| Popis: |
In this paper, the chip morphologies and sizes of hardened PM steel S790 (68 HRC) using four types coated end mills (TiAlN TiCrAlN TiSiN and TiAlSiN) under different cutting parameters in dry milling condition were studied. During the process of high speed milling hardened steel S790, the chip morphologies change from continuous strip to sawtooth with the increase of cutting speeds. When cutting speed reaches 100 m/min, obvious shear slip occoured on the top surface of the chips, which are formed by multilayer metal unit piled by shear slip plane segmentation. The bottom of the chips, which squeeze and slid with rake face of end mills, show shiny smooth surface. TiAlSiN and TiSiN coatings are more suitable for high speed milling than TiAlN and TiCrAlN coatings. With the increase of cutting parameters such as cutting speed, feed rate and axial cutting depth, the chips morphology of S790 change from continuous strips to trapezoidal and triangle sawtooth, and the chips trend easy separation. |
