Abstract
The effect of hydrogen on high-cycle fatigue property of shielded metal arc welded joints for gas piping was investigated. The thermal desorption spectroscopy (TDS) and the thermal desorption analysis (TDA) showed that a large amount of hydrogen was desorbed from weld metal, while hydrogen was not desorbed from HAZ and base metal. The hydrogen desorbed from weld metal is latent in the welded joint, because the welded joint is not hydrogen-charged. The hydrogen is considered to be nondiffusible, because it takes more than five months from welding. The growth of fatigue crack initiated from the small hole on the first layer of weld metal was faster at 0.2 Hz than at 2 and 20 Hz. The nondiffusible hydrogen in weld metal increased fatigue crack growth rate at the lower frequency of 0.2 Hz.
