Metallurgical Analysis of Chip Forming Process when Machining High Strength Bainitic Steels

Fares Haddad,Christophe Lescalier,Jean-Edouard Desaigues,Anne Bomont-Arzur,Olivier Bomont

doi:10.3390/jmmp3010010

Abstract

In the following work, we propose a metallurgical approach to the chip formation process. We focus on a turning application of high strength steel in which chips are produced by adiabatic shear bands that generate cutting force signals with high frequency components. A spectral analysis of these signals is applied and highlights peaks above 4 kHz depending on the cutting conditions. A microscopic analysis on the chip sections provided data on chip breaking and serration mechanisms. Shear band spacing and excitation frequency of the whole cutting system were calculated and gave a good correlation with cutting forces spectra.

Highlights

Companies involved in powertrain applications are increasingly relying on bainitic steels due to their opportune correlation between high mechanical resistance and ductility [1]
In the following work, we propose a metallurgical approach to the chip formation process
We focus on a turning application of high strength steel in which chips are produced by adiabatic shear bands that generate cutting force signals with high frequency components

Summary

Introduction

Companies involved in powertrain applications are increasingly relying on bainitic steels due to their opportune correlation between high mechanical resistance and ductility [1]. This structure can plainly be obtained by air cooling after hot forming processes such as forging or rolling, providing a major economic advantage in manufacturing process of the automotive parts. Since bainite presents similar mechanical properties to martensitic structures, its machinability is still problematic, and high tool-wear rates are often encountered. This is the outcome of several microstructural characteristics. The aim of this study is to compare the behaviors of martensite and bainite structures during a high-speed turning process on both macroscopic and microscopic scales

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