X-rays Reveal Why High-Speed Welding Goes Wrong

The Science

Laser welding is used to join thin metal parts, like those in fuel cells and electronics. It's a fast and clean process. However, at high speeds, it can leave bumps on the surface of the metal. These bumps make the weld weaker. Scientists used a powerful X-ray camera to watch the metal melt and move during welding. They then ran computer tests to study the flow of melted metal, which revealed key causes of the bumps forming. They created a new index to predict when and where the bumps will form.

The Impact

This research could speed up and improve laser welding. That improvement would result in stronger, smoother joints in car parts, fuel cells, and tiny devices. With fewer defects, these parts could last longer and work more efficiently. The new index scientists created can help engineers fix problems before they happen, which will save time, money, and materials. The work will also help scientists learn more about how hot metal moves and changes. That knowledge could lead to better tools in fields such as energy, electronics, and medical devices.

Summary

Laser welding is used in many industries because it's fast, precise, and creates clean joints. But when welding is done at high speeds, a common problem called "humping" can occur. These are small bumps that form on the surface of the weld, which makes the connection weaker. Until now, most studies have used computer models to predict what causes these humps. However, investigations into exactly how the metal behaves in real time would provide greater details and insights.

In this research, scientists used synchrotron X-ray imaging at the Advanced Photon Source, a Department of Energy (DOE) Office of Science User Facility, to watch what happens inside a weld as it forms. This tool allowed them to see the shape and motion of the melted metal with remarkable precision. They also used computer simulations to better understand how the metal flows and how that affects the weld. Researchers discovered that the flow of melted metal at the end of the weld plays a big role in forming humps. Based on their findings, they created a new "humping index" to predict when and where defects are likely to happen. This index can help improve welding quality in many technologies, from fuel cells and electric motors to electronics and medical tools, by reducing flaws and increasing strength.

Contact

Jingling LiPennsylvania State [email protected]

Funding

This work was supported by the DOE Office of Science and Office of Energy Efficiency and Renewable Energy. The research used resources at the Advanced Photon Source, a DOE Office of Science User Facility operated by Argonne National Laboratory.

Publications

Zen-Hao Lai, et al., "Unveiling mechanisms and onset threshold of humping in high-speed laser welding," Nat Commun 15, 9546 (2024). [DOI: 10.1038/s41467-024-53888-w]