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Steel blowing through the ladle gate port, using the tuyere with the slot nozzle, allows to reduce the temperature and chemistry inhomogeneity of the metal in the ladle space by 3 - 5 times. In this way its teeming improves and as a result the surface defects of the ingots on the first process stage are reduced by 1,5 - 2,5 times. The unit of crushed materials introduction into the steel pouring stream ensures the realisation of the "late steel modification" technology. In the process of the device's functioning, ferroalloy particles arrive from the loading hopper into the chamber of the distribution unit through the flexible conduit and get equally scattered over the surface of the centre funnel. After that the particles are entrained by the steel pouring stream and are carried over into the moulds cavities, where they melt and equally dissolve in the crystallizing metal. In this way, when introducing the alloys, it is possible to avoid negative consequences of the ladle discharge port clogging, which often happens during the process of the dosed tapping of aluminium or titanium grain-refined steel. When compared with the methods of steel microalloying in the steel-teeming ladle, this steel treatment technology has a number of advantages due to zero contact of the introduced active components with the oxidizing furnace slag and acid lining, and also due to reduction of the total period of atmospheric oxygen attack on the microalloyed metal. When applying the technology of 65G steel modification with titanium and boron, the indicated advantages of the ladle gate, equipped with a distribution unit, allowed to increase the assimilation degree of these elements up to 94.1 and 92.9% respectively. During the process of steel microalloying with the introduction of the reagents into the ladle, the degree of their assimilation didn't exceed 18 and 42% because of the increased waste. While using the slide gate, equipped with the unit of gas-dynamic protection of the steel pouring stream against the negative influence of the atmospheric oxygen, the attendants don't get distracted from the fulfillment of their direct duties, as the optimal rates of the shielding gas flow are maintained automatically within the fixed bounds. At the same time the acceptable level of the oxygen impoverishment (5%) in the space, surrounding the steel pouring stream, is achieved in case of the shielding gas feed (N2, Ar, CO2) with the flow of 40 - 50 m3/h. The application of the steel protection against secondary oxidation allows to reduce the oxygen concentration in the finished metal on the average by 30 - 50 %. The working conditions of the slide gate can be improved by means of removing its single components overheating during the sequence casting process. For this purpose it is suggested to equip the ladle gate with an ejector which creates rarefaction to promote air exhaust from the cavity of the submerged nozzle, attached to it. Compressed air from the shop main is used as the working gas which ensures the ejector's functioning. If injected under overpressure through the nozzle into the ejector's mixing chamber, connected with the nozzle cavity by the pipeline, compressed air creates rarefaction in the nozzle cavity, which causes oxygen impoverishment. That allows to diminish the rate of secondary oxidation of continuously cast steel. |
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