Effect of Microstructure on the Granule Strength of Hollow Granulated Mold Fluxes for Continuous Casting

During the automatic powder‐feeding process, the hollow granulated mold fluxes are easily broken due to insufficient granule strength, which leads to dust pollution and the deterioration of the properties of mold fluxes during the continuous casting. Herein, a drum‐type granule strength testing device, laser granule size analyzer, and scanning electron microscope are used to analyze the attrition mechanism of three kinds of hollow granulated mold fluxes and the effect of microstructure on the attrition mechanism. The results show that: 1) the result of the drum‐type granule strength test is in good agreement with the practical application effect of mold fluxes; 2) abrasion has dominated the breakage of three kinds of mold fluxes and the dust pollution is caused by the generation of a large number of granules with granule sizes ranging from 20 to 80 μm; 3) the uniform and dense surface film structure on the surface of mold flux effectively inhibits the abrasion and improves the granule strength of mold flux; and 4) the difference in granule size and solubility of different raw materials in the spray granulation process leads to the deposition of Na2CO3, binder, and carbon black on the surface to form the film structure.