Study On Interfacial Properties Of Mold Fluxes For High Aluminum Silicon Steel

High aluminum silicon steel is widely used as an electrical steel,which has high aluminum,high silicon,ultra-low carbon characteristics.Research at home and abroad shows that the key problem in the continuous casting of high alumina silicon steels is that the reaction between the the flux(SiO2)and the [Al] in the molten steel at the interface which leads to changes in the composition of the flux and the molten steel.Basicity of mold flux increases,and a large amount of Al2O3 is formed into the mold powder at the same time,which makes the physical and chemical properties of the mold flux and the metallurgical function change greatly.In particular,the surface(interfacial)tension sudden changes,resulting in wettability of slab by flux unstable.Hook formation and flux entrapment which common in the process of continuous casting of ultra low carbon steel are controlled by the wettability of steel by flux.In this paper,it has explored that the relationship between the interfacial properties of slag and the change of slag composition in during high aluminum silicon steel continuous casting,in order to provide theoretical guidance for the selection of high aluminum silicon steel flux composition.However,the current mesurement method of interfacial properties of flux such as sessile drop method can not meet the needs of systematic research.Those nethods have complex operation and waste time,so it is necessary to establish a new mesurement method of interfacial properties and to determine the new characterization method.In the paper it establish two new mesurement methods of interfacial properties by using Confocal Laser Scanning Microscope(CLSM)and DHTT.The change of interfacial properties during CaO-SiO2 based flux conversion to CaO-SiO2-Al2O3 based flux was studied based on the establishment of characterization method of the wettability of steel by flux.The results of the paper are as follows:?The research method of the interfacial properties of mold flux was determined.The contact angle between slag and steel measurement method based on CLSM method and DHTT method was developed.By comparing of measured contact angle between CLSM method,seat drop method and other researches,the result indicates that CLSM method and DHTT method can accurately measure contact angle between solid steel and molten slag,and the deviation value is in the range of 0°-2°.Spreading coefficient S characterize the wettability of solid steel by molten flux,the greater spreadingcoefficient,the greater wettability of solid steel by molten flux.The calculation of S requires the surface tension of flux and the contact angle data between slag and steel.?The wettability of solid steel by molten high aluminum silicon steel flux was studied by CLSM method.There are the following conclusions: With he increase of temperature the contact angle of the slag on the steel substrate decrease,the spreading coefficient increases,and the wettability of slag steel increases.The increase in particle spacing caused by the increase in temperature plays a decisive role in the wettability of solid steel by molten slag.The increase of CaO/SiO2 ratio To wettability play a hindrance.With the increase of CaO/SiO2 ratio,the O2-depolymerized silica tetrahedron,with formation of simple structure,higher electrostatic potential anionic group.It cause the increasing of surface tension and decreasing of wettability.With the increase ofAl2O3/SiO2 ratio,the spreading coefficient decreases,slag and steel are easier to separate.The reason is part of the Al instead of Si involved in the formation of the network structure,while the other part of Al in the form of Al3+ exist in the slag.The interaction between Al3+and the anions of the surface is larger.The wettability increased slightly,but not obvious while F-instead of Na2 O.It is speculation that,on the one hand,,although the electrostatic potential of F-is less than O2-,part of the F-participate in the coordination of Al to form [AlO3F];on the other hand,the electrostatic potential of Na+is lower,and the decrease of the content of Na+ has an negative effect on the wettability.