Erosion Mechanism and Protection of Converter Lining
Converter smelting is a series of physical and chemical reaction processes under high-temperature conditions. During this process, the furnace lining is eroded by a series of strong mechanical, physical and chemical effects.
1. Mechanical Impact Erosion.
The operations of adding scrap steel and adding molten iron are all directed against the large-faced furnace lining of the converter, which produces strong impact, wear, and erosion on the large-faced furnace lining, which is the main factor for the erosion of the furnace lining refractory.
2. Physical Effects.
During the smelting process, the airflow in the furnace scours the furnace wall, furnace cap, and other refractory materials, the melting and scouring of the furnace lining by molten steel and slag, and the melting loss of the furnace lining caused by the high-temperature reaction during the smelting process.
3. Chemical Effects.
The working layer of the converter lining is generally made of magnesia-carbon bricks. The magnesia-carbon bricks contain a certain amount of graphitic carbon, which has poor wettability with the slag, which can hinder the penetration of the slag into the brick body; Improve the thermal vibration resistance of the lining brick, so that the life of the magnesia carbon brick lining is longer. However, there is a strong oxidizing atmosphere in the converter furnace.
During the smelting process, the high-temperature oxidizing gas will oxidize and remove part of the carbon in the bricks, resulting in the loosening and embrittlement of the brick body structure, which will be lost under the erosion of flue gas and fluid and be corroded.
The maintenance methods of the converter are mainly:
1. Converter Gunning
Converter gunning is the most important means of converter maintenance. By spraying refractory materials with certain humidity, the corroded or falling off furnace lining can be repaired, which can ensure normal and safe production and improve the furnace age of the converter.
The selection of gunning material needs to consider the sintering property, and the gunning material with good wettability with the converter lining refractory material, easy sintering, and high refractoriness is selected to improve the repair quality and reduce the gunning consumption and repair cost.
2. Slag Splashing to Protect the Furnace
Slag splashing is also an important means of converter maintenance. After the converter is tapped, the slag with adjusted viscosity and properties is sprayed and hung on the furnace wall with nitrogen gas through an oxygen lance to form a lining-like protective layer to slow down the furnace. Erosion and melting loss of the furnace lining during the smelting process.
Under normal conditions, the economic furnace age of large and medium-sized converters is generally within 5000-8000 furnaces. Generally, about 500 new furnaces need to be protected by slag splashing and gunning maintenance.
In the initial stage, 2 or 3 furnaces are generally protected once, and then the frequency of furnace protection increases with the increase of furnace age.
In the later stage, slag splashing is required for each furnace to protect the furnace.