"Liquid metal" is an amorphous alloy made of titanium, zirconium, nickel, copper and other metals. It has the characteristics of high strength, wear resistance and high strength/weight ratio. If there is something like liquid in it, it is: First, to make parts with this kind of metal, a method similar to plastic injection molding can be used, thereby greatly improving the accuracy of the parts. Second, the surface of this material is as smooth as a liquid to the touch.

Hydraulic characteristics of liquid metal filling and flow process

At present, in actual casting production, the sand mold still accounts for a considerable weight, and the liquid metal shows the following hydraulic characteristics when flowing in the sand mold:

1. Viscous fluid flow: Liquid metal is a viscous fluid. The viscosity of liquid metal is related to its composition. It increases with the decrease of the temperature of the liquid metal during the flow process. When crystals appear in the liquid metal, the viscosity of the liquid increases sharply, and its flow rate and flow state also change sharply.

2. Unstable flow: During the filling process, the temperature of the liquid metal keeps decreasing and the temperature of the mould keeps increasing, the heat exchange between the two is in an unstable state. As the temperature of the liquid stream decreases, the viscosity increases, and the flow resistance also increases; in addition, the pressure head of the liquid stream increases or decreases during the filling process, and the flow rate and flow state of the liquid metal are constantly changing, resulting in the liquid metal filling the mold. Unstable flow in the process.

3. Flow in porous pipe: Since the sand mold has certain pores, the pouring system and cavity in the sand mold can be regarded as porous pipes and containers. When liquid metal flows in a "porous tube", it often does not adhere well to the wall of the tube. At this time, external air may be drawn into the liquid flow, forming pores or causing the oxidation of the molten metal to form slag inclusions.

4. Turbulent flow: Tests and calculations in production practice prove that when liquid metal flows in the gating system, its Reynolds number Re is greater than the critical Reynolds number Relin, which is a turbulent flow. For example, when ZL104 alloy is poured at 670°C, when the liquid stream flows at a speed of 50cm/s in a sprue with a diameter of 20mm, its Reynolds number is 25000, which is much greater than the critical Reynolds number of 2300. For the filling of some horizontally poured thin-walled castings or thick and large castings, the rising speed of the liquid flow is very slow, and laminar flow may also be obtained. Research on the gating system of light alloy high-quality castings shows that when Re<20,000, the oxide film on the surface of the liquid stream will not be broken. If the Reynolds number is controlled at 4000~10,000, it can meet the requirements of producing high-quality aluminum and magnesium alloy castings. Some people have proved through hydraulic simulation and actual pouring test of aluminum alloy castings that the maximum allowable Reynolds number should not exceed 10,000 in the sprue, 7,000 in the runner, 1100 in the inner runner, and 280 in the cavity. In summary, the main factors affecting the stability of molten metal flow are the flow rate of molten metal and the shape and cross-sectional dimensions of the gating system. For this reason, it is necessary to study the flow of liquid metal in the gating system. Mercury &Nbsp; Mercury is a chemical element, commonly known as mercury (mercury can also be written as 銾). Its chemical symbol is Hg, and its atomic number is 80. It is a heavy, silver-white liquid transition metal. Because of this characteristic, mercury is used to make thermometers.