镧对高碳硬线钢中Al2O3夹杂物改性的晶体学分析

 为了控制与改善高碳硬线钢中氧化铝夹杂物的数量、形状和分布,提高钢的洁净度,细化钢的组织结构,均匀钢的化学成分,在高碳硬线钢中添加稀土镧元素研究其对氧化铝夹杂物的改性问题。通过对高碳硬线钢中添加稀土镧形成的稀土氧(硫)化物,采用扫描电镜和能谱分析进行表征,研究其对氧化铝的改性问题,发现镧的加入可以改变夹杂物的形状,夹杂物从不规则形状转变为较规则的椭圆形,随着夹杂物面间距增大,其逐渐弥散化。利用热力学以及边-边匹配模型计算其与γ-Fe和Al₂O₃之间沿密排晶向的原子间错配度和密排晶面的面间错配度,探究含镧夹杂物作为钢液凝固时初生相异质形核核心的可能性及有效性。结果表明,加入镧后,在1 000～2 000 K温度范围内根据生成夹杂物的吉布斯自由能的大小,得出钢中可能生成夹杂物的顺序为La₂O₃＞La₂O₂S＞LaAlO₃＞LaS＞La₃S₄。利用边-边匹配模型计算稀土氧(硫)化物与γ-Fe和Al₂O₃之间的原子匹配情况,发现了La₂O₃、LaS、La₂O₂S和La₃S₄均可能作为Al₂O₃和γ-Fe异质形核的核心,且La₂O₂S可能优先成为γ-Fe异质形核核心, LaS可能优先成为Al₂O₃异质形核核心,揭示了钢中氧化铝夹杂物的改性机理,为高碳硬线钢中非金属夹杂物的处理提供了理论依据。

Crystallographic analysis of modification of Al2O3 inclusions in high carbon hard wire steel by lanthanum

In order to control and improve the number, shape and distribution of alumina inclusions in high carbon hard wire steel, improve the purity of steel, refine the structure of steel, and even the chemical composition of steel, rare earth lanthanum is added to high carbon hard wire steel. The element studies its modification of alumina inclusions. The rare earth oxygen (sulfide) compound formed by adding rare earth lanthanum to high carbon hard wire steel was characterized by scanning electron microscopy and energy spectrum analysis, and the modification of it on alumina was studied. It is found that the addition of lanthanum can change the shape of inclusions. The inclusion changes from an irregular shape to a more regular ellipse, and as the distance between inclusion surface increases, it gradually disperses. Thermodynamics and edge-edge matching model were used to calculate the interatomic mismatch along the dense row crystal direction between γ-Fe and Al₂O₃and the interplanar mismatch of the dense row crystal plane. The possibility and effectiveness of lanthanum inclusions as the nucleation core of primary phase during solidification of molten steel were explored. The results show that after adding lanthanum, according to the Gibbs free energy of inclusions in the temperature range of 1 000-2 000 K, the order of possible inclusions produced in steel is, La₂O₃>La₂O₂S>LaAlO₃>LaS>La₃S₄. The edge-edge matching model was used to calculate the atomic matching between rare earth oxygen (sulfide) compounds and γ-Fe and Al₂O₃. It is found that La₂O₃, LaS, La₂O₂S and La₃S₄ may all be the cores of Al₂O₃ and γ-Fe heterogeneous nucleation. Moreover, La₂O₂S may preferentially become the nucleation core of γ-Fe heterogeneous, while LaS may preferentially become the core of Al₂O₃ heterogeneous nucleation,the modification mechanism of alumina inclusions in steel is revealed, which provides a theoretical basis for the treatment of non-metallic inclusions in high-carbon hard wire steel.