【作者】 龚伟；

【导师】 王文忠； 姜周华；

【作者基本信息】 东北大学 ， 钢铁冶金， 2006， 博士

【摘要】 含C 1.0％、Cr 1.5％的高碳铬轴承钢是轴承钢的代表品种，是代表着优质洁净钢生产技术水平的重要特殊钢品种。因为氧化物夹杂是影响轴承钢疲劳寿命的重要原因，所以钢中的氧含量是衡量轴承钢质量的一个重要指标。因此，如何降低轴承钢中的氧含量，控制钢中的有害夹杂是生产优质轴承钢的关键问题之一。 本论文首先应用冶金学基本原理，分析了几种典型的精炼渣的脱氧和脱硫能力以及对点状夹杂物的控制效果，为选择合适的轴承钢精炼渣提供理论依据。同时计算了轴承钢中几种主要夹杂物的生成热力学条件。计算结果表明：CaO-Al₂O₃系高碱度精炼渣由于稳定了渣中的SiO₂组元，可以保持钢中较低的溶解氧含量；通过降低钢水中的氮含量来控制TiN的生成是很困难的，为了减少钢中TiN夹杂物的数量，就必须控制钢水中的钛含量。在计算条件下，轴承钢的酸溶铝含量在0.01～0.04％的范围内时，只要有微量的镁存在，钢中就有可能生成MgO·Al₂O₃，因此可以尝试用镁来对轴承钢进行夹杂物变性处理，以消除铝酸钙夹杂对轴承钢质量的影响。 在热力学计算的基础上，在实验室条件下进行了不同精炼渣对轴承钢氧含量和夹杂物性质的影响实验，同时考察了用镁铝合金处理轴承钢后，钢中夹杂物的变性效果。实验中发现，CaO-Al₂O₃系高碱度精炼渣对降低轴承钢全氧含量有很好的效果，生成的夹杂物以Al₂O₃-MgO-CaO为主。用镁铝合金处理轴承钢生成的夹杂物类型单一，基本上都是镁铝尖晶石，而且夹杂物颗粒细小，说明用镁铝合金对轴承钢夹杂物变性效果明显。最后在现场120t VD精炼炉上，应用镁铝合金包芯线进行了工业试验，试验结果表明，采用镁铝包芯线处理后，轴承钢中夹杂物以MgO·Al₂O₃为主，有的包裹了其它的复合相和硫化物，夹杂物尺寸细小，夹杂物细化和变性效果很好。 论文中以现场应用的200mm×200mm四流方坯连铸中间包为研究目标，通过优化中间包内部结构的水模型实验研究，提出了中包结构改造方案。 以理论分析和实验室研究为基础，结合现场的生产实践，以降低钢中氧含量和改进和优化钢厂原有的电炉、精炼和连铸工艺，将整套控制技术系统集成，实际生产中应用有效地控制了连铸轴承钢中的氧含量和夹杂物，提高轴承钢的质量水平。更多还原

【Abstract】 High carbon bearing steel with 1.0% C, 1.5% Cr is an important special steel grade, which represents technology level of high quality clean steels. Oxygen content in bearing steel is a major index to judge its quality because oxide inclusions greatly affect the fatigue life of bearing steel. Therefore one of the bottleneck problems to produce high-quality bearing steel is how to reduce oxygen content and get rid of the harmful inclusions.In this subject, the capacities of various typical refining slags that are used to deoxidate, desulphurize and control spot inclusions are analyzed, which is the theoretical basis to choose proper refining slag. Meanwhile the thermodynamic calculations about the formation of some main type inclusions were carried out. The results of calculation and comparison showed that slag system of CaO-Al₂O₃ with high basicity could reduce SiO₂ content in slag, and then it would keep dissolved oxygen content lower in molten steel. And it was very difficult to control the formation of TiN inclusions by reducing nitrogen content in bearing steel, so the titanium content has to be reduced in order to reduce TiN inclusions in molten steel. On the conditions of calculation of this subject, if dissolved aluminum content in steel was in the range of 0.01% - 0.04%, microcontent of magnesium in bearing steel could lead to the formation of MgO·Al₂O₃ spinel. Therefore, it was possible to make attempts to modify inclusions by treating with magnesium, aiming at elminating the negative influence of calcium aluminate on bearing steel.Based on the thermodynamic calculation, the experiments with different refining slags have been carried out to compare its effect on oxygen content and character of inclusions in bearing steel, and to investigate the modification results to inclusions by treating with magnesium aluminum alloy. The experimental results showed that slag system of CaO-Al₂O₃ with high basicity has a good effect on reducing oxygen content in bearing steel, and the composition of inclusions in molten steel was mostly Al₂O₃-MgO-CaO after treating with it. Another conclusion was that the type of inclusions in steel was single after treating with magnesium aluminum alloy; and the inclusions were mostly更多还原