超超临界电站用含Nb马氏体/奥氏体耐热钢的合金化现状

Alloying status of martensite/austenite heat-resistant steel containing Nb for ultra-supercritical power station

为了提高耐热钢的高温强度,在钢中添加微量合金元素是合金设计时的一种有效措施,其中Nb微合金化为耐热钢的主要强化方式,一直是耐热钢研究的热点。围绕Nb的应用,阐述了蒸汽发电机转子用马氏体耐热钢、超超临界锅炉用马氏体耐热钢和奥氏体耐热钢的合金化发展历程及现状。大多数转子用马氏体耐热钢中均含有少量的Nb,尤其近40年来开发的马氏体转子用钢中均含质量分数约为0.05%的Nb;蒸汽轮机中小部件用马氏体耐热钢中一般Nb质量分数约为0.05%~0.25%;蒸汽轮机壳体用马氏体耐热钢中Nb质量分数约为0.05%~0.10%;主蒸汽管道和换热管用T/P91和T/P92钢中Nb质量分数为0.04%~0.25%。在马氏体耐热钢中Nb通常和V复合使用,V含量约为Nb的2~4倍。典型奥氏体耐热钢中Nb的含量比在马氏体耐热钢中高约1个数量级,在奥氏体耐热钢中Nb通常单独添加,或与少量Ti复合添加。整体而言,随电站锅炉蒸汽参数的提高,马氏体耐热钢和奥氏体耐热钢的合金化程度越来越高,钢中合金元素的种类也越来越多;对奥氏体耐热钢而言,控制和改善一次富Nb相的存在形态是未来一定时期的主要研究热点;而随着钢中强化因素的增多,强化因素间的定性/定量作用也可能成为未来的重点研究方向。

In order to improve the high-temperature strength of heat-resistant steel,adding trace alloying elements to the steel is an effective measure when designing alloy.Nb microalloying is the main strengthening method of heat-resistant steel and has always been a hot research topic in heat-resistant steel.Based on the application of Nb,the alloying development process and current situation of martensitic heat-resistant steel for steam generator rotor,martensitic heat-resistant steel and austenitic heat-resistant steel for ultra-supercritical boiler are described.Most of the rotor martensitic heat-resistant steels contain a small amount of Nb,especially the martensitic rotor steels developed in the last 40 years contain about 0.05%Nb(mass fraction).The general Nb mass fraction of martensitic heat-resistant steel for small and medium-size parts of steam turbines is about 0.05%-0.25%.The Nb mass fraction of martensitic heat-resistant steel used for steam turbine shell is about 0.05%-0.10%.And T/P91 and T/P92 steels for main steam pipes and heat exchange tubes are containing 0.04%-0.25%Nb.Nb and V is used together in martensitic heat-resistant steel,and the V content is about 2 to 4 times that of Nb.The content of Nb in typical austenitic heat-resistant steel is about an order of magnitude higher than that in martensitic heat-resistant steel,and Nb is generally added separately in austenitic heat-resistant steel,or a small amount of Ti is added in combination.On the whole,with the increase of steam parameters for power plant boiler,the alloying degree of martensitic heat-resistant steel and austenitic heat-resistant steel becomes higher and higher,and the types of alloying elements in steel become more and more.For austenitic heat-resistant steels,controlling and improving the existing form of primary Nb-rich phase is the main focus in the future.With the increase of strengthening factors in steel,the qualitative/quantitative interaction between strengthening factors may become a key research direction.