CaF_(2)-Al_(2)O_(3)-MgO-CaO电渣重熔渣系成分与性质演变行为

Evolution of composition and property of CaF_(2)-Al_(2)O_(3)-MgO-CaO slag system for electroslag remelting

电渣重熔过程熔渣成分变化使其性质发生改变,将影响重熔工艺顺行和铸锭质量。针对CaF_(2)-Al_(2)O_(3)-MgO-CaO电渣重熔渣系,研究氟化物挥发导致的熔渣成分变化规律,分析随成分变化熔渣结晶行为及流动性质的演变规律。研究结果表明,在电渣重熔过程因氟化物挥发造成熔渣中CaF_(2)和Al_(2)O_(3)含量下降,CaO含量上升,而MgO含量基本保持不变。随熔渣成分变化,渣层中析出的CaF_(2)晶体由点状或球状变为块状或条状,MgO·Al_(2)O_(3)晶体由球状变为树枝状,作为主要析出相的铝酸钙晶体由CaO·6Al_(2)O_(3)变为CaO·2Al_(2)O_(3)并最终变为12CaO·7Al_(2)O_(3)。生产中结晶器上部的渣皮更易发生分层结晶现象,析出相中靠近熔池侧主要为CaF_(2)晶体,靠近结晶器侧主要为12CaO·7Al_(2)O_(3)晶体。本研究可为电渣重熔渣系成分优化与工艺过程控制提供借鉴和依据。

The composition change of slag during electroslag remelting(ESR)will change its properties,which will affect remelting process and ingots quality.Based on CaF_(2)-Al_(2)O_(3)-MgO-CaO slag system,the changes of slag composition caused by fluoride volatilization were studied,and the evolution of slag crystallization behavior and fluidity was analyzed.The results show that the content of CaF_(2)and Al_(2)O_(3)in the slag decreases,while the content of CaO increases due to fluoride volatilization in the process of ESR,which has little effect on MgO content.With the change of slag composition,CaF_(2)crystals precipitated in slag layer change from point or sphere to block or strip,and MgO·Al_(2)O_(3)crystals change from sphere to dendritic shape.As the main precipitated phase,calcium aluminate crystals change from CaO·6Al_(2)O_(3)to CaO·2Al_(2)O_(3)and finally to 12CaO·7Al_(2)O_(3).The slag film on upper part of the mold is more prone to delamination crystallization.In the precipitated phase of the slag film,CaF_(2)crystals are mainly on the side near the molten pool,and 12CaO·7Al_(2)O_(3)crystals are mainly on the side near the mold.This study can provide reference and basis for composition optimization and process control of electroslag remelting slag system.