Microstructure, properties, and application of low carbon Al₂O₃‐C refractories used as submerged entry nozzles

Abstract

With the aim to achieve the application of low carbon Al2O3‐C refractory as submerged entry nozzle (SEN) materials, a comprehensive study on the microstructure, thermo‐mechanical properties, as well as application performance during use in the continuous casting was carried out by comparing with the traditional one. Both hot and cold modulus of ruptures of the low carbon Al2O3‐C refractory were superior to the traditional one, and its thermal shock resistance still kept in an acceptable level. The increase in the amount of SiC whiskers and the enhancement in the sintering are considered as the strengthening mechanism. In the industrial trial, the rapid loss of graphite caused by the large level fluctuation made the traditional Al2O3‐C refractory more susceptible to flux corrosion. For the low carbon Al2O3‐C refractory, however, the dense structure and the adhesion of viscous slag layer suppressed the slag penetration. Besides, the remaining SiC phases were also difficult to be wetted and dissolved by the flux. As a consequence, a better corrosion resistance was obtained, achieving a decrease of 27.6% in the average depth of the corrosion groove after working for 8 hous.

Nanocarbon containing low carbon Al 2 O 3 –C refractories: Comparison between N220 and N990 nanocarbons

“…The formed SiO gas reacts with carbon or carbon monoxide in the system to form SiC 2,19,24,28,29,34,38 according to Equations () and (): $$\begin{equation}{\rm{Si}}{{\rm{O}}_{\left( {\rm{g}} \right)}} + {\rm{\;}}2{{\rm{C}}_{\left( {\rm{s}} \right)}}\mathop \to \limits^{ > 1200^\circ {\rm{C}}} {\rm{\;Si}}{{\rm{C}}_{\left( {\rm{s}} \right)}} + {\rm{C}}{{\rm{O}}_{\left( {\rm{g}} \right)}}\end{equation}$$ $$\begin{equation}{\rm{Si}}{{\rm{O}}_{\left( {\rm{g}} \right)}} + {\rm{\;C}}{{\rm{O}}_{\left( {\rm{g}} \right)}}\mathop \to \limits^{ > 1200^\circ {\rm{C}}} {\rm{\;Si}}{{\rm{C}}_{\left( {\rm{s}} \right)}} + {\rm{\;}}{{\rm{O}}_{2{\rm{\;}}\left( {\rm{g}} \right)}}\end{equation}$$…”

“…The formed SiO gas reacts with carbon or carbon monoxide in the system to form SiC 2,19,24,28,29,34,38 according to Equations (10) and (11):…”

Interface Wetting and Reaction Behavior between Mold Flux and Submerged Entry Nozzle under an External Electric Field

“…[4,5] During continuous casting, the lower part of the nozzle is inserted into the mold, and the refractory material outside the nozzle can be continuously corroded by the mold flux inside the mold. [6][7][8] Although ZrO 2 -C materials with good corrosion resistance have been used on the outside of nozzle as slag-line materials, the corrosion problem still exists. [6,7,9,10] This phenomenon not only limits the production efficiency of continuous casting but also brings hidden dangers to production safety.…”

Anti-ablation properties of ZrB2 modified carbon/phenolic composites in plasma wind tunnel

“…Thermal Protection System (TPS) is critical in hypersonic vehicles subjected to severe aerodynamic heating. 1,2 Low-density carbon/phenolic (C/Ph) composites have been extensively applied in the heatshield of hypersonic vehicles because of their excellent ablation resistance. 3 The thermal protection mechanism is that C/Ph composites absorb heat mainly through phenolic pyrolysis and the thermal blocking effect generated by pyrolysis gas to prevent heat transfer to the back face.…”