晶粒拉长形态对S30432不锈钢管组织与性能的影响

Effect of grain elongation morphology on microstructure and properties of S30432 stainless steel tube

为研究晶粒拉长形态对锅炉用S30432不锈钢管高温服役性能的影响,通过光学显微镜、扫描电镜、硬度测试、拉伸测试、持久测试等方法,对晶粒拉长形态和等轴晶形态的S30432不锈钢管的微观组织与性能进行了研究分析,并对不同晶粒形态钢管的性能差异性进行分析。结果表明:拉长形态晶粒(晶粒延伸度≥3)会造成S30432不锈钢的室温拉伸强度升高、硬度升高;同时,在持久过程中晶粒拉长形态(晶粒延伸度≥3)S30432不锈钢的显微组织中M_(23)C_(6)碳化物快速在晶界链状析出且迅速粗化,表现出更快的微观组织老化速度,从而降低其高温持久性能;建议严格控制S30432不锈钢的晶粒形态,晶粒延伸度在1.0~2.0的范围区间,可获得理想的晶粒形态和良好的持久性能,保障电站锅炉高温部件的服役安全性。

In order to study the influence of grain elongation morphology on the high-temperature service performance of S30432 stainless steel tube for boiler,the microstructure and properties of two types of S30432 stainless steel tube,namely grain elongation morphology and equiaxed crystal morphology,were studied and analyzed by optical microscopy,scanning electron microscopy,hardness testing,tensile testing and stress-rupture testing,and the performance differences of steel tubes with different grain morphologies were also analyzed.The results show that the elongated grain morphology(Grain elongation degree≥3)can cause an increase in room temperature tensile strength and hardness of S30432 stainless steel.At the same time,during the stress-rupture process,the microstructure of S30432 stainless steel in grain elongation morphology(Grain elongation degree≥3)shows that carbides M_(23)C_(6) rapidly precipitate in a chain like manner at grain boundaries and coarsen rapidly,exhibiting a faster microstructural aging rate,thereby reducing its high-temperature stress-rupture performance.It is recommended to strictly control the grain morphology of S30432 stainless steel and limit the grain elongation degree within 1.0-2.0,which can achieve the ideal grain morphology and good stress-rupture performance to ensure the service safety of high-temperature components in power plant boilers.