关键词: 锅炉, 末级过热器, 碳化物, 珠光体耐热钢, 蠕变裂纹, 断裂失效

Abstract:

In the long-term overheating operation condition, the boiler high temperature superheater is easy to cause the deterioration of materials and the decline of material structure and performance, and causes the pipe explosion accident. The causes of burst tube of final-stage superheater tube in a power plant boiler were analysed through macroscopic examination, Brinell hardness test, tensile strength test and metallographic structure test. The analysis results show that final-stage superheater tube operates at high temperature and pressure for a long time, resulting in the carbide enrichment at grain boundary and weaken the grain boundary strength. Under the action of tensile stress, creep cavities and creep cracks occur at grain boundary, resulting in the decrease of durable strength and tensile strength of pearlite heat-resistant steel, and finally the fracture failure occurs.

Key words: boiler, final-stage superheater tube, carbide, pearlite heat-resistant steel, creep crack, fracture failure