Die Casting refer to the process that fully or semi melted aluminum alloy injected into cavity to form the castings at high speed and pressure.Die casting has following features.
- High efficiency.The filling time is about 1.5-2 seconds normally.The cycle time is about 15 seconds.It is very suitable for volume production.
- High precision for raw casting.The profile of raw casting in good condition.Tight tolerance and low roughness.Less requirement for secondary machining for assembly.It is very suitable for thin wall casting parts.To compare with cast iron parts,aluminum die casting parts has advantage on density,mechanical property,tensile strength,fatigue strength etc.
- Insert appliable.By applying insert,it can simplify the assembly.Insert material can be steel,cast iron,cooper and some insulation material.
- Limited heat treatment.The air easily trapped into parts and become porosity inside since the filling speed is too fast.Porosity really affect heat treatment.
Special types of aluminum die casting
- Vacuum die casting.It refer to process that melted aluminum alloy injected into cavity which is free of air by vacuum equipment.Firstly,vacuum die casting can eliminate pinhole inside castings and improve mechanical property and surface finishing.Secondly,vacuum die casting can reduce pressure inside cavity and use less pressure for big parts with thin wall.Thirdly,It can use poor castability aluminum alloy.
- Oxygen added die casting.It refer to the process that the air inside cavity replaced by oxygen before melted aluminum alloy injected into cavity.During filling cavity,oxygen will be pushed out of cavity and melted aluminum alloy can react with remaining oxygen,which can create small particles that can fill up pinhole inside castings.Firstly,it can eliminate pinhole and improve quality of casting.Secondly,Castings can work at very high temperature.Thirdly,Oxygen added die casting is cost effective and easy operated.
- Semi solid die casting.It refer to the process that melted aluminum alloy stirred before solidification and acquire melted alloy which contain lots of solid composition.This kind of melted alloy will be used for die casting.Firstly,the heat impact on cavity reduced since the temperature lower by stirring the melted aluminum alloy.Secondly,semi solid alloy is more sticky than liquid alloy and has low speed in runner,which reduce air trapped inside castings.Thirdly,shrinkage of semi solid alloy is quite small so it is hard to have shrinkage hole.Forthly,Easy operate as semi solid alloy were injected into chamber like soft material.
- Simulation of die casting.1.Filling and solidification simulation.2.Shrinkage and Shrinkage porosity simulation.3.Stress in solidification simulation.4.Mirco composition in solidification simulation.
Future in die casting
- Development of sensor for die casting and monitor all process in die casting in order to improve quality of final castings
- Take advantage of high technology,especially servo control technology that can program automatically and control pressure and correct tolerance during high pressure injection.
- High performance die casting tooling design.Unproper tooling design will affect tooling life span and lower efficiency and quality.
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