Study of Low Flow Rate Ladle Bottom Gas Stirring Using Triaxial Vibration Signals
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UCTION
THE steel melt poured to continuous casting operations should maintain a minimum temperature and chemical composition stratification as well as have its impurities absorbed thoroughly to improve the quality of the final product. This is achieved by stirring molten steel by a pressurized argon gas in ladles. Low gas flow rates are intended to rinse the steel and attain thermal or chemical homogenization, while intense stirring is often practiced to facilitate slag-metal reactions.[1–3] Hence, monitoring the status of the stirring is important in attaining the desired quality as well as in optimizing argon gas consumption. Leaks in the argon supply system, variable back pressure because of variable plug conditions, and resistance to flow are some of the difficulties facing ladle operators in precisely evaluating stirring status at low volumetric gas flow rates.[2,4] Efforts are under way
JAEFER YENUS, GEOFFREY BROOKS, and MICHELLE DUNN are with the Swinburne University of Technology, Hawthorn, VIC 3122, Australia. Contact e-mail: [email protected] ZUSHU LI is with the University of Warwick, Coventry CV4 7AL, UK. TIM GOODWIN is with the Tata Steel, Rotherham S60 1DW, UK. Manuscript submitted April 28, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
to detect ladle wall vibration due to gas injection to explain the level of agitation inside.[5–16] Mucciardi[17] used an accelerometer to measure ladle vibration due to stirring to correlate the mixing power and vibration signal. He reported that an accelerometer is a viable transducer for controlling the interaction between liquids and gases when direct contact with the liquid phase is not practical. Minion et al.[7] developed a vibration signal-based monitoring technique for ladle stirring. Kemeny et al. developed commercial sensors based on ladle vibration to predict the degree of stirring.[8] A vibration-based control system (TruStir) developed by Nupro Corporation was implemented in various steel plants, such as Hadeed[14] and Dongbu.[16] It was reported that the monitoring system improved steel cleanliness and reduced argon consumption.[14] Others, such as Burty et al.,[9–11] Yuriy et al.,[12] and Kostetskii et al.,[18] measured vibration, sound, or ladle eye size both on industrial and laboratory scales to characterize the stirring process. Xu et al. used a different approach by combining the vibration, bubbling sound, and ladle eye size to find the latent variable to predict the stirring power.[4] However, detecting the stirring status at low flow rates as well as the effect of sensor location is not fully understood. The authors of this article previously studied bottom gas stirring at different flow rate ranges in a plastic-walled water model using triaxial vibration. They discovered specific informative frequency ranges that correspond to each flow rate range. They also
investigated the effect of accelerometer location on the vessel external wall. They reported that sensor location does not change the amount of the information but does influence the location of the f
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