In order to analyze the cause of the accident

the chemical composition analysis

mechanical property test

macro and micro structure analysis were used to analyze the samples

and the field operation environment parameters were checked.The results show that the chemical composition of the explosion material is normal

but the mechanical properties are decreased The metallographic structure of the material shows that pearlite spheroidization is serious

and there is no overtemperature in the field operation after investigation

but there is white corrosion in the macroscopic appearance

and Na+ion in the corrosion exceeds the standard. As a result

the large bend is in the stress concentration position

and there is alkali corrosion in operation. Under high temperature and high pressure environment

the material structure is spheroidized seriously

and the high temperature resistance performance is reduced

which eventually leads to the failure of the large bend and tube explosion.