HE Sheng-ping
,
HUANG Qing-yun
,
ZHANG Guo-xing
,
LU Yong-jian
,
WANG Qian
钢铁研究学报(英文版)
In continuous casting of peritectic steel grades sensitive to longitudinal cracking, the solidification properties of mold fluxes play an important role in keeping smooth running of continuous casting process and achieving high surface quality of casting strands. To reduce fluorine pollution in molten slag, types of CaO-SiO2-TiO2 (CTS) based mold fluxes were investigated. The solidification and crystallization properties, including viscosity η at 1573 K, break temperature Tbr, crystallization ratio Rc and solidification mineragraphy were measured, which were compared with those of CaO-SiO2-CaF2 based mold fluxes. The experiments show that there are unstable viscosity-high temperature properties and high Tbr in part of CTS slag system, which are bad for lubrication between liquid flux film and strand. And when temperature is below Tbr, the viscosities change slowly during cooling in some part of this slag system, which imply that liquid mold fluxes solidify slowly and it is easy to cause surface longitudinal cracks on strand. Major mineragraphy of the CaO-SiO2-TiO2 based mold fluxes are CaO·TiO2 or CaO·TiO2 and CaO·SiO2·TiO2. TiN and Ti(C,N) can be formed in mold fluxes bearing high TiO2 during the continuous casting.
关键词:
mold flux
,
solidification property
,
peritectic steel
,
mineragraphy
LONG Xiao
,
HE Sheng-ping
,
XU Jian-fei
,
HUO Xu-ling
,
WANG Qian
钢铁研究学报(英文版)
In high speed continuous casting of peritectic steel slabs, mold fluxes with high basicity are required for less surface defect product. However, the basicity of remaining liquid slag film tends to decrease in casting process because of the crystallization of 3CaO·2SiO2·CaF2. Thus, a way is put forward to improve mold fluxes′ properties by raising the original basicity. In order to confirm the possibility of this method, the effect of rising original basicity on the properties of mold fluxes is discussed. Properties of high fluorine based mold fluxes with different basicities and contents of CaF2, Na2O, and MgO were measured, respectively. Then, properties of higher basicity mold fluxes were discussed and compared with traditional ones. The results show that increasing the basicity index can improve the melting and flow property of mold fluxes. With the increasing basicity, crystallization rate of mold fluxes increases obviously and crystallization temperature tends to decrease when the basicity exceeds 1.35. The method presented before is proved as a potential way to resolve the contradiction between horizontal heat transfer controlling and solidified shell lubricating for peritectic steel slab casting. But further study on improving the flow property of liquid slag is needed. This work can be used to guide mold fluxes design for high speed continuous casting of peritectic steel slabs.
关键词:
mold flux
,
high basicity
,
crystallization property
,
peritectic steel
青雪梅，谢兵，刁江，王水波
钢铁研究学报
运用热线法测试了不同碱度(11、13)，不同TiO2含量(0~8%，质量分数，下同)的连铸保护渣在不同温度下(400~1300℃)的热传导系数，并结合DSC和XRD分析结果，探讨了碱度和TiO2含量对保护渣导热性能的影响规律及原因。结果表明：本试验条件下液态渣(1200~1300℃)的导热系数为027~05W/(m·K)，固态渣(400~1000℃)的导热系数远大于液态渣，为153~209W/(m·K)。在800℃以下的低温区域，试样的导热系数随着碱度的增加而增加，1100℃以上的高温区域，导热系数随着碱度的增加而减小。TiO2的加入抑制了渣中枪晶石晶体的析出，促进了钙长石、钙钛矿生成，削弱了试样的导热能力；随着TiO2含量的增加，试样的导热系数近似线性减小，TiO2含量每增加2%，试样的导热系数减小约5%。
关键词:
保护渣
,
lattice conductivity
,
TiO2
