Tube-burst and leakage on the steam-cooled wall of boiler no.1 in one power plant had occurred more than thirty times in ten years of operation.By using chemical analysis

metallurgical structure analysis

as well as scanning electron microscope

and auger spectrometer etc.

the tube-burst and leakage have been analysed.Resrlts show that the harmful elements content of As + Sn being too high in pipe material of said steam-cooled wall made the pipe material to produce temper brittleness

and unsuitable weld procedure made the said brittleness to be more serious

were the main causes leading to tube-burst and leakage.For this

it is recommended that the pipe material of said steam-cooled wall has to be replaced.