Crucible used flake graphite

Graphite as refractory raw materials

The use of graphite as a refractory material began before 1900 with the graphite crucible used to hold molten metal; this is now a minor part of refractories. In the mid-1980s, the carbon-magnesite brick became important, and a bit later the alumina-graphite shape. As of 2017 the order of importance is: alumina-graphite shapes, carbon-magnesite brick, monolithics (gunning and ramming mixes), and then crucibles.

Crucibles began using very large flake graphite, and carbon-magnesite brick requiring not quite so large flake graphite; for these and others there is now much more flexibility in the size of flake required, and amorphous graphite is no longer restricted to low-end refractories. Alumina-graphite shapes are used as continuous casting ware, such as nozzles and troughs, to convey the molten steel from ladle to mold, and carbon magnesite bricks line steel converters and electric-arc furnaces to withstand extreme temperatures. Graphite blocks are also used in parts of blast furnace linings where the high thermal conductivity of the graphite is critical. High-purity monolithics are often used as a continuous furnace lining instead of carbon-magnesite bricks.

Natural Graphite's brief Introduction

Graphite is an industrial mineral with unique physical properties which includes superior thermal/electrical conductivity and generally occurs in one of three forms – Microcrystalline or amorphous, Crystalline lump or vein and Crystalline flake. 

Natural Flake Graphite occurs in host rocks such as quartz-mica schist, feldspathic or micaceous quartzite and gneiss. Flake graphite may also occur in metamorphosed carbonate rocks, though these occurrences are currently of little economic significance. Flake graphite deposits are usually strata bound, with individual beds or lenses ranging from 30cm to more than 30m thick, and extending for lengths of two kilometres or more. Ore bodies are normally tabular, occasionally lenticular, and occur locally as irregular bodies in the hinge zones of folds. Most economic deposits of flake graphite are of Archean to late Proterozoic age. 

An industrial mineral has many unique physical properties:

• Superior thermal/electrical conductivity

• Stable wide temperature range

• High melting point

• Excellent lubrication

• Malleable

• Resistant to chemical attack

• Fire retardant and thermally efficient building products