摘要
以Cr5大型锻钢轧辊探伤缺陷为研究背景,通过对轧辊探伤不合缺陷部位进行解剖取样,利用扫描电镜(SEM)和能谱仪(EDS)确定探伤缺陷类型,并对合金炉→LF→VD→VC冶金过程进行跟踪取样溯源,分析冶金过程中夹杂物成分、形貌以及尺寸的变化,并结合FactSgae 8.1软件对导致探伤不合缺陷的形成机理进行了理论计算。研究结果表明,Cr5锻钢轧辊探伤不合格的缺陷主要由呈线性聚集的SiO_(2)-MnO-Al_(2)O_(3)大尺寸夹杂物组成,单个夹杂物尺寸可达200μm,缺陷夹杂物成分与浇注前SiO_(2)-MnO-Al_(2)O_(3)夹杂物的成分一致。在合金炉出钢前发现大量的SiO_(2)-MnO-Al_(2)O_(3)型夹杂物,在LF精炼过程中没有得到完全去除,而VD过程大搅拌条件下进一步使得SiO_(2)-MnO-Al_(2)O_(3)大颗粒夹杂物卷入钢液。因SiO_(2)-MnO-Al_(2)O_(3)夹杂物与钢液的接触角过小,与钢液具有良好的润湿性,精炼过程中不易上浮去除,凝固过程中聚集并残留于钢锭中形成聚集性的大颗粒夹杂物区域而导致锻钢轧辊探伤不合。热力学计算表明,在Cr5轧辊目标成分下,当钢液铝质量分数为0.003%以下且氧质量分数为0.015%以上时,SiO_(2)-MnO-Al_(2)O_(3)液态夹杂物稳定存在;随着铝含量不断上升,SiO_(2)-MnO-Al_(2)O_(3)液态夹杂物相区稳定存在所需的溶解氧含量不断升高;当钢液的铝质量分数达到0.023%以上,液态夹杂物完全消失。在实际生产过程中将合金炉出钢前及在后续工序中钢液的铝质量分数控制为0.023%以上可使SiO_(2)-MnO-Al_(2)O_(3)液态夹杂物改性为Al_(2)O_(3)或富含Al_(2)O_(3)的夹杂物,易于上浮、吸收并去除,有效减少了Cr5锻钢轧辊的废损率。
Based on ultrasonic flaw detection on the large forged Cr5back-up roll during manufacturing process,the flaw detection was analyzed by anatomical sampling,IF→LF→VD→VC smelting process of forged roll was traced and sampled,defects type on the forged roll and source of the whole smelting process was determined by scanning electron microscope(SEM)and energy dispersive x-ray spectroscopy(EDS).Combined with FactSgae 8.1software,the formation mechanism and control of flaws leading to the ultrasonic flaw detection were calculated theoretically.The research results show that the defects leading to the incompatibility of flaw detection are linearly aggregated SiO_(2)-MnO-Al_(2)O_(3)large-size inclusions,the size of single particle can reach 200μm,the compositions of inclusion of flaws are consistent with the inclusions before pouring of vacuum casting(VC).A large amount of SiO_(2)-MnO-Al_(2)O_(3)inclusions are found before the tapping of IF and still a few remained at the end of LF process,while large SiO_(2)-MnO-Al_(2)O_(3)inclusions are entrapped to the roll melt during VD process under large stirring conditions.SiO_(2)-MnOAl_(2)O_(3)inclusions with a low contact angle can be well wetted by the liquid steel,it is difficult to float and remove from the liquid steel during the LF refining process.The inclusions are aggregated and remained during the solidification process to form the area of large inclusions and lead to ultrasonic flaw detection after forging eventually.Thermodynamic calculations show that SiO_(2)-MnO-Al_(2)O_(3)liquid inclusions will be stable with the steel composition containing mass fraction of Al below 0.003%and O above 0.015%,and SiO_(2)-MnO-Al_(2)O_(3)liquid inclusions are stable with a higher O content with increasing of Al content in liquid steel.SiO_(2)-MnO-Al_(2)O_(3)phase stable field will disappear with Al increasing to 0.023%in the liquid steel.Before the tapping of IF and in the subsequent processes,controlling the Al mass fraction in the liquid steel above 0.023%can effectively modi
作者
张威风
石如星
张延玲
王冠博
成国光
王鹏飞
ZHANG Wei-feng;SHI Ru-xing;ZHANG Yan-ling;WANG Guan-bo;CHENG Guo-guang;WANG Peng-fei(State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing,Beijing 100083,China;Research Institute of Casting and Forging,Luoyang CITIC HIC Casting and Forging Co.,Ltd.,Luoyang 471039,Henan,China)
出处
《钢铁》
CAS
CSCD
北大核心
2022年第6期91-99,共9页
Iron and Steel
