Microstructure Change and Primary Slag Melting of Sinter in the Cohesive Zone of a Blast Furnace

Softening, Melting, and Permeation Phenomena of CaO–FeO–SiO₂ Oxide on a Coke Bed

“…9,10) The softening and liquidus temperatures are relatively similar under an atmosphere with a higher oxygen partial pressure, therefore, it is possible that equilibrium can be achieved at a faster rate under an atmosphere with a high oxygen partial pressure.…”

“…6,7) Since, the softening, melting, and dripping of ore are comprehensively evaluated during the softening test under loading, it was not possible to clarify each phenomenon and their causal relationships. In order to reduce the thickness of the cohesive zone, researchers have proposed to increase the liquid phase formation temperature of the ore. 9,10) However, the studies that have been conducted on the high temperature softening and low temperature dripping of iron ore are insufficient. It is important to clarify the effect of the ore composition, reduction ratio, and atmosphere on the softening, melting, and dripping temperatures in order to design the iron ore and to control both the burden charging and the blast gas.…”

“…9) The contact angle of the CaO-SiO 2 -Al 2 O 3 -MgO melt on carbonaceous material varies significantly from 40 to 160° depending on the presence of ash in the coke and the concentration of FeO in the oxide. At 1 500°C, the contact angle of the CaO-SiO 2 -Al 2 O 3 -MgO-FeO melt decreases from 125 to 105° in approximately 300 s.…”

Role of MgO in Sinter from Perspective of MgO Distribution between Liquid and Magnetite Phases in FeO_x–CaO–SiO₂–MgO System

“…In the cohesive zone of a blast furnace, the olivine-like melt is primarily formed around 1 373 K, 25) and then, the melt volume increases owing to the two eutectic reactions of the olivine-wüstite-C 2 S pseudo-ternary system in the range 1 493-1 503 K and the C 2 S-wüstite-gehlenite(2CaO·Al 2 O 3 · SiO 2 ) pseudo-ternary system above 1 487 K. 5,25) In these reactions, wüstite and silicate produce the slag melt and increase the melt volume, which decreases the gas permeability. There are two proposals to avoid such a situation: one is to improve the reducibility of sinters to metallic iron so as to decrease the amount of residual wüstite in reduced sinters, and the other is to dissolve MgO into magnetite in sinters to form magnetio-ferrite.…”

Effects of 2CaO∙SiO₂ and 2CaO∙Al₂O₃∙SiO₂ on Primary Slag Melting of Sinters in the Cohesive Zone of a Blast Furnace

“…With respect to the primary slag melting, the authors have concluded from the microstructure observation as well as the phase diagram that the olivine-like slag melts are locally formed as the primary melts around 1 100-1 120°C, 9) and have also found that when the olivine-like slag melts are adjacent to 2CaO•SiO 2 (hereinafter denoted as C2S), the olivine-like slag melts could be dissolved into C2S as a solid solution, resulting in the decrement in the slag melt volume. 9) On the other hand, with respect to the behavior of Al 2 O 3 , the authors have suggested that Al 2 O 3 , which is mostly included in columnar calcium ferrite in sinters, goes into the C2S slags surrounding the columnar calciowüstite at temperatures lower than 1 000°C, and C2S is partly changed to 2CaO•Al 2 O 3 •SiO 2 (hereinafter denoted as C2AS) at tem-peratures higher than 1 200°C.…”