The Method of Making Steel from Iron Ore

Making steel from iron ore methods can be generally divided into converter steelmaking and open-hearth steelmaking. Now they are introduced as follows:

1. Converter steelmaking process

The oxidant used in this method of iron ore steelmaking is oxygen. Air is blown into molten raw iron ore to oxidize impurities such as silicon and manganese. In the process of oxidation, a large amount of heat (containing 1% silicon can increase the temperature of raw iron ore by 200 ℃) can make the furnace reach a high temperature. Therefore, converter steelmaking does not need additional fuel.

Converter steelmaking is carried out in the converter. The shape of the converter is like a pear. There are refractory bricks on the inner wall and many small holes (tuyeres) on the side of the converter. Compressed air is blown into the converter from these holes, which is also called side blown converter. At first, the converter is horizontal, and liquid raw iron ore of 1300 ℃ is injected into the converter, and a certain amount of quicklime is added, then air is blown in and the converter is rotated to make it stand upright. At this time, the violent reaction on the surface of liquid raw iron ore causes the oxidation of iron, silicon, and manganese (FeO, SiO2, MnO,) to generate slag. The reaction is spread throughout the furnace by the convection of molten steel and slag.

After a few minutes, when there is only a small amount of silicon and manganese left in the molten steel, the carbon begins to oxidize, producing carbon monoxide (exothermic) which makes the molten steel boil violently. There is a huge flame in the furnace mouth due to the combustion of the spilled carbon monoxide. Finally, phosphorus also oxidizes and further forms of ferrous phosphate. Ferrous phosphate reacts with quicklime to form stable calcium phosphate and calcium sulfide, which together become slag.

2. Open hearth process (also known as Martin process)

The oxidizer used in open-hearth steelmaking is the air introduced and the oxide in the charge (scrap iron, scrap steel, iron ore). The heat needed for the reaction is provided by burning gas fuel (blast furnace gas, producer gas) or liquid fuel (heavy oil).

The furnace of an open heart is a trough made of firebricks, which is covered by a top made of firebricks. There is a charging port on the front wall of the open-hearth furnace, from which the charging machine loads the charging. Close the door made of firebrick during smelting. Both ends of the furnace are built with furnace heads, each of which has two channels for introducing fuel and hot air or guiding furnace gas from the furnace.