Abstract
Mechanical properties of base metals and welding materials of the high strength Cr-Mo steels have been reviewed and studied in the activity of the ECM committee in the Japan Welding Engineering Society. The ECM committee collected about 60 papers and reports on the high strength Cr-Mo steels manufactured in Japan, published and non-published in and outside Japan, to establish the data base of the steels required for their JIS material standardization. The base metal mechanical property data of the high strength Cr-Mo steels: Enhanced 2 1/4Cr-1 Mo, Modified 2 1/4 Cr-1 Mo and Modified 3Cr-1 Mo steels, were analyzed in terms of manufacturing procedures and product forms', plate or forging.
The present report summarizes the characteristics of mechanical and physical properties of the steels such as tensile strength at room and elevated temperatures, impact toughness, creep rupture strength, low cycle fatigue life, elastic modulus, thermal expansion constant and so on. The comparison of these characteristics between the steels and with the standard 2 1/4 Cr-1 Mo steel is also shown. Based on the analyses of the tensile strength at room and elevated temperatures and creep rupture strength, the allowable stress and design stress were calculated for JIS 8270 (formerly JIS 88243 and B8250 respectively) and compared with the corresponding values specified in the ASME code cases. It is confirmed that the high strength Cr-Mo steels show almost equivalent values to the ASME allowable and design stresses, significantly higher than those of standard 2 1/4 Cr-1Mo steel as expected. They also exhibit good impact toughness and low cycle fatigue property.
