In the process of ladle refining, only by selecting different slag systems for different steel grades can the expected metallurgical effect be achieved. Various types of slag systems widely used in the world are selected for different metallurgical environments, different atmospheres and different steel grades. Therefore, the composition range of the premelting type refining slag fluctuates greatly, and the change of alkalinity is particularly obvious, which can vary from 1.0 to about 12; other components can vary from 0 to 40. The components of pre-melting refining slag are mainly as follows.
CaO is an indispensable component in slag making, dephosphorization, and desulfurization in metallurgical production. The main component of slag. In order to ensure good desulfurization effect, it is required that the pre-melting refining slag contain high free state CaO.
Al2O3 mainly comes from raw materials and deoxygenation products. It has two effects on the desulfurization effect: on the one hand, with the increase of the amount of Al2O3, the slag viscosity decreases, which promotes the slag-steel reaction and is beneficial to desulfurization; on the other hand, it increases and reduces the activity of Al2O3 and inhibits the progress of desulfurization.
SiO2 mainly comes from impurities (gangue) and deoxidation products in the raw materials, and has a certain fluxing effect. However, increasing the content is unfavorable for both deoxidation and desulfurization.
CaF2 can significantly reduce the viscosity of the pre-melting refining slag, improve the fluidity of the slag, increase the mass transfer, and be beneficial to desulfurization. For foaming performance, the effect is two-fold. On the one hand, the increase of the amount of CaF2 reduces the surface tension, which is beneficial to the foaming of the slag, but on the other hand, it reduces the viscosity of the slag, which is not conducive to the foaming, and the tension plays a leading role.
The MgO in the premelting refining slag mainly comes from slag and refractory materials, and its desulfurization ability is slightly lower than that of CaO.
Applications and Features
Premelting type refining slag is mainly used for LF furnace, open hearth and converter ladle refining to remove impurities such as sulfur and oxygen in molten steel and reduce the content of harmful elements and impurities in steel. It is suitable for plain carbon steel and high carbon steel. Steel, high and low alloy steel. It has long been used in foreign countries, such as South Korea, Japan, Europe and the United States and other developed countries .
Pre-melted refining slag has the following characteristics:
1. The chemical composition is uniform, the melting point is low, and the melting speed is fast, which can shorten the smelting time;
2. No fluorine, no erosion of furnace lining and ladle;
3. The structure is compact, does not absorb water, and is convenient for storage, transportation and warehousing; due to the stable phase and fast slag formation, it can reduce the dust pollution of iron and steel plants and fully stabilize the refining process;
4. It does not contain impurities such as hydrogen, nitrogen and carbon, which is beneficial to improve the quality of steel.