重轨D_(60)钢中Al_2O_3夹杂物形貌和形成机理的研究

MORPHOLOGY AND FORMATION OF Al_2O_3 INCLUSION IN D_(60) HEAVY-RAIL STEEL

本文采用金相检验、扫描电镜等检测手段对重轨D_(60)钢中Al_2O_3夹杂物和工业纯铁加铝脱氧生成的Al_2O_3夹杂物的组成、形貌进行了对比分析.结果表明,重轨钢中Al_2O_3夹杂物是一次脱氧产物,其颗粒尺寸小(5μm左右),且以单晶存在.采用铝锭冲入法进行终脱氧时,钢水中局部残余铝含量高,氧浓度低是引起Al_2O_3夹杂物集中出现的重要原因之一,常形成重轨钢的"条沟带"分层缺陷.

Based on the metallographic test, scanning electron micrographic examination and composition analysis for the inclusions existing in the D_(60) heavy-rail steel, it is shown that the Al_2O_3 inclusions consist of 98% Al_2O_3 and 2% FeO, and exist in the form of single crystal sized about 5 μm. Compared with the deoxidization product of an aluminum-killed pure iron, the Al_2O_3 inclusions of D_(60) heavy-rail steel are first deoxidization products. The method of adding Al ingot into the ladle normally results in the layered structure defect of D_(60) heavy-rail steel, becaues of localized high content of [Al] and low content of [O] in the ladle during the final deoxidization treatment procees. Therefore, the accumulative Al_2O_3 inclusion removal can be inproved by feeding Al wire deoxidant or Al-Ca, Al-Ba alloys, and by increasing stirring with Ar blowing.