Numerical Simulation Of Distortion And Microstructure Evolution Of Large-scale Conplex Workpiece During Hot Work Process

The large-scale thin-wall workpiece is prone to distort during hot work process. The improper process parameters will lead serious distortion which affects the use of the workpiece. Additionally, the mechanics properties of the heavy forgings are very poor because of large-scale of grain size. And the grain size can be refined by forging.In this paper, we focus on two problems. One is the problem of distortion of large-scale complex thin-wall workpiece during hot work process such as welding and heat-treatment, the other is grain refinement problem of heavy forgings during free forge process. In order to solve the actual engineering problems, we use the finite element analysis software ABAQUS and DEFORM to simulate those hot work process, respectively.The heating and quenching process of an axis-symmetry large-scale thin-wall workpiece made by steel has been described by using the ABAQUS program. The distributing of temperature and stress field as well as rule of deformation during heating and quenching can be obtained from the calculated results. The results show that the deformation of the thin-wall workpiece is not symmetrical after quenching. The shape of section of the thin-wall worpiece will become ellipse and the top of the workpiece will become bell-mouthed after quenching. The maximum radial displacement reached 30.89mm. The radial displacement of some selective sections accord with the value of real radial displacement well and the rule of deformation is uniform. The effects of process parameters on the deformation of heating and quenching have been researched. The result shows that the optimum quenching process parameters is quenching as faster as you can by using the weak quenching medium such as oil, nitrogen.The welding and annealing process of a large-scale complex thin-wall workpiece made by titanium alloy has also been simulated by using ABAQUS software. The calculated results of deformation show that the length of the workpiece has no change after the welding process while elongate after anneal heat treatment process. The value of elongation is 2.55mm which fit in with the real value preferably. In this part, we pay more attention on the force analysis of clamp during welding and annealing process. The calculation results approve the right design on the clamp.The free forge process of a heavy forging has been calculated by using DEFORM software. The evolution of grain size has been studied carefully in this part. The results reveal that the grain size of core materials is about 15μm when the velocity of first forging is 10mm/s. The grain size of surface which is hard to deform is between 40μm and 100μm in average, indicating that the grain size decreases evidently. We also research the effects of forging parameters on the grain refinement. The results show that the optimum forging process parameters for our calculated workpiece is that the forging speeds should be faster and forge times should be fewer to ensure that workpiece do not produce the craze.