Filling velocities and defects of plate shaped diecastings.

Iwata, Yasushi; Tozawa, Katsutoshi; Yamamoto, Yoshiaki; Nakamura, Motoyuki; Mizuno, Kuniaki; Tuboi, S.

doi:10.2464/jilm.37.48

Cited by 2 publications

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“…6,8) However, a large temperature drop in the molten metal due to a long injection time gives rise to other defects, such as surface folds, cold shut, even misrun. 9,10) Therefore, it is necessary to clarify the causes and conditions of surface defects in order to perform die casting under optimal conditions. Aluminum alloy die castings for silicon content lower than that of JIS AD12.1 aluminum alloy (referred to hereinafter as AD12.1 alloy) is also required due to the diversification of needs with respect to the properties of die casts.…”

Section: Introductionmentioning

confidence: 99%

Effects of Solidification Behavior during Filling on Surface Defects of Aluminum Alloy Die Casting

et al. 2013

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Die castings are prone to contain considerable porosities due to the entrapment of air or gases in the molten metal during mold filling. Reducing the die filling velocity is effective for reducing the entrapment, but it increases surface defects, such as surface folds and cold shut on die castings.In this research, the solidification behavior of molten metal during mold filling was investigated by developing a highly sensitive thermosensor with a response time of 0.015 s that can correctly measure the temperature of flowing molten metal. The criterion for the formation of surface defects was further examined based on the solidification behavior of molten metal during mold filling.It was found that the type of surface defects varies with the solidification manner of aluminum alloys. Surface fold defects occur on die castings made of JIS AD12.1 alloy with skin-formation type solidification. The occurrence of surface folds can be predicted by the thickness of the solidified layer of the molten metal from the surface of cavity. The critical thickness for the formation of surface folds increases with increasing casting pressure. On the other hand, cold shut defects occur on die castings made of JIS AC4C alloy with mushy-formation type solidification. The molten metal temperature drops toward the tip of the molten metal flow. The occurrence of cold shut defects can be estimated by the temperature of this molten metal flow tip at the time this flow converges with other flows.

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Section: Introductionmentioning

confidence: 99%

Effects of Solidification Behavior during Filling on Surface Defects of Aluminum Alloy Die Casting

et al. 2013

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Change in Molten Metal Pressure and Its Effect on Defects of Aluminum Alloy Die Castings

et al. 2014

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Surface defects of die castings, such as surface folds, cold shuts and misruns, etc., are thought to occur due to the solidification of molten metal during mold filling. In the die casting process, mold filling and solidification are completed under high pressure. Thus, varying the casting pressure may also have some effects on surface defects.In this study, we investigated the effects of solidification on mold filling and pressure transmission and elucidated the influences of casting pressure on the quality of die castings.In the mold filling process of JIS AC4C (A356) alloy (hereinafter called AC4C alloy), flow resistance was found to increase with the increase of the amount of solid phases, and thus decreased the velocity of molten metal flow. Cold shut occurred due to the rapid drop of the temperature of molten metal as a result of the decrease in flow velocity. A similar phenomenon was also observed for JIS AD12.1 (A38X) alloy (hereinafter called AD12.1 alloy), although this alloy showed a skin-formation type solidification. The pressure transmission in molten metal weakened gradually with the increase in the amount of solid phases and eventually stopped completely to cause casting defects as the result. In addition, resistance to molten metal flow due to the back pressure, shape of mold cavities, etc., was also noticed. These results indicate that a high plunger pressure is necessary to obtain die castings without defects.

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Filling velocities and defects of plate shaped diecastings.

Cited by 2 publications

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Effects of Solidification Behavior during Filling on Surface Defects of Aluminum Alloy Die Casting

Effects of Solidification Behavior during Filling on Surface Defects of Aluminum Alloy Die Casting

Change in Molten Metal Pressure and Its Effect on Defects of Aluminum Alloy Die Castings

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