T/P23, 24, 911 and 92: New grades for advanced coal-fired power plants—Properties and experience

After the development of the well-known T/P91 grade in the early 1980s and the long industrial experiences since the early 1990s, it has been necessary to develop new steels to answer the demand of the powergen industry. New (ultra) super critical boilers require materials with advanced creep properties to reach severe steam parameters.For the 2.25% Cr family, grades 23 and 24 are now available to be used instead of the previous grade 22 with many technical and economical advantages.For the 9% Cr steels, new grades such as T/P911 and T/P92 have been developed with higher creep properties than T/P91.Thanks to its large industrial experience in these new grades, Vallourec & Mannesmann Tubes and Boehler Thyssen Schweisstechnik have now worldwide references of use with these new steel grades. In this paper, information on properties, behaviour and workability will be presented with a focus on
• elevated temperature properties and allowable stresses,
• oxidation and maximum service temperature and
• weldability procedures and recommendations.