Study The Effect Of Mold Slag Film Structure On Heat Transfer

Mold powder play an important role in increasing casting speed, stabilizing continuous casting process,expanding steel grades,improving the quality of products and enhancing the output of products. Among the five metallurgical functions of mold powder, controlling the heat transfer and lubrication during continuous casting process is significant for increasing casting speed and expanding steel grade. However, until now, there hasn't been the unitive criterion for evaluating the properties of mold powder heat transfer and quantitative basis, which lacks systemic theoretic guidance. Practice has shows that heat transfer of mold flux is relates to the slag film structure, especially the crystallization property and surface roughness. Therefore,in order to control the heat transfer of mold flux, based on the heat flux been measured, the paper mainly analyzed the reasons for heat transfer with slag film structure.Supported by the National Natural Science Foundation of China, Firstly, the heat flux and slag film were achieved by the homemade equipment named HF-200 Heat Flux Simulator of Mold Slag Film, and the crystal types, morphology, size, and heat flux were compared, which shows that they are in good agreement with each other except crystal size and the value of heat flux. Therefore, as a fundamental research, the study method is feasible to simulate for plant. Secondly, the slag system of CaO-SiO₂-CaF₂-Na₂O and CaO-SiO₂-CaF₂-Na₂O-Al₂O₃ were studied in the paper, and the relations between heat transfer and slag film structures, such as thickness, surface roughness, crystal phase, grain morphology and size etc were researched by square calliper,surface coarseness profiting instrument,mineralographic microscope,X-ray diffraction instrument and scanning electron microscope respectively. The study showed that the heat flux was mainly influenced by surface roughness that is relates to crystalline ratio and grain size for crystalline slag film, and with surface roughness increasing, the heat flux decreases. The surface roughness of glassy slag film is mainly influenced by characteristics of solidification and contraction. The relations between the basicity, content of [F^-], Na₂O, trace component of Li₂O, MnO, B₂O₃, MgO and slag film structure and heat transfer were acquired respectively.In a word, the research method can reflect the heat transfer characteristics of mold powder well, and the conclusions can provide the theoretical basis for collocating the mold powders,and the heat transfer can be controlled by improving the slag film structure .