中厚板表层超细晶对止裂性能的影响

发布时间：2018-06-26 13:52

本文选题：中厚板 + 返温轧制　；参考：《金属学报》2017年05期

【摘要】：研究了返温轧制(TRRP)中厚钢板表层的组织特征及其对止裂性能的影响。力学性能测试结果表明,与传统的控轧控冷(TMCP)钢相比,TRRP钢表层的韧、塑性较好,韧脆转变温度低至-100℃,而在1/4厚度处,两者性能差异不大。显微组织分析表明,TRRP钢表层组织为等轴状铁素体晶粒+弥散分布的马氏体-奥氏体(MA)组元,晶粒等效直径约2 mm。通过数值模拟分析了TRRP工艺中间坯温度场的变化,发现中间坯冷却时,表层被冷却到相变温度以下,形成以贝氏体为主的组织,返温后轧制,表层组织发生动态再结晶形成超细晶。示波冲击测试表明,TRRP钢表层试样启裂后,载荷-位移曲线斜率绝对值(|k|)由0.66降低到0.27,与止裂相关的冲击吸收功达到44.3 J,断口表层组织有明显的塑性变形,吸收了裂纹扩展的能量,有效地抑制了裂纹扩展。晶粒取向分析表明,TRRP钢表层超细晶粒取向呈随机分布,晶界角度平均值和大角度晶界(15°)比例分别达到32.8°和69.8%,能够有效阻碍裂纹扩展。使用纳米压痕分析了实验钢的硬度,TRRP钢表层的纳米压痕硬度统计分布集中在2.0 GPa以下,组织特征为少量的硬质相弥散分布在较软的铁素体基体上,相界面处萌生的裂纹在基体中不易扩展。
[Abstract]:The microstructure characteristics of the surface layer of the medium and thick steel plate in the back temperature rolling (TRRP) and its effect on the crack arrest have been studied. The results of mechanical properties test show that, compared with the traditional controlled rolling and controlled cooling (TMCP) steel, the toughening and plastic properties of the TRRP steel are better, the transition temperature of the ductile and brittle transition is low to -100 C, and the properties of the two are not very different at the thickness of 1/4. Microstructure analysis shows that TRR The surface structure of P steel is an equiaxed ferrite grain + diffusion distributed martensitic austenite (MA) component. The equivalent diameter of the grain is about 2 mm., and the change of the temperature field of the intermediate billet in the TRRP process is analyzed by numerical simulation. It is found that the surface layer is cooled to below the phase transition temperature when the medium is cooled, and the bainite is the main structure, and the surface is rolled and the surface is rolled. The dynamic recrystallization of the tissue is superfine crystal. The oscilloscope impact test shows that the absolute value of the slope of the load displacement curve (|k|) is reduced from 0.66 to 0.27 after the cracking of the TRRP steel surface specimen, and the impact absorption work related to the crack arrest is 44.3 J, and the surface structure of the fracture surface has obvious plastic deformation, absorbing the energy of the crack expansion and effectively restraining the crack. Grain orientation analysis shows that the grain orientation of the TRRP steel surface is randomly distributed, the average value of the grain boundary angle and the large angle grain boundary (15 degrees) reach 32.8 and 69.8%, respectively, which can effectively prevent the crack growth. The hardness of the experimental steel is analyzed by nano indentation. The statistical distribution of nano indentation hardness on the surface of TRRP steel is concentrated at 2 GPa The microstructure is characterized by a small amount of hard phase dispersed on the softer ferrite substrate, and the cracks at the interface are not easy to expand in the matrix.
【作者单位】：洛阳船舶材料研究所;钢铁研究总院工程用钢所;
【分类号】：TG142.1;TG335.5

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