A study on the development of creep rupture and temper embrittlement properties in 21/4Cr-1Mo-V steel weld metal

Abstract

21/4Cr-1Mo-V steel, such as the ASTM A542/A542M type D, which has remarkable anti-hydrogen embrittlement and creep rupture properties, is widely used in main components such as pressure vessels in oil refinery plants. Submerged arc welding (SAW), shielded metal arc welding (SMAW), and gas-shielded tungsten arc welding (GTAW) consumables, equivalent to base metal, are selected for the welding of this steel. As referred to in American Society of Mechanical Engineers (ASME) Section VIII, various properties, such as tensile strength and impact toughness in addition to creep rupture, are required in 21/4Cr-1Mo-V steel weld metal. Especially in creep rupture properties, the lower limit of the design temperature, which is required in main components (mentioned above), was lowered from 470 to 440 °C, based on the revision of the ASME code in 2009. Additionally, temper embrittlement behavior, occurring under high temperature over a long period of time, should be considered as well when dealing with this deposited metal. In this study, we have discussed the validity of precipitates in order to develop the creep rupture and temper embrittlement properties of 21/4Cr-1Mo-V steel weld metal. As a result, it was found that MX in crystal grains improves creep rupture lifetime and that, in the prior γ grain boundaries, it inhibits embrittlement caused by the segration of impurities.