Refining Slag

Pubdate: 06-16 2021

Refining slag

Refining slag refers to the technology used after mixing raw materials in a certain proportion and particle size, heating them below the melting point of the raw materials, sintering the raw materials together, and then crushing them into particle sizes. The main components are CaO-CaF2 base, CaO-Al2O3 base, and CaO-Al2O3-SiO2 base. The form of refining slag mainly includes sintered type, pre-melted type and mixed type.

The composition of the sintered refining slag is more uniform, stable, and the melting speed is faster, but the cost is relatively increased, and due to the low density of the sintering slag and more pores, it is easy to cause gas in the refining process.

Pre-melted refining slag refers to the refining slag used for steelmaking after mixing the raw materials in a certain proportion, using high temperature in a special equipment to melt the raw materials into a liquid state at a temperature higher than the melting point of the slag system, and then cooling and crushing. The pre-melted refining slag has high purity, uniform chemical composition, stable phase, low melting point and fast slag formation speed, which can greatly shorten the refining time and can be directly used for slag washing in the converter ladle tapping process to improve the cleanliness of molten steel . And it does not contain fluorine or a small amount of fluorine, which reduces the corrosion of the furnace lining and effectively reduces the pollution of fluorine to the environment. Due to the compact structure of the pre-melted refining slag, it does not absorb water, is convenient for storage, transportation and storage, does not pulverize, and is not volatile, which can significantly reduce dust pollution in steel plants, but the production cost is high.

In the metallurgical process, the slag composition has a very important influence on the cleanliness of molten steel. After the converter is tapped, the highly oxidizing slag that enters the ladle due to the high content of unstable oxides such as FeO and MnO will continuously transmit oxygen to the molten steel, which will seriously affect the yield of aluminum and the cleanliness of the molten steel. Lead to clogging of the nozzle and defects in the surface quality of the board. Refining slag control technology has been used in the production of IF steel by Armco, Posco, Nippon Steel and other manufacturers in the last century. By reasonably controlling the composition of the refining slag, it can effectively reduce the content of inclusions and harmful elements in the molten steel to obtain high cleanliness. Steel. Therefore, it is particularly important to apply refined slag control technology on the basis of minimizing the amount of slag under tapping. A domestic plant analyzes and studies various physical and chemical properties of IF steel’s refined slag control technology, and provides a basis for the selection of refined slag systems in the production of clean steel. The composition of sintered refined slag is more uniform and stable , The melting speed is faster, but the cost is relatively increased, and due to the low density of the sintered slag and more pores, it is easy to cause gas in the refining process.

Refining slag properties:

The main components of refining slag are calcium aluminate, alumina, silicon oxide, calcium fluoride, magnesium oxide, etc. These metal ions are combined into calcium oxide-calcium fluoride base, calcium oxide-alumina base, calcium oxide-alumina- Silicon oxide base; The formed composite material is the refining slag. Refining slag is a necessary additive for deoxidation and desulfurization in the refining process of iron and steel enterprises.

Characteristics of refined slag:

Refining slag has the advantages of uniform chemical composition, low melting point, fast melting speed, reduced refining power consumption, and shortened refining time. It has attracted more and more attention from iron and steel enterprises and is currently one of the more important steelmaking additives.

The refined slag produced by us does not contain fluorine, hydrogen, nitrogen, carbon and other impurities, which is conducive to improving the quality of the steel produced; it does not absorb water and will not corrode the furnace lining and ladle; the structure is compact, which is convenient for transportation and storage; the product itself has a physical phase Stable, fast slag formation, significantly reducing dust pollution in steel mills. The widespread use of refining slag makes the current steelmaking companies change the production process of refining relying on high-alkali materials, mixing slag and steel, and desulfurizing outside the furnace, greatly improving the efficiency of steel production and improving the quality and performance of steel products .

The Usage of Refining Slag:

Put the refining slag into the ladle before tapping, because the molten steel flows into the ladle from the upper layer, the molten steel and the refining slag are vigorously stirred, and the refining slag is quickly melted into the molten steel, and then aggregates and floats. Because of the strong reducibility of the refining slag, it has a strong deoxidation and desulfurization ability, which can remove oxygen and sulfur impurities in the molten steel during the mixing process of molten steel. At present, the desulfurization capacity of refined slag can reach more than 85%, which is a very good steelmaking additive.

CaO A2LO3 SiO2 Fe2O3 MgO S P TiO2
47-52 38-42 ≤2.5 ≤1.0 1.0 0.1 0.05 ≤1
45-50 37-45 5-2 ≤1.5 3-5 0.1 0.05 ≤1
47-55 50-55 6-8 ≤1.5 1.0 0.1 0.05 ≤1
30-35 50-55 ≤2.0 ≤0.1 ≤0.1
≥50 ≥30 ≤1.5 ≤0.1 ≤0.1 0.15

Features:

  1. Low melting point and fast melting speed, shorten refining time and reduce refining power consumption;
  2. Good fluidity, good desulfurization and removal of inclusions;
  3. There is no flame, little dust, and good safety;
  4. No water absorption, no dust, no deterioration during storage and transportation;
  5. The submerged arc has a good effect, which reduces the erosion of the lining caused by the arc and improves the life span.
CaO AL2O3 S SIO2 Fe2O3 CaF2 MgO P
≥45 ≥38 0.1 ≤4 ≤1.5
50±5 31±5 ≤7 ≤5 7±4
50±3 30-40 ≤7 ≤1.5 ≤7
≥45 ≥40 ≤4 ≤1.5 4-6 ≤4
45-55 35-45 ≤6 ≤1.5 ≤5
45-50 35-40 ≤7 ≤1.5 ≤5
45-53 39-44 ≤5 ≤5
20±2.5 30±3 ≤0.05 7±1.5 ≤0.5 40±3 3±1 ≤0.05
45-50 41-46 ≤5 ≤1.5 ≤5
≥48 ≥38 ≤3 ≤1.5 ≤3
50-55 36-44 ≤0.1 ≤4 ≤1.5 (TIO2≤1.5) ≤0.05
48-58 28±3 ≤0.3 ≤6 (TIO2<0.5) ≤0.3
48-52 42-45 ≤4.5 (TIO2<1)
  1. Desulfurization

In the refining process, the desulfurization of the refining agent mainly uses the ratio between the molten slag and the molten steel to control the sulfur content in the steel. Because sulfur is one of the common harmful elements in steel and has many adverse effects on the properties of steel, the greater the desulfurization ability of the refining agent, the lower the sulfur content of the molten steel.

  1. Desulfurization

There are dissolved oxygen and chemical oxygen in molten steel.

Compound oxygen can be removed by slag in the form of inclusions. A certain amount of deoxidizer is added during the refining process to convert the dissolved oxygen in the steel into oxides to a large extent, and it can float up through its own buoyancy and suitable low-blown argon agitation, and finally enter the slag layer to be adsorbed. In addition, oxygen obeys the law of distribution in the slag and molten steel. When the reducing refining agent contacts the molten steel, the dissolved oxygen in the steel can diffuse into the slag to deoxidize the molten steel.

  1. Adsorption of impurities

During the refining process, due to the strong stirring effect of the low-blown argon gas, the emulsified slag liquid comes into contact with the molten steel in a large area, and the chances of the slag liquid coming into contact with the impurities in the steel (especially large particles) increase sharply. The slag is an ionic melt formed by the melting of oxides, and most of the impurities in the steel are also oxide melts. According to the principle of similar compatibility, the impurities in the steel are easily integrated with the slag droplets and dissolve each other. Combine to form larger slag droplets, and then capture other droplets of impurities. Large-volume droplets will quickly float up and merge into the slag layer on the surface of the molten steel due to greater buoyancy. The emulsified slag droplets can become the nucleation crystals of the deoxidation product, so that the deoxidation product will quickly form a stable compound , Reduce the chemical potential of deoxidation products in molten steel, make the reaction develop in the direction of favorable deoxidation, and accelerate the progress of deoxidation reaction. Due to the high content of AL2O3 in the refining agent, the composition of the slag becomes very stable and will not change the properties of the slag with the entry of deoxidation products (AL2O3). Therefore, the refining agent always maintains a very stable deoxidation, desulfurization and removal Ability to impurity.

  1. Protective effect on furnace lining

Because there is about 8%-10% MgO in the refining agent, the MgO in the slag is basically saturated, so the MgO contained in the lining near the slag line can only be dissolved in a small amount in the slag, so as to reduce erosion of the lining. Secondly, the foaming submerged arc effect of the refining agent is good, which reduces the erosion of the arc to the lining, thereby improving the life span.

  1. Packaging

It is packaged in a plastic lining composite woven bag (1000Kg), and other forms of packaging can also be used according to customer requirements.

6.The ingredients can be adjusted according to the composition of the user’s molten steel, and the indicators can be changed to meet the needs of refined steel.

Sintering refining slag

The sintered and pre-melted refining slag (calcium aluminate) produced by our factory is sintered or smelted and synthesized with superior materials. It has the functions of rapid slag formation, submerged arc, slagging, absorption of molten steel inclusions and desulfurization. , Desulfurization effect.

It can reduce the gas in the steel and reduce the inclusions in the steel. The product is selected from various raw materials to be sintered or melted to generate 12CaO•7Al2O3 as the main mineral, with a content of more than 85%. A large amount of calcification components can react with oxygen and sulfur in molten steel to form a product with a low melting point and easy to float for the purpose of purifying molten steel.

In ladle refining, it can effectively shorten the steelmaking time, has a strong ability to absorb non-metallic inclusions in steel, and has a significant effect on purifying molten steel.

Features:

  1. Reasonable chemical composition is conducive to slag formation as soon as possible and shorten the smelting time.
  2. Due to the fast slag formation, it can reduce the power consumption of the refining time.
  3. Reduce the consumption of refractory materials in the ladle and increase the age of the ladle.
  4. It has a good desulfurization and deoxidation effect.
  5. Due to its low melting point, it has a good effect of adsorbing impurities during the process of ladle argon blowing and electric furnace tapping.
  6. The composition is stable and uniform, and can be produced and packaged according to the requirements of the user.
Item Content
Calcium Oxide CaO 45-50%
Aluminum oxide Al2O3 35-40%
Silica SiO2 <=4%
Sulfur <=0.1%

Synthetic refining slag

Refined synthetic slag is a new generation of steelmaking auxiliary materials developed by our company. It is suitable for use as a purifier of molten steel during ladle refining. It has strong deoxidation and desulfurization capabilities, which can reduce the content of oxygen and inclusions in the steel. This product is made of a variety of refined materials through uniform stirring and pelletizing at high temperature, casting and melting. The refined slag is used with an appropriate amount of Lime produces 7A12.C-based low-melting aluminate products, which can fully react with oxygen and sulfur in steel and absorb the reaction products to achieve the purpose of purifying molten steel.

has the following characteristics:

  1. Low melting point and fast melting speed, shorten refining time and reduce refining power consumption.
  2. Good fluidity, strong desulfurization and removal of inclusions.
  3. There is no flame in use, little dust, and good safety.
  4. No water absorption, no powdering, no deterioration during storage and transportation.

High magnesium refining slag

Our company’s high-magnesium refining slag is integrated with deoxidation, submerged arc foaming, and refining. It not only simplifies the production process, improves the working environment, but also improves the stability of molten steel composition, reduces smelting costs, shortens refining time, and increases the yield of precious metals Yield, reduce the secondary oxidation of molten steel, increase the recovery rate of molten steel, reduce arc and noise pollution, and increase the service life of refractory materials. Good results have been proved by the majority of users.

Application scope and method of high magnesium refining slag:

  1. The composition of the finished product can be adjusted according to user requirements;
  2. It is better to add the ladle after moving to the refining furnace or add it in batches;
  3. 0.8-1.5 kg of steel consumption per ton.

Packaging, storage and transportation of high magnesium refined slag:

  1. The packaging material and unit weight are based on user needs.
  2. Waterproof, rainproof and moisture-proof measures should be taken during storage and transportation.

High aluminum refining slag

High calcium refining slag

Features of high-calcium refining slag:

(1) The composition is uniform, the melting point of the minerals in the slag is low (<1300 degrees), and the melting speed is fast, which can shorten the smelting time, fast slag formation, and reduce dust pollution;

(2) The viscosity and fluidity of the molten slag are appropriate to promote the desulfurization and deoxidation reaction between the slag and molten steel;

(3) Fast desulfurization (>60%), effectively inhibiting phosphorus reversion, and effectively adsorbing impurities in steel;

(4) It can improve the protective effect of ladle lining;

(5) It does not absorb water and is convenient for storage and transportation.


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