Metal castings, furnace slag

The slag is batch tapped into a receiving room where it is cooled and broken up for disposal. The metal buUion is tapped from the furnace periodically via a siphon into 2-t cast-iron molds. Typical buUion content from an electric furnace in wt % is Sb, 13—18 Sn, 1—2 As, 0.5—1 Cu, 0.3—0.4 and Ni, 0.05—0.1. The balance is lead. 

Uses. The sinter oxide form is used as charge nickel in the manufacture of alloy steels and stainless steels (see Steel). The oxide furnishes oxygen to the melt for decarburization and slagging. In 1993, >100, 000 metric tons of nickel contained in sinter oxide was shipped to the world s steel industry. Nickel oxide sinter is charged as a granular material to an electric furnace with steel scrap and ferrochrome the mixture is melted and blown with air to remove carbon as CO2. The melt is slagged, pouted into a ladle, the composition is adjusted, and the melt is cast into appropriate shapes. A modification of the use of sinter oxide is its injection directiy into the molten metal (33). 

Once cooled, the metal from a blast furnace is known as a cast metal. (When the ore is an iron ore, the cast metal is known as pig iron) A cast metal is brittle and soft because it still contains impurities, such as phosphorus, sulfur, and carbon. To remove these impurities, oxygen is blown through the molten cast metal in a basic oxygen furnace, shown in Figure 18.25. The oxygen oxidizes the impurities to form additional slag, which floats to the surface and is skimmed off. 

The first stage in the conversion of iron ore to steel is the blast furnace (see Panel), which accounts for the largest tonnage of any metal produced by man. In it the iron ore is reduced by coke, while limestone removes any sand or clay as a slag. The molten iron is run off to be cast into moulds of the required shape or into ingots ( pigs ) for further processing — hence the names cast-iron or pig-iron . This is an... 

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