Corrosion mechanism and protection of BOF lining

 BOF smelting is a series of physical and chemical reaction processes under high temperature conditions. In this process, the furnace lining is corroded by a series of strong mechanical, physical and chemical effects. The main mechanism is as following,

1. Mechanical impact erosion.

The operations such as adding scrap steel and mixing molten iron directly face the large-surface furnace lining of the BOF, which produces strong impact, wear and erosion on the large-surface furnace lining, which are the main factors for the corrosion of the refractory lining of the furnace.

2. Physical effects.

During the smelting process, the airflow in the furnace scoured the furnace wall, the furnace cap and other refractory materials, the molten steel and slag melted and washed the furnace lining, and the high temperature reaction during the smelting process caused physical erosion of the furnace lining.

3. Chemical action.

The working layer of the BOF 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 and can hinder the penetration of the slag into the brick body; the thermal conductivity is good and can greatly improve the thermal vibration resistance of the lining brick, so that the magnesia carbon brick lining life is longer. However, there is a strong oxidizing atmosphere in the BOF furnace. During the smelting process, high-temperature oxidizing gas will oxidize and remove part of the carbon in the brick, causing the brick structure to become loose and brittle, which will be lost and eroded by the flue gas and fluid.

Article Source: Corrosion mechanism and protection of BOF lining
Company name: Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: info@cxrefractories.com
Website:http://www.cxrefractories.com

BOF furnace classification and related refractories

 BOF is a vertical cylindrical furnace that does not require an external heating source and mainly uses liquid pig iron as raw material for steelmaking. According to the nature of refractory lining, it can be divided into acid BOF and alkaline BOF. According to the position where the gas is blown into the furnace, it is divided into bottom blowing, top blowing, side blowing and top and bottom combined blowing BOFs.

Because of the different components of molten iron and refractory resources in different countries in the world, the choice of furnace lining bricks is also emphasized. The United States mainly uses tar-combined magnesia bricks, periclase bricks, and tar impregnated and fired periclase bricks. Magnesia carbon bricks have also been used since the 1990s. France mainly uses dolomite bricks, magnesia dolomite bricks, dolomite carbon bricks, asphalt bonded magnesia bricks and magnesia carbon brick. The United Kingdom once used tar dolomite bricks and fired dolomite bricks. After 1989, a large number of MgO C bricks were used.

Russia mostly uses tar dolomite bricks, and a few factories also use tar magnesia bricks and periclase spinel bricks. Japan is the first country to move magnesia-carbon bricks from electric furnaces to BOFs, and its use effect is in a leading position in the world. The development of BOF lining in China has gone through the process of tar combined with dolomite bricks, tar combined with magnesia bricks, magnesia dolomite bricks, high calcium magnesia bricks, magnesia dolomite carbon bricks and magnesia carbon bricks. In summary, all countries in the world are gradually using magnesia carbon bricks to replace other bricks. Magnesia carbon brick has good thermal shock resistance, strong corrosion resistance, excellent stability at high temperatures, good thermal conductivity, good wear resistance and good spalling resistance, plus the improvement and progress of smelting technology and gunning technology Since the 1990s, the service life of furnace lining has been greatly improved, and the consumption of refractory materials per ton of steel generally does not exceed 2kg.

Article Source: BOF furnace classification and related refractories
Company name: Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: info@cxrefractories.com
Website:http://www.cxrefractories.com