Relaxation of Residual Stress in AISI 347 Welded Pipe: A Time-of-Flight Neutron Diffraction Study

Abstract

Abstract The residual stress state in an AISI 347 welded pipe for nuclear applications has been investigated by means of neutron time-of-flight diffraction. Two kinds of welds were compared: a ‘bare’ manual and a dressed tungsten inert gas (m-TIG with and without last pass heat sink, respectively). Thorough investigations along a line transverse to the weld seam and through-thickness have been carried out with very fine-step scans. Complementary microstructural investigations have been carried out by means of optical microscopy. Results show that the grain size varies from the parent material to the heat affected zone and weld pool. Some martensite is present in the parent material because of the cold working following each welding pass. In the weld pool, the heat flow seems to be redistributed effectively by the cap pass of the LPHSW. Although the microstructural heat affected zone is rather small, the effect of the weld on the stress state seems to extend further (the so-called strain affected zone). In...