1, magnesium alloy traditional die casting.
The traditional die-casting technology allows the magnesium alloy liquid to fill the die-cast cavity with high-speed turbulence and diffuse form filling, so that the gas in the cavity and the gas generated by the die-casting paint can not be discharged smoothly. These gases may melt at high pressure Inside, perhaps the shape of scattered in the castings within the high-pressure micro-pores. At high temperatures, these high pressure ablation of gas and micropores of precipitation or expansion lead to casting deformation and appearance of the bubble. So the traditional die-casting method of magnesium alloy die casting, can not be heat treatment to strengthen, can not be used at higher temperatures.
2, magnesium alloy vacuum die casting
Vacuum die-casting of the main strengths are: to reduce the internal porosity of the casting to improve the appearance of casting and is conducive to the production process of casting the invariance of the size. Other aspects are: the injection of the specific pressure can be reduced by about 40%, is conducive to extend the die life; use a small die casting machine; add die casting heat treatment and solderability. The effect of vacuum die casting and popular die casting on porosity of castings was simulated by finite element simulation software. The effect of vacuum die casting and popular die casting on the porosity of magnesium alloy AZ91D was simulated by universal die casting and vacuum die casting. Consequences: Compared with die casting, vacuum die casting can be useful to reduce the porosity of castings to improve the quality of castings. In view of this, vacuum die casting in the reduction of gas content is undoubtedly very useful, but then. As long as the conventional die-casting as the foundation, vacuum die casting will have a clear result, and the use of vacuum die casting, but also pay attention to the design of the vacuum airway and its area of accounting, in particular, accounting for critical area. So as to avoid the result of vacuum die-casting vacuum die-casting mold processing accuracy requirements are higher, the other need to attach a set of vacuum special equipment, mold precision requirements are higher. Progress has added the skills to the difficulty and cost.
3, magnesium alloy thixotropic die casting
Magnesium alloy semi-solid die-casting is a very new metal forming skills. And die-casting, extrusion forging and traditional forging comparison. There are many advantages to brewing. With the demand for magnesium alloy castings, magnesium alloy thixotropic die-casting forming can be carried out with each passing day, roughly through two stages: thixotropic injection molding and a new generation of thixotropic injection molding. JSW and the Japanese car wheel factory has developed a magnesium alloy / aluminum alloy composite material wheel, this two-piece wheel with cast and forged group just, first with thixotropic injection molding magnesium alloy wheels, remove the runner, the The hub is reheated for warm forging, with progressive mechanical function, and then with aluminum rims (with chrome-plated bolts). The whole process only need a needle forming, a forging, and then after the heat treatment. With a small amount of machining can be completed. The second generation thixotropic injection molding machine has improved the shape of the tranquility, dimensional accuracy and excellent rate, can be more easily produced thin-walled notebook shell and so on.