Knowledge of Dephosphorization
Date:2019-04-19 keywords:knowledge, dephosphorization
Dephosphorization refers to a chemical reaction that reduces the amount of phosphorus in molten steel. Phosphorus is a harmful element in most steel grades and is easily segregated at grain boundaries, causing low temperature brittleness and temper brittleness of steel. Steels containing more phosphorus are easily brittle when used at room temperature or lower, which are called "cold brittle". The higher the carbon content in the steel, the more severe the brittleness caused by phosphorus.
In recent years, with the rapid development of science and technology, users' requirements for steel quality have been continuously improved. For example, for low-temperature steel, marine steel, hydrogen-resistant crack-resistant steel, and some heavy-plate steel, in addition to requiring extremely low sulfur content, the phosphorus content in steel is also required to be < 0.101% or 0.1005%. Besides, in order to reduce the production cost of oxygen converter steel and to implement less slag steelmaking, the phosphorus content of molten iron is also required to be <0.1015%. Therefore, many metallurgists since the 1980s have been working on the pretreatment dephosphorization of molten iron and developed various treatment methods. The pre-dephosphorization treatment of hot metal can be divided into oxidative dephosphorization and reduction dephosphorization. At present, oxidative dephosphorization processes are commonly used in various steel mills. The dephosphorization method is classified into a SARP method, a molten iron tank method, an ORP method, a converter method, and an NRP method according to different dephosphorization agents. There're two types commonly used: one is dephosphorization in a ladle or torpedo car in Shengtie Water; the other is dephosphorization pretreatment in molten iron in a converter. Both methods have been practically applied in this industry.