Shaotao Gong

The Micro Structural Characteristic Parameters of High Grade Pipeline Steel and its Mechanical Properties

The microstructure of high grade pipeline steels, including X65, X70, X80, X100, were studied by SEM and EBSD, respectively. It was found that the microstructures of high grade pipeline steels were composed of lower bainite, granular bainite and acicular ferrite. The phases of kinds of pipeline steels were composed of Fe3 C, retained austenite and ferrite. And their percentage content, grain size and its distribution were studied respectively also. These micro structural parameters were correlated to the mechanical properties of kinds of pipeline steels. Furthermore, all kinds of angles of grain boundaries were studied, and the relationship between the angles of grain boundaries and mechanical properties was obtained. It was shown that as the improving of the steel grade, the grain boundary including small angle and large angle increased. And only when grain boundary was greater than 15 degree, it was effective to the toughness behavior.© 2006 ASME

Deformation Behavior Prediction of X80 Steel Line Pipe and Implication on High Strain Pipe Specification

The use of strain based design in pipeline technology has been widely discussed during the last decade for pipelines in harsh environment. In such cases pipelines should be designed based on strain criterion. Strain based design poses a number of challenges, particularly on pipe size and material properties. This paper presents preliminary studies on prediction of buckling strain and buckling mode for X80 high-strain line pipe by finite element methods based on full-scale test. The effects of several parameters such as internal pressure, material properties pipe size and geometric imperfection, were investigated to predict the critical strain for 48″ diameter line pipe under compression and pure bending with 12MPa internal pressure. Material parameters of a specification for high strain line pipe were analyzed to promote its application in the 2nd West-East pipeline of China National Petroleum Corporation.Copyright

Fracture Characteristics of 9%Ni Steel at Low Temperature

The fracture characteristics of several types of tensile specimens of 9%Ni steel at low temperature was studied, and the Notch (Crack) Sensitivity and Notch (Crack) Relative Strength decreased (increased) Ratio of notch (crack) specimen were studied, while the crack preparation method of the crack specimen was discussed. The results indicate that the Notch (Crack) Sensitivity and Notch (Crack) Relative decreased (increased) Ratio can be used to evaluate the low temperature low stress brittle fracture resistance of the material. 9%Ni steel has good brittle fracture resistance at low temperature. The crack preparation principle of the crack tensile specimen was put forward.Copyright

Study on Tensile Property and Strain Ageing Behavior of X100 Linepipe

A series research programs and industrial trials of X100 linepipe have been launched by CNPC so as to build an X100 trial in China for long-distance gas pipeline in the coming years. In present paper, tests have been conducted on 20.6mm×1016mm diameter Grade X100 linepipe. The microstructures, tension properties will be presented. In order to investigate the influence of anti-corrosion coating process on the performance of pipe, strain aging tests in lab have been carried out as well. It is found that testing method, tensile specimen size and sampling location had a noticeable effect on the testing results. The difference is also observed between the flattened strap specimen and round bar. The influence of time, temperature and pre-strain amount of aging tests on the shape of S-S (stress-strain) curve, tension tests results, yield ratio of pipes are presented as well.Copyright

Key Issues in the Specification of High Strain Line Pipe Used in Strain-Based Designed Districts of the 2nd West to East Pipeline

The 2nd West-East Pipeline Project which are building now is the longest of X80 gas pipeline in China even in the world. The geological conditions along it are very complicate. Both stress-base and Strain-based design are all used in the pipeline design. Strain-based design are considered when the pipeline shall via seismic activities, fault crossing and other geological disaster area where ground moving may happen. The pipe which will be used in this kind of special area shall have some special properties besides the properties requirement of the ordinary line pipe. So Tubular Goods Research Center of China National Petroleum Corporation drafted “the Supplementary Technical Specification of High Strain LSAW Line Pipe for the 2nd West-East Pipeline Project”. In this specification, the strain capacity of current X80 line pipe and the testing methods for the mechanical properties are considered. In the mean time, the risk of aging when the pipes are coated is also be noted, and the coating temperature is specified in the specification. Certainly, besides the deformability of the pipe, strain-based design also needs more measures from pipeline construction, girth welding, etc. to ensure the pipeline can endure certain deformation. This paper introduced the general situation of the 2nd West-East Pipeline Project, and several key issues in the specification of high strain line pipe used in strain-based designed districts. At the end of the paper, the mechanical properties and the deformability of X80 pipe which are possible to be manufactured and used in this gas line are be presented.Copyright