The operation of adding one or several alloying elements to molten steel to meet the requirements of the composition specifications of the finished steel is called alloying. In most cases, deoxidation and alloying are carried out at the same time. Part of the deoxidizer added to the steel is consumed by the deoxidation of the steel and converted into deoxidation products to be discharged; the other part is absorbed by the molten steel for alloying. Before the deoxidation operation is completely completed, the alloying effect of the alloy added at the same time as the deoxidizer is absorbed by the molten steel is called pre-alloying.
Ensure that all finished steel components meet the requirements of the standard. Composition control runs through every link from batching to tapping, but the focus is on the control of alloying element composition during alloying. For high-quality steel, the composition is often required to be accurately controlled within a narrow range; generally, under the premise of not affecting the performance of the steel, the middle and lower limits are controlled.
The melting period of steelmaking is mainly for open hearth and electric furnace steelmaking. Electric arc furnace steelmaking is called the melting period from the start of power-on to the time when the charge is completely melted, and the small vacuum melting furnace steelmaking is called the melting period from the time the molten iron is added to the charge. The task of the melting period is to melt and heat up the charge as soon as possible, and make the slag in the melting period.
In ordinary power electric arc furnace steelmaking operations, the period from the completion of slagging at the end of oxidation to tapping is usually called the reduction period. Its main task is to create reduced slag for diffusion, deoxidation, desulfurization, chemical composition control and temperature adjustment.