材料期刊网

通过采用扫描电镜对BOF-LF-RH-CC非钙处理工艺生产车轮钢系统取样样品中夹杂物的形貌、尺寸及组成的分析,研究了精炼和凝固过程氧化物夹杂的形成、上浮去除和析出过程,以及轧制过程夹杂物的变形行为.研究发现,在非钙处理条件下,LF精炼过程会形成大量MgO-Al2O3夹杂和CaO-Al2O3夹杂,并且在RH精炼过程中存在MgO-Al2O3夹杂向CaO-Al2O3夹杂的转变过程,最终导致铸坯中出现低变性CaO-Al2O3夹杂;在软吹和镇静过程中,炉渣或空气对钢液的二次氧化与钢液中夹杂物上浮去除存在动态平衡;在钢液凝固过程中,固液界面的Al2O3等氧化物夹杂为MnS的析出提供了异质形核点,形成半包裹状的Al2O3-MnS类复合夹杂物;在轧制过程中,团簇状Al2O3夹杂容易被轧碎在板卷中形成点链状,高熔点半包裹的Al2O3-MnS类复合夹杂物被轧制成小尾巴状,而低熔点的CaO-Al2O3-MnS的复合夹杂形成连续的条状.

The formation and deformation mechanism of oxygen inclusions in Al-killed wheel steel without calcium treat-ment were studied by industrial trials based on systematic sampling and electron microscopy analysis on inclusions mor-phology,size and composition. It can be found that,under the condition of no calcium treatment,massive MgO-Al2O3 in-clusions and CaO-Al2O3 inclusions were formed during LF refining and there was a transformation process from MgO-Al2O3 inclusions to CaO-Al2O3 inclusions during RH refining,which leads to generate massive low-modified CaO-Al2O3 inclusions in slab.;During the process of soft bottom stirring and holding process,there can exist a dynamic equilibrium between reoxidation of molten steel by slag or air and flotation removal of inclusions in ladle;During solidification pro-cess,Al2O3 based inclusions surrounding a little MnS were formed because Al2O3 based inclusions provided the position of heterogeneous nucleation of MnS precipitation in the interface of solid and liquid during solidification,which made MnS easier precipitate on the surface of Al2O3 based oxygen inclusions. During hot rolling process,alumina inclusions of clusters were often deformed to chain-like ones,Al2O3 based inclusions surrounding a little MnS to tiny tail-like ones, and low-temperature point CaO-Al2O3 inclusions to long striped ones.