45钢块体超细晶棒材3D-SPD轧制法

提出了一种基于斜轧原理的块体超细晶棒材剧烈塑性变形(SPD)成形法,称为3D-SPD法:利用特殊曲面锥形轧辊及导板,坯料从轧辊直径最大端咬入,采用超大送进角及径缩率等变形参数,构建了剧烈扭转压缩复合变形区,单位成形载荷为兆帕级,可实现块体等效应变大于6.5的SPD.建立了基于Oyane损伤准则的裂纹萌生控制模型,通过对...

3D-SPD Rolling Method of 45 Steel Ultrafine Grained Bar with Bulk Size

Based on the limitations of severe plastic deformation (SPD) technology, such as a small effective deformation area and huge forming load, in the preparation of ultrafine grained/nanocrystalline materials, preparing industrial grade bulk ultrafine grained materials is difficult. In this work, a new SPD method, titled 3D-SPD, for preparing bulk ultrafine grained bars is proposed based on the cross-rolling principle. A severe torsion and compression deformation region was constructed using specially-curved conical rolls and guide plates, super large feed angles, and diameter reduction ratios. During the 3D-SPD process, a billet entered the deformation region from the large diameter side of the roll, where the deformation pressure was MPa grade and able to realize the SPD process with effective strains greater than 6.5. A crack control model based on Oyane criteria was established. Through the optimization analysis of damage factors under different deformation conditions, the crack induced by the Mannesmann effect was effectively restrained. Based on theoretical and experimental results, optimal parameters were determined as follows: cone angle 5 degrees, feed angle 24 degrees, diameter reduction ratio 50%, temperature 700 degrees C, ovality coefficient 1.02, and roll speed 40 r/min. A 25 mm-diameter ultrafine grained bar of 45 steel was obtained by the single pass deformation. The average grain size was refined from 46 mu m to 1 mu m, and the yield and tensile strengths were increased by 46% and 42%, respectively.