炉外精炼 铁水预处理2.ppt

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1、3、Fundmentalprinciplesforsteelrefining3.1Degassing3.2InclusionRemoval3.1Degassing3.1.1BasicconceptsMeasurestobetakenforhydrogenremovalfrommoltensteel(1)Drymaterials(alloy,flux,deoxidizer)added;(2)Steeltappingladletobeheatedmorethan800℃；(3)Highvacuumdegree---vacuumchamberpressurehav

2、ingtobereducedasloweraspossible；(4)Strongstirring;(5)Air-sealedpouringandcasting;(6)WeatherMeasurestobetakenfornitrogenremovalfrommoltensteel(1)Materials(alloy,flux,deoxidizer,recarbonagent)addedinmoltensteelorslagbeingdryerandnitrogencontainedlowerenough;(2)Steeltappingladletobehe

3、atedmorethan800℃；(3)Highvacuumdegree---vacuumchamberpressurehavingtobereducedasloweraspossible；(4)Strongstirring;(5)Air-sealedpouringandcasting;(6)Surfactantinsteel;(7)Weather3.1.2Degassingprocess(1)HydrogenremovalHydrogendegassingisappliedinthecaseofsteelgradeswhicharesensitivetof

4、lakes,i.e.,forgingingots,railsteel,pipesteelandheavyplates.Incaseofhydrogendegassing,thepressureinthevacuumvesselandtheamountofstirring/circulationgasareessentialfactors.Thesolubilityofhydrogeninsteelat1mbaislowerthan1ppm[H].Inpractice,contentsoflessthan2ppm[H]areusuallyrequested.I

5、tisthereforeofimportancetokeepthemeltunderverylowpressureinordertoachievethetargetvalue.06312918152124273002468101212410InertgasFlowrate(l/min/t)DurationVacuumTreatment≤4mbarin[min]Hydrogencontent[ppm]Thefigureaboveillustratesthedecreaseinhydrogeninrelationtotimeasafunctionofdiffer

6、entspecificinertgasflowratesforVDprocess.Intensiveinertgasstirringresultsinshorttimerangesforremovalofhydrogen.Practicalexperiencehasshownthatamaximumflowrateof3~4L/(min.t)shouldbeappliedinordertoavoidpossibleslagreactionsresultinginuncontrolledfoaming.Tocompensateforsuchpossiblere

7、action,asteelfreeboardexceeding900mmwithinanewlinedladleisapreconditionforhydrogenremovalinaVDunit.Inordertoachievereasonabletreatmenttime,theamountofstirringgas,comparedwiththetreatmentforhydrogenremovalissubstantiallyhigher,resultinginasteelfreeboardexceeding1200mmwithinanewlined

8、ladle.02422201816141281022