HARD TURNING PLUS GRINDING–A COMBINATION TO OBTAIN GOOD SURFACE INTEGRITY IN AISI O1 TOOL STEEL MACHINED PARTS

Abstract

The establishment of adequate machining guidelines requires the study of several factors (residual stresses, roughness, hardness, microstructural changes, etc.) that define the surface integrity generated in the part by a machining operation. This work studies the surface integrity generated in AISI O1 tool steel by four hard turning (conventional, laser assisted, MQL and conventional with worn tool) and two grinding (production and finishing) processes, as well as by a combined machining process (conventional hard turning + finishing grinding). Hard turning generates tensile stresses and strong structural changes in the machined surface while grinding causes compressive stresses and negligible structural changes. Below the surface, grinding generates slightly tensile or nearly null stresses whereas turning generates strong compressive stresses. The results obtained show that an optimum machining process would imply the combination of hard turning plus a slight final grinding.

Keywords:

• grinding
• hard turning
• residual stresses
• surface integrity
• tool steel

ACKNOWLEDGMENTS

The results presented in this article are part of the investigation carried out in the framework of a Cooperation Project (Ref. 121402, INTEK Programme) financed by the Basque Government. V. García Navas would also like to thank the Industry and Commerce Department of the Basque Government the concession of a grant for the realisation of her thesis.