Refractory materials
Refractory materials used in the foundry include molding and core sands, clays, and firebrick. These materials have high melting temperatures, and are therefore suitable for various foundry purposes. The materials are conveniently divided into two classes: those used in forming castings, and those used for furnace work. The properties of the refractory and fluxing materials used in forming castings have been described earlier in this text; therefore, only refractory materials used for furnace work will be described here.
Fire clay and firebrick are refractory materials used in high-temperature furnaces. There are two kinds of fire clays: flint clays and plastic clays. Flint clays are used where materials of maximum refraction are needed, although they are not plastic. The plastic clays are less refractory than the flint clays, but have the plastic properties which make them suitable for conditions where rigid clays would not perform a satisfactory service. Firebricks are manufactured by burning the flint clays, and then crushing and mixing them with the plastic clays to form bricks which are burned to different degrees of hardness to suit different requirements. There is quite a variation in chemical analyses of fire clays. They are never obtained in their pure state; therefore, their melting points have a considerable variation, which factor must be accounted for in the manufacture of firebricks.
Foundry fuels
Fuels for foundry use should be of high quality. These fuels include coal, coke, charcoal, wood, oil, gas, and electricity. Foundry fuels are of two kinds: those used to melt metals or metallurgical fuels, and those used for heating purposes, such as in core ovens or heating plants. The metallurgical fuels only will be discussed here.
Charcoal is one of the purest forms of carbon. In addition to serving as a fuel, it is also used to cover metal in crucible melting furnaces for brass and bronze, and for covering molten cast iron to prevent the metal from oxidizing, especially when it is desired to hold the iron in large quantities for large castings.
Hard and soft coals are used for melting metal. Depending upon the locality, hard coal is used instead of coke for crucible furnaces since it is cheaper. It also may be used for cupola melting, but coke is preferred in the latter case. Air furnaces used for melting malleable cast iron employ soft coal as a fuel, but the coal must be checked for sulphur and ash content which should be as low as possible. The coal should also contain the least amount of moisture. Coal is selected which gives a long flame and does not melt in the firebox. It is difficult to base the quality of coal on the chemical analysis alone, since it is proven that coals having the same chemical analysis often have a different burning quality.
Литье металла и материалы литейного завода
Литейные заводы работают с большим количеством материалов. Они классифицируются под тремя главными заголовками: отливая металлы, формовочные смеси, и невосприимчивый литейный завод.
Есть две больших группы литья металлов: черных и цветных. Металл черной группы всегда несет другие элементы, и, поэтому, больше сплавов чем чистого металла. В цветной группе, металлы обычно продают столь же чистыми, какими находятся они в чистом состоянии. Литейные заводы смешивают относительно чистые металлы, чтобы произвести желательные сплавы. К черным сплавам относят все литейные чугуны, углеродистые стали, и лигированную сталь. Цветные металлы включают медные-основные сплавы, алюминиевые-основные сплавы, сплавы магния, цинковые-основные сплавы, и другие менее используемые сплавы.