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Slag made by sintering and melting limestone, magnesite, dolomite, witherite and fluorite in a cupola.
Pre-melted refined slag is made by sintering and melting limestone (containing CaO), magnesite (containing MgO), dolomite (containing CaO·MgO), witherite (containing BaO) and fluorite (containing CaF2) in a cupola. This slag has a very low melting point and can be melted at the fastest speed, shortening the residence time of molten steel in the refining bag and strengthening the smelting process. At the same time, this refining agent has good fluidity, optimizes the kinetic conditions of the desulfurization reaction, and can achieve deep desulfurization.
Production method: At present, pre-melted refined slag can be produced by electric furnace, pilot kiln, rotary kiln, horseshoe kiln and cupola for ironmaking. Different production methods and processes have an important influence on the quality of pre-melted slag.
Application characteristics: Pre-melted refining slag is mainly used for LF furnace, open hearth furnace, converter ladle refining to remove sulfur, oxygen and other impurities in molten steel, reduce the content of harmful elements and impurities in steel, and is suitable for ordinary carbon steel, high carbon steel, high and low alloy steel. It has been maturely applied in foreign countries, such as South Korea, Japan, Europe and the United States.
Pre-melted refining slag has the following characteristics:
1. Uniform chemical composition, low melting point, fast melting speed, which can shorten the smelting time;
2. It does not contain fluorine, does not corrode the furnace lining and ladle;
3. It has a compact structure, does not absorb water, and is easy to store and transport; due to the stable phase and fast slag formation, it can reduce dust pollution to the steel plant and stabilize the refining process;
4. It does not contain impurities such as hydrogen, nitrogen, and carbon, which is conducive to improving the quality of steel.
During the ladle refining process, only by selecting different slag systems for different steel grades can the expected metallurgical effect be achieved. At present, various slag systems widely used in the world are selected for different metallurgical environments, different atmospheres, and different steel grades. Therefore, the composition range of pre-melted refining slag fluctuates greatly, and the change of basicity is particularly obvious, which can change from 1.0 to about 12; the change of other components can be from 0 to 40. The components of pre-melted refining slag are mainly the following.
1.CaO
CaO is an indispensable component for slag making, dephosphorization, desulfurization, etc. in metallurgical production. It has a wide source (natural limestone as raw material, and significant smelting effect). It is the main component of blast furnace slag, converter slag, electric furnace slag and various pre-melted refining slags. In order to ensure a good desulfurization effect, it is required that the pre-melted refining slag contains a higher free state CaO.
2.Al2O3
Al2O3 mainly comes from raw materials and deoxidation products. It has two effects on the desulfurization effect: on the one hand, with the increase of Al2O3, the viscosity of the slag 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.
3.SiO2
SiO2 mainly comes from impurities (gangue) and deoxidation products in the raw materials, and has a certain fluxing effect. However, the increase in content is not conducive to deoxidation and desulfurization.
4.CaF2
CaF2 can significantly reduce the viscosity of pre-melted refined slag, improve the fluidity of slag, increase mass transfer, and is beneficial to desulfurization, but its amount is too large, not only is it not conducive to deoxidation, but also erodes the furnace lining faster. For foaming performance, its influence is two-fold. On the one hand, the increase in the amount of CaF2 reduces the surface tension, which is beneficial to slag foaming, but on the other hand, it reduces the viscosity of the slag, which is not conducive to foaming, and tension plays a dominant role.
5.MgO
MgO in pre-melted refined slag mainly comes from slag and refractory materials, and its desulfurization ability is slightly lower than that of CaO.
Slag Sand Grit 1 mm - 10 mm, Silicon Slag Lump Block 10 mm - 100 mm, Tailor-made size, Briquette Ball 40 mm - 60 mm.
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