Development of Creep and Mechanical Properties for SMAW Cr-Mo-X Steel Welds

Abstract

This research describes the development of new welding materials with high strength and high heat resistance for Cr-Mo-X type steels. Through thermodynamic simulation, the newly designed welding electrode had excellent mechanical properties, especially in high temperature tensile testing at 600℃ with 393.2 MPa tensile strength, 385.3 MPa yield strength and 23.5% elongation. Refinement of second phase particles were key to the success of the newly designed electrodes. Presence of M<sub>23</sub>C<sub>6</sub> is noticeable in the new electrode welds which contributed to the high temperature strength and creep properties. Compared to conventional products, it was confirmed that the amount of M23C6 precipitates, measured in area fraction, increased substantially, from 5.9 to 11.9%. Z-phase, known to degrade weld mechanical properties, was reduced through adjusting chemical composition of the experimental welds. The reduction in Z-phase precipitates improved the brittle fracture resistance.