摘要
针对某石油套管钢管壁内缺陷,采用扫描电镜-能谱仪(SEM-EDS)分析,并结合FactSage8.0软件计算进行研究,结果表明缺陷纵向面主要由浅条纹及深条纹组成,浅条纹处存在大量MgO·Al_(2)O_(3)夹杂物,深条纹处有大量的Al_(2)O_(3)、MgO·Al_(2)O_(3)、CaO·Al_(2)O_(3)·SiO_(2)等夹杂物聚集在一起.缺陷横截面上的夹杂物主要为Ca O·Al_(2)O_(3)·SiO_(2)、CaO·Al_(2)O_(3)·MgO和CaO·Al_(2)O_(3)·MgO·SiO_(2)3类.推测钢管壁内缺陷形成机理主要为:(1)大包钢水在浇注末期钢水卷带钢包渣进入中间包钢水中,该渣滴随后吸附钢中高Al_(2)O_(3)含量的微细x Al_(2)O_(3)·y CaO或Al_(2)O_(3)夹杂物,导致渣滴中的Al_(2)O_(3)含量升高;(2)大包钢水在真空脱气(VD)精炼过程大Ar气搅拌下卷入了钢包渣,该渣滴随后吸附钢中的微细Al_(2)O_(3)夹杂物,导致渣滴中的Al_(2)O_(3)含量升高;以上两种形式形成的渣滴在凝固冷却过程中,转变为CaO·Al_(2)O_(3)·SiO_(2),CaO·Al_(2)O_(3)·MgO,CaO·Al_(2)O_(3)·SiO_(2)·MgO_(3)种类型的夹杂物.圆管坯在穿孔变形过程中,在纵向拉应力和横向切应力作用下,使卷入的大型渣滴沿纵向及横截面延伸扩展,最终形成钢管壁内的缺陷.
In this study,the defects in the wall of petroleum casing steel pipe were investigated.The morphology and composition of inclusions in the defects of the steel pipe were analyzed using scanning electron microscopy–energy-dispersive X-ray spectroscopy.The thermodynamic calculation of the Ca-Al equilibrium phase diagram of molten steel in tundish and the changes of the ladle slag phase composition with cooling temperature was performed using FactSage8.0.The results show that the longitudinal surface of the defect is mainly composed of shallow and deep stripes.A large number of MgO·Al_(2)O_(3) inclusions containing a small amount of Mn is detected at shallow stripes,and a large number of inclusions,such as Al_(2)O_(3),MgO·Al_(2)O_(3),and CaO·Al_(2)O_(3)·SiO_(2) are detected at deep stripes.The three main types of inclusions in the cross-section of the defect zone are CaO·Al_(2)O_(3)·SiO_(2),CaO·Al_(2)O_(3)·MgO,and CaO·Al_(2)O_(3)·MgO·SiO_(2).According to the analysis results of inclusions in the cross-section and the calculation results of the phase transformation of slag droplets during solidification and cooling,the formation mechanism of the defects in the wall of steel pipe can be speculated as follows:(1)At the end of pouring,the ladle slag in molten steel in the ladle enters the tundish.Further,the slag droplets adsorb the fine x Al_(2)O_(3)·y CaO or Al_(2)O_(3) inclusions with high Al_(2)O_(3) content in molten steel,increasing the Al_(2)O_(3) and CaO contents in the slag droplets.(2)Ladle slag in molten steel is subjected to strong stirring in Ar gas in the vacuum degassing(VD)refining process.Moreover,the slag droplets adsorb the fine Al_(2) O_(3) inclusions in molten steel,increasing the Al_(2) O_(3) content in the slag droplets.During solidification and cooling,the slag droplets formed in the two aforementioned forms of inclusions are transformed into three types of inclusions:Ca O·Al_(2) O_(3)·Si O_(2),Ca O·Al_(2) O_(3)·Mg O,and Ca O·Al_(2) O_(3)·Si O_(2)·Mg O.In the process of round billet piercing deformation,under the action of longitudinal tensile stress and transverse shear stress,the large slag droplets involved extend along the longitudinal crosssection and finally form defects in the wall of the steel pipe.
作者
杨文魁
杨健
宋景凌
李恒华
周旋
刘合萍
YANG Wen-kui;YANG Jian;SONG Jing-ling;LI Heng-hua;ZHOU Xuan;LIU He-ping(School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China;State Key Laboratory of Advanced Special Steel,Shanghai University,Shanghai 200444,China;Technology Center of Hunan Hengyang Valin Steel Tube Co Ltd.,Hengyang 421001,China)
出处
《工程科学学报》
EI
CSCD
北大核心
2022年第9期1566-1574,共9页
Chinese Journal of Engineering
基金
国家自然科学基金资助项目(U1960202)。
关键词
钢管
缺陷
渣的相转变
相图
钢包渣
steel pipe
defect
phase transformation of slag
phase diagram
ladle slag
