Steelmaking production safety technology

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Steelmaking production safety technology 1. The main features of safe steelmaking production are that molten iron contains impurities such as C, S, and P, which affect the strength and brittleness of iron. The molten iron needs to be resmelted to remove the above impurities and add Si, Mn, etc. to adjust its composition. The process of re-smelting molten iron to adjust its composition is called steelmaking. The main raw materials for steelmaking are molten iron or pig iron with high carbon content and scrap steel. In order to remove impurities in the molten iron, oxidants, deoxidizers, slagging materials, and ferroalloys and other materials need to be added to the molten iron to adjust the composition of the steel. After the molten iron or pig iron with high carbon content is added to the steel-making furnace, the impurities in the molten iron are oxidized and removed through oxygen supply blowing, ore addition, decarburization and other processes. Finally, alloy is added for alloying, and molten steel is obtained. There are three types of steelmaking furnaces: open hearth, converter and electric furnace. The open hearth steelmaking method has been gradually phased out due to high energy consumption and poor operating environment. In converter and open-hearth steelmaking, molten iron is first put into a mixing furnace for preheating, scrap steel is added to the converter or open-hearth furnace, and then the high-temperature molten iron in the mixing furnace is mixed into the converter or open-hearth furnace using a mixing car to melt and raise the temperature. When the temperature is suitable, the oxidation period is entered. Electric furnace steelmaking is to add all cold scrap steel into the electric furnace steel, and then enter the oxidation period after a long period of melting and temperature raising. (1) Melting process. Molten iron and scrap steel contain impurities such as C, Mn, Si, P, and S. During the low-temperature melting process, C, Si, P, and S are oxidized, even if the impurities in the single substance state become impurities in the combined state, which will facilitate the further removal of impurities in the later stage. Oxygen comes from the rust in the charge (composition is Fe2O3·2H2O), iron oxide scale, added iron ore, oxygen in the air and oxygen blowing. The oxidation process of various impurities takes place between the interface of slag and molten steel. (2) Oxidation process. The oxidation process is a decarburization, phosphorus removal, gas removal, and impurity removal reaction carried out at high temperature. (3) Deoxidation, desulfurization and tapping. At the end of oxidation, the steel contains a large amount of excess oxygen. The excess oxygen in the molten steel is removed by adding lump or powdered iron alloy or multi-element alloy to the molten steel. The harmful gas CO produced is discharged with the furnace gas, and the generated slag can be further desulfurized. That is, in the final tapping process, the slag and steel are intensively mixed and flushed to increase the desulfurization reaction. (4) Refining outside the furnace. The molten steel smelted from the steel-making furnace contains a small amount of gas and impurities. Generally, the molten steel is injected into the refining ladle, and processes such as argon blowing, degassing, and ladle refining are performed to obtain purer steel. (5) Pouring. The pure molten steel coming out of the steelmaking furnace or refining furnace can be tapped when its temperature is appropriate and its chemical composition is adjusted appropriately. The molten steel passes through the molten steel ladle and enters the steel ingot mold or continuous casting machine to obtain the steel ingot or continuous casting billet. Pouring is divided into two methods: mold casting and continuous casting. Mold casting is divided into two types: upper casting method and lower casting method. The upper casting method is to inject molten steel from the molten steel ladle through the upper opening of the casting mold directly into the mold to form a steel ingot. The pouring method is to pour the molten steel in the molten steel ladle into the injection pipe and flowing steel bricks, and the molten steel enters the mold from the lower opening of the steel ingot mold. The molten steel solidifies in the mold to obtain the steel ingot. After removing the insulation cap, the steel ingot is sent to the soaking furnace of the steel rolling mill for heating, and then the steel ingot mold and other materials are transported back to the steelmaking plant for mold shaping. In continuous casting, molten steel is poured from a ladle into a tundish and then into a cleaner. After being quenched, the molten steel is pulled out of the crystallizer at a certain speed by the blanking machine. After secondary cooling and forced cooling, after all cooling, it is cut into continuous casting slabs of a certain size and finally sent to the steel rolling workshop. 2． The main safety technology for steelmaking production is oxygen lance system safety technology. Converter and open hearth furnaces use oxygen lances to supply oxygen to the molten pool to strengthen smelting. The oxygen lance system is the focus of oxygen safety work in steel plants. (1) Prevention of explosion accidents in elbows or reducing pipes. The oxygen pipe bend or reducer in the upper part of the oxygen lance has a large flow rate and a large local resistance loss. If there is slag in the pipe or the degreasing is not clean, it is easy to induce explosion of high-purity, high-pressure, high-speed oxygen. Accidents should be avoided by improving the design, preventing sharp bends, slowing down the flow rate, blowing the pipe regularly, cleaning the filter, and improving degreasing. (2) Prevention and control of backfire and explosion accidents. The use of low-pressure oxygen leads to negative pressure in the oxygen pipe and clogging of the oxygen lance nozzle holes, which can easily cause the gas generated in the high-temperature molten pool to backfire and cause explosion accidents. Therefore, oxygen pressure should be closely monitored. When multiple furnaces use oxygen, do not rush to use oxygen to avoid backfire in the pipelines. (3) Prevention of vapor lock explosion accidents. Due to operational errors, the water return to the oxygen lance was blocked. The accumulated water in the oxygen lance vaporized in the high temperature of the molten pool, preventing high-pressure water from entering. When the vapor pressure in the oxygen lance is higher than the strength limit of the lance wall, an explosion occurs. 4) Scrap steel and blasting safety technology (1) Possible hazards of blasting: explosion seismic wave ； explosion shock wave ； Debris and flying debris hazards ； noise. (2)Safety measures: One is heavy scrap steel blasting. Scrap steel must be carried out in underground blasting pits. The blasting pits must be strong and have pressure relief holes. Column retaining walls must be set up around the pressure relief holes. ； The second is to dismantle the furnace for blasting, limit the amount of charge, and control the blasting energy. ； The third is to take necessary prevention and control measures. 5) Steel, iron, and slag burn protection technology The temperature of iron, steel, and slag liquid is very high, the heat radiation is very strong, and it is easy to splash. In addition, the temperature of the equipment and the environment is very high, and burn accidents are very easy to occur. (1) Burns and their causes: Equipment is missing, such as steel-making furnaces, molten steel tanks, molten iron tanks, iron mixing furnaces, etc. that are overflowing ； Physical and chemical explosions and secondary explosions when iron, steel and slag liquids meet water ； Superheated steam pipeline leaking or exposed ； Hot gas or flames are ejected when changing the direction of the flame and exhaust gas in the open-hearth furnace ； Violation of operating procedures. (2)Safety measures: Regular inspection and maintenance of steel-making furnaces, molten steel tanks, molten iron tanks, iron mixing furnaces and other equipment ； Improve safety technical regulations and strictly implement them ； Take good personal protection ； Flanges and valves that are prone to air leakage must be replaced regularly. 6) Safety technology for hoisting and transportation operations in steelmaking plants. The raw materials, semi-finished products, and finished products required in the steelmaking process all require lifting equipment and locomotives for transportation. There are many dangerous factors during the transportation process. (1) Existing dangers: Injury caused by falling objects ； Hoisted objects collide with each other ； Molten iron and steel tip over and injure people ； A vehicle hits a person. (2)Safety measures: Consider sufficient space when designing the factory building ； Innovate equipment and strengthen maintenance ； Improve workers' operational level ； Strictly abide by safety production regulations.