摘要
S45C钢是一种含铝含硫钢,被广泛应用于高负荷机械零件的制造中。国内某钢厂在用电弧炉(electric arc furnace,EAF)-精炼炉(ladle furnace,LF)-真空脱气炉(vacuum degassing,VD)-连铸(continuous casting,CC)工艺生产该钢种过程中经常出现水口结瘤和轧材探伤不合格问题,影响生产顺行和用户评价,前期探明主要与钢中夹杂物有关。为了深入了解S45C钢的夹杂物特性及演变规律,以优化生产工艺,采用全流程系统取样,并结合夹杂物自动分析扫描与热力学计算等手段开展了系列研究。结果表明,LF进站时钢中夹杂物以Al_(2)O_(3)为主,LF终点时逐渐演变为CaO-MgO-Al_(2)O_(3);VD破空和吊包时夹杂物主要为CaO-MgO-Al_(2)O_(3)-CaS,而在中间包中部分夹杂物演变为CaO-Al_(2)O_(3)-CaS。铸坯中夹杂物类型复杂,主要为Al_(2)O_(3)-CaS、MgO-Al_(2)O_(3)-CaS、CaO-MgO-Al_(2)O_(3)-CaS、CaO-Al_(2)O_(3)-CaS以及CaS,还有少量的Al_(2)O_(3)、MgO·Al_(2)O_(3)和TiN,在过程样中检测到的CaO-MgO-Al_(2)O_(3)在铸坯样中几乎不存在。统计了铸坯内弧1/4处、1/2处、中心、外弧1/4处的夹杂物数量和尺寸,结果表明,内弧1/4和外弧1/4处的夹杂物数密度分别为12.3个/mm^(2) 和12.9个/mm^(2) ,尺寸大多为1~2μm。而内弧1/2和中心处夹杂物数密度分别为15.1个/mm^(2) 和14.6个/mm^(2) ,尺寸大多为2~5μm,个别不小于5μm。利用FactSage 8.3热力学软件计算分析了S45C钢中夹杂物的形成原因,结果表明,随着钢中硫含量增加、氧含量和温度降低,CaS更容易形成,因此铸坯中出现了大量的CaS类夹杂;为抑制MgO·Al_(2)O_(3)和CaS夹杂生成可能造成的水口结瘤和DS类夹杂物超标问题,可将钢中总氧质量分数控制为0.0018%~0.0026%。此外,计算了钢液冷却过程中夹杂物的相转变和成分变化。
S45C steel,an Al-and S-containing steel,is widely used in the manufacturing of high-load mechanical components.A domestic steel mill frequently encountered issues such as nozzle clogging and ultrasonic testing failures in rolled products during the production of this steel using the electric arc furnace(EAF)-ladle furnace(LF)-vacuum degassing(VD)-continuous casting(CC)process,which disrupted production efficiency and customer satisfaction.These issues are typically associated with inclusions in the steel.To gain an in-depth understanding of the characteristics and evolution of inclusions in this steel and to optimize the production process,industrial sampling throughout the whole process was conducted.The samples were analyzed using automatic inclusion analysis and scanning,combined with thermodynamic calculations.The results show that inclusions in steel at the LF station entry are primarily Al_(2)O_(3),which evolves into CaO-MgO-Al_(2)O_(3) by the LF endpoint.During VD vacuum breaking and ladle transfer,the dominant inclusions are CaO-MgO-Al_(2)O_(3)-CaS.In the tundish,inclusions consists mainly of CaO-Al_(2)O_(3)-CaS.In the billet,the primary inclusion types are Al_(2)O_(3)-CaS,MgO-Al_(2)O_(3)-CaS,CaO-MgO-Al_(2)O_(3)-CaS,CaO-Al_(2)O_(3)-CaS and CaS,along with minor amounts of Al_(2)O_(3),MgO·Al_(2)O_(3),and TiN.Notably,CaO-MgO-Al_(2)O_(3) inclusions detected in intermediate process samples are nearly absent in the billet.A statistical analysis of inclusion quantity and size distribution was conducted at the 1/4 inner arc,1/2 inner arc,centerline,and 1/4 outer arc positions of the billet.The results demonstrates that the inclusion number densities at the 1/4 inner arc and 1/4 outer arc positions reach 12.3/mm^(2) and 12.9/mm^(2) respectively,with the majority of inclusion sizes distribute within the range of 1-2μm.The inclusion number densities at the 1/2 inner arc and centerline positions are measured as 15.1/mm^(2) and 14.6/mm^(2) respectively,with particle sizes predominantly distribute in the 2-5μm,while a small fraction of inclusions exceeds 5μm in size.Thermodynamic calculations using FactSage 8.3 elucidated the formation mechanisms of inclusions in the steel.The results indicate that increasing sulfur content,decreasing oxygen content and lowering temperature in the steel promote CaS formation.To alleviate issues such as nozzle clogging and DS inclusions caused by MgO·Al_(2)O_(3)and CaS inclusions,the total oxygen in steel can be controlled at 0.0018%-0.0026%.Additionally,phase transformations and compositional changes of inclusions during steel solidification were theoretically analyzed.
作者
陈依盛
周垚
唐海燕
王凯民
张明军
CHEN Yisheng;ZHOU Yao;TANG Haiyan;WANG Kaimin;ZHANG Mingjun(School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China;Baoshan Iron and Steel Co.,Ltd.,Shanghai 200941,China)
出处
《钢铁》
北大核心
2025年第10期92-102,共11页
Iron and Steel
关键词
含铝含硫钢
S45C钢
夹杂物特性
热力学计算
凝固
演变机理
钙处理
DS类夹杂物
Al-and S-containing steel
S45C steel
inclusion characteristics
thermodynamic calculation
solidification
evolution mechanism
Ca treatment
DS inclusions
