Surface quality in milling of hardened H13 steel

In the final milling process of free-form surfaces, commonly employed in the production of molds and dies, knowledge of the cutting conditions and a strategy for choosing adequate processing routes can provide a significant reduction in the manufacturing times. The objective of this work is to evaluate quantitatively and qualitatively the surface quality behavior of a steel used in the production of dies and molds. The analysis was carried out for hardened AISI H13 tool steel inclined at an angle of 60° and for different cutting path orientations. The roughness of milled surfaces was measured and verified by scanning electron microscopy in order to compare the strategies and the surface textures obtained. Four different cutting path strategies were employed in these experiments, with horizontal and vertical single-direction rastering, both upward and downward. The conclusion is that, in the vertical upward strategy, the surface displays greater roughness and an irregularity with regard to plastic deformation. The other strategies showed lower roughness and similar regularity. Magnetic Barkhausen noise, used for sub-surface characterization, was found to be largest when measured along the cutting direction of the inserts. These directions coincided with the directions of greatest plastic deformation in the sub-surface region.