Converter large surface hot repair compound is mainly used to maintain the feeding side, furnace bottom and tapping side of the converter. Currently, its materials mainly include asphalt or resin-bonded magnesium carbon hot repair compound, SiO2 micro powder combined magnesium water system environmental protection hot repair compound Magnesium self-flowing heat repair compound combined with sodium metasilicate nonahydrate, etc.
1. Comparison of construction methods
Magnesium-carbon hot repair materials mainly use magnesia, asphalt or resin powder as the main raw materials, and wetting agents, flow enhancers, antioxidants, etc. are added to the matrix. It is poured into the converter through the hopper, and with the help of the shaking furnace and the liquefaction of the binder when it is heated, the large fabric quickly flows to the area requiring maintenance and is self-flowing and dense, and is closely combined with the furnace lining.
The magnesia-siliceous water-based environmental protection hot repair material mainly uses magnesia and SiO2 micropowder as the main raw materials, and the matrix is added with water-reducing agents, anti-sedimentation agents, and anti-explosion agents. Pour it into the converter, with the help of the shaking furnace and the evaporation of water when it is heated, the large fabric quickly flows to the area to be maintained and is self-flowing and dense, and is closely combined with the furnace lining.
The magnesia hot repair compound combined with sodium metasilicate nonahydrate mainly uses magnesia and sodium metasilicate nonahydrate as the main raw materials. The water released when heated and the evaporation of water make the repair material boil, flow and precipitate, and combine with the furnace lining, so as to achieve the goal of maintenance.
The above three kinds of large fabrics all use the waste heat after tapping the converter and the timely shaking of the converter to realize the repairing operation. The maintenance cost for each time is 0.7~3.2t, so it needs to be timely when the residual temperature after tapping the converter is high. Repair and ensure sufficient sintering time. During the sintering process of magnesia-carbon hot-repair materials, pitch/resin burns and carbonizes, accompanied by a lot of smoke, which is not friendly to the environment, and the sintering time is generally 30-60min. Magnesium siliceous water-based environmental protection heat repair material and magnesium heat repair material combined with sodium metasilicate nonahydrate mainly evaporate moisture in the sintering process, which has no adverse effects on the environment, and the sintering time is generally within 20 minutes, which is beneficial to the improvement of the converter. production efficiency is of great significance.
2. Physical and chemical properties and application comparison
The main physical and chemical properties and usage conditions of the above three hot repair materials are shown in Table 1. It can be seen from Table 1 that the density and strength of the magnesium-silicon environmental protection hot-repair compound are the highest, followed by that of sodium metasilicate nonahydrate combined with the magnesium-based heat-repair compound, and that of the magnesium-carbon heat-repair compound is the lowest. This difference is related to its chemical composition: the main components of magnesium-silicon thermal repair materials are MgO and SiO2, which will form a high melting point phase M2S (melting point 1890 °C) at high temperatures; the main components of magnesium-carbon thermal repair materials are MgO and C , which will form carbon bonds at high temperatures; the main components of sodium metasilicate nonahydrate bonded magnesium heat repair materials are MgO, SiO2 and Na2O, and there will be more low-melting point phases at high temperatures.
Due to the difference in density and strength, the service life of magnesium-silicon environmental protection thermal repair material is the longest, but because it is restricted by the construction method and belongs to the emerging technology developed in recent years, its current application range ranks second; The service life of magnesia-carbon heat repair compound is second, but because of its convenient construction and mature technology that has been used for many years, it is currently used in the widest range; sodium metasilicate nonahydrate combined with magnesium heat repair compound has the shortest service life. The scope of use is also the narrowest.