Views: 10 Author: Site Editor Publish Time: 2022-01-28 Origin: Site
Steelmaking refers to the steel obtained by smelting scrap steel or pig iron into a steelmaking furnace according to a certain process, and the excess carbon and other impurities are converted into gas or slag to be removed; the encyclopedia below will introduce what steelmaking is? Commonly used steelmaking smelting methods and principles and steelmaking process flow.
Steel is a solid solution of carbon, silicon, manganese and other elements in iron. It is used to improve the performance of steel to meet the needs of engineering construction materials. Other elements such as phosphorus, sulfur and oxygen, hydrogen and nitrogen will be present in most steels to make their performance worse. Therefore, steelmaking is to remove these impurities through chemical reactions, and meet the requirements to cast into qualified steel ingots.
Principles of steelmaking and common steelmaking smelting methods
The principle of steelmaking is to use oxygen or iron oxides to convert carbon, phosphorus, sulfur and other impurities in scrap steel or pig iron into gases and slag to get rid of steel.
There are three common steelmaking smelting methods, namely: open hearth steelmaking, converter steelmaking and electric furnace steelmaking.
1. Open-hearth steelmaking method:
Put the raw material scrap steel, scrap iron, iron ore, limestone and quicklime solvent into the steelmaking furnace, use blast furnace gas or liquid fuel heavy oil to heat, add oxidizer to remove impurities.
When the steelmaking starts, the fuel meets the hot air and burns on the fuel surface. The temperature can reach 1800 degrees. The heat energy is melted by the flame. At the same time, the partially melted pig iron produces ferrous oxide. The impurities in the pig iron are silicon and manganese. Iron oxidizes to produce slag, and then the limestone, phosphorus and sulfur impurities in the furnace produce calcium phosphate and calcium sulfide to become slag; excess carbon is also oxidized, and carbon monoxide emerges from the molten steel as if the molten steel is boiling.
2. Converter steelmaking method:
The oxidant used in this steelmaking method is oxygen. Air is blown into the molten pig iron to oxidize impurities such as silicon and manganese in the charge. A large amount of heat is released during the oxidation (1% silicon can increase the temperature of the pig iron. 200 degrees Celsius), the furnace can reach a sufficiently high temperature. Therefore, converter steelmaking does not require other fuels.
The shape of the converter of the converter steelmaking is like a pear, with refractory bricks on the inner wall and many small holes (tuyere) on the side of the furnace. Compressed air is blown into the furnace from these small holes, which is also called a side blown converter. Horizontally, inject liquid pig iron at 1300 degrees Celsius and add a certain amount of quicklime, then blow in air and turn the converter to make it stand upright. At this time, the surface of the liquid pig iron reacts violently to oxidize iron, silicon and manganese (FeO, SiO2). ,MnO,) generates slag, and uses the convection effect of the molten steel and slag to make the reaction in the furnace uniform; after a few minutes, when there is only a small amount of silicon and manganese in the molten steel, the carbon begins to oxidize to produce carbon monoxide (exothermic ) Make the molten steel boil violently. A huge flame appeared at the furnace mouth due to the overflow of carbon monoxide; finally, phosphorus also oxidized and further produced ferrous phosphate, which then reacted with quicklime to produce calcium phosphate and calcium sulfide slag. If the converter steelmaking blows high-pressure industrial pure oxygen, it can further improve efficiency and steel quality.
Electric furnace steelmaking is a heat source that converts electrical energy into heat energy, also known as electric arc furnace steelmaking. Graphite electrodes, a thermally conductive material, are used to generate electric arcs between the electrodes and the charge in the electric furnace. Electric arc heating melts metal and slag to smelt steels of various compositions. Electric furnace steelmaking mainly uses scrap steel as raw materials, which consumes less pig iron and no longer needs a lot of coke.