锆脱氧钢中非金属夹杂物及对显微组织的影响

实验用钢在低碳锰钢基础上采用锆脱氧及钛微合金化,研究了连续冷却和等温热处理条件下的组织转变行为,分析了夹杂物的析出类型及对组织转变的影响机理.统计结果表明:夹杂物在0.2~1μm尺寸范围内有较高的数量密度,主要为Zr O2·Mn S和Zr O2·Mn S·Ti N复相夹杂,与热力学分析结果一致.实验钢以1℃/s连续冷却及500℃等温时均得到晶内针状铁素体组织,促进铁素体形核的主要夹杂物类型为Zr O2·Mn S·Ti N.Mn S以Zr O2为核心复合析出形成贫锰区是促进铁素体形核的重要因素,Ti N的复合析出降低了铁素体形核界面能,进一步促进了针状铁素体转变.

Non-metallic Inclusions and Its Effect on Microstructure of Zr Deoxidized Steel

Transformation behaviors of a Zr deoxidized and Ti microalloyed low C-Mn steel under continuous cooling and isothermal treatment were studied. The precipitation of non-metallic inclusions and its influence on the microstructure were analyzed. Statistical results showed that the inclusions are mainly ZrO₂·MnS and ZrO₂·MnS·TiN composites， which are in accordance with thermodynamic analysis. The size of inclusions is in the range of 0.2~1μm and the number density of inclusions is high. Intragranular acicular ferrite is obtained under both conditions of continuous cooling with 1℃/s and isothermal treatment at 500℃. Inclusions， which can promote ferrite nucleation， are mostly ZrO₂·MnS·TiN type. Formation of Mn-depletion zone with MnS precipitation on the ZrO₂ core is an important factor in ferrite nucleation. Composite precipitation of TiN can reduce the interface energy of ferrite nucleation， which can further promote acicular ferrite transformation.