The inclusion characteristics and microstructure in the low carbon microalloyed steel with addition ZrO₂ nanoparticles were investigated by high temperature experiment and metallurgical analysis. The results showed that after ZrO₂ nanoparticles were added, a large number of Zr–Al–Si–O+MnS inclusion, ZrO₂+Al–Si–O+MnS inclusion, and ZrO₂+MnS inclusion appeared in the steel, and these Zr-containing inclusions were effective to induce acicular ferrite (AF) formation. With the amount of added ZrO₂ nanoparticles increased from 0.013% to 0.054%, the inclusions types had no significant effect, but the inclusions size distribution, number density and average diameter were affected. When the addition amount of ZrO₂ nanoparticles was 0.027%, the proportion of large inclusions (larger than 5.0 µm), the inclusions number density and average diameter all were reached the extremum values, respectively 10.81%, 111/mm², 2.62 µm. Moreover, as ZrO₂ nanoparticles adding into steel, the majority solidification microstructure changed from bainitic ferrite (BF) to AF. With the adding amount of nanoparticles increase, the proportion of AF first increased and then decreased, also reached the maximum of 67.65% as the addition amount was 0.027%. Finally, Mn-depletion zone (MDZ) in the vicinity of Zr-containing inclusion was observed, and the MDZ was believed to be one of the possible mechanisms of Zr-containing inclusions inducing AF formation.

通过高温实验和冶金分析研究了添加ZrO ₂纳米粒子的低碳微合金钢的夹杂物特征和组织。结果表明，加入ZrO ₂纳米粒子后，钢中出现了大量Zr–Al–Si–O + MnS夹杂物，ZrO ₂ + Al–Si–O + MnS夹杂物和ZrO ₂ + MnS夹杂物。这些含Zr的夹杂物可有效诱导针状铁素体（AF）的形成。随着ZrO ₂纳米颗粒的添加量从0.013％增加到0.054％，夹杂物类型没有明显影响，但夹杂物的尺寸分布，数量密度和平均直径受到影响。ZrO的添加量_2个纳米颗粒为0.027％，大夹杂物的比例（大于5.0 μ M），夹杂物个数密度和平均直径都分别达到极值，10.81％，111个/ mm ²，2.62 μ米。此外，随着ZrO ₂纳米颗粒的加入，钢的大部分凝固组织从贝氏体铁素体（BF）转变为AF。随着纳米粒子添加量的增加，AF的比例先增加然后减少，当添加量为0.027％时，AF的比例也达到最大值67.65％。最后，在含Zr夹杂物附近观察到Mn耗尽区（MDZ），并且认为MDZ是含Zr夹杂物诱导AF形成的可能机制之一。