Constituents of molding sand

Involves the main ingredients of silica sand molding sand, binder, the moisture content and additives.

Silica sand: sand silica in the form of quarts granular the main constituent of sand molding is enough refractoriness can taste strength, stability and permeability of molding and core sand: Besides silica small amounts of iron oxide, alumina, stone lime, magnesia, soda and potash are present as impurities. The chemical composition of silica sand thinking of impurities like lime, magnesia, alkalis present etc. The presence of excessive amounts of iron oxide, can alkali oxides and lime to lower the fusion point to a large extent are undesirable. Moisture: The size varies moisture content in molding sand generally between 2-8 percent. The following the combination of clay and silica sand for developing bonds. This is the amount of water needed to fill the pores between soil particles without separating them. The amount of water held tightly by soil and is largely responsible for developing the strength in the sand. Reduces the effect of clay and water to increase permeability clay and moisture content. The green compressive strength initially increases with the increase in clay content, but after a certain value, it starts to decline. Add: Add the following topics in general with the molding and core sand mixture in the sand some special property development. Some common additives used to improve the properties of molding and core sand.

(i) Coal dust: coal dust is added primarily for producing a reducing atmosphere during casting. This reduction results in no oxygen in the atmosphere becoming bound chemical poles so it can oxidize the metal. (ii) dextrin: Dextrins family relates to starch carbohydrates. It increases the molds dry strength. (iii) Pitch: It is distilled form of soft coal. It can be added from 0.02% to 2% in mold and sand core. It offers hot strengths, surface finish on model surfaces. (iv) Wood flour: This is the fibrous material mixed with granular material like sand; a relatively long thin fibers prevent sand grains from contact with each other. It can be added from 0.05% to 2% in mold and sand core. It increases both mold collapsibility and heart.

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