Mechanical Properties of 11Cr-0.4Mo-2W-CuVNb Steel Welded Joints at Elevated Temperatures

摘要

High Cr ferritic heat resisting steels are nowrecognized to be the most potential materials for thermal powerplants. In view of such trend, the present paper investigates thecreep properties of a W strengthened 1lCr-0.4Mo-2W-CuVNbsteel welded joints. Joints were prepared by using gas tungstenarc (GTA) welding and electron beam (EB) welding. In order tosimulate the microstructure of heat affected zone (HAZ), atechnique of furnace heating was adopted with varying peak-temperature. Specimens of the welded joints and simulated HAZwere subjected to creep tests at 923K. Most of the jointspecimens were ruptured at their HAZ, and inevitably resultedin certainly shorter creep lives of welded joints than those of thebase metals. The comparison of creep properties of simulatedHAZ specimens showed that fine grains produced by heating toaround Ac_3 were obviously responsible for such degradation ofcreep strength in welded joints. The creep lives were longer forEB welded joints by about 2 times than for GTA welded joints.For GTA welded joints creep rupture was always located on thehigher bevel angle sides. From these results, it is considered thatnarrower HAZ width with lower bevel angles surely producehigher creep strength of joints. The EB welded joints, however,showed relatively brittle fracture in the fine-grained HAZ afterlong-term creep tests.