Nitronic 50不锈钢低温冲击韧性大幅降低原因分析

Cause Analysis on Significant Decrease of Impact Toughness of Nitronic 50 Stainless Steel at Cryogenic Temperature

针对低温风洞运动机构用Nitronic 50奥氏体不锈钢在复检中出现低温冲击吸收能量显著偏低的现象,对该批次不锈钢和参考样品分别取样,进行了化学成分、金相、扫描电镜以及能谱等分析。结果表明:该批次Nitronic 50不锈钢中存在大量短棒状的Al N脆性夹杂物,是导致其低温冲击韧性大幅度降低的主要原因;材料晶粒尺寸偏大且存在混晶现象也降低了其冲击韧性。

Regarding to the obvious low impact absorption energy of Nitronic 50 austenitic stainless steel used in the movement mechanism of cryogenic wind tunnel at cryogenic temperature during reinspection,a series of testing methods were adopted on the specimens of raw material and reference sample, such as chemical composition analysis,metallographic analysis,scanning electron microscope and energy spectrum analysis,and so on. The results show that numerous short rod-like AlN brittle inclusions existing in this batch of Nitronic 50 stainless steel were the main reason for the significant decrease of the impact toughness at cryogenic temperature. The coarse grain and the mischcrystal in the material also reduced the impact toughness.