Li Dianzhong, Wang Pei, Chen Xing-Qiu, Fu Paixian, Luan Yikun, Hu Xiaoqiang, Liu Hongwei, Sun Mingyue, Chen Yun, Cao Yanfei, Zheng Leigang, Gao Jinzhu, Zhou Yangtao, Zhang Lei, Ma Xiuliang, Dai Chunli, Yang Chaoyun, Jiang Zhonghua, Liu Yang, Li Yiyi
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, P. R. China.
Nat Mater. 2022 Oct;21(10):1137-1143. doi: 10.1038/s41563-022-01352-9. Epub 2022 Sep 8.
Rare earth (RE) addition to steels to produce RE steels has been widely applied when aiming to improve steel properties. However, RE steels have exhibited extremely variable mechanical performances, which has become a bottleneck in the past few decades for their production, utilization and related study. Here in this work, we discovered that the property variation of RE steels stems from the presence of oxygen-based inclusions. We proposed a dual low-oxygen technology, and keeping low levels of oxygen content in steel melts and particularly in the raw RE materials, which have long been ignored, to achieve impressively stable and favourable RE effects. The fatigue life is greatly improved by only parts-per-million-level RE addition, with a 40-fold improvement for the tension-compression fatigue life and a 40% enhancement of the rolling contact fatigue life. We find that RE appears to act by lowering the carbon diffusion rate and by retarding ferrite nucleation at the austenite grain boundaries. Our study reveals that only under very low-oxygen conditions can RE perform a vital role in purifying, modifying and micro-alloying steels, to improve the performance of RE steels.
为了改善钢材性能，在钢中添加稀土（RE）以生产稀土钢已得到广泛应用。然而，稀土钢的力学性能表现出极大的变异性，这在过去几十年里一直是其生产、应用及相关研究的瓶颈。在本研究中，我们发现稀土钢性能的变化源于氧基夹杂物的存在。我们提出了一种双低氧技术，即保持钢液特别是长期被忽视的稀土原材料中的低氧含量，以实现令人印象深刻的稳定且良好的稀土效果。仅添加百万分之一级别的稀土就能显著提高疲劳寿命，拉伸 - 压缩疲劳寿命提高了40倍，滚动接触疲劳寿命提高了40%。我们发现稀土似乎通过降低碳扩散速率以及阻碍奥氏体晶界处铁素体的形核来发挥作用。我们的研究表明，只有在极低氧条件下，稀土才能在净化、变质和微合金化钢方面发挥关键作用，从而提高稀土钢的性能。
