Precipitation behavior in W alloyed weld metal -study of effect of PWHT conditions on properties of W alloyed 9Cr weld metal (report 1)-

摘要

Effects of PWHT (Post Weld Heat Treatment) conditions on the precipitation behavior in W alloyed GTA weld metal for 9Cr-i .8W ferritic heat resistant steel were studied. Extracted residues of the as-welded weld metal and the weld metals after PWHT were chemically analyzed and X- ray diffraction analyses were conducted on the extracted residues to determine precipitates in the weld metals. Results of chemical analysis of the extracted residues were compared with predicted values calculated byTHERMO-CALC.Obtained results are summarized as follows;(i) Presence of M{sub}23C{sub}6 and MX type carbo-nitrides of Nb and V in weld metals before and after PWHT were revealed by X-ray diffraction analysis.(2) M{sub}23C{sub}6 and Nb-rich MX type carbo-nitrides precipitated during cooling after welding. MX type carbo-nitrides which precipitated during PWHT were rich in V(3) There was little change in amounts of precipitated elements with PWHT temperature from 1013K to 1073K for 2 hours.(4) There was little change in amount of precipitated elements with time during PWHT at 1013K.