The hottest semi-solid metal casting process

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Semi solid metal casting process (Part 2)

4.2 thixoforming (thixocast)

reheat the prepared non dendritic structure ingot to the solid-liquid two-phase region to reach the appropriate viscosity, and then carry out die casting or extrusion forming

eopco, HPM Corp., Prince machine, tht press in the United States, Buhler company in Switzerland, Idra USA, italpress of America in Italy, producer USA in Canada, toshib a machine Corp and Ube machine services in Japan have all been able to produce special equipment for thixoforming semi-solid aluminum alloys. This method is easy to automate the heating and conveying of billets, so it is the main process method of semi-solid casting today

4.3 injection molding

directly cool the molten metal liquid rather than the semi-solid slurry after treatment to the appropriate temperature, supplemented by certain process conditions, and press it into the mold cavity for forming. For example, Wisconsin made the center of gravity of the instrument low and placed the thixotropic forming development center, which is safe and reliable. This method has been used for semi-solid casting of magnesium alloys. Professor ng of Cornell University in the United States and others developed a similar magnesium alloy injection molding device, which adds semi-solid slurry from the feed pipe, and then injects it into the mold cavity after proper cooling

4.4 low temperature continuous casting

the so-called low temperature continuous casting is a casting method that controls the superheat of liquid metal, which is equipped with two special fpl14 mixing heads at about 0 ℃, and carries out forced cooling under the mold. Central segregation is a big problem in continuous casting, and may break during continuous rolling. Therefore, this process is of great significance

4.5 strip continuous casting

flemings has used sn-15%pb low melting point metal to conduct experimental research on strip continuous casting, and analyzed heat transfer, solidification and deformation. It is considered that the thickness of strip is related to the pressure of roll, solid rate, rheological shear speed and continuous casting speed. When the specific pressure under extrusion is large, it promotes micro segregation. In order to ensure the surface and internal quality and dimensional accuracy, it is necessary to strictly control the process parameters of semi-solid metal manufacturing, such as solid rate, primary crystal shape and size, and metal emission

for high melting point metals such as phosphor bronze cu-sn-p alloy (Cu-8% sn-0), its utilization can avoid corrosion and solve CO and no in automobile exhaust х Pollution problem 1% P), liquidus temperature 10300 ℃, difficult to hot work, using this semi-solid alloy to make thin plate has obvious effect. At present, semi-solid stainless steel ingots and high-speed tool steel ingots with excellent microstructure can be prepared

5 technical advantages

the advantages of semi-solid die casting process can be summarized into process advantages and product advantages

5.1 process advantages

1) fine grain structure can be obtained without adding any grain refiner, eliminating columnar crystals and coarse dendrites in traditional casting

2) low forming temperature (for example, aluminum alloy can be reduced by more than 1200 ℃), which can save energy

3) longer die life. The shear stress of semi-solid slurry with low solid temperature during forming is three orders of magnitude smaller than that of traditional dendritic slurry, so the filling is stable, the thermal load is small, and the thermal fatigue strength is reduced

4) reduce pollution and unsafe factors. Because the operation is free from high-temperature liquid metal environment

5) the deformation resistance is small, and the homogeneous processing can be achieved by using a small force, which is easy to form difficult to machine materials

6) the solidification speed is accelerated, the productivity is improved, and the process cycle is shortened

7) it is suitable for computer-aided design and manufacturing, and improves the automation of production

5.2 product advantages

1) high quality. Due to grain refinement, uniform structure distribution, reduced volume shrinkage and hot cracking tendency, the shrinkage porosity tendency is eliminated on the matrix, and the mechanical properties are greatly improved

2) the solidification shrinkage is small, so the formed body has high dimensional accuracy, small machining allowance and near net shape

3) wide range of forming alloys. Non ferrous alloys include aluminum, magnesium, zinc, tin, copper and nickel base alloys; Iron base alloys include stainless steel, low alloy steel, etc

4) manufacturing metal matrix composites. Using the high viscosity of semi-solid metals, metals with large density difference and small solid solubility can be made into alloys, and different materials can also be effectively mixed to make new composites

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