Graphite variety is much, how should different magnesia-carbon brick choose?
Graphite is an indispensable part of magnesium carbon brick. Flake graphite is mainly used in the production of magnesia-carbon bricks. It is natural crystalline graphite, which belongs to the hexagonal crystal system and is layered in structure. It is insoluble in water, dilute acid, dilute alkali and organic solvents. The graphite used in the production of magnesia-carbon brick is generally in the following range: fixed carbon 85% ~ 98%, ash content 13% ~ 2%(main components SiO2, Al2O3, etc.), relative density 2.09 ~ 2.23, melting point 3640K(volatilization). But graphite is very easy to oxidize, which is the fatal drawback of graphite.
During field use of magnesia-carbon brick, the graphite is oxidized mainly for the following reasons:
(1) free oxygen in atmospheric environment;
(2) various oxides in slag;
(3) impurities in graphite in magnesia carbon brick and oxides in magnesia.
According to the national standard, flake graphite can be divided into four types according to its fixed carbon content: high purity graphite, high carbon graphite, medium carbon graphite and low carbon graphite. The graphite commonly used in refractory is high carbon graphite and medium carbon graphite. But because the national standard of graphite division is more complex, and the name is not easy to remember, so enterprises have been using the common standards between enterprises.
With 100 mesh as the standard, the bottom of the sieve is negative, the sieve is positive, in short, the scale of positive graphite is larger than the scale of negative graphite. The fixed carbon content of graphite is added after the symbol to classify and name graphite. Such classification and naming method is intuitive and clear. Even in enterprises, many non-technical personnel are easy to distinguish the taste of graphite, which is easy for workers to identify the taste of graphite when purchasing and producing.
The graphite used to produce magnesia-carbon brick is as follows:
(1)-190, -192, -193, -194, -195, -196, -197, -198
(2) + 194, + 195, + 196, + 197, + 198
The graphite in magnesia-carbon brick is oxidized, making the product structure loose, the porosity increases, the strength decreases, the impurities contained in the graphite will accelerate the oxidation of graphite, so in order to obtain high-performance magnesia-carbon brick, production tends to choose high purity, large scale graphite. But large scale and high purity graphite are expensive, for industrial production, can not blindly pursue the high index of raw material, the price index also cannot ignore, after years of exploration and investigation found that the demand of high grade graphite is not large, demand the greatest graphite is – 194, 196-195, – these three kinds of graphite, of course also useful in the low-grade magnesium carbon brick – 190-192 graphite. The main purpose of the factory is to create profits, the cost of graphite in the production of magnesia-carbon brick occupies a large proportion, so the rational selection of graphite is crucial.
Below we introduce a few kinds of magnesium carbon brick should choose what kind of taste of graphite:
With magnesia carbon brick: (1) converter in the smelting process of converter, magnesia carbon brick furnace cap parts by mechanical wear and tear is larger, the slag erosion is weak, we choose – 194 graphite furnace body parts of magnesium carbon brick by slag erosion is stronger, we choose – or 195-196 graphite, a magnesia carbon brick at the bottom of the furnace is mainly affected by wear steel agitation, basic not steel slag erosion, so we choose – 192 graphite, graphite above the selection of basic can satisfy the domestic present the use of various steel mills.
(2) ladle slag line brick: ladle slag line brick is divided into many types, ordinary non-refined ladle slag line brick turnover time is fast, the use of -193 graphite, refined ladle slag line brick is basically used above -195 graphite. The wall and bottom part of the steel slag erosion is small, can choose -192, -193 and -194 graphite.
(3) electric furnace with magnesia carbon brick, electric furnace in the smelting process, molten pool parts of magnesium carbon brick by steel slag erosion is very small, but also part of the buried inside the furnace bottom ramming material, so the selection – 192 graphite, slag line parts in addition to the steel slag erosion, but also by the arc ignition, here we choose – or 195-196 graphite, basic don’t erosion on the furnace wall parts, so we choose – 190 graphite.