外部加入钛氧化物细化晶粒的基础研究

氧化物冶金技术利用钢中细小弥散的氧化物钉扎奥氏体晶界和诱导晶内铁素体形核，以优化组织。钛氧化物作为最有效的夹杂物之一，其引入方式包括内部生成法和外部加入法，后者的稳定性和有效性一直是研究的重点。预研中，申请人利用外部加入法，在低碳钢中实现了纳米级和微米级二氧化钛的稳定加入和有效诱导形核，并探索了随后的合金化处理。本项目拟进一步开展系统研究，通过调节加入二氧化钛的粒度(纳米级、微米级)、合金组合(种类、加入量)和加入参数(二氧化钛/合金的加入顺序、静置时间)，一方面将钛氧化物稳定有效的加入到钢液中，解析加入后夹杂物性质的演变进程，探索其与钢液的反应机制，避免增加夹杂物的危害，另一方面基于热模拟工艺的调整，协同匹配生成含钛复合氧化物的钉扎效应和诱导晶内铁素体形核能力，解析外部加入法各参数与其晶粒细化能力之间的内在关联性，以实现组织的最优化，为其实用化奠定理论和工艺基础。

The oxide metallurgy was proposed to utilize the positive effect of fine inclusion to refine the grain. Accordingly, the fine inclusions can not only inhibit austenitic grain growth through the pinning effect, but also induce nucleation of intragranular ferrite (IGF) during the austenite-ferrite transformation. Among many types of non-metallic inclusions, which have been proposed in oxide metallurgy, Ti-bearing inclusion has attracted much attention. Its intrduction includes Internal Precipitation Method (IPM) and External Addition Method(EAM). For the latter, stability and effectiveness are the study focus. According to our previous studies, the proposer found that TiO2 with nano and micron sizes can be successfully added into molten steel, respectively. Moreover, the resultant Ti-bearing inclusion can act as nucleation sites for intragranular ferrite. The following alloy treatments were also explored. Thus, the objective of this proposal is to carry out systemic study for TiO2 adding by adjusting its size range (nano-scale and micron-scale), alloy treatment (type and amount) and adding parameters (adding sequence of TiO2 and alloy, and holding time). On the one hand, the relationship between the evolution of complex inclusions and adding parameters will be elucidated. Based on the relationship, reaction mechanism between adding particles and molten steel will be revealed, which may be helpful to reduce the harm of adding particles. On the other hand, based on the adjustment of heat-treatment process, the coordination between pinning effect and inducing nucleation will be realized for different size range of Ti-bearing oxide. These results will be helpful to clarify the power of adding particles for grain refinement and promote the application of oxide metallurgy.