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2 alloy casting the crystal 1 west growth

by:AAG     2020-11-10


2 alloy casting the crystal 1 west growth of aluminum alloy melt after furnace and online refining, filtering, can enter the casting process. In casting process, the aluminum melt to nucleation, growth, phase change, condensed crystals. This is a complex physical and chemical process, is to determine the quality of the product to the process, this chapter on the nucleation and growth problems in the process of casting is discussed. Homogeneous nucleation theory about the melt in the electrolytic aluminium liquid cast-rolling strip foil, production ( Metallurgical industry press, 2011) Book have a more detail description, here only combining with the characteristics of casting and discuss some issues with the different. Continuous casting of aluminium alloy ingot, when people melt injection mould, due to the mold with cooling water around, aluminum melt the heat released by the mold wall to the cooling water, aluminum melt is starting from the surface of solidification, then extend to the center; And because of cooling water to 20. _30° Spray direction toward the base, or has solidified ingot casting, heat melt through the base (at the bottom of the Pouring the starting stage) Or ingot ( The normal casting stage) To the cooling water, and starting at the bottom of the crystallization, melt subsequently extended upwards. That is to say, for the crystallization of ingot solidification, outside-in propulsion in diameter direction, from down to up in the height direction. Ingot casting its surrounded by crystallization front upper melt is called liquid hole ( Figure 2 - 1) 。 Liquid hole depth of crystallizer in the level of crystallization to the crystallization front at the bottom of the range of the height of the metallic melts, with units of latent heat of crystallization in the type calculation formula under the kJ/kg metal specific heat on average, kJ/( 公斤· Art) p— — Ingot casting density, field 3 kg/t1 - Alloy liquidus temperature skarn arts & ndash; — Ingot surface temperature, ℃} — — The casting speed, m/h ( 2 - 1) Figure 2 - 1 a ingot pouring liquid hole schematic bligh radius, tian B— — Coefficient, 2 of slab ingot, round spindle take 4 k a coefficient of thermal conductivity, W eight m· K) 。 The crystallization of ingot is in this is called liquid hole area. Study this happened in the solidification process of liquid cavity, understanding the influence of the casting process parameters on the fluid hole, aluminum exploration to improve the shape of the liquid cavity and crystallization conditions, improve and optimize the process, is very important to improve the quality of ingot casting, aluminum processing and technical workers for a long time continuously explore an important topic of the research, and improved. On fluid acupuncture point at any cross section there are three areas solid, solid liquid phase coexistence area ( Two phase zone) , liquid phase area ( Figure 2 - 2) 。 High temperature melt in the mould cooling to the freezing point, release of latent heat of phase change crystallization into solid matter, the solid phase, higher than the freezing point can't melt crystallization, still for the liquid phase, it is easy to understand; But why the two phase coexistence crystallization front zone, the coexistence of two phase zone is formed, the impact of the melt crystallization process, the following to discuss this question & quot; 】 。
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