基于S35140钢的超低碳成分设计和力学性能研究

S35140钢是一种基于25Ni-20Cr的奥氏体耐热钢,为了获得高强度,通常会提高碳含量,但碳含量较高不利于高温时效稳定性和长期耐腐蚀性能.本文在S35140钢的基础上,大幅度降低碳含量,并通过调控N和Nb等微合金元素含量,以及加入Ti元素,促使析出新的强化相,弥补减少碳含量所导致的强度降低.同时引入一定量的Al元素,增强S35140钢的高温强度和抗氧化性能.研究表明,加入微量Nb,N,Ti元素的热轧态实验钢析出了氮化物和细小的Laves相,这些析出相具有较强的强化作用,使其拉伸性能不亚于具有较高碳含量的S35140钢;加入4.7％Al(质量分数)元素后,实验钢的基体中出现了铁素体和奥氏体双相组织,同时析出大量B2-NiAl相,使其室温和高温拉伸强度以及室温韧性均高于其它成分的实验钢.

Research on composition design and mechanical properties of S35140 based austenitic steel with ultra-low carbon content

S35140 austenitic stainless steel, which is based on 25Ni-20Cr, is a kind of high strength heat resistant steels. This steel usually contains high content of carbon to obtain high strength. However, high carbon content is not conducive to high temperature aging stability and long-term corrosion resistance. In this work, S35140 based steels with ultra-low carbon content are developed. By tuning the content of Microalloying elements such as N and Nb, and adding Ti element, new strengthening phases are precipitated to compensate the loss of the strength induced by low carbon content. At the same time, a certain amount of aluminum was introduced to enhance its high temperature strength and oxidation resistance. The results showed that nitrides and fine Laves phases were precipitated in hot-rolled steels with minor Nb, N and Ti additions. These precipitates showed strong strengthening effects, making the tensile properties of these experimental steels as good as S35140 steel with high carbon content. In steel with the addition of 4.7wt.% Al element, the matrix shows both ferrite and austenite phase, and a large number of fine B2-NiAl phase precipitated, resulting in higher tensile strength and toughness at room temperature and high temperature than the other steels.