70, selected, and the longitudinal and transverse tensile stress-strain curve and strain-hardening characteristics were analyzed. The results showed that the strain hardening exponent of the double-phased line pipes derived from the transvers stress-strain curve maintains relatively low level at early stage and increased gradually with variation of strain, which was different from the strain hardening behavior for the rest line pipes in this study. Phase ratio, grain size and dislocation density, precipitation, texture, etc. have an effect to the strain hardening behavior of pipeline steel.

Abstract: Tensile and impact toughness test on X100 line pipe with different pre-strain at different aging temperature were conducted to study the effect of pre-strain and aging temperature on properties of X100 line pipe. The result shows that yield strength and tensile strength of X100 line pipe would increase significantly with the introduction of pre-strain, while the impact toughness would decrease significantly. Effect of strain aging on tensile properties of X100 line pipe are more significantly. The yield strength, and tensile strength would increase significantly with the introduction of strain aging both transversal and longitudinal direction.

Abstract: The distribution of hoop stress calculated and simulated by Finite Element Method and theoretical calculation in this paper, when the hydrostatic pressure was carried out on the line pipe of Φ 762mm×31.8 mm API SPEC 5L[1] X70 longitudinal seams submerged arc welding(LSAW). The results of simulated by Finite Element Method were accord well with that of theoretical calculation, both of them shown that the hoop stress deviation between pipe inside surface and outside surface was nearly 40MPa, which was about 9% of the hoop stress of outside surface. Besides, the influence of the D/t(diameter-thickness ratio)on the hoop stress were also researched, which shown that the larger the value of D/t was , the fewer that influence on the hoop stress, when D/t=200, the deviation was less than 1%; Or else, the D/t may cause a great stress gradient in the direction of the thickness, even when the D/t=42, the deviation was up to 5%. So that, the effect of the d/t should be taken into account when calculating the hoop stress of pipe with D/t≤42. In other word, a new hydrostatic pressure formula for the heavy wall thickness pipe( D/t≤42) was put forward and adopted when calculating its hydrostatic pressure, that was P =c* Sh (Do² - Di²) / (Do² + Di²), where, c, specification coefficient; Sh, hoop stress; Do, outside diameter; Di, inner diameter.

Abstract: The development of oil&gas steel products in Baosteel in the past two decades is reviewed. After years of R&D works of steel products used in energy industry such as drilling, exploitation, collection, transportation, and storage of oil and gas, the alloy system and manufacturing processes of oil&gas steel products have been established in Baosteel. The oil&gas steel products of Baosteel consist of two major categories, i.e. the Oil Country Tubular Goods used in underground service, and the pipes used for pipeline construction on the ground. Currently, the product quality has been maintained stable, and the involved products have been extensively used in worldwide oil&gas exploration and transportation industry.

Abstract: Full-scale burst test data of high-grade line pipes for high-pressure gas pipelines were referred to, and 3-D elastic-plastic finite element analysis was carried out using the test data for the calculation of fracture parameters. Ductile crack initiation was evaluated by the intersection of a toughness locus and a crack driving force curve, where the toughness locus was indicated by the relationship between the critical equivalent plastic strain and the stress triaxiality, and the crack driving force curve was shown by a history of the equivalent plastic strain and the stress triaxiality at characteristic distance. In addition, ductile crack rapid propagation was assessed by the relationship between the critical CTOA and the global constraint factor, where the critical CTOA remained almost constant because of high constraint.

Abstract: This study has been conducted to analyze the effect of texture and microstructure on the anisotropy of yield strength and Charpy fracture toughness of an X80 line pipe steel. The texture and microstructure were investigated by X-ray diffractometer and electron backscattered diffraction (EBSD). The yield strength and impact energy were measured along 0o (longitudinal), 30o and 90o (transverse) to the rolling direction. It was found that the microstructure of the developed steel consisted of fine acicular and polygonal ferrite with small pearlite and martensite or retained austenite (MA constituents). The major components of textures were {332}<113> and {113}<110> orientations. In order to investigate the effect of both morphological and crystallographic texture on yield strength anisotropy, the prediction of the plastic property was carried out by using a viscoplastic self-consistent (VPSC) polycrystal model. The predicted anisotropy of yield strength with VPSC model assuming ellipsoidal grain shape was in a good agreement with experimental observation. EBSD results showed that the density of {001} cleavage planes of Charpy specimen, 30 degree to rolling direction, was the highest compared with that of other specimens. Therefore, the highest susceptibility to the cleavage fracture, i.e. increased ductile-brittle transition temperature, can be seen in the 30 degree direction.