Study On The Castability Of Low-Carbon And Low-Silicon Steel

In smelting low-carbon and low silicon steel, aluminum is used to deoxidize, but it will bring much influence on fluidity and casting of molten steel during continuous casting. If deoxidant is not enough, the strand will generate subsurface pinhole and surface defect, while if it is added to much, the viscidity of molten steel will increase, its fluidity become serious and it will produce much Al2O3, which is a kind of high-melting point inclusion. Usually Al2O3 is easy to make the nozzle clogging, influence casting process and result in more inclusions in strand as well. Therefore, the key of producing low carbon and low silicon steel between converter and continuous casting is how to control oxidation of molten steel to prevent nozzle clogging.In order to solve the practical problem of nozzle clogging and provide theory reference to promote the level of casting for producing 12LW steel in Chongqing Steel Steelmaking Plant, the influence of process conditions on nozzle clogging was investigated, and the focus is to analyze the formation mechanism of nozzle clogging.The result of study shows that the main origin of nozzle clogs is Al2O3,SiO2 and sulfuret, most of which are less than 50μm, especially between 5μm to 10μm. The main component of the nozzle clogs is Al2O3 inclusions. It also includes some other component, such as SiO2, CaO and Fe2O3. Meanwhile, the research finds that Al, Ca, C and Zr in clogging thing distribute with a rule, which shows that the transfer of inclusions from molten steel to refractory is a course of conglutination and collecting. So, improving the cleanliness of molten steel by removing or reducing the inclusions can be effective to control the quantity of solid inclusions in steel and reduce the problem of nozzle clogging. Also, through the survey and trial, it is found that the period of hard blowing in Ar blowing station nearly 2 min., the period of soft blowing more than 5min and the flow rate of soft blowing between 12-13m3/h can effectively remove the oxide inclusions. What's more, the analysis of deoxidation shows that the content of [O] in tundish between 20-30ppm and the content of [O] after Ar blowing between 20-40ppm is in favor of controlling subsurface pinhole and preventing nozzle clogging during the casting.