Liquid metal filling technology.

Technical News
2018/01/24 21:57
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"Liquid metal" is an amorphous alloy made of titanium, zirconium, nickel, copper and other metals. It is characterized by high strength, wear resistance and high strength/weight ratio. If there is anything like a liquid, it is: first, to make parts with this metal, you can use plastic injection molding, which greatly improves the precision of the parts. The second is that the surface of the material feels as smooth as a liquid.
Hydraulic characteristics of liquid metal filling flow process.
At present, in the actual casting production, the sand type still occupies a considerable portion, while the liquid metal flows in the sand mold with the following hydraulic characteristics:
1. Viscous fluid flow: liquid metal is a viscous fluid. Liquid metal viscosity and its composition, and in the process of flow of liquid metal temperature, and increasing, when the liquid metal in the crystal, the liquid viscosity increases sharply, the flow velocity and flow pattern will change dramatically.
2. Unstable flow: in the process of filling, the temperature of liquid metal keeps decreasing and the casting temperature increases constantly, and the heat exchange between the two is unstable. As the flow temperature drops, the viscosity increases and the flow resistance increases. In addition, the fluid flow in the filling process increases or decreases, and the flow rate and flow state of the liquid metal are constantly changing, which leads to the unstable flow of liquid metal in the filling casting process.
3. Flow in the perforated pipe: because the sand type has certain porosity, the casting system and the cavity in the sand mold can be regarded as a porous pipe and container. Liquid metal flow in the perforated pipe, can not be well attached to the wall, at this time may be involved in fluid flow of gas to the outside world, forming pores or cause oxidation of liquid metal forming oxide slag.
4. Turbulent flow: the test and calculation in the production practice show that when liquid metal flows in the pouring system, its Reynolds number is greater than the critical Reynolds number Re, which belongs to turbulent flow. ZL104 alloy at 670 ℃ pouring, for example, fluid flow in the SPR of 20 mm diameter at the speed of 50 cm/s flow, the Reynolds number is 25000, more than 2300 of the critical Reynolds number. For some horizontal castings of thin-walled castings or heavy castings, the flow rate of liquid flow is slow, and laminar flow may be obtained. Light alloy castings with high quality gating system's research shows that when the Re < 20000, oxide film on the surface of the liquid flow won't be broken, if the Reynolds number control at 4000 ~ 10000, can meet the requirements of the production of aluminum alloy and magnesium alloy castings with high quality. Someone by hydraulic simulation and solid aluminum alloy castings pouring test proved that the maximum allowable Reynolds number, the SPR shall be no more than 10000, runner within no more than 7000, in the sprue within no more than 1100, within the cavity is not more than 280. In summary, the main factors that affect the stability of metal liquid flow are the flow velocity of metal liquid and the shape and section size of the pouring system. Therefore, it is necessary to study the flow of liquid metal in the pouring system. Mercury & have spent Mercury is a kind of chemical elements, commonly known as mercury (mercury can also be writing 銾). Its chemical symbol is Hg, and its atomic number is 80. It is a heavy, silver-white liquid transition metal. With this characteristic, mercury is used to make thermometers.
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