Research On The Mold Flux Of Continuous Casting For Non-Newtonian Fluid

The traditional mold flux has the characteristics of Newton fluid whose viscosity tends to be a constant value.In order to meet the demand on the characteristics of mold flux for high speed casting production,it is necessary to develop a new kind of mold flux with shear thinning property,which viscosity is relatively high at low shear rates and relatively low at high shear rates.After adding different content of B₂O₃ or Si₃N₄ to the CaO-SiO₂-CaF₂ system mold flux,the mold flux had the characteristics of Non-Newtonian fluid.The thermodynamic analysis of NonNewtonian fluid mold flux was carried out by using Fact Sage thermodynamic software.The optimal reaction and reaction temperature were established,the main mineral phases formed in the mold flux were analyzed.Meanwhile,the rotational viscometer was used to determine whether the mold flux had the shear thinning property or not.The result showed that,compared with the traditional mold flux,the shear thinning property of CaO-SiO₂-CaF₂-B₂O₃ or CaO-SiO₂-CaF₂-Si₃N₄ system NonNewtonian fluid mold flux was strong.With the increasing of the content of additives in the mold flux,the shear thinning property of the mold flux increased at the very beginning and then decreased.As a result,when the concent of B₂O₃ was 9.71 % or the concent of Si₃N₄ was 0.83 %,the shear thinning property of the mold flux was the strongest.At the same time,the microstructure of the new type of mold flux under different composition was studied by Raman spectroscopy,XPS and infrared spectrum.The mechanism of shear thinning property was clarified.The study found that the intensity of shear thinning property of NonNewtonian fluid mold flux was positively correlated with the size of the degree of polymerization in a certain range,and the mechanism of the shear thinning property was a kind of temporary viscosity loss because of the application of one direction shear stress.Finally,the Non-Newtonian fluid mold flux was used for laboratory throwing trials,the experimental results showed that,under the action of this kind of mold flux,the phenomenon of slag entrapment and steel leakage has been reduced,which laid a good foundation for the study of NonNewtonian fluid mold flux in the future.