钇微合金化超高强海工钢耐蚀性能优化机理研究

Ocean engineering steel must possess excellent service performance due to the harsh operating environment. Yttrium micro-alloying is the effective measures that obtained ocean engineering steel possesses high toughness, high corrosion resistance and high heat input welding performance. In this project, the relationship among inclusions, tissues and corrosion resistance is established, and the optimization mechanism of the corrosion resistance of ultra high strength ocean engineering steel containing yttrium was studied by inclusions modification and tissue regulation. This project is based on the thermodynamics calculation of inclusions containing yttrium, studying the inclusions modification and matrix tissue evolution law of steel with different yttrium content, exploring the inclusions induce matrix corrosion behavior, analyzing the influence of matrix tissue evolution on the corrosion resistance, at last, the optimization mechanism of the corrosion resistance of steel matrix was proved in combination with first principles. On the other hand, this project studies the pinning effect of inclusions containing yttrium on the grain boundary in the high heat input welding, analyzing the tissue evolution law in the welding joint, establishing the nucleation theory of acicular ferrite in the heat affected zone for ultra high strength ocean engineering steel containing yttrium, the optimization mechanism of the stress corrosion performance in the welding joint was revealed in combination with corrosion electrochemical analysis and first principles. This project takes full advantage of rare earth resources in China, and provides guidance for the industrial production of ocean engineering steel with high toughness, high corrosion resistance and high heat input welding performance.

海工钢因作业环境苛刻而需具备良好的服役性能。钇微合金化是获得高强韧性、高耐蚀性以及高热输入焊接性能海工钢的有效措施。本项目拟建立夹杂物-组织-耐蚀性能之间内在关系，通过夹杂物改性及组织调控研究含钇超高强海工钢耐蚀性能优化机理。技术思路是基于含钇夹杂物平衡热力学计算，研究不同钇含量的海工钢中夹杂物性质变化与基体组织演变规律，探究夹杂物诱发基体腐蚀行为，分析基体组织演变对耐蚀性能的影响规律，结合第一性原理手段，探明含钇超高强海工钢基体耐蚀性能优化机理；通过研究含钇夹杂物在大线能量焊接过程中对晶界的钉扎效应，分析焊接接头组织演变规律，建立钇微合金化超高强海工钢大线能量焊接热影响区针状铁素体形核理论，结合腐蚀电化学分析及第一性原理计算，揭示含钇超高强海工钢焊接接头应力腐蚀性能优化机理。项目研究充分发挥我国稀土资源优势，为高强韧性、高耐蚀性以及高热输入焊接性能海工钢工业化生产提供指导。

超高强海工钢必须具有高强度、高韧性、抗疲劳性、抗层状撕裂性，优良的焊接性能以及耐海水腐蚀性能。随着钢铁制造技术的进步和稀土资源的高效开发利用，稀土资源在钢中运用得到重视。稀土钇由于其原子半径小、性质特殊，在改善钢材综合性能方面具有其独特优势。海工钢在服役过程中，钢中夹杂物存在状态以及组织特征势必会对钢材的耐腐蚀性能产生重大影响。.本项目针对钇微合金化超高强海工钢耐蚀性能优化问题，分别从钇微合金化超高强海工钢夹杂物调控、钇微合金化超高强海工钢基体腐蚀机理研究、大线能量焊接接头应力腐蚀机理研究、钇微合金化超高强海工钢耐蚀性能优化四个方面开展研究。通过理论计算结合实验分析研究了不同钇含量的海工钢中夹杂物演变规律，探明了含钇超高强海工钢基体耐蚀性能优化机理，建立了第二相粒子与钢铁材料韧性和强度之间的作用关系，获得了钇微合金化超高强海工钢耐蚀性能优化方案。.以添加不同含量稀土钇的E690超高强海工钢为研究对象，研究发现未添加稀土Y时，E690钢中典型夹杂物为MnS夹杂物、Al2O3夹杂物。稀土Y可起到脱氧、脱硫作用，E690钢中析出Y2O3夹杂物、YS夹杂物、Y2O2S夹杂物。添加适量稀土元素Y可提高E690钢自腐蚀电位，从而提高E690钢的耐腐蚀性能。稀土Y添加量存在最优值，使得E690钢的耐腐蚀性能最佳，稀土Y含量的过高或过低均导致E690钢耐腐蚀性能的下降。.依托本项目，发表论文19篇（其中SCI、EI检索12篇），授权发明专利4项，培养硕博研究生5名。上述研究结果丰富了钇微合金化超高强海工钢中夹杂物控制理论，尤其是对钇微合金化超高强海工钢中夹杂物的腐蚀机理及钇微合金化超高强海工钢中最佳钇含量的探索，对于提高国产海工钢耐腐蚀性能具有重要意义。