Toughening mechanisms of a high-strength acicular ferrite steel heavy plate

Zhi-qiang Cao1,2), Yan-ping Bao1), Zheng-hai Xia2), Deng Luo3), Ai-min Guo3), and Kai-ming Wu3) 1) Engineering Research Institute, University of Science and Technology Beijing, Beijing 100083, China 2) Research & Development Center, Xiangtan Iron and Steel Co. Ltd., Xiangtan 411101, China 3) Hubei Province Key Laboratory for Systems Science on Metallurgical Processing, Wuhan University of Science and Technology, Wuhan 430081, China

摘 要：An ultra-low carbon acicular ferrite steel heavy plate was obtained with an advanced thermo-mechanical control process-relaxed precipitation controlled transformation （TMCP-RPC） at Xiangtan Steel, Valin Group. The heavy plate has a tensile strength of approximately 600 MPa with a lower yield ratio. The impact toughness of the heavy plate achieves 280 J at ?40°C. The fine-grained mixed microstructures of the heavy plate mainly consist of acicular ferrite, granular bainite, and polygonal ferrite. The high strength and excellent toughness of the heavy plate are attributed to the formation of acicular ferrite microstructure. The prevention of blocks of martensite/retained austenite （M/A） and the higher cleanness are also responsible for the superior toughness.

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