Intrinsic Mechanisms of Ductile-brittle Transition for F460 Steel Welding Coarse Grained Heat Affected Zones with Different Heat Inputs
LI Jing1, CAO Rui1, MAO Gao-jun1, LIU Dong-sheng2, CHEN Jian-hong1
1. State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China;
2. Institute of Research of Iron and Steel, Shasteel, Zhangjiagang 215625, Jiangsu, China
Abstract：Coarse grain heat affected zone (HAZ) of F460 steel was simulated by a Gleeble 3800 thermo-mechanical simulator. The microstructure, critical event of the HAZ formed at various heat inputs (E) were characterized and determined by optical microscopy (OM) and scanning electronic microscopy (SEM), and cleavage fracture stress σf was also calculated by ABAQUS software. Based on above systematic analysis, the intrinsic mechanism of ductile-brittle transition for F460 steel heat affected zones with different heat inputs were revealed. The results indicate that:with the improvement of heat input, the microstructures in sequence are a minority of lath martensite and massive fine lath bainite, more lath bainite with less granular bainite, more granular bainite with less lath bainite, bulky of granular bainite; and the maximum size of the original austenite grain and bainite packet becomes bigger with the improvement of heat input. The size of bainite packet is critical event of the cleavage fracture for coarse grain heat affected zone specimens with various heat inputs by comparing the relationships among residual crack length, original austenite grain size and bainite packet size. With the decreasing of the bainitic packet, the ductile to brittle transition temperature decreases. In addition, cleavage fracture stress σf is also calculated by ABAQUS software, σf gradually decreases with the increase of the heat input, which can explain the intrinsic mechanism of ductile to brittle transition temperature Tk with the change of the heat input.
李静, 曹睿, 毛高军, 刘东升, 陈剑虹. 不同热输入下F460钢焊接粗晶热影响区韧脆转变的内在机理[J]. 材料工程, 2016, 44(8): 70-76.
LI Jing, CAO Rui, MAO Gao-jun, LIU Dong-sheng, CHEN Jian-hong. Intrinsic Mechanisms of Ductile-brittle Transition for F460 Steel Welding Coarse Grained Heat Affected Zones with Different Heat Inputs. Journal of Materials Engineering, 2016, 44(8): 70-76.
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