Heat-affected zone

About: Heat-affected zone is a research topic. Over the lifetime, 18787 publications have been published within this topic receiving 231744 citations.

Welding of thick stainless steel plates up to 50 mm with high brightness lasers

Abstract: Thick-section stainless steels are widely used in the components and structures for nuclear power plants. Laser welding is being considered as a high-efficiency method instead of arc welding for some components, so as to improve the production efficiency and reduce the residual stresses of the heat-affected zone. In this paper, multipasses narrow-gap welding of 50 mm thick Type 316L plates with an 8 kW disk laser was first investigated. The effect of welding conditions on the weld bead geometry and welding defects was studied. It shows that lack of fusion could be prevented by optimizing the relationship between laser power intensity and the deposited metal volume. Butt joint of 50 mm thick plates with narrow gap could be performed with eight-layers welding at laser power of 6 kW and welding speed of 0.4 m/min. In order to reduce the weld passes further, gas jet assisted laser welding was tried to weld thick Type 316L plates with a 10 kW fiber laser. The result shows that butt-joint welding of 40 mm plates without filler wire could be carried out at 0.3 m/min welding speed with no porosity or other welding defects. As for 50 mm thick plate, a good weld bead could be obtained with bead-on-plate welding from both sides at 0.2 m/min welding speed.

Heat treatment for weld beads

Abstract: Two parts are welded together at a weld spot in a groove. A spot adjacent the weld spot is heated simultaneously and independently of the welding so that the heating and welding form a heat-treated weld bead along the groove. Preheat treatment, postheat treatment, or both, may be used simultaneously with welding to maximize performance of the resulting weld joint. Preheat and postheat treatment may be performed using lasers while the welding may be performed by TIG welding or laser welding. The welding torch and preheat and postheat lasers are coplanarly aligned.

Mode I fracture and microstructure for 2024-T3 friction stir welds

Abstract: Detailed microstructural studies and mode I fracture experiments have been performed on both base material and three families of friction stir welds (FSWs) in 7 mm thick, 2024-T3 aluminum plate, designated hot, medium and cold due to the level of nominal heat input during the joining process. Microstructural studies indicate that the FSW nugget grain structure is relatively uniform in all welds, with a banded microstructure existing on horizontal cross-sections traversing the weld region; the spatial wavelength of the bands corresponds to the tool advance per revolution. The microstructural bands have elevated particle concentrations, with the particles having the same elemental content as base metal impurities, implying that the FSW process is responsible for the observed particle redistribution and microstructural banding. Furthermore, particle redistribution in all welds resulted in (a-1) particle size and volume fraction reduction on the advancing side of the weld nugget and (a-2) an attendant increase in particle volume fraction on the retreating side of the weld nugget. Finally, results indicate that hardness minima are present in the heat affected zone (HAZ) outside of the weld nugget on both the advancing side and retreating side for all welds, with the hot weld having the lowest overall weld hardness. Results from mode I fracture tests indicate that the measured critical COD at a fixed distance behind the crack tip is a viable fracture parameter for FSW joints that is capable of correlating the observed load-crack extension response for both the base metal and all FSWs. In addition, critical COD measurements indicate that FSW joints have a through-thickness variation in fracture resistance. Finally, the observed ductile crack growth path (which remained in the FSW region for all FSW joints) can be correlated with the locations of hardness minima, with microstructure variations affecting local fracture processes and the corresponding crack path.