Ti--Mg复合脱氧钢中夹杂物细化机制

Refinement mechanisms of inclusions in steel by Ti- Mg complex deoxidation

为了探讨钢中细小夹杂物的形成机制,采用扫描电镜和能谱仪表征了钢中夹杂物的形貌、尺寸、成分及数量,理论计算了脱氧产物的生成优势区图,讨论了夹杂物长大的影响因素.钢中夹杂物的组成以Mg O-Al2O3-Ti Ox为核心,表面包裹析出Mn S,钢液中未发现单独的Al2O3和Ti Ox夹杂;夹杂物的形貌为近球形,平均尺寸为1μm左右,数量在1000 mm-2以上.镁含量较高的钢中含有少量以Mg O-Al2O3和Mg O为核心的夹杂物,不利于夹杂物的球形化,镁含量宜控制在50×10-6以下.镁的脱氧能力强,形核临界尺寸小、形核数量多以及钢液中镁、铝和钛复合脱氧的高熔点产物的特性有效地控制了钢中夹杂物的扩散与碰撞长大趋势.

To understand the refinement mechanisms of inclusions in steel,the morphology,size,composition and number of inclusions in low C-Mn steel were characterized by scanning electron microscopy and energy dispersive spectroscopy. The predominance area diagram of deoxidation products was calculated. Some factors which influence the growth of inclusions was discussed. It is found that inclusions in Ti-Mg deoxidized steel are composed of Mg O-Al2O3-Ti Ox,then Mn S encapsulated and precipitated on them,isolated Al2O3 and Ti Oxdo not appear in the steel. The inclusions＇ morphology is spherical,the average size is about 1. 0 μm,and the number is more than 1000 mm- 2. Few Mg O- Al2O3 and Mg O inclusions exist in the steel with high Mg content. Therefore,high Mg content in molten steel is harmful to the control of sphericizing,and it should be restricted to below 50 × 10- 6. Magnesium has strong deoxidation ability,and the deoxidation products have the characteristics of small critical radius,large number of nucleation,and the formation of Al- Ti- Mg- O complex inclusions,which both control the supersaturation of oxygen and the growth of inclusions in the steel.