刀具表面状态对电工钢板剪切断面完整性的影响

Effect of Tool Surface State on Shear Surface Integrity of Electrical Steel Plate

目的研究电工钢板材精密剪切加工过程中,刀具表面粗糙度与润滑条件对剪切断面完整性的影响。方法使用不同表面粗糙度的刀具,分别在干切和润滑下对0.5mm厚的无取向电工钢进行剪切加工实验,使用MahrXT20粗糙度轮廓仪检测刀具表面粗糙度,使用Kistler三向测力仪测量剪切过程中的三向力,使用Keyence超景深显微镜检测断面形貌和截面轮廓,使用维氏显微硬度计测试剪切边缘硬度分布,使用有限元方法计算刀具表面粗糙度和润滑油膜对刀具-工件表面接触面积和摩擦力的影响。结果干切条件下,刀具表面粗糙度Rα值越大,剪切力越大,剪切边缘加工硬化越大,剪切断面完整性越差。润滑条件下,随刀具表面粗糙度Rα值的增加,剪切断面完整性先变好后变差,且加工硬化与剪切力都呈现出先减小后增加的趋势。刀具表面粗糙度Rα值较小或较大时,加注润滑剂难以改善加工效果,甚至产生负面影响。板材与刀具接触界面润滑条件下,刀具表面粗糙度Rα=0.2μm时有最优加工效果,相对干切条件,其光亮带高度和表面完整性分别增加16.9%和4.3%,塌角高度、硬化层相对深度以及Fy和Fz分别减少15.4%、28.1%、26.9%和7.1%。结论刀具表面粗糙度Rα增大,工件材料的附加微观变形增大,造成剪切断面完整性恶化;当刀具表面粗糙度合适时,添加润滑剂,可以在接触界面形成连续油膜,显著减少刀具与板材间固体接触面积和摩擦力,提高剪切断面完整性。工业生产中,刀具会逐渐磨损,导致表面粗糙度增大,故必须关注刀具表面粗糙度对剪切断面完整性的影响,并注重与润滑油的配合。

The work aims to study the influence of tool surface roughness and lubrication conditions on the integrity of shear surface during precision shearing of electrical steel plate. The shearing tools with different surface roughness were used, 0.5 mm thick non-oriented electrical steel was sheared under dry shearing and lubrication, and the surface roughness of the shearing tool was measured with MahrXT20 roughness profiler. Kistler three-way force instrument was used to measure the three-way force during the shearing process, the Keyence Ultra Depth of Field Microscope was used to detect the cross-sectional shape and profile, and the Vickers microhardness tester was used to test the shear edge hardness distribution. The influence of the surface roughness of the shearing tool and the lubricant film on the contact area and friction of the tool-work surface was calculated with the finite element method. Under dry shearing conditions, the greater the surface roughness Rα of the shearing tool, the greater the shearing force, the greater the hardening of the shearing edge and the worse the integrity of the shearing surface. Under the lubrication condition, with the increase of the surface roughness Rα of the shearing tool, the shear surface integrity first became better and then deteriorated, and the work hardening and shearing force both decreased first and then increased. When the shearing tool surface roughness Rα was relatively small or large, it was difficult to improve the processing effect or even have a negative effect when the lubricant was added. Under the lubrication condition of the interface between the plate and the shearing tool, the optimum processing effect was obtained when the surface roughness of the shearing tool was Rα=0.2 μm. Compared with dry-cut condition, the height of the burnish zone and the surface integrity were increased by 16.9% and 4.3% respectively and the height of rollover, the relative depth of the hardened layer, Fy and Fz were reduced by 15.4%, 28.1%, 26.9% and 7.1%, respectively. With the increased surface roughness Rα of the shearing tool, the additional microscopic deformation of the workpiece material increases, resulting in deterioration of the shear surface integrity. When the shearing tool surface roughness is appropriate, the addition of lubricant can form a continuous oil film at the contact interface, which can significantly reduce the solid contact area and friction between the shearing tool and the plate, and improve the integrity of the shear surface. In actual production, the shearing tool wears gradually, resulting in increased surface roughness. Therefore, it is necessary to pay attention to the influence of the surface roughness of the shearing tool on the integrity of the shear surface, and its cooperation with the lubricating oil.