Mg-Al-Ti系氧化物冶金工艺夹杂物控制的热力学分析

Thermodynamic analysis of inclusion control in Mg-Al-Ti system oxide metallurgy technology

开展低铝含量海工钢氧化物冶金研究,扩大海工钢成分调整范围,促进诱导针状铁素体形核的有效夹杂物生成,对改善大线能量焊接热影响区韧性具有重要应用潜力。以EH420钢为研究对象,利用FactSage热力学软件,进行钢液-夹杂物平衡热力学计算,系统分析了Mg-Al-Ti脱氧体系与氧含量耦合变化对钢中夹杂物析出类型、析出条件、析出量的影响,并设计试验进行验证,为实际大线能量焊接用EH420海工钢的目标夹杂物控制提供理论指导。结果表明,控制钢中Mg、Al、Ti含量分别在0.0020%水平、0.0080%~0.010%、0.010%~0.020%时,当T.O.含量在0.0030%水平,析出Mg-Al-Ti-O复合夹杂物+MgO夹杂物;当T.O.含量在0.0060%水平时,单独析出Mg-Al-Ti-O复合夹杂物。

The oxide metallurgy technology with the low aluminum condition is carried out in marine steel and further expands the adjustment range of alloy compositions,which is beneficial to promote the effective inclusion of inducing acicular ferrite.This research has a significant potential application to improve the toughness of heat-affected zones in high-heat input welding.Thermodynamic equilibrium calculations between liquid steel and inclusion are based on EH420 steel using FactSage software.The effects of coupling changes of the Mg-Al-Ti deoxidation system and oxygen content on the types,conditions,and amounts of inclusions precipitated in steel were systematically analyzed.Equilibrium experiments are designed to confirm the validity of thermodynamic calculations.This study provides theoretical guidance to control inclusion in high heat input welding for EH420 marine steel.The results recommended controlling the Mg,Al,and Ti in steel are 0.0020%,0.0080%~0.010%,and 0.010%~0.020%,respectively.On this basis,Mg-Al-Ti-O composite inclusion+MgO inclusion are formed when the content of T.O.is 0.0030%.The composite inclusion of Mg-Al-Ti-O is formed separately,with the T.O.content at 0.0060%.