Design of die casting die Due to chemical and physical parameters and casting characteristics of magnesium alloy and aluminum alloys are very different, so casting design is not completely applied aluminum-casting principle [8].

Liquid magnesium alloy oxidized burning hot tearing tendency than when casting aluminium alloys-big, melting, casting and Diecasting mold temperature control is more complex than aluminum alloy die-casting. Magnesium alloy short filling time, exhaust, especially prominent, magnesium alloy with low specific heat and latent heat than aluminum and die casting process are prone to local (thin-section parts) early crystallization phenomenon, causes the feeding channel blocked, resulting in defects of misrun. Design of die casting die of magnesium alloy mainly take into account the following aspects:

(1) selection for die casting machine. What types of die casting machines are production largely depends on the wall thickness of the casting. Roland Fink in the "optimization of magnesium alloy die casting process" issues of process, through economic, cold Chamber die casting of magnesium alloy die casting and hot Chamber die casting process analyses of General 1kg of casting hot Chamber die casting machines are needed, to ensure full of thin-walled parts, large is recommended for cold Chamber die casting machines.

(2) the processing parameters. In die casting production process, select the appropriate process parameters is prerequisite to obtaining maximum productivity high quality casting die casting machine to play, is the correct basis for die casting die design. When you die, many factors influence the forming of alloy liquid filling, main injection pressure and injection speed, injection time and the die temperature, and so on. As die casting wall thickness and complexity of different process parameters selection varies greatly. Compared with aluminum, zinc alloy of magnesium alloys, liquid, secondary injection velocity range, punch about faster than aluminum magnesium alloys 30%, Max even more than 10m/s. Due to the properties of magnesium alloy casting on temperature sensitive gentle pouring of liquidity, liquid easily solidified magnesium alloys during mold filling, must be accurately controlled mild temperature, otherwise it is easy to waste.

(3) design of gating system. Gating system exhaust overflow of liquid metal flow direction, passing conditions, mold temperature, pressure and filling time and the speed and flow of molten metal through the sprue and other aspects, plays an important role in controlling and regulating. Design of gating system are summarized as follows:

Ingate: magnesium alloy in-cavity faster than aluminum, zinc alloy and magnesium alloy die castings for thin-walled parts and gate location chosen will directly impact the cavity surface must be avoided to ensure flow of molten metal in the cavity of the shortest path in order to prevent low water and cold shuts.

Filling speed: by and large, due to the thermodynamic properties of magnesium alloys, alloys to dies heat transfer speed, and large freezing range, less liquid, so in order to avoid premature solidification of liquid magnesium runner, should enable magnesium liquid-filled cavity with high speed [9]. Ingate velocities for 90~100m/s, for some thin-wall magnesium alloy die castings, Ingate speeds as high as 20m/s.

Gate size: in many cases, the gate through the machine to remove. Gate width should be less than the thickness of 50% to avoid trimming of castings in the process causing injury. In order to obtain the minimum thickness of the gate, while ensuring the requirements of thin-wall magnesium die castings, gate width should be as large as possible in order to ensure proper Ingate cross-sectional area.

Filling time: it was closely related with Ingate speed, for high surface quality of thin-walled castings has a great effect. Filling time is less than the original aluminum alloy 0%, usually taken as 10~100ms.

Overflow tank design for thin-wall magnesium alloy die castings, best overflow inlet area approximately as Ingate area of 20%~25%[9].