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a method of improving the removal of aninvestmentcastingshell surrounding a metallic article. the shell is made from the deposit of layers refractory slurry and stucco onto a pattern. the shell contains, after firing, an amount of an alkali metal oxide or an alkaline earth metal oxide sufficient to reduce the strength of the shell. by this invention, after firing of the shell and pouring of the molten metallic part into the shell, the shell is hydrated to further reduce the strength of the shell, to facilitate its removal from the metallic part.
investmentcasting, which has also been called lost wax, lost pattern and precisioncasting, is used to produce high quality metal articles that meet relatively close dimensional tolerances. typically, aninvestmentcastingis made by first constructing a thin-walled ceramic mold, known as aninvestmentcastingshell, into which a molten metal can be introduced. shells are usually constructed by first making a facsimile or pattern from a meltable substrate of the metal object to be made byinvestmentcasting. suitable meltable substrates may include, for example, wax, polystyrene, or plastic.
next, a ceramic shell is formed around the pattern. this may be accomplished by dipping the pattern into a slurry containing a mixture of liquid refractory binders such as colloidal silica or ethyl silicate, plus a refractory powder such as quartz, fused silica, zircon, alumina, or aluminosilicate, and then sieving dry refractory grains onto the freshly dipped pattern.
the steps of dipping the pattern into a refractory slurry to form a layer, and then sieving onto the freshly dipped pattern dry, refractory grains as an added “stucco” layer, may be repeated until the desired thickness of the shell is obtained. however, it is preferable if each coat of slurry and refractory grains is air-dried before subsequent coats are applied.
as an investment casting factory in china , olym metal products improve their technology and change their machine ,july 24ththey purchase a new heat accumulating type shell baking furnace.using natural gas as fuel of heat accumulating type baking furnace ,the characters of this equipment:1)energy conservation,cost 1/3 of ordinary furnace.2)high efficient. 3)automatic: automatic temperature control.
from past till now we improve our technology and continuously change new equipment to high efficient working .