Heat treatment experiments of heavy rail steel samples are performed with varied total calcium (T.Ca) in the steel to investigate the transformation of inclusions. Before heat treatment, original inclusions in the heavy rail steel are homogeneous Al₂O₃–SiO₂–CaO–MgO with little CaS. After soaking for 60 min at 1473 K, the precipitation of the CaS outer layer and MgO·Al₂O₃ core is clearly observed. The transformation ratio of CaO to CaS in inclusions increases with T.Ca in the steel under current steel compositions. When the T.Ca content in the steel increases from 3 to 9 ppm, the CaS content of inclusions increases by 5.31–16.14%, while the CaO content of inclusions varies in an opposite way by 5.40–14.01%. In addition, the content of Al₂O₃ in inclusions increases by 1.73–6.33%, the SiO₂ content decreases by approximately 6%, while the content of MgO changes little. Thermodynamic calculation performed by FactSage 7.0 verifies the transformation of inclusions from CaO–SiO₂ to CaS–Al₂O₃ in the solid heavy rail steel during heat treatment. A kinetic model is developed to predict the evolution of inclusions in the heavy rail steel during the heat treatment process.

中文翻译：

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重轨钢中总钙对 1473 K 热处理过程中夹杂物转变的影响

使用不同的钢中总钙 (T.Ca) 对重轨钢样品进行热处理实验，以研究夹杂物的转变。热处理前，重轨钢中的原始夹杂物是均质的Al ₂ O ₃ -SiO ₂ -CaO-MgO，含有少量CaS。在 1473 K 浸泡 60 min 后，CaS 外层和 MgO·Al ₂ O ₃析出核心清晰可见。在当前钢成分下，夹杂物中 CaO 与 CaS 的转变比随钢中 T.Ca 的增加而增加。当钢中 T.Ca 含量从 3 ppm 增加到 9 ppm 时，夹杂物的 CaS 含量增加 5.31-16.14%，而夹杂物的 CaO 含量则以相反的方式变化 5.40-14.01%。此外，夹杂物中Al ₂ O ₃含量增加1.73-6.33%，SiO ₂含量减少约6%，而MgO含量变化不大。FactSage 7.0 执行的热力学计算验证了夹杂物从 CaO-SiO ₂到 CaS-Al ₂ O ₃的转变在热处理过程中的实心重轨钢中。开发了一个动力学模型来预测热处理过程中重轨钢中夹杂物的演变。