Development and application of inverse heat transfer model between liquid metal and shot sleeve in high pressure die casting process under non-shooting condition

Abstract

A s one of the most cost effective near-net-shape manufacturing processes, high pressure die casting (HPDC) accounts for almost 70% of aluminum components production [1] . It has been demonstrated that the HPDC process involves rapid temperature fluctuations on the surface of the die during the fast casting cycles. This behavior could result in steep thermal gradients on and below the die surface [2][3][4][5][6] . According to research articles [7,8] , the solidification rate is highly dependent on the interfacial heat transfer behavior in both the shot sleeve and the die. Subsequently, solidification rate has a significant influence on the microstructural defect formation and mechanical Abstract: To predict the heat transfer behavior of A380 alloy in a shot sleeve, a numerical approach (inverse method) is used and validated by high pressure die casting (HPDC) experiment under non-shooting condition. The maximum difference between the measured and calculated temperature profiles is smaller than 3 °C, which suggests that the inverse method can be used to predict the heat transfer behavior of alloys in a shot sleeve. Furthermore, the results indicate an increase in maximum interfacial heat flux density (q max ) and heat transfer coefficient (h max ) with an increase in sleeve filling ratio, especially at the pouring zone (S2 zone). In addition, the values of initial temperature (T IDS ) and maximum shot sleeve surface temperature (T simax ) at the two end zones (S2 and S10) are higher than those at the middle zone (S5). Moreover, in comparison with fluctuations in heat transfer coefficient (h) with time at the two end zones (S2 and S10), 2.4-6.5 kW•m -2 •K -1 , 3.5-12.5 kW•m -2 •K -1 , respectively, more fluctuations are found at S5 zone, 2.1-14.7 kW•m -2 •K -1 . These differences could theoretically explain the formation of the three zones: smooth pouring zone, un-smooth middle zone and smooth zone, with different morphologies in the metal log under the non-shot casting condition. Finally, our calculations also reveal that the values of q max and h max cast at 680 °C are smaller than those cast at 660 °C and at 700 °C. Key words: inverse method; A380 casting; filling ratio; heat transfer behavior CLC numbers: TG146.21 Document code: A Article ID: 1672-6421(2016)04-269-07properties of the final product. Furthermore, the solidification condition could affect the morphology and quantity of externally solidified crystals (ESCs) or cold flakes in the casting [9,10] . Therefore, to reduce defects in castings and achieve an optimized control condition, a thorough understanding of the heat transfer between the molten metal and the shoot sleeve is necessary. Temperature measurement is the most difficult task in interfacial heat transfer determination in HPDC. Dour et al. [11] pointed out that improper installation of the thermocouples could bring uncertainties in temperature measurement. To date, there are two main problems existing in casting and die temperature measurement: (I) accurate and reproducible measurements are ...

Possibility of Utilization of Gate Geometry to Modify the Mechanical and Structural Properties of Castings on the Al-Si Basis

“…On the basis of the aforementioned and pursuant to the described experiments and expressed mutual relations between the observed and evaluated factors influencing the die casting process and the experiments described in the professional literature [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ], the mutual correlation between the gate structure, the mechanical properties of the casting, its structural composition, and the technological parameters can be expressed as in Figure 8 .…”

“…Solidification speed significantly influences the formation of microstructural defects and the mechanical properties of the final product. Except for the aforementioned, the conditions of solidification could affect the morphology and amount of externally solidified crystals (ESC) or cold flakes within the casting [5,6]. Cooling speed thus significantly influences the structure improvement and the volume ratio of the porosity within the casting.…”

Evaluation of Thermal Conditions at Cast-Die Casting Mold Interface

“…Individual parameters and their values are listed in Table 2. To determine the heat dissipated by the cast according to the relation [Klobčar 2008, Majernik 2019, Wladysiak 2017, Yu 2016. To determine the amount of the heat dissipated by cooling of the cast according to it should be noted that each part of the cast will cool under different conditions.…”

“…In order to optimize the design of runners, it is preferable to know the temperature influence of the individual mold zones. Temperature measurement is the most difficult task in determining the interfacial heat transfer in HPDC [Majernik 2019, Yu 2016, Krenicky 2011. A group of authors led by ZHI-PENG designed a special temperature sensor unit (TSU) to obtain a sufficiently fast response to the HPDC process and accurate temperature measurement inside the mold.…”

Optimization of Ladle Tilting Speed for Preventing Temperature Drops in the Die Casting Process

“…The problem is that the temperature of the molten metal drops significantly while it is flowing from the ladle to the shot sleeve. Therefore, a method to minimize the temperature drop at the stage before injection is necessary [2,3]. One solution to this casting problem is to raise the temperature of the metal before injection it.…”