高碳帘线钢中钛夹杂的形核机理、性质及其固溶行为研究

The tire cord steel is the ideal skeleton material for the car radial tire, but the high-hardness birttle titanium incusions can cause the fracture and stratification during the drawing and stranding process or deterioration the fatigue performance for the tire cord steel. With the improvement of strength level for the tire cord steel, its harmfulness is more serious, so the control of titanium inclusions is one of the main challenges in the production process of high carbon tire cord steel. If the nucleation mechanism and properties of titanium inclusions and its solid solution behavior for the high carbon tire cord steel can be understanded, It will be of great significance for the exploitation of high strength cord steel wire rod. Therefore, the project proposes to research the nucleation and growth mechanism on titanium incusions of high carbon tire cord steel during solidification, and explore the effects of particle sizes of heterogeneous nucleus and solidification conditions on the growth of titanium incusions, then combined with RTO token mehtod to ascertain the internal structure informations of titanium inclusions. In addition, the project plans to study the internal relations between the properties of titanium inclusions and the carbon content for the tire cord steel of different strength level. Finally, researching the solid solution behavior and influence factors of titanium inclusions in the slab of high carbon tire cord steel during reheating process. Thus, to provide a theoretical basis for the control of titanium inclusions during the smelting and rolling process for the high strength tire cord steel.

帘线钢是汽车子午线轮胎最为理想的骨架材料，而高硬度脆性钛夹杂的存在会在帘线钢盘条拉拔和捻股成绳过程中导致断丝、分层，或使钢帘线疲劳性能恶化。随着帘线钢强度级别的提高，其危害性更为突出，是高碳帘线钢生产过程中需要解决的主要难题之一。若能探明高碳帘线钢中钛夹杂的形核机理，性质及其固溶机制，对高强度帘线钢盘条的开发意义重大。为此，本项目拟研究高碳帘线钢凝固过程中钛夹杂的形核长大机制，探讨异质形核核心的粒径大小和凝固条件对最终钛夹杂长大程度的影响，并结合RTO表征法明确复合钛夹杂内部结构信息；探明不同强度级别帘线钢凝固过程中析出的钛夹杂性质与碳含量之间的内在关系；最后，研究高碳帘线钢铸坯再加热过程中钛夹杂的固溶行为与影响机制，为高强度级别帘线钢冶炼及轧制过程中钛夹杂的控制提供理论依据。

摘要：帘线钢是汽车子午线轮胎最为理想的骨架材料，而高硬度脆性钛夹杂的存在会在帘线钢盘条拉拔和捻股成绳过程中导致断丝、分层，或使钢帘线疲劳性能恶化。随着帘线钢强度级别的提高，其危害性更为突出。若能探明高碳帘线钢中钛夹杂的形核机理，性质及其固溶机制，对高强度帘线钢盘条的开发意义重大。为此，本项目拟结合现场实际生产数据、实验室检测分析和热力学理论，研究高碳帘线钢凝固过程中钛夹杂的析出机理；探明不同强度级别帘线钢凝固过程中析出的钛夹杂性质与碳含量之间的内在关系；最后，研究高碳帘线钢铸坯再加热过程中钛夹杂的固溶行为与影响机制。主要结果如下：. （1）讨论了在不同的初始w[N]0×w[Ti]0积条件下，TiN夹杂在凝固前沿析出的影响因素。由计算结果可知，在实际生产过程中所控制的Ti、N范围内，TiN夹杂基本在凝固末期才开始析出。并且初始Ti和N含量乘积越小，TiN夹杂也越晚在凝固前沿析出，与Ti或N单一元素含量的高低无关。即碳含量一定时，TiN夹杂在凝固前沿析出先后顺序的决定因素是：初始w[N]0×w[Ti]0。. （2）探究了不同强度级别帘线钢中钛夹杂的性质。实验及理论分析表明不同强度级别的帘线钢中钛夹杂析出的驱动力有差异。帘线钢的强度级别越高，钛夹杂形成元素的过饱和度也越高，其形核-析出-长大的驱动力就越大，从而加剧钛夹杂的析出和长大。高碳帘线钢中同时存在钛的碳化物和钛的氮化物夹杂。随着帘线钢强度级别的提高，钛夹杂中碳化钛所占的摩尔分数呈增加的趋势。. （3）探索了铸坯在高温加热过程中钛夹杂的固溶机理，帘线钢强度级别越高，钛夹杂分解温度越高；对同一强度级别的帘线钢，钢中Ti或N含量越高，钛夹杂开始分解温度也越高。并据此提出了通过适当提高帘线钢铸坯轧前加热温度控制轧后盘条中钛夹杂尺寸和数量的工艺措施。. 该研究成果可为高强度级别帘线钢冶炼及轧制过程中钛夹杂的控制提供理论依据，从而实现对高级别帘线钢中钛夹杂的控制能力和高质量生产。