Abstract:

There was a crack on the fillet weld of the ventilation tube of the outlet header socket of a hightemperature reheater in a power plant which was found during maintenance.The tube cracked again and the steam leaked after 6000h ours operation since the tube patching.Though macroscopic examination,spectral examination,hardness test,metallographic examination and scanning electron microscopic analysis,reasons for the crack are found out to be the improper repair welding which cause incomplete fusion and and other welding defects.Unreasonable structure design makes the expansion of ventilation tube hampered by the enclosed wall.Weld on the outer surfaces cracks under stress,and the crack spreads along the fusion line to the heat affected zone.It is suggested that the whole socket should be rewelded as soon as possible and the perforation structure of ventilation tube should be optimized.

Key words:

font-size: 10.5pt, mso-spacerun: 'yes', mso-font-kerning: 1.0000pt">highfont-size: 10.5pt, mso-spacerun: 'yes', mso-font-kerning: 1.0000pt">font-size: 10.5pt, mso-spacerun: 'yes', mso-font-kerning: 1.0000pt">temperature reheater；repair welding, incomplete fusion, welding defects, crack propagation, expansion impediment；stress