稀土Ce对钎具钢中夹杂物的改质机理研究
作者简介 黄 宇,男,1992年生,博士
收稿日期: 2018-03-05
网络出版日期: 2018-06-07
基金资助
国家自然科学基金项目No.51674024
Modification Mechanism of Cerium on the Inclusions in Drill Steel
Received date: 2018-03-05
Online published: 2018-06-07
Supported by
Supported by National Natural Science Foundation of China (No.51674024)
通过向钎具钢中加入稀土Ce元素,研究了Ce对钎具钢中镁铝尖晶石和硫化物的改质过程和改质机理。结合SEM和EDS对钢中夹杂物的形貌、组成、数量和尺寸进行分析,采用Thermo-Calc和Factsage 6.3热力学软件对Ce改质尖晶石和硫化物的改质机理以及钢中合适Ce的质量分数进行理论计算。结果表明,稀土Ce对Al2O3、MgAl2O4和(Ca, Mn)S都具有很好的改质效果。无Ce添加时,钎具钢中夹杂物以MgAl2O4和(Ca, Mn)S为主;当钎具钢中的稀土含量为0.0078%时,MgAl2O4被改质为Ce-O,(Ca, Mn)S被改质为Ce-S,同时还存在一定量的Ce-O和MgO共生相,钢中夹杂物的尺寸减小。热力学计算结果表明,钢中不同的Ce含量对应不同的稀土夹杂物(CeAlO3、Ce-O)类型。稀土Ce对MgAl2O4的改质顺序为：MgAl2O4→CeAlO3+MgO→Ce2O3+MgO→Ce2O3,Factsage 6.3的理论计算结果与实验观察基本吻合。
黄宇 , 成国光 , 谢有 . 稀土Ce对钎具钢中夹杂物的改质机理研究[J]. 金属学报, 2018 , 54(9) : 1253 -1261 . DOI: 10.11900/0412.1961.2018.00079
Fatigue fracture is the main failure forms of drill steel, and the hard oxide with large size is one of the main reasons for the fatigue fracture of drill steel. Therefore, the miniaturization and softening of inclusion can effectively improve the anti-fatigue performance of drill steel and prolong its service life. Rare earth elements have very good affinity with oxygen and sulfur in molten steel, and the hardness of resulting rare earth compounds is very low. In this work, the rare earth element cerium was added into drill steel to investigate the effect of Ce on the MgAl2O4 and sulfides. The composition, morphology, number, and size of inclusions in drill steel were analyzed by using SEM and EDS. The evolution process and modification mechanism of Ce on MgAl2O4 and sulfides were clarified by experimental results and calculated by thermodynamic software. The type of inclusions in drill steel without Ce addition is MgAl2O4 and (Ca, Mn)S. As the Ce content in drill steel reaches to 0.0078% (mass fraction), the type of inclusions changes to Ce-O and Ce-S. In addition, a few complex inclusions, mixture of Ce-O and MgO, were also found. The size of inclusions in drill steel decreases significantly as the oxides and sulfides were modified into Ce-O and Ce-S. The calculated results show that MgAl2O4 and (Ca, Mn)S in drill steel can be effectively modified into Ce-O and Ce-S as the Ce added into molten steel, and the modification sequence of Ce on the MgAl2O4 is as follows: MgAl2O4→CeAlO3+MgO→Ce2O3+MgO→Ce2O3. The content of Ce in drill steel has great influence on the type of inclusions. The modification mechanism of Ce on MgAl2O4 calculated by Factsage 6.3 agrees well with the experimental observations.
Key words： rare earth cerium; drill steel; inclusion; thermodynamic calculation
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