STEEL MAKING Steel-making units Stages of steel-making: fusion of smelting charge and bath heating; bath "boil“; deoxidizing.

STEEL MAKING Metallurgical processes in the smelting of steel 1) Melting of the charge and bath heating. Oxygen oxidizes all impurities, but iron is most intensely oxidized: Fе + О2 = 2FеО; Si + O2 = SiО2; 2Мn + O2 = 2МnO. Iron oxide goes into steel and slag. Iron oxide dissolved in the metal reacts with impurities and removes them into the slag: 2FеО + Si = SiО2 + 2Fе; FеО + Мn = МnО + Fе. Phosphorus is removed by oxidation and slagging: 2Р + 5FеО + 4СаО = (СаО)4Р2O5 + 5Fе. Sulfur removal occurs by reaction : FеS + СаО = СаS + FеО, with the transition of CaS into slag. 2) "Boiling" bath. There is an intense burnout of excess carbon from steel to form carbon monoxide: 2С +О2 = 2СО. CO bubbles float to the surface and the bath begins to “boil”. 3) Dexidizing. The deoxidizing elements, combining with oxygen, form insoluble oxides that float into the slag: Mn + FеО = МnО + Fе; Si + 2FеО = SiO2 + 2Fе; 2А1 + 3FеО = А12O3 + 2Fе.

STEEL MAKING The scheme of Martin furnace: 1 – regenerators, 2 – furnace head, 4 – charging holes, 5 – working space, 6 – mixture, 7 – torch, 9 – hearth, 10 – arch

STEEL MAKING Steel smelting in the oxygen converter: b c d e f Steel smelting in the oxygen converter: a – scrap charge, b – hot-metal charging, c – lime charging, d – pure oxygen lancing, e – steel tapping, f – slag tapping

STEEL MAKING а – top casting; b – uphill teeming; Normal ingot making: 1 – ladle; 2 – liquid steel; 3 – central gate; 4 – pipe lining; 5 – ingot; 6 – bottom plate; 7 – fused channel

Ingots of rimming steel (a); killed steel (b), and balanced steel (c) STEEL MAKING According to the degree of deoxidation steels are subdivided into killed steels (completely deoxidized with ferromanganese, ferrosilicon and aluminum), rimming steels (deoxidized with ferromanganese only; they “boil” in ingot mould because bubbles of CO rise) and semikilled, or balanced steels (deoxidized with manganese and silicon). a b c Ingots of rimming steel (a); killed steel (b), and balanced steel (c)

Continuous casting of steel: continuous-casting machine STEEL MAKING a c b Continuous casting of steel: a – scheme of the process; b – vertical continuous-casting machine ; c – radial continuous-casting machine

Direct reduced iron (DRI): STEEL MAKING c a b Direct reduced iron (DRI): a – ore pellets; b – scheme of the process; c – ball-shaped sponge iron c