亚包晶钢板坯连铸保护渣凝固结晶行为的研究

对≤1.3 m/min常规拉速(TCaO/SiO₂=1.19)和≥1.5 m/min高拉速(TCaO/SiO₂=1.40)0.07～0.10C亚包晶钢板坯用两种保护渣(%:2.54～3.0Al₂O₃、7.34～8.35Na₂O、8.83～8.87F、0.79～3.00Li₂O)降温凝固过程中结晶特性以及结晶对熔渣粘度的影响进行了研究,得出高拉速保护渣在凝固之前有明显的结晶行为,结晶矿相主要为枪晶石(3CaO·2SiO2·CaF₂);常规拉速保护渣在凝固温度以上时,没有明显的结晶现象。与常规拉速保护渣相比,高拉速保护渣完全凝固后晶粒粗大,组织中有大量空隙,有利于增加渣膜热阻,减缓结晶器传热。TCaO/SiO₂=1.40保护渣在结晶温度以上时,具有较低的粘度,有利于结晶器润滑;结晶温度以下时,粘度迅速增加,有利于增加固渣膜厚度,减缓结晶器传热。

A Study on Solidifying Crystallization Behavior of Mold Flux for Hypoperitectic Steel Slab Casting

Crystallization characteristics of two mold fluxes (%:2.54～3.0Al203 、7.34~8.35Na₂0 、8.83～8.87F、 0.79~3.00Li₂O)during temperature decreasing and solidifying process for≤1.3 m/min normal speed casting (mold powder  TCaO/SiO₂=1. 19)and≥1.5m/min high speed casting (mold powder TCaO/SiO₂=1.40) of 0.07～0. 10C hypoperitectic steel and effect of crystallization on viscosity of fluxes have been studied. It was obtained that above solidification temperature there was obvious crystallization behavior for high-speed casting flux and the main crystal phase was cuspidine (3CaO ·2SiO₂ ·CaF₂); but above solidification temperature there was no obvious crystallization phenomenon in normal speed casting flux. Compared with normal speed casting flux, after completed solidification the grain in high-speed   casting flux was larger with a lot of gaps between grains being favorable to increase heat resistance of flux film and decrease heat transfer in mold. Above crystallization temperature, the TCaO/SiO₂=1.40 high speed casting flux had lower viscosity being available to lubricate the mold, and below crystallization temperature, its viscosity rapidly increased being favorable   to increase the thickness of solid film and slow down mold heat transfer.