Session: 05-01-1: Materials and Joining - High-strength Line Pipe

Paper Number: 133660

133660 - Effect of Microstructure on Mechanical Properties of X80 Pipeline Steel 

Abstract: 

The microstructure and mechanical properties of two kinds of X80 pipeline steel with basically the same composition were studied in this paper. The experimental results show that both X80 pipeline steels have small grain size, high tensile strength and excellent impact toughness, which meet the requirements of X80 pipeline steel in the Specification of Steel Pipe for Gas Pipeline Project (DEC-NGP-S-PL-003). The microstructures of the two X80 pipeline steels are composed of granular bainite and a small amount of M-A, and the number of precipitated phases in the matrix is basically the same. The grain size of N084 is more uniform and finer, but the size of precipitates in N092 is slightly larger. By analyzing the grain size, dislocation density and precipitation phase of two X80 pipeline steels, the contribution of various strengthening mechanisms to strength is studied. The results show that refinement strengthening contributes the most to strength, followed by deformation strengthening. Given the small amount of precipitated phase, its contribution is relatively small. Although the amount of precipitated phase is not much different, the dislocation density of N092 is lower than that of N084, the hindering effect of interaction between precipitates and dislocations is weak in the process of tensile deformation is weak, and the interaction between dislocations is also weak. Therefore, the hardening ability of N092 is low, resulting in the tensile strength of N092 is significantly lower than that of N084. Although the hardening ability of N084 is higher than N092, the impact toughness of N084 has only a slight decrease compared to N092, indicating that N084 also has good impact toughness. By studying the microstructure and mechanical properties of the two X80 pipeline steels, it can be seen that N084 has outstanding comprehensive mechanical properties. In the case of maintaining the grain size, increasing the dislocation density can ensure that it has good impact toughness and improve its tensile strength.

Presenting Author: Yuefeng Chen CNPC Tubular Goods Research Institute

Presenting Author Biography: Dr. Yuefeng Chen graduated from University of Science and Technology Beijing in 2020 with a PhD in Materials Science and engineering. Dr. Chen Yuefeng joined CNPC Tubular Goods Research Institute in January 2020 and is mainly engaged in research work in the field of oil and gas long distance pipeline welding and additive manufacturing of oil and gas equipment.

Authors:

Yuefeng Chen CNPC Tubular Goods Research Institute
Yaobin Yang CNPC Tubular Goods Research Institute
Hongjie Zhang CNPC Tubular Goods Research Institute
Xiaodong He CNPC Tubular Goods Research Institute
David Han International Welding Technology Center