Designing And Optimizing Of Hot Stamping Tool’s Cooling Ducts Of High Strength Steels

High strength steel can greatly reduce the weight of the motor vehicle parts in the condition of ensuring the body strength. Hot Stamping of high strength steel is a non-isothermal sheet metal-forming process which combines the forming and the heat treatment stages in order to enhance the mechanical properties of the metal sheet. The cooling system determines the quality of the hot stamping. Hence, making in-depth study of cooling effect of hot stamping mould has great significance for ensuring the quality of the formed parts.The relevant theories of heat transfer and fluid mechanics are discussed and at the same time the mode of heat transfer and the flow state of cooling water during press hardening of formed parts are analyzed. Design parameters such as diameter of the cooling duct, the distance between ducts, the distance between duct’s circumference surface and the working surface, and the distance between duct’s circumference surface and the side surface are presented. Based on the design parameters, nine different cooling duct’s patterns are designed. An appropriate orthogonal table and some reasonable values of the parameters are also designed.Under the condition of multi-process cycle, thermal-mechanical coupled numerical simulation of the press hardening stage is performed by fluid dynamics software FLUENT, and the cooling effects of the different cooling duct’s patterns are obtained. The design parameter which affects cooling effect mostly and the influence trend of each factor to cooling effect are obtained with intuitive analysis method.The studies show that under the request of structure strength the smaller the value of each design parameter we take, the better the cooling effect could be. Through the simulation, the best design parameters of cooling system can be reached. Diameter of the cooling duct should be 8mm, the distance between ducts 8mm, the distance between duct’s circumference surface and the working surface 6mm, and the distance between duct’s circumference surface and the side surface 6mm. For the ducts near die fillet, smaller diameter should be better, so that they can be placed closer to the tool surface and it is more helpful to enhance the cooling effect.