A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density (HFD) and interfacial heat transfer coefficient (IHTC) during the high pressure die cas...A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density (HFD) and interfacial heat transfer coefficient (IHTC) during the high pressure die casting (HPDC) process.Experiments were carried out using step shape casting and a commercial magnesium alloy,AM50.Temperature profiles were measured and recorded using thermocouples embedded inside the die. Based on these temperature readings,the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values,after which their values decrease to a much lower level until the dies are opened.Different patterns of heat transfer behavior were found between the die and the casting at different thicknesses.The thinner the casting was,the more quickly the HFD and IHTC reached their steady states.Also,the values for both the HFD and IHTC values were different between die and casting at different thicknesses.展开更多
The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of t...The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of the commercial casting simulation package, ProCASTTM, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient values. The simulation results were used to estimate the centerline cooling curve at various locations through the casting. The centerline cooling curves, together with the die temperature and the thermodynamic properties of the alloy, were then used as inputs to compute the solution to the Stefan problem of a moving phase boundary, thereby providing the through-thickness cooling curves at each chosen location of the casting, Finally, the local cooling rate was used to calculate the resulting grain size via previously established relationships. The effects of die temperature, filling time and heat transfer coefficient on the grain structure in skin region and core region were quantitatively characterized. It was observed that the grain size of skin region strongly depends on above three factors whereas the grain size of core region shows dependence on the interracial heat transfer coefficient and thickness of the samples. The grain size distribution from surface to center was estimated from the relationship between grain size and the predicted cooling rate. The prediction of grain size matches well with experimental results. A comparison of the predicted and experimentally determined grain size profiles enables the determination of the apparent interracial heat transfer coefficient for different locations.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No. 50675114) the National Basic Research Program of China (2006CB605208-2) The experiments were conducted at the Tsinghua-TOYO R&D Center of Magnesium and Aluminum Alloys Processing Technology with the help of engineers from the TOYO Machiuery & Metal Co., Ltd.
文摘A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density (HFD) and interfacial heat transfer coefficient (IHTC) during the high pressure die casting (HPDC) process.Experiments were carried out using step shape casting and a commercial magnesium alloy,AM50.Temperature profiles were measured and recorded using thermocouples embedded inside the die. Based on these temperature readings,the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values,after which their values decrease to a much lower level until the dies are opened.Different patterns of heat transfer behavior were found between the die and the casting at different thicknesses.The thinner the casting was,the more quickly the HFD and IHTC reached their steady states.Also,the values for both the HFD and IHTC values were different between die and casting at different thicknesses.
基金jointly supported by Canadian Network for Research and Innovation in Machining TechnologyNatural Sciences and Engineering Research Council of Canada-Automotive Partnership Canada programNRCan’s Office of Energy R&D through the Program on Energy R&D
文摘The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of the commercial casting simulation package, ProCASTTM, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient values. The simulation results were used to estimate the centerline cooling curve at various locations through the casting. The centerline cooling curves, together with the die temperature and the thermodynamic properties of the alloy, were then used as inputs to compute the solution to the Stefan problem of a moving phase boundary, thereby providing the through-thickness cooling curves at each chosen location of the casting, Finally, the local cooling rate was used to calculate the resulting grain size via previously established relationships. The effects of die temperature, filling time and heat transfer coefficient on the grain structure in skin region and core region were quantitatively characterized. It was observed that the grain size of skin region strongly depends on above three factors whereas the grain size of core region shows dependence on the interracial heat transfer coefficient and thickness of the samples. The grain size distribution from surface to center was estimated from the relationship between grain size and the predicted cooling rate. The prediction of grain size matches well with experimental results. A comparison of the predicted and experimentally determined grain size profiles enables the determination of the apparent interracial heat transfer coefficient for different locations.