Determination of Interfacial Heat Transfer Behavior at the Metal/Shot Sleeve of High Pressure Die Casting Process of AZ91D Alloy

doi:.10.1016/j.jmst.2016.02.003

Abstract

Abstract:

The interfacial heat transfer behavior at the metal/shot sleeve interface in the high pressure die casting (HPDC) process of AZ91D alloy is carefully investigated. Based on the temperature measurements along the shot sleeve, inverse method has been developed to determine the interfacial heat transfer coefficient in the shot sleeve. Under static condition, Interfacial heat transfer coefficient (IHTC) peak values are 11.9, 7.3, 8.33kWm^-2K^-1 at pouring zone (S2), middle zone (S5), and end zone (S10), respectively. During the casting process, the IHTC curve displays a second peak of 6.1kWm^-2K^-1 at middle zone during the casting process at a slow speed of 0.3ms_-1. Subsequently, when the high speed started, the IHTC curve reached a second peak of 12.9kWm^-2K^-1 at end zone. Furthermore, under different slow casting speeds, both the calculated initial temperature (T_IDS) and the maximum temperature (T_simax) of shot sleeve surface first decrease from 0.1ms_-1 to 0.3ms_-1, but increase again from 0.3ms_-1 to 0.6ms_-1. This result agrees with the experimental results obtained in a series of “plate-shape” casting experiments under different slow speeds, which reveals that the amount of ESCs decreases to the minimum values at 0.3ms_-1 and increase again with the increasing casting slow speed.

Key words: High pressure die casting (HPDC), Interfacial heat transfer behavior, Inverse method, Slow casting speed

Yu Wenbo,Cao Yongyou,Li Xiaobo,Guo Zhipeng,Xiong Shoumei. Determination of Interfacial Heat Transfer Behavior at the Metal/Shot Sleeve of High Pressure Die Casting Process of AZ91D Alloy[J]. J. Mater. Sci. Technol., 2017, 33(1): 52-58.

Figures/Tables 8

Fig.1 Schematic description of experimental setup of the shot sleeve including the cross section. Length unit is millimeter

Table 1 Chemical composition of AZ91D alloy and H13 steel (wt%)

AZ91D	Al	Zn	Mn	Si	Fe	Cu	Ni	Be	Mg
AZ91D	9.02	0.66	0.199	0.0311	0.0010	0.0023	0.0007	0.0010	Bal.
H13	C	Mn	Si	S	P	Cr	Mo	V	Fe
H13	0.396	0.36	0.94	<0.005	<0.025	5.05	1.25	0.82	Bal.

Table 2 Thermal properties of related materials

Thermal properties	AZ91D	H13
Thermal conductance λ (W^{m^-1K^-1)}	72	31.2-0.013^{T^a}
Specific heat C_p (J^{kg^-1K^-1)}	1050	478-0.219^T
Density ρ (kg^{m^-3)}	1810	7730-0.24^T
Solidus temperature T_S (°C)	470	1471
Liquidus temperature T_L (°C)	595	1404
Latent heat L_s (J^{kg^-1)}	373000	209350

Fig.2 Configuration of plate-shape casting

Fig.3 Calculated 2D temperature distribution of the metal inside the shot sleeve during slow filling (a), fast filling (b), and end of filling (c)

Fig.4 Typical calculated and measured results of shot sleeve at S2 (a), S5 (b), and S10 (c). (Tmu, Tmi—temperatures of the metal upper surface and interface; Tsi—shot sleeve surface temperature; T1 and T6—measured temperatures at 1 and 6mm from interface in the shot sleeve; T3c—calculated temperature at 3mm from interface in the shot sleeve).)

Fig.5 Statistics of calculated values under different pouring temperature at three positions (S2 S5 and S10) in the fifth casting cycle: (a) hmax, (b) qmax, (c) TIDS, and (d) Tsimax

Fig.6 ESCs distribution in the cross section of 2.5mm plate after the “plate-shape” cast under different slow speeds, 0.2, 0.3, and 0.4ms-1

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