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本文对在540℃、100个大气压条件下使用的高压过热蒸汽管道进行了研究。样品取自运行23年的12CrlMoV过热蒸汽管。由断口分析看出:管子内外表面都存在一个Fe_3O_4氧化层,厚度300μm左右。氧化层与基体交界面之间为沿晶氧化区,厚度为20～40μm。断口呈现沿晶断裂,晶界面上大量分布含有铬的粒状析出物(照片1、2)。再向内是50μm左右厚的含有极少量的沿晶断裂区。内部基体组织珠光体基本消失。使用过的管子碳化物晶格常数明显变小,而且还出现M_2C、MC相。文章还讨论了表面氧化,组织变化和使用寿命等问题。通过计算:φ325壁厚26mm的管子内表承受最大
In this paper, the use of high pressure superheated steam pipe at 540 ℃, 100 atm was studied. Samples were taken from a 12CrlMoV overheated steam pipe run for 23 years. From the fracture analysis shows that: there is a pipe inside and outside the surface of a Fe_3O_4 oxide layer, the thickness of about 300μm. Between the oxide layer and the interface between the substrate for the crystalline oxide along the thickness of 20 ~ 40μm. The fractures show intergranular fracture, and a large number of granular precipitates containing chromium are distributed on the grain boundaries (Photos 1, 2). Re-inward is about 50μm thick with a very small amount of intergranular fracture zone. The internal matrix pearlite disappeared. The lattice constants of the used tube carbides are obviously smaller, and the M_2C and MC phases also appear. The article also discussed the surface oxidation, tissue changes and service life and other issues. By calculation: φ325 26mm wall thickness of the tube to withstand the largest