高洁净轴承钢中稀土变质夹杂物行为分析

为了阐明稀土变质高洁净轴承钢中夹杂物的行为,进而优化轴承钢的稀土处理过程,通过向高洁净轴承钢中加入高纯稀土的方法,借助SEM、EDS和EPMA等观察和分析手段,重点对不同稀土含量轴承钢中夹杂物类型和析出行为进行表征和分析。研究结果表明,在不完全变质条件下,微量稀土能够优先变质钢中长条状MnS为RE₃S₄颗粒,RE₃S₄可在冶炼时独立析出或以Al₂O₃为核心析出,也能在凝固时与MnS以RE₃S₄·yMnS (y<1)复杂夹杂物的形式共同在Al₂O₃基底上形成。随着稀土含量的增加,在完全变质条件下,稀土元素与夹杂物的形成元素的结合序列依次为O、S、As、P和C,夹杂物类型演化序列为RE₂O₃、RE₂O₂S、RES、RE-S-As、RE-As(-P)/RE-O-As(-P)、RE-P-C/RE-O-P(-C)和RE-O-C。

Analysis on modification behavior of rare earth to inclusions in high clean bearing steel

To clarify the modification behavior of rare earth to inclusions in high clean bearing steel, and then optimize the rare earth treatment process of bearing steel, high-purity RE alloy was added into high clean bearing steel, and inclusions and their precipitation behaviors in bearing steels with different RE contents were characterized and analyzed using scanning electron microscopy, energy disperse spectroscopy and electron probe microanalysis. The results show that the trace amount of RE can preferentially modify elongated MnS inclusions into RE₃S₄ particles under the condition of the incomplete modification of inclusions in bearing steel. And RE₃S₄ inclusions can not only form independently or at the nuclei of Al₂O₃ inclusions during the steelmaking process, but also precipitate together with MnS inclusions in the form of RE₃S₄·yMnS (y<1) complicated inclusions during the solidification process, also taking Al₂O₃ inclusions as the nuclei. With the increase of RE content, the reaction sequence of RE elements with inclusion forming elements should be O, S, As, P and C successively under the condition of the complete modification of Al₂O₃ and MnS inclusions, and the evolution sequence of inclusion type is expected to be RE₂O₃, RE₂O₂S, RES, RE-S-As, RE-As(-P)/RE-O-As(-P), RE-P-C/RE-O-P(-C) and RE-O-C.