稀土对超级铁素体不锈钢组织和性能的影响

摘要

Scanning Electron Microscopy ( SEM) , Optical Microscopy ( OM) , image analysis, room-temperature impact test and potentiodynamic polarization technique were used to evaluate the influence of different rare earth ( RE) quantity on grain size, second phase separation, mechanical properties and corrosion resistance of super ferritic stainless steel ( SFSS) . The results show that a proper amount of RE can refine grains, increasing the grain grade from 6. 9 to 8. 6. The percentage of precipitation phase was significantly decreased in the annealing at 930 ℃ and no chain structure was observed. RE can increase the solid solubility of carbon and nitrogen, thus suppressing carbonitride precipitation. The impact energy of SFSS containing 0. 106% RE was 45. 25 J, rising by 217% compared with the steel without RE. Meanwhile, RE promoted the impact fracture mechanism to transit from brittle fracture to ductile. With the content of sulfur reducing and the inclusions improved, the pitting corrosion resistance was enhanced effectively. The steel containing 0. 106% RE exhibited the lowest corrosion rate.%通过光学金相显微镜、金相定量图像分析仪、透射电子显微镜、室温冲击和动电位极化等分析测试手段,研究不同稀土含量的超级铁素体不锈钢的晶粒特征、930℃退火时析出相、冲击韧性和耐腐蚀性。研究表明：适量的稀土可有效细化晶粒,使晶粒度从6.9级提高至8.6级；添加稀土后,退火时析出相所占面积百分数明显降低,且未见以链状形式出现；稀土提高了C、N的固溶度,使碳氮化物析出减少；稀土含量为0.106%时,冲击功为45.25 J,较未添加稀土时提高了2倍；同时,稀土促使断裂机制由脆性断裂向韧性断裂转变。稀土可有效增强超级铁素体不锈钢的耐点蚀性能。稀土含量为0.106%时,腐蚀速率最小。钢中S含量降低且夹杂物得到改善是稀土提高该钢种耐点蚀性主要原因。