Industrial mould slags for continuous casting of stainless steel – analysis of the crystallisation behaviour using the Single Hot Thermocouple Technique
During continuous casting the liquid slag infiltrates into the gap between the solidified strand and the mould generating a thin slag film. Due to the high temperature gradient the slag solidifies partially and remains partially liquid on the hot side. In the solid films taken in the tail-out phase at the end of the cast the cuspidine as the crystalline phase in the most part of the square section was detected. The crystalline phase in the slag film is formed partially during the solidification and partially via the devitrification process from solid phase and undergo changes with time. It is known that the solid film adhere at the mould wall with residence times of up to several hours. The crystallization of the solid layer affects the heat flux from the liquid steel into the mould cooling water and it affects the rate and uniformity of the steel shell solidification. The understanding and the control of the crystallization phenomena in the solid layer is important to be able to obtain desired cooling regime for different steel grades during a cast. In the collaborative work between Freiberg University of Mining and Technology, Germany, and Outokumpu Tornio Works, Finland, the crystallisation of complex industrial mould slags (CaO-SiO2-Na2O-Al2O3-Fe2O3-MgO-CaF2(-MnO-K2O-Li2O-TiO2)) used in the continuous casting of austenitic and ferritic stainless steels were investigated using the Single Hot Thermocouple Technique (SHTT) as well as heat flux measurement in the industrial process. With the SHTT technique time-temperature-transformation diagrams (TTT diagrams) were developed for various industrial slags, investigating the kinetics of crystallisation after quenching to different temperatures and isothermal holding. The solidification behaviour was observed in situ with cooling rates up to 3000 °C/min. In industrial experiments the local heat flux during casting was recorded with thermocouples installed in the mould wall. At the beginning of cast the liquid mould flux solidifies quickly against the mould wall forming a glassy solid layer. While casting the decrease of heat flux can be detected at the thermocouples and from mould cooling water. Recorded data from continuous casting machine is compared with the results achieved with the SHTT experiments.
stainless steel mould powders hot thermocouple technique continuous casting
Marko Petajajarvi Jeferson L. Klug Paavo Hooli Hans P. Heller Piotr R. Scheller
Outokumpu Tornio Works, Finland Federal University of Rio Grande do Sul, Brazil Freiberg University of Mining and Technology, German Freiberg University of Mining and Technology, Germany
国际会议
Ninth International Conference on Molten Slags,Fluxes and Salts(第九届国际熔渣、溶剂与熔盐学术会议 MOLTEN12)
北京
英文
1-12
2012-05-27（万方平台首次上网日期，不代表论文的发表时间）