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为了研究灰铸铁中TiN颗粒形成与长大规律及其组织特征,采用显微组织及热力学计算研究某汽车发动机缸体铸件中TiN颗粒形态、尺寸及分布,并对TiN形成与长大机理进行了分析讨论。结果表明,因回炉料中TiN的遗传性形成的TiN颗粒尺寸相对较大,超过20μm;从铸铁熔体中结晶的TiN颗粒尺寸为4~8μm;从过冷奥氏体中析出的TiN颗粒尺寸相对较小为1~2μm。热力学计算表明,TiN结晶取决于铸铁熔体中[%Ti]·[%N]的溶度积,当铸铁熔体中[Ti]在0.045%附近([%Ti]·[%N]=2.47×10~(-4))时,铸铁熔体过冷到1368℃,即开始结晶TiN。由于TiN与MnS晶体结构相同,点阵常数相近,过冷铸铁熔体中TiN多以MnS为基底非自发成核长大。
In order to study the rule of formation and growth of TiN particles in gray cast iron and its microstructure and microstructure, the morphology, size and distribution of TiN particles in engine block casting were investigated by microstructure and thermodynamics. The formation and growth mechanism of TiN Analysis and discussion. The results show that the size of TiN particles formed by the genetic inheritance of TiN is larger than 20μm, the size of TiN particles crystallized from cast iron melt is 4 ~ 8μm, the size of TiN particles precipitated from undercooled austenite Relatively small 1 ~ 2μm. Thermodynamic calculations show that the TiN crystallinity depends on the solubility product of [% Ti] · [% N] in the cast iron melt. When [Ti] is around 0.045% ([% Ti] · [% N] × 10 ~ (-4)), the cast iron melt overcooled to 1368 ℃, which began to crystallize TiN. Due to the same crystal structure of TiN and MnS, the lattice constants are similar, and TiN in the supercooled cast iron melt mostly grows non-spontaneously based on MnS.