Unshaped refractory materials for ladle

Unshaped refractory materials for ladle

Ladle, also known as steel drum, steel ladle, ladle, etc., is a container for storing, transporting and processing molten steel, and is an important equipment for refining tasks. Ladle has two main functions: the first is to receive molten steel; the second is refining outside the furnace. With the diversification of secondary refining, the consumption of refractory materials is relatively high and the service life is shortened. In the late 1970s, in order to reduce resource consumption and reduce labor intensity, the method of pouring refractory materials was gradually adopted in the lining of the ladle.

Working environment of ladle lining refractory materials during use

With the increasing demand for high-quality steel in society, the steel industry is required to continuously refine molten steel, which has led to the rapid development of off-furnace refining technology and the diversification of ladle functions. The increase in ladle functions has led to an increase in operating steps in the ladle, which will make the working environment of the ladle worse. These changes in conditions ultimately force the quality of the refractory lining of the ladle to be further improved.

With the change of smelting technology and the improvement of steel smelting system, vacuum treatment, argon blowing and stirring are added in the steel smelting process. The increase of smelting steps prolongs the residence time of molten steel in the ladle, and makes the refractory lining of the ladle experience more complex and harsh working environment during use. These complex and harsh working environments are as follows:

high temperature

During the smelting process, the temperature of molten steel in the ladle furnace is generally between 1600℃ and 1700℃. The temperature at the slag line where the ladle is heated by submerged arc will be even higher. Therefore, the refractory material of the ladle lining must first meet the requirements of high temperature resistance.

 

Slag erosion

During the smelting process, a layer of slag will form on the top of the molten steel. The presence of slag aggravates the erosion and damage to the refractory materials. However, slag can keep the molten steel warm and slow down the oxidation of the molten steel by air. Therefore, it is sometimes necessary to slag on the surface of the molten steel. Commonly used slag-making raw materials include: lime, fluorite, dolomite, calcium carbide, etc. The liquid slag formed by these slag-making raw materials contains corrosive calcium fluoride, calcium aluminate, etc., which aggravate the erosion and damage to the refractory materials.

 

Long heat preservation time

The increase in smelting steps increases the storage time of molten steel in the ladle. During the transportation of the ladle, in order to maintain the temperature of the molten steel, the molten steel in the ladle needs to be continuously heated and insulated. The heating time plus the insulation time of the ladle is as long as 4-5 hours. The extension of refining time increases the degree of penetration and erosion of the slag on the refractory material inside the ladle.

 

Strong stirring

During the ladle refining process, argon is blown into the molten steel for stirring, or oxygen is blown in for decarbonization, which increases the flow rate of slag and molten steel. This increases the relative movement of molten steel, slag and the refractory material of the ladle lining, which will ultimately increase the degree of scouring and damage to the lining by slag and molten steel.

 

Vacuum treatment

Some refining processes require vacuum treatment. The vacuum condition will cause the gas inside the pores to leak out, increasing the penetration of slag and molten steel into the ladle lining material, making the reaction between the ladle lining refractory material and the molten steel and slag more intense, accelerating the damage rate of the ladle lining refractory material and reducing the stability of the ladle lining in safe use.

Types of commonly used ladle refractory materials

Clay Brick

The Al2O3 content in clay bricks is generally between 30% and 50%, and the price is low. It is mainly used for the permanent layer and bottom of the ladle.

High Alumina Brick

The A1203 content in the brick is between 50% and 80%, and it is mainly used in the working layer of the ladle.

Silica Brick

The brick features high SiO2 content (SiO2)>80%, better corrosion resistance and integrity than clay bricks, and no slag. Commonly used for ladle walls and bottoms.

Zircon Brick

This brick is mainly used in the ladle slag line. The ZrO2 content in the brick is generally between 60% and 65%. It is characterized by good corrosion resistance, but the price is relatively high and it is generally not often used.

Magnesia Carbon Brick

This brick is mainly used in the ladle slag line, especially for multi-furnace continuous casting. The MgO content in the brick is generally around 76%, and the C content is between 15% and 20%. It is characterized by low slag erosion, good corrosion resistance and spalling resistance.

Aluminum-magnesium castable

This castable is mainly used for steel ladle. Its characteristic is that under the action of molten steel, MgO and A1203 in the castable react to form aluminum-magnesium spinel, which improves the compression resistance and thermal shock resistance of the lining.

Alumina-magnesia-carbon brick

The brick is developed on the basis of aluminum-magnesium castable for ladle lining, which has a long service life.

Unfired bricks

At present, almost all materials used for ladle fired bricks can be made into corresponding unfired bricks. Its characteristics are relatively simple production process and low price. The brick itself has certain mechanical strength and corrosion resistance, which is convenient for construction and masonry.