What are the characteristics of refractory materials used in steelmaking converters?

Converter is a vertical cylindrical smelting furnace that does not require an external heat source and mainly uses liquid pig iron as raw material for steelmaking. According to the properties of refractory materials for furnace lining, there are two types: acidic converter and alkaline converter. According to the location of gas blowing into the furnace, it is divided into bottom blowing, top blowing, side blowing, and top bottom composite blowing converters.

Due to differences in the composition of molten iron and the resources of refractory materials in various countries around the world, the selection of furnace lining bricks has also been emphasized. The United States mainly uses tar combined with magnesia bricks, magnesia bricks, and magnesia bricks made by impregnating and firing with tar. Magnesia carbon bricks have also been used since the 1990s. France mainly uses dolomite bricks, magnesium dolomite bricks, dolomite carbon bricks, asphalt bonded magnesium bricks, and magnesium carbon bricks. The UK has used tar dolomite bricks, fired dolomite bricks, and extensively used magnesia carbon bricks since 1989. Russia often uses tar dolomite bricks, and a few factories also use tar magnesium bricks and periclase spinel bricks. Japan was the first to use magnesia carbon bricks for converters, and its usage effect is leading in the world. The development of converter lining in China has gone through processes such as tar bound dolomite bricks, tar bound magnesium bricks, magnesium dolomite bricks, high calcium magnesium bricks, magnesium dolomite carbon bricks, and magnesium carbon bricks.

In summary, countries around the world are gradually using magnesia carbon bricks to replace other types of bricks. Due to the excellent thermal shock resistance and corrosion resistance of magnesia carbon bricks, as well as their excellent stability, thermal conductivity, wear resistance at high temperatures, and the carbon network formed after solidification with binders, magnesium oxide particles are tightly and firmly connected together, which has the advantage of good peeling resistance. In addition, the promotion and application of spray repair technology, slag splashing protection technology, and other technologies have greatly improved the service life of furnace lining since the 1990s, The consumption of refractory materials per ton of steel generally does not exceed 2kg.

The lining of the converter consists of an insulation layer, a layer, and a working layer. The insulation layer is generally built with polycrystalline refractory fibers, and the insulation layer of the furnace cap is also tied with resin magnesium sand; The bricks used in various parts of the layer are not exactly the same, and low-grade magnesia carbon bricks, tar dolomite bricks, or sintered magnesia bricks are often used for masonry; The working layer is all built with magnesia carbon bricks. There are ordinary and high-strength magnesia carbon bricks for the masonry work layer, and industry standards have been established in China.

The working layer of the converter is directly in contact with high-temperature molten steel and slag, and is subjected to chemical erosion by high-temperature slag, erosion by molten steel, slag, and furnace gas, as well as mechanical impact during the addition of scrap steel. The working environment is very harsh. During the blowing process, due to different working conditions in different parts, the corrosion status and amount of the lining are also different. In response to this situation, depending on the degree of damage to the lining bricks, refractory bricks of different materials or different levels of the same material are laid, which is called comprehensive furnace lining. Build magnesium carbon bricks in areas that are easily damaged or difficult to repair; Lightly damaged and easily repairable parts can be built with medium or low grade magnesia carbon bricks. After adopting the slag splashing technology for furnace protection, the wettability between the lining bricks and the slag should also be considered when selecting the lining bricks. If the carbon content is too high, the wettability between the slag and the lining bricks is poor, and the slag is not easy to adhere during slag splashing, which is unfavorable for furnace protection. After adopting comprehensive furnace lining, the corrosion degree of the entire furnace lining bricks is relatively balanced, which can extend the overall service life of the furnace lining.

The steel outlet is severely damaged due to high-temperature molten steel erosion and rapid temperature changes. Therefore, magnesia carbon bricks with good erosion resistance and high oxidation resistance should be built. Generally, integral magnesia carbon bricks or composite bricks are used, and they need to be replaced after about 200 heats.

There are two ways to replace the steel outlet, one is to replace it as a whole, and the other is to remake the steel outlet. When remaking the steel outlet, first clean the original outlet, place a steel pipe with the inner diameter of the outlet size, and then fill the outer wall of the steel pipe with magnesium sand and sinter it.

The bottom gas supply brick is used to supply Ar, N2, CO2, or a mixture of the three with oxygen from the bottom of the converter. During combined blowing, high temperature and strong stirring effect are generated, so the bottom gas supply brick must have high temperature resistance, corrosion resistance, erosion resistance, wear resistance, and strong resistance to peeling; From the perspective of blowing, it is required that the bubbles generated by the gas passing through the supply brick should be small and uniform; The use of gas supply bricks is safe and reliable, and their lifespan should be synchronized with that of the furnace lining as much as possible. Therefore, magnesia carbon bricks are still the better material.