| 摘要 |
<p>A martensitic stainless steel which comprises, in mass %, 0.01 to 0.1 % of C, 9 to 15 % of Cr, 0.1 % or less of N, wherein it contains carbides present in old austenite grain boundaries in an amount of 0.5 vol % or less, or wherein carbides contained therein have a maximum short diameter of 10 to 200 nm, or wherein carbides contained therein have a ratio of an average Cr concentration to an average Fe concentration of 0.4 or less, or wherein it contains carbides of M23C6 type in an amount of 1 vol % or less, carbides of M3C type in an amount of 0.01 to 1.5 vol %, and nitrides of MN type or M2N type in an amount of 0.3 vol % or less. The martensitic stainless steel has a relatively high Cr content resulting in high strength, and also exhibits improved toughness, and accordingly has a wide range of applications including those for an oil well containing carbon dioxide and a small amount of hydrogen sulfide, in particular, an oil well pipe for a greatly deep oil well.</p> |
