电站用T22及与T91管高温蒸汽氧化的失效分析

对T2 2、T91钢锅炉再热器管高温水蒸气氧化失效进行分析 ;利用能谱分析仪测试分析氧化皮截面合金元素的浓度变化。结果表明 :T2 2、T91钢管在高温蒸汽环境下产生的氧化皮恶化其传热性能 ,导致管壁有一定的超温现象 ;氧化皮可分为双层结构 ,内层为含Cr的保护性氧化膜 ,外层主要为Fe2 O3 氧化物 ,内外层之间存在着大量的细小空洞缺陷 ;外氧化层有较明显的剥落 ,剥落的外氧化层聚集在弯头处导致管壁的过热、过烧 。

Analysis of High-temperature Boiler Tube Failure for T91 &T22

The tube failures took place frequently in the superheater of 2x600MW units in a power plant. According to the condition of tube failures, the mechanical property and microstructure on running and failed tubes were tested and evaluated. The chemical composition and structure phase of inner oxide scale and deposit inside of the tubes were examined.The fractured surfaces of failed tube samples were observed. And the material examination was performed for original tube steels SA213-T91 and SA213-T22. The results show that raw materials of SA213-T91 and SA213-T22 tube in superheater are qualified. Besides, the characteristics of the SA213-T91 and SA213-T22 tube failure are typical short-term overheated rupture. The rupture temperature is located between two phase Ac1 ～ Ac3 of the two steels. It is recognized that putting SA213-T22 tubes in operation under the condition of long-term over heating causes the rupture of SA213-T91 and SA213-T22.

锅炉末级过热器爆管原因分析及措施

通过宏观形貌、成分分析、低倍观察、金相组织、硬度检验、室温拉伸和冲击试验等对某电厂2×362MW机组锅炉末级过热器爆管原因进行了分析。结果表明,爆管I(材质T22)断裂与焊道设计不合理、母材管金相组织及力学性能不合格有关;爆管II(材质T91)断裂系焊接工艺执行不当,焊缝熔合线处存在夹渣和焊缝硬度偏高所致。对此提出了顶棚穿墙管与密封板的角焊缝应尽量避开密封板对接焊缝,改进密封板与管的焊接结构,减小定位块厚度等建议。