With an increasing pressure on automotive weight reduction, the demand on the lighter weight automotive components continues to increase. In recent years, squeeze casting processes have been used with different aluminium alloys to produce high integrity automotive parts. In this study, the indirect squeeze casting processes is adopted to cast a motorcycles component originally produced by a high pressure die casting process using aluminium alloy ADC12. To minimize amount of gas porosity inside squeeze casts, concepts of (1) minimization of ingate velocity along with (2) bottom filling pattern during the die filling, and (3) maximization of intensifications casting pressure are applied. Then parts are casted with both conventional high pressure die casting and indirect squeeze casting processes. Comparative evaluation of mechanical properties was made between HPDC casts and squeeze casts both in as-cast and heat treated conditions. Results from the experiment have shown that squeeze casts can pass the blister test at 490 °C for 2.5 hours. Then, squeeze casts are heat treated by solution treatment at 484 °C for 20 minutes and artificial age at 190 °C for 2.5 hours, respectively. This improves UTS of the heat treated squeeze cast to 254.14 MPa with 1.84% of elongation, while the UTS of as cast condition from both processes is not significantly different.
Squeeze casting is process capable to produce high integrity parts. To minimize gas porosity, melt front’s speed must be kept as minimum as possible to ensure the laminar flow pattern with adequate flow rate to be able to fill the cavity before liquid metal is solidified. In this study, the indirect squeeze casting process was adopted to cast a motorcycle’s component originally produced by a high pressure die casting (HPDC) process. Based on shape and dimension of the parts to get the real castings for the mass production, melt’s speed must be higher than the level reported by the literatures (around 1 m/sec). As a result, a fully laminar flow may not be achievable. This is confirmed by the primary study of the process parameters and tooling design using the casting process simulation. Castings from two processes were casted and then mechanically and micro-structurally compared for both as cast and heat treated conditions. Results from the experiment have shown that size of gas porosity found in squeeze casts reduced significantly, while gain size of the squeeze casts trended to be bigger than that of HPDC casts. In terms of the mechanical properties, the ultimate tensile strength of as cast from both processes was not significantly different, while the heat treated squeeze casts has shown the big improvement compared with the as casts.
To achieve the laminar flow filling pattern in squeeze casting processes, many literatures [1-4] have reported that ideal velocity of liquid metal passing through the ingate should be between 0.1 – 0.5 m/sec. John Campbell [1] reported that liquid metal front speed velocity should be 0.4 m/sec in order to eliminate the gas porosity inside the casting. However, such slow speed requires the higher temperature of liquid metal and die. This results in not only the longer cycle time but also a coarser microstructure of the casting. In addition, the sample castings used in the literature are simple form castings which do not reflect the real castings used in daily life. In this study, the indirect squeeze casting processes is adopted to cast a motorcycle’s component originally produced by a high pressure die casting process. Based on shape and dimensions of the casting to get the real casting out for the mass production, melt’s speed must be higher than the level reported by the literatures (around 1 m/sec). As a result, a fully laminar flow may not be achievable. This is confirmed by the primary study of the process parameters and tooling design using the casting process simulation. However, by clinging on the two principles of the squeeze casting processes; (1) minimizing the amount of entrapped air by slowly fill the cavity and (2) reducing the amount of solidification shrinkage by pressurized solidification; the casting from two processes will be casted in order to compared the micro-structure and mechanical properties.
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