Abstract: A hydrogen permeability testing device can measure hydrogen amount(s) entering a metal material by electrochemical hydrogen permeation. The device may include: a metal specimen having a hydrogen entry face through which hydrogen enters, a hydrogen detection face on which the entered hydrogen is detected, and a metal plating formed on the hydrogen detection face to detect the entered hydrogen; a reference and counter electrode for making an electrochemical reaction progress; an electrolytic vessel provided on a hydrogen detection face side, housing the reference and counter electrode, and containing an aqueous sodium silicate solution having a freezing point of ?0° C. and capable of suppressing residual current to ?10 nA/cm2 when an electric potential of the hydrogen detection face is ?1 to 1 V relative to the reference electrode; and a measurement unit which measures the amount of hydrogen based on a current value resulting from the electrochemical reaction.

Abstract: Disclosed herein is a duplex stainless steel material including a ferrite phase and an austenite phase, wherein the steel material contains, as metal component composition, at least one X-group element selected from 0.01 to 0.50 mass % of V, 0.0001 to 0.0500 mass % of Ti, 0.0005 to 0.0500 mass % of Nb, and 0.01 to 0.50 mass % of Ta. The steel material has composite inclusions or has composite inclusions and inclusions, in which each of the inclusions includes at least one of an oxide, a sulfide, and an oxysulfide; each of the composite inclusions includes one of the inclusions as a nucleus and includes an outer shell existing around the nucleus and having a carbide or a nitride containing Cr and the at least one X-group element, and the proportion of the number of the composite inclusions with respect to the total number of the inclusions is 30% or more.