Research On The Interior Void Detection For Large Hot Axial Forgings Based On The Temperature Field

Large hot axial forgings are critical components of machinery equipment in electric power industry, petroleum industry, energy industry and so on. Stand or fall of the quality for hot axial forgings has a significant embodiment of the industrial level for a country. Void is a metallurgical defect which forms in the process of ingot casting. The existence of the defect frequently breaks forgings in the border of the void. The possibility o f the accidents occurring increases greatly, and even the security of people’s lives and property are threatened. Therefore, the detection research of interior voids plays a very important role in eliminating defects effectively and ensuring safe operation of the axial forgings. However, for existing detection means, it is difficult to realize the detection for interior void when axial forgings are in the state of high temperature. Therefore, how to detect interior void in high temperature state has become the urgent issue to be solved.The detection of interior void is researched on the basic of the fundamental detection theories of interior defect in this paper. The main contents are represented as follows:Firstly, on the basis of studying the heat transfer theories of the large hot axial forgings, the unsteady heat transfer characteristics of large hot axial forgings with void are researched, which lay the foundation for establishing void detection model of large hot axial forgings.Secondly, the interior irregular void detection model and regular void detection model of the large hot axial forgings are established respectively based on analyzing the heat transfer characteristics of hot axial forgings with void. For the regular void detection model, the numerical solution of the model can be acquired successfully by the finite difference method. For the irregular void detection model, interior boundary condition of the model is obtained by introducing the idea of lumped parameters. Then, combining the separation variable method, the analytical solution of the model can be obtained. Based on solving the two detection models established above, the interior temperature field distributions of hot axial forgings with different type voids can be got.Finally, the experimental verification is conducted based on experimental system designed by us. The interior temperature field change rules of forgings under different void size conditions are obtained according to the void detection model. The internal void defect of the forgings can be detected by these change rules. The feasibility of the void detection model is verified.