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 te...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.展开更多
The effect of heat treatment parameters on the strength and plasticity and the metallographic structures and substructures of Crl2W2MoVNbNB steel has been studied. The regularity among the different heat treatment pro...The effect of heat treatment parameters on the strength and plasticity and the metallographic structures and substructures of Crl2W2MoVNbNB steel has been studied. The regularity among the different heat treatment processes, the strength and plasticity, the feature of its structure and substructure have been analyzed. The results show that after being normalized and tempered, the structure of tempered lath martensite and blocky ferrite has been acquired, the grains do not grow up with the increasing of normalizing temperatures. During the tempering process, instead of recrystallization, polygonization of tempered martensite only takes place. Tempering temperature is chief effective factor to the strength of the steel. Moreover the proper heat treatment parameters of Crl2W2MoVNbNB steel have been given.展开更多
文摘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.
文摘The effect of heat treatment parameters on the strength and plasticity and the metallographic structures and substructures of Crl2W2MoVNbNB steel has been studied. The regularity among the different heat treatment processes, the strength and plasticity, the feature of its structure and substructure have been analyzed. The results show that after being normalized and tempered, the structure of tempered lath martensite and blocky ferrite has been acquired, the grains do not grow up with the increasing of normalizing temperatures. During the tempering process, instead of recrystallization, polygonization of tempered martensite only takes place. Tempering temperature is chief effective factor to the strength of the steel. Moreover the proper heat treatment parameters of Crl2W2MoVNbNB steel have been given.
