Welding is a critical procedure in production, and the vital element is knowing how the atoms are put together to form a complete structure. Pre-pandemic research by the Center for Welding, Joining and Coatings Research of Colorado School of Mines, Tim Pickle and Ben Schneiderman, conducted at the Department of Energy’s (DOE’s) Oak Ridge National Laboratory (ORNL) revealed that you could use neutrons to comprehend the fusion process in welding.
These students are part of the team engineering major research at the National Renewable Energy Laboratory (NREL). This research entails determining the welds’ capacity in developing enormous thermal energy storage tanks to receive solar energy without yielding and melting down. Pickle explained that they are evaluating the performance of two manufacturing procedures for welds, with one containing the post-weld heat treatment step and the other lacking this step. Additionally, he said that they are analyzing the suitable and finite procedures to conduct post-weld heat treatment processes and idealize the cracking challenge’s resolution.
The research team observes the stress relaxation cracking (SRC) and how vulnerable the weld is to give in due to excessive stress and superheating. Furthermore, thermal fatigue brought about by the high temperature of the energy under storage is a primary factor leading to SRC. The team discovered that continuous temperature change creates stress, which results in deformations. The solar energy storage tanks are enormous, with a width of approximately 100 feet and a height of 30 feet. These tanks host molten salt material, which is hot and liquefied to keep solar energy trapped by the solar panels. To obtain solar energy, the liquid molten salt would enter the steam system and boil the water for turning the turbines to produce electricity from solar energy.
The tank is composed of large stainless steel plates compounded to form a cylinder. The ends have weld seams and filler material to maintain the stability of the tank. Pickle noted that when the temperatures exceed 500 degrees Celcius, stress starts intruding in the welds leading to dentations. He stated that they are establishing the possibility of minimizing the tensile strength imparted on the cylinder to increase the steel plates’ lifespan and impede premature cracking by determining the terminal stresses that develop after every procedure.
The team found out that neutrons would be crucial in determining the terminal stress and displaying atomic changes in the tank components’ internal components since they can sip into the internals. The team utilized the HIDRA instrument to evaluate the residual stress accumulated into the weld beads, making them crack. Schneiderman noted that they are evaluating how the metal deforms under stress as drilling proceeds down the material. The challenge noted with this procedure is that the stress determined is for only a specific steel material location. Finally, Schneiderman added that they would need to dimensionally dissect the steel with stress to measure its tensile strength using neutrons. He stated that more suitable methods are still under the research and development section to mitigate the SRC challenge.