高Cr铁素体耐热钢的相变行为研究

Research on Phase Transformation Behavior of High Cr Ferritic Heat Resistant Steel

利用差热分析（DTA）、扫描电镜（SEM）以及X射线衍射分析研究了一种超超临界火力发电机组用高铬铁素体系耐热钢的显微组织和相变行为。结果表明试验钢加热时在600-1100℃依次发生磁性转变、奥氏体形成、M23C6型碳化物溶解和奥氏体向δ-铁素体转变,奥氏体开始形成温度为853℃,空冷或以40℃/min的速度冷却时发生马氏体转变,马氏体开始转变温度为382℃。含Nb的MC型碳化物非常稳定,在试验温度范围不能完全溶解到奥氏体中。

The microstructure and phase transformation behavior of high Cr ferrite heat resistant steel used in ultra super critical power plants were studied using differential thermal analysis （DTA）, scanning electron microscope （SEM） and X-ray diffraction （XRD）. The results show that the steel generates magnitic transformation, austenite formation, M23C-type carbide dissolution and transformation from austenite to B-ferrite, successively, at 600-1100℃. The starting formation temperature of austenite is 853 ℃ . The martensitic transformation occurs during air cooling or cooling at 40℃/min. The starting transformation temperature of martensitic is 382 ℃. Nb-containing MC-type carbide is very stable, which cannot completely dissolve into austcaite at testing temperature range.