Effect of PWHT conditions on mechanical properties of W alloyed 9Cr weld metal -study of effect of PWHT conditions on properties of W alloyed 9Cr weld metal (report 2)

摘要

Effects of PWHT (Post Weld heat Treatment) conditions on the mechanical properties of the W alloyed GTA weldment of 9Cr-1.8W ferritic heat resistant steel were studied. Tensile test at 293K and Charpy impact test at 293K were conducted on the weld metals. Creep rupture tests of the weld metals and the welded joints were carried out. Obtained results are summarized as follows(1) Tensile strength of the GTA weld metals decreased as PWHT temperature and PWHT time increased.(2) Toughness of the GTA weld metals increased as PWHT temperature increased. However, toughness of the weld metals decrased as PWHT time increased at PWHT temperature of 1013K. This increase of toughness with temperature seemed to due to the drop ofdislocation density and the decrease of toughness with time seemed to due to the growth of precipitates.(3) At 873K and 973K, the creep rupture strength of the GTA weld metals decreased as PWHT temperature increased. However, the influence of PWHT temperature on the creep rupture strength of the weld metals became small as the rupture lives becamelonger.(4) When the stress was higher than around 60 MPa in the creep rupture test of GTA welded joints at 973K, the location of rupture depended on the PWHT temperature. At higher PWHT temperature, welded joint ruptured in the weld metal because of decreasedcreep rupture strength of the weld metal. And at lower PWHT temperature, welded joint ruptured in the base metal. However lower than around 60 MPa, all welded joints ruptured in HAZ and there was little difference in rupture lives between weld metals with 993K-1073K PWHT temperatures.