Abstract

Aiming at the problem of severe steel-flux reaction and fluorine pollution occurred in the process of continuous casting La-bearing FeCrAl alloy with conventional CaO–SiO₂–Na₂O–CaF₂-based mold fluxes, the low-reactive and environmentally friendly CaO–Al₂O₃–La₂O₃–B₂O₃ slag system was designed, and rheological behavior of the slags with different B₂O₃ contents was studied. Results showed that with the increase of B₂O₃ from 0 to 15 wt%, the slag viscosity and activation energy decreased gradually. Structural analysis indicated that B³⁺ mainly existed in the form of planar [BO₃]-triangular structure with the addition of B₂O₃. With increasing B₂O₃ contents, [BO₃] units entered into the initial aluminate network structure via destroying Al_IV–O–Al_IV linkages to form more Al_IV–O–B_III and B–O–B linkages, resulting in the increase of bridging oxygen and the polymerization of slag structure. Due to the layered structure of [BO₃] units, the molecular attraction of B–O bonds between the layers was weak, which reduced the overall slag structural strength, thus, leading to the decrease of viscosity. The break temperature decreased gradually on the whole with the addition of B₂O₃. The precipitated amount of CaAl₂O₄ reduced with increasing B₂O₃ content, which resulted from the decrease of high-polymerized [AlO₄]-tetrahedral structure. In this study, Ca²⁺ played the charge compensation effect owning to its small cationic field strength, while La³⁺ mainly interacted with NBOs for balancing charges.

Graphical Abstract

中文翻译：

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不同 B2O3 含量的 CaO-Al2O3-La2O3-B2O3 渣的流变性质和结构

摘要

针对常规CaO-SiO ₂ -Na ₂ O-CaF ₂基保护渣连铸含La FeCrAl合金过程中钢-熔剂反应严重和氟污染问题，低反应性环保设计了CaO-Al ₂ O ₃ -La ₂ O ₃ -B ₂ O ₃渣体系，研究了不同B ₂ O ₃含量渣的流变行为。结果表明，随着B ₂ O _3的增加从 0 到 15 wt%，渣粘度和活化能逐渐降低。结构分析表明，B ^{3+主要以平面[BO} ₃ ]-三角形结构的形式存在，并添加了B ₂ O ₃。随着 B ₂ O ₃含量的增加，[BO _{3 ] 单元通过破坏 Al IV} -O-Al _IV键进入初始铝酸盐网络结构，形成更多的 Al _IV -O-B _III和 B-O-B 键，导致桥氧的增加和熔渣结构的聚合。由于 [BO ₃]单元，层间B-O键的分子吸引力较弱，降低了整体渣结构强度，从而导致粘度降低。_{随着B 2} O ₃的加入，断裂温度总体上逐渐降低。_{CaAl 2} O ₄的析出量随着B ₂ O ₃含量的增加而减少，这是由于高聚[AlO ₄ ]-四面体结构的减少所致。本研究中，Ca ²⁺因其较小的阳离子场强发挥了电荷补偿作用，而La ³⁺主要与NBOs相互作用以平衡电荷。

图形概要