| 摘要 |
A steel for a steel pipe which has a chemical composition that C: 0.2 to 0.7%, Si: 0.01 to 0.8%, Mn: 0.1 to 1.5%. S: 0.005% or less, P: 0.03% or less, Al: 0.0005 to 0.1%, Ті: 0.005 to 0.05%, Ca: 0.0004 to 0.005%, N: 0.007% or less, Cr: 0.1 to 1.5%. Mo: 0.2 to 1.0%, Nb: 0 to 0.1%, Zr: 0 to 0.1%, V: 0 to 0.5%, B: 0 to 0.005%, and the balance: Fe and impurities, and contains non-metal inclusions containing Ca, Al, Ті, N, О (oxygen) and S, wherein the inclusions have a ratio of (Ca%)/(Al%) of 0.55 to 1.72, and a ratio of (Ca%)/(Ti%) of 0.7 to 19. The above steel for a steel pipe can be used as a raw material of a steel pipe for an oil well pipe, such as a casing and a tubing of a greatly deep oil or natural gas well and an oil or natural gas well located in a severe corrosion circumstance and a drill pipe and a drill collar for use in excavation. |
