Difference in Growing Mechanism between Nose and Wedge Types of the Built-Up Edge

Abstract

The shape of the built-up edge (BUE) when machining steels at low cutting speed is a nose type. If a jet of oxygen (oxygen jet) is supplied to the tool edge at the same cutting conditions, the BUE no longer is a nose shape but is replaced by the wedge shape. Various tests were conducted on the two types of BUE: cutting tests by surface oxidized tools, observations of quick-stopping cutting test pieces by SEM, their ultimate analysis by EPMA and simulations of stress distribution of the cutting area by FBM. The results are as follows: 1) The rake face of the nose-type BUE is rough, like a rock surface, due to adhesions of chips; by contrast, that of the wedge-type BUE is very smooth. 2) Oxide layers are observed on the interface between the rake face of the wedge-type BUE and the chip. 3) Due to the lubricant of the oxide layer, the equivalent stress area of the cutting zone with the wedge-type BUE is smaller than that of the nose-type BUE.