| In order to improve the quality of IF steel, thus improve market competitive power, the metallurgical technology of Super clean IF steel was discussed based on production conditions at Panzhihua steel making plant. Restricted links of super clean IF steel produced at Panzhihua steelmaking plant were desulphurization , dephosphorization, decarburization, T[O] cut down through LF+RH refining and carbon pick-up in hot metal by analysing it's development present conditions at home and abroad.These technologies were studied separately.Industry text has shown that the total of [C], [P], [S], T[O], [N], [H] in strand can be controlled within80×10-4%.The requirement of [SJ before LD steelmaking was meted by development of a Mg-desulphurizer, [S] has been possible by 700×10-4% about to escape to 7×10-4% A desulphurizer was developed through the research based on characters of Super clean IF hot metal and slag.The results obtained show that the desulphurising percentage of CaO-CaF: system is between 40% to 50% when it used in RH vacuum treatment, the sulphur content in molten steel can be controlled in within 10×10-4%.The molten iron at the beginning of pretreatment the dephosphorization divides into exchanges hard and the blowing two stages, exchanges the hard stage in the converter, escapes the phosphore in to exchange in front of the iron to join in the stove, exchanges into along with the molten iron, escapes the phosphore to participate in the dephosphorization responding unceasingly, when the molten iron pretreatment with escapes the phosphore to join measures >25kg/tFe, the dephosphorization rate may achieve above 90%, coordinates the converter slag formation dephosphorization, may cause the end point molten steel [P] to escape to (8 12)×10-4%.A systematic investigation in the initial [C] and [O], vacuum degree, pressure reduced system and flow of Ar at RH has shown if the initial [C] and [O] are controlled 0.02%0.04%, (400-600) × 10-4% separately, the vacuum degree <=160Pa, pressure controlling time <=5min, that can get [C] <=10 X 10-4% after RHtreatment, it was satisfied with the demand of Super clean IF steel.Chemical composition and physical properties of tundish powder without free carbon is designed by reference to the II steel continuous casting process parameters. The application experiment was carried out in IF steel continuous casting in Panzhihua steelmaking plantthe result show the powder not only can prevent carbon picking-up in tundish molten steel,but also has functions of general tundish powder.A mold powder was developed through the research upon effect of basic materials and fluxes on the properties of mold powder and the model of melting speed conditioner added based on conditions of Super Clean IF steel continuous casting.Industrial experiment has shown that the developed prefused mold powder was satisfied with the demand of Super clean IF steel casting process ,such as a good melting behavior in mold,the rate without slab surface finishing reached 98.5%,carbon pick-up in strand was controlled about 2X10%. |
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