| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a steel composition exhibiting good toughness under corrosive environment.SOLUTION: There is provided a steel composition having the copper (Cu) content of 0.15 wt.% or less, and other steel composition of specific amounts, having a fine structure with the martensite content of 95 vol.% or more and the bainite content of less than 5 vol.% based on the total volume of the steel composition, having a cementite deposition having an average martensite packet size dpacket of less than 3μm, a particle diameter dp of 70 nm or more and an average cementite shape factor calculated according to 4Aπ/P2, where A is an area of particle projection part and P is a length around the particle projection part, of 0.62 or more, and the surface of copper is protected for reducing transparency of hydrogen by forming an adhesive corrosion product layer of mackinawite close to the surface of copper.</p> |
