The Study On Hydrogen Diffusion And Hydrogen-induced Fatigue In Large Forgings Under Micro Views

The flake is the common defect in the large forging.The hydrogen element and various defect in the large forging is the basic factor for the formation of flake.Once the flake is found in the forging,the forging must be scrapped.Therefore,the study on hydrogen diffusion in forging and hydrogeninduced fatigue is the foundation to reduce production cost and improve economic efficiency.In this paper,the finite element analysis software is used to study the micro-void defect in the support roller.Based on the theory of hydrogen pressure,the fatigue life of the micro-void defect under the coupling of internal hydrogen pressure and external load is emphatically analyzed.For the finite element cellular model with single micro-void defect,the effects of hydrogen pressure,distribution position of micro-void in supporting roller,the size of micro-void and the angle between micro-void and external load on fatigue life are studied.At the same time,the influence of the coupling between two micro-voids defect in supporting roller is studied.The main research is conducted from three aspects: the distance between micro-voids,the size of micro-voids,and the angle between micro-voids and external load.The results provide a theoretical basis for analyzing the mechanics of flake formation.In addition,the diffusion and excitation model of hydrogen element in the microscopic field of view is established by random function.Based on hydrogen desorption test,the impact of the hydrogen trap binding energy,heating rate,sample thickness,initial hydrogen concentration and hydrogen trap density on hydrogen diffusion is studied.The results provide strong support for the dehydrogenation process of large forging and the development of precautionary measures for the initiation of flake.Finally,there is still some controversy about the diffusion mechanism of hydrogen atoms in the grain boundaries of the samples during electrochemical hydrogen charging.Therefore,a new hydrogen diffusion model is proposed in this paper.The microscopic lattice model of alloy steel is established by Voronoi diagram.The effects of hydrogen charging current density,hydrogen charging time and grain boundary area on hydrogen diffusion are mainly analyzed.