1999 年 17 巻 3 号 p. 474-483
We evaluated not only total hydrogen content in duplex stainless steel and its weld metal but also hydrogen content in austenite by using internal friction measurement. The internal friction measurement was conducted over the temperature range from liquid nitrogen temperature to room temperature at a frequency of about 1.5 Hz. We investigated relationship between peak height and volume fraction of austenite and, also cleared influence of microstructure on internal friction peak.
(1) SUS304 austenitic stainless steel was cathodically charged with hydrogen. After charging, internal friction peak due to hydrogen was found at 260 K. This hydrogen induced peak height increased with increase of hydrogen content. Consequently it is apparent that this peak is attributed to hydrogen in austenite.
(2) The internal friction peak was observed at 260 K in SUS329J1 duplex stainless steel subjected to hydrogen charging. However this peak was not found for SUS444 ferritic stainless steel. Therefore it is clear that this peak is associated with hydrogen in austenite in SUS329J1 duplex stainless steel.
(3) The volume fraction of austenite for SUS329J1 duplex stainless steel and SMAW 329J4L and SMAW 329J3L weld metal was approximately 40%. The base metal has the microstructure with austenite elongated toward rolling direction in rod shape in ferrite matrix, and the weld metal has the microstructure with widmanstatten austenite in ferrite matrix. Hydrogen content and peak height value was plotted on same straight line, therefore their relationship is independent of microstructure morphology. The relationship between peak height and hydrogen content in austenite in SUS329J1 base metal is applicable to that of weld metal. Internal friction peak height due to hydrogen is proportional to volume fraction of austenite in case hydrogen content in austenite is same.