Metal Casting Processes; Overview, Classifications, Advantages And Disadvantages
Most metal parts are produced with various metal casting methods. Sand casting is one of the most prominent metal casting method around other casting methods. Because of its differences, poruing of molten metal into sand casting mold cavity is not an easy thing. You need to design the pouring and fluxing of molten metal inside the gatings. So in that way, you need to design a proper gating system to optimize the pouring parameters;
As we stated above, there are three parameters to design pouring and gating to obtain required pouring form. The first parameter is pouring temperature.
Pouring temperature is the temperature that when a metal is entered to the mold cavity in sand casting. Pouring temperature is also called as ‘superheat’. Pouring temperature is generally adjusted above the melting temperature of molten metal.
The molten metal must not start to solidify up to end of the pouring process in sand casting. If the molten metal starts to solidify in the pouring process, uneven solidification and casting can occur. Uneven distribution of metal can also occur. But if the difference between the melting temperature and pouring temperature of molten metal is too high, it means that excessive energy is consumed to heat the material. This can be too expensive in commercial basis.
So, a designer, or engineer must design the pouring temperature according to these parameters. Optimization of pouring temperature is very important thing in sand casting.
The second parameter in the pouring process of sand casting is pouring rate. Actually, other parameters that are affecing the casting performance, depend on this parameter. If the pouring rate is too high, excessive turbulence can occur. Excessive turbulance is not desired thing because of some reasons that we explain below.
If the pouring rate is low, uneven solidifications of molten metal inside gates can occur, and this is a very serious problem for healthy metal casting process. So, pouring rate must be optimized according to the own parameters of different sand casting scenes. This is an also very important and professional thing.
The third parameter that affect the casting pouring performance is turbulance. In fluid dynamics, turbulance is one of the most important parameters. So, in metal pouring, incompressible fluid flux is prominent phenomenon. If the turbulance is very high, it can damage the sand mold and sand gates. Unlike water, the density of molten metal is very high. Because of that, the destruction effect of turbulance of molten metal is also high compared with water. If the surface of mold cavity is damaged, the part that will be produced will be defected.
To prevent the mold erosion caused by turbulance of molten metal in gates, turbulance of fluxing molten metal must be calculated professionally. Pouring rate and shape of pouring cup and gates are designed to prevent turbulances. Streamlined, laminar flow is desired.
As you understand that, these three parameters are interrelated to each other. Actually, you can not design of define a pouring parameter of molten metal inside mold cavity individually. All of these three parameters must be considered same time. So, this requires an engineering profession.
These are the general characteristics of pouring molten metal inside sand casting mold cavity succesfully. Do not forget to leave your comments and questions about pouring molten metal into mold cavity in sand casting below.
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