Numerical Simulation Of Partial Hardening And Experimental Research On B1500HS Hot Stamping

In recent years, with gradually increasing the increase in vehicle ownership, haze environmental issues as well as increase traffic accidents, people on vehicle safety and comfort concerns, while more attention to its energy saving performance. Under the premise to ensure the safety car, the major car manufacturers began to explore how to reduce body mass as possible, energy conservation, improve overall vehicle environmental performance. High-strength steel hot stamping technology is fully austenite of the sheet using the cooling effect of the cooling system inside the die stamping at the same time, the emergence of martensite tissue, thereby obtaining high strength, high hardness sheet. Thermoforming sheet applied to the automobile body structure member, can significantly improve vehicle safety, reduce vehicle mass. In some parts of the body structure, the different needs of different parts of the strength, should be shipped produced locally hardened sheet thermoforming technology. Thermoforming partial hardening technique by changing the cooling rate of the mold to achieve the strength of the ladder of the ladder parts.High-strength steel hot-stamping technique, the mold and the sheet metal interfacial heat transfer coefficient are key factors for thermoforming, sheet metal microstructure change the basis for determining the mechanical properties of experimental research, this paper for both. Sheet in an oven heated to 1203 K, heat 3 minutes, quickly placed on the mold, presses applied respectively 1MPa, 5MPa, 10 MPa, 15 MPa, 20 MPa load, measuring and recording sheet and the mold temperature changes, introducing Inverse Model obtained interface heat transfer coefficient. Separately heating the mold 323 K,373K, 473 K, 573 K, 673 K, 723 K hot stamping experiment measuring the sheet and the mold temperature was determined interface heat transfer coefficient, calculated by analyzing color metallography microstructure Sheet when the ratio between the organization of organizations, test samples of sheet tensile strength and hardness, thermal forming numerical simulation of temperature field analysis provides a quantitative reference.Finite element analysis software FLUENT establish cooling section and the heating part of the model, simulation twenty dwell cycle, in accordance with the sheet metal mold temperature field changes, combined with sheet metal microstructure transition study on the optimum cooling parameters, through the series with mold cooling portion and the heating portion of the mold with a cooling system heat source hot stamping, sheet metal case hardened to achieve the requirements, optimization model mold, hot stamping die processing experiments, the results of comparative experiments and simulation results. Concluded as follow:(1) Mold interface heat transfer coefficient with the sheet experiments show that when the mold temperature is lower than 473 K, the temperature is the main factor affecting the heat transfer coefficient of heat transfer coefficient with the mold temperature decreases; when the die temperature is higher than 473 K, the pressure is the main factor affecting the heat transfer coefficient of heat transfer coefficient as the pressure increases.(2) Hot stamping packing hardening phase, along with the mold temperature, feed plate reduce the proportion of martensite, bainite structure to increase the proportion of hardness declined. Reduced tensile strength. Provide the basis for the realization of local hardening technology.(3) Finite element analysis of hot stamping process shows that the greater the flow velocity, the cooling rate of the mold and the cooling uniformity as possible; the longer the dwell time, mold cooling better. Comprehensive practical reasons to choose the best air speed 5m / s, dwell time 10 s. At partial hardening model, select the portion of cooling air flow velocity 5m / s, mold temperature heating portion 573 K.(4) Internal mold cooling portion diameter D smaller vent holes, the smaller the spacing of the vent hole L, the vent hole H from the bottom surface of the mold from the smaller, the better the cooling rate of the mold, the cooling uniformity as possible, considering the actual processing conditions, determine D- 10 mm, L-20 mm, H-10 mm optimize structural parameters as a mold.