METHOD FOR EVALUATING CREEP DAMAGE OF WELD OF HIGH-CR FERRITE STEEL

摘要

PROBLEM TO BE SOLVED: To provide a highly reliable method by which the creep damage of a fine grain area in the welding heat-affected part of an actually damaged material can be evaluated, by manufacturing a damaged material which has the same creep damage as that of the actually damaged material without using any large-scaled testing device, preparing a calibration curve with which the creep damage of the damaged material can be evaluated with accuracy, and evaluating the creep damage of the fine grain area based on the curve. SOLUTION: In a method for evaluating creep damage of weld of high-Cr ferrite steel, (1) a material which reproduces a fine grain area in the welding heat-affect part of a damaged material is produced, (2) a creep rapture specimen having two or more notches 10 is prepared by working the material, and (3) the creep damage factor in a bottom 11 of each notch 10 in the other part than a ruptured part is calculated through creep rupture tests using a uniaxial load. Then (4) the relation between the states (the intergranular cavity forming amount, etc.), of micro-textures in the cross sections of the bottoms 11 of the notches 10 in the ruptured part and the other part than the ruptured part and the creep damage factors is found, and a calibration curve for evaluating creep damage is prepared from the found relation. Finally, the creep damage of the weld of high-Cr ferrite steel is evaluated based on the calibration curve.