Affiliation:
1. School of Metallurgic Engineering Anhui University of Technology Ma'anshan Anhui 243002 China
2. R&D Center of Wuhan Iron & Steel Co., Ltd. Baosteel Central Research Institute, Hot Rolling Research Institute Baowu Iron and Steel Group Wuhan Hubei 430080 China
3. Changxing Huaqiang Electron Co., Ltd. Zhenhuai Street Huzhou Zhejiang 310019 China
4. Anhui Engineering Laboratory for Intelligent Applications and Security of Industrial Internet Anhui University of Technology Ma'anshan Anhui 243032 China
Abstract
Herein, the effect of molybdenum (Mo) and postrolling cooling processes on the mechanical properties and microstructure transformation characteristics of an X80 thick‐wall high‐strength pipeline steel are deeply investigated. The results reveal that the yield strength and tensile strength of the steel are enhanced with Mo addition at the equalization temperature of 480 °C at a cooling rate of 25 °C s−1, accompanied by the improvement in the yield ratio. However, when the postrolling cooling temperature is reduced to 380 °C, the mechanical properties of steels with Mo‐free and 0.29 wt% Mo are comparable. The mechanistic study indicates that the Mo addition would inhibit the transformation from deformed austenite to polygonal ferrite, and promote the transformation of acicular ferrite/granular bainite at medium–low temperatures, as well as significant differences in the volume fraction, size, and morphology of martensite/austenite (M/A) in the matrix. Notably, the volume fraction of M/A decreases from 7.2% to less than 1.0% with Mo content increasing, while its average size also reduces from 1.5 to less than 1.0 μm. And the fine, spheroidal, and dispersed M/A is found to play a vital role in the high‐strength and excellent low‐temperature toughness of the steel.
Funder
National Natural Science Foundation of China
Subject
Materials Chemistry,Metals and Alloys,Physical and Theoretical Chemistry,Condensed Matter Physics