Properties of a creep resistant 9Cr-1.5Mo-1Co cast steel joint welded with a matching flux-cored wire

Abstract

For years, it has been the aim to improve the efficiency of thermal power plants by increasing the steam temperature. Therefore, appropriate steels and welding consumables are needed. Latest developments in cast materials have shown that the boron-alloyed 9Cr1.5Mo1Co steel called CB2 enables steam temperatures up to 620°C. As flux-cored wires for gas metal arc welding offer several technical and economic advantages, they are getting more and more popular. Therefore, a matching flux-cored wire for production welding of cast components has been developed. To obtain the required mechanical properties in weld metal and the heat-affected zone, an appropriate welding technology has been established. This paper deals with the influence of welding parameters on the mechanical properties at ambient temperature. Best results could be obtained with higher heat input and a lower cooling rate. Additionally, the first results of creep tests are presented and show that weld metal and cross-weld samples are within the scatter band of the base material. MatCalc calculations describe the microstructural evolution in the heat-affected zone (HAZ) during welding, post-weld heat treatment (PWHT), and service.