Wear Characteristics of Cutting Tool in Brittle Removal of a Ductile Meta in High-Speed Machining

Guosheng Su,Zhanqiang Liu,Yuhao Wang,Peirong Zhang,Hongxia Zhang,Baolin Wang,Zhitao Han

doi:10.3390/sym13091679

Guosheng Su, Zhanqiang Liu + Show 5 more

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https://doi.org/10.3390/sym13091679

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Abstract

The contact stress and heating effect between the cutting tool and workpiece in metal machining is symmetrical. However, the symmetry may be destroyed by changes in the workpiece material mechanical properties, such as ductility. The goal of this study is to reveal the wear characteristics of the cutting tool in machining a ductile metal with the cutting speed at which the metal is embrittled by the high-strain-rate-embrittle effect (HSREE). Orthogonal high-speed turning experiments were carried out. Pure iron type DT8 was cut at different cutting speeds, ranging from 1000 m/min to 9000 m/min. The shape and morphology of the chips obtained in the experiment were observed and analyzed by optical microscope and scanning electron microscope (SEM). Tool wear characteristics at different cutting speeds were observed. It shows that the pure iron becomes completely brittle when the cutting speed is higher than 8000 m/min. On the rake face, the coating of the cutting tool bursts apart and peels off. A matrix crack originates in the cutting edge or rake face and extends to the flank face of the cutting tool. The effects of HSREE on the tool wear is discussed. The findings of this study are helpful for choosing a suitable tool for brittle cutting of the ductile metal pure iron with very high cutting speed and solving the problems in machining due to its high ductility and high stickiness.

Highlights

High-speed machining (HSM) has advantages of low cutting force and cutting heat, so HSM can reduce the stress and thermal deformation of a workpiece and improve the machining accuracy of the workpiece
The high strain rate may lead to great changes in the mechanical properties of a workpiece material
The results show that, in the strain rate range of 2800–8000 s−1, the fracture strain of the material increases with the increase in the strain rate; obvious strain softening occurs at the strain rate of 8000 s−1 ; the breaking strain of pure iron decreases when the strain rate increases to 10,000 s−1

Summary

Introduction

High-speed machining (HSM) has advantages of low cutting force and cutting heat, so HSM can reduce the stress and thermal deformation of a workpiece and improve the machining accuracy of the workpiece. HSM has high material removal rate and resultant high machining efficiency. The strain rate in the deformation zone in HSM is very high, and may reach a level of. The high strain rate may lead to great changes in the mechanical properties of a workpiece material. It is known that the yield strength and flow strength of a material increases with the increase in deformation rate [2,3]. The strengths sharply increase when the strain rate in the deformation zone exceeds 103 –104 s−1 [4,5]

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