Three-dimensional transient cutting tool temperature field model based on periodic heat transfer for high-speed milling of compacted graphite iron

摘要

The new material, compacted graphite iron, plays a key role in the reliability of engine and the realization of high emission standard, but it is a difficult-to-machine material. In high-speed milling process of compacted graphite iron, thermal crack induced by thermal stress is the main reason for tool breakage and chipping. In order to reveal the initiation and propagation mechanisms of thermal cracks, and improve tool life by controlling the formation of thermal crack, it is necessary to study the three-dimensional transient cutting tool temperature field under the condition of periodic heat transfer in intermittent cutting. In this paper, the three-dimensional transient FEM cutting tool temperature field model for high-speed milling of compacted graphite iron was established by using the heat source method. The uneven spatial distribution of the heat flux on the rake face of the tool, and the changes of heat flux density due to the transient cutting thickness and tool-chip contact length over time were considered, and the influence of boundary conditions in the cutting stage and the non-cutting stage were also all taken into account. The heat flux action time and the ratio of cutting time and non-cutting time in the model were set according to the experimental conditions of actual milling process. The established three-dimensional transient cutting tool temperature field model was finally verified by measuring the real temperature in highspeed orthogonal turning experiment. The results showed that the predicted value of the model was consistent with the experimental value, and the predicted error was less than 6.0%, indicating that the model has high accuracy for simulation. This model has great theoretical significance for the development of new tool materials for compacted graphite iron processing, studying the mechanism of thermal crack, controlling and preventing tool failure caused by thermal crack.