Building P-S-N Curves of Weld Metal of Spiral Submerge-Arc Welded X70 Steel Pipe

Fatigue tests were conducted on weld metal specimens cut from spiral submerge-arc welded X70 steel pipe. Fatigue life data at different stress amplitudes and stress rations were obtained. The probability distribution of these data was analyzed. Based on the equivalent fatigue life formula, values of fatigue resistant coefficient and equivalent fatigue limit were obtained and their probability distribution were also analyzed. The P-S-N curves of weld metal were built up. Fatigue life curves at given survivability were given. The results show that fatigue life of weld metal follows 1ogarithmic normal distribution, fatigue resistant coefficient follows logarithmic distribution and equivalent fatigue limit follows normal distribution.