Research On Cooling Water Flow Distribution Method Of Multi-cavity Hot Stamping Die

The multi-cavity hot stamping die can complete the forming of multiple sheets at one time.At the same time,the production efficiency is higher by adopting this structure.However,due to the difference in the thickness of the hot forming parts inside each cavity,the temperature of the parts with smaller thickness value is likely to be lower while the temperature of the thick plate parts is significantly higher after the same pressure holding time.Under the condition of constant total flow,by adjusting the valve opening to reduce the flow through the mold cavity of the thin plate parts,the flow in the thick plate cavity can be increased to achieve the purpose of promoting the cooling of the thick plate parts,but the specific amount of valve adjustment is difficult to control.The research on flow distribution by the way of trial-manufacture of hot forming parts will undoubtedly lead to the increase of manufacturing cost.In view of the above problems,the main research contents of this paper are as follows:Firstly,taking A-pillar side beam of automobile as the research object,a model temperature analysis method based on FLUENT and LS-DYNA co-simulation method is proposed,which can consider the influence of flow field distribution difference caused by complex water channel structure.This method uses the convective heat transfer coefficient which changes with the flow velocity to define the convective heat transfer between the mold and the cooling water,and it overcomes the limitation of using the constant value to define the convective heat transfer.The comparison between the simulation analysis results and the measured temperature information shows that: Compared with the convective heat transfer defined by constant values,the model temperature analysis method considering the influence of flow field can obtain the temperature distribution consistent with the measured results.Moreover,the maximum temperature difference of 12 temperature monitoring points is 3.6?,and the maximum error is 3.5%,which confirms the feasibility of using this method to analyze practical engineering problems.Secondly,taking temperature uniformity as the goal,the influence of channel spacing on the surface temperature distribution of the die was investigated through mold temperature analysis.The results show that: Under the condition that the diameter of the water pipe is 8mm and the distance between the water channel and the hot stamping die surface is 12 mm,the temperature fluctuation of the die surface is 2? when the distance between the water channel increases from 15 mm to 20 mm,which basically does not affect the uniformity of the overall temperature.Moreover,the increase of water pipe spacing can effectively reduce the number of water channels in the hot stamping die,which can improve the flow rate of the die surface and reduce the manufacturing cost.Then,for sheet metal with different thickness,the change law of cooling rate of forming parts with the change of pressure holding time and flow velocity of mold surface was studied.By fitting the data,the function model between the temperature and the pressure holding time of the hot forming parts under the condition of different flow rates of the molded surface was established.When the pressure holding time is determined,according to the established cooling relationship model of hot forming parts,the specific flow rate needed for cooling of sheet parts can be determined quickly,and the reasonable distribution of cooling water in each cavity can be realized.Finally,according to the established cooling relationship model of different thickness,the valve opening on the outlet of the thin plate cavity is adjusted by taking the one die and three cavity hot stamping die as the research object,and then the analysis results before and after the adjustment are compared.The results show that: Under the condition of not changing the rated flow rate and holding time,the temperature on the beam after adjustment increases by 19.2?,and the temperature on the sill decreases by 10.3?,and the cooling of the thick plate is promoted.