| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a fire-resistant steel material excellent in high temperature strength and its production method, and to secure a stable desired high temperature strength even if its composition is decreased in Mo content as much as possible. <P>SOLUTION: A steel raw material which includes C:0.01-0.1%, Si:0.01-1.0%, Mn:0.1-2.0%, Al:0.003-0.1%, Mo:0.010-0.30%, Nb:0.010-0.20%, is adjusted and contained so as to meet a carbon equivalent Ceq below 0.46. After this steel raw material is heated at the temperature range 1,000-1,350°C, a hot rolling is performed with a rolling end temperature over 850°C, then this steel raw material is air-cooled or rapid cooled into the temperature range ((Ar3 transformation point)-30°C)-((Ar3 transformation point)-130°C), the hot rolling is conducted at least one pass at the temperature range ((Ar3 transformation point)-30°C)-((Ar3 transformation point)-130°C) at the range of rolling reduction 1.0-10%. As a result, by the rolling at bi-phase temperature region, a distortion induced precipitation is enhanced, and at the rolling state, a fine Nb precipitate of particle diameter less than 20 nm is voluminously precipitated in the range of 0.01-0.08% in terms of Nb conversion. By large amount precipitation of the fine Nb precipitate of particle diameter less than 20 nm, when a fire occurs, a fine Mo carbide precipitation is enhanced with its high temperature heating, and even it is a low Mo system, high temperature proof strength is increased, so a fire-resistant performance is remarkably increased. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
