Carbon and graphite refractories have been used in iron blast furnaces for a long time, and have been developing with the development of iron blast furnaces. Now, the world's large blast furnace from the bottom, hearth to the furnace belly and other parts are used carbon bricks (carbon blocks) masonry, some blast furnace has been built to the furnace body, and even the iron outlet. With the adoption of water-cooled furnace wall, the inside of the blast furnace bell also adopts carbon brick masonry.

In the early stage, metallurgical coke was mainly used as the main raw material, asphalt as the binder, and extrusion molding was adopted. But this kind of brick often has the local abnormal erosion phenomenon in the use. Therefore, metallurgical coke was changed to roast anthracite coke with good corrosion resistance of hot metal and its performance was improved. It shows that the melting amount increases in the order of roasted anthracite coke < natural cryptocrystalline graphite > artificial graphite > asphalt coke. However, calcined anthracite coke has the advantage of good corrosion resistance to molten iron, but it has the disadvantage of poor alkali resistance due to its high ash content. In order to overcome the disadvantage of roasting anthracite coke, artificial graphite was used.

The ability of carbon and graphite to form refractories or to be important raw materials of refractories is based primarily on their properties as follows:

(1) High heat resistance of graphite, the highest temperature can be up to 3850℃, graphite in ultra-high temperature arc, its mass loss is small.

(2) High chemical stability of graphite, not easy to react with other inorganic materials and molten metal, and is difficult to be wetted by oxide slag, strong anti-permeability ability.

(3) The thermal conductivity of graphite is high, but it decreases with the increase of temperature. Even at extremely high temperature, it is in an adiabatic state.

(4) Graphite has anisotropic structure, and the linear expansion coefficient is small, so the thermal shock resistance is good.

In order to reduce the damage of carbon brick caused by molten iron penetrating into pores, various improvements have been made:

(1) Alumina was added to the ingredients to improve the corrosion resistance of molten iron.

(2) In order to reduce the pore diameter of the gas, silicon metal was added to the ingredients, which reacted to generate whiskers during sintering, making the pores microfine and preventing the infiltration of molten iron.

(3) In order to improve the cooling effect, graphite injection ratio was increased.

(4) The binder was changed from asphalt to resin to improve the high temperature strength.

(5) By adding SiC, the pores are micronized to prevent the intrusion of molten iron.

(6) At the bottom of the furnace, in order to improve the cooling effect, graphite bricks with high thermal conductivity and C-SIC bricks are used outside the furnace.

The largest consumer of carbon and graphite refractories is the metallurgical industry, mainly used as lining refractories for blast furnaces (blast furnace carbon and graphite refractories), ferroalloys, metal refining (including electric furnaces and cuboirs), and so on. More than 70 per cent of them are used (75 per cent in Japan). In the steelmaking furnace, the use of artificial graphite bricks in harsh parts has the effect of prolonging life.

Physical And Chemical Indicators