Contrary to that old cooking adage, “a watched pot never boils,” keeping a careful eye on things—in the kitchen or in the laboratory—can be essential to making a useable (or edible!) final product. Take chocolate, for instance, that foundational block of the food pyramid. An important part of creating high-grade chocolate is a step called tempering, or the melting, stirring, and cooling of the liquid chocolate to align the crystals that give it a smooth texture and a glossy shine. One of the key senses chocolatiers use to monitor tempering is sight, giving them information on the thickness and color of the batch to make sure it tempers evenly as it cools.
But what if they had to do it blind?
For many years, that’s exactly what has been happening in metallurgy laboratories across the world. While the crafting of specialty metal alloys, like titanium or zirconium, can be far more complex than making chocolate, metals are often put through a process that is somewhat akin to chocolate tempering—vacuum arc remelting (VAR). VAR is an important step in metal fabrication, the process by which the chemical and physical homogeneity of the material is refined to ensure a quality end-product.
During the process, electrical power is used to heat a consumable electrode by means of an electric arc—a luminous electrical discharge like a lightning strike—and the melting material drops into a water-cooled copper crucible. Like chocolate, flaws in specialty metals are often caused by solidification problems that arise during the melting and refining process—problems that can lead to failure of the final product. Unlike chocolate, these products are often used in aerospace and aviation applications, where lives can depend on the quality of the metal components that make up their vehicles.
Previously, the conditions that cause flaws in the alloys could not be identified during furnace operations, requiring manufacturers to perform extensive testing on the resulting ingots to test for safe levels of homogeneity. However a new process developed by NETL metallurgists, called arc position sensing (APSallows operators to digitally monitor arc location during VAR processing. Being able to “see” the arcs during melting helps the engineer to control them and the melting process to produce consistently defect-free materials—something that was not possible prior to the development of this technology.
The APS system has the potential to revolutionize the fabrication of specialty metals. Adoption of this technology can improve the quality of the ingots produced and reduce the amount ingot testing required, saving manufacturers millions of dollars. In addition, APS could also lead to the production of materials with better chemical homogeneity, resulting in higher performance alloys.
This patented and award-winning technology has been licensed by AmpSci, an Oregon-based company founded by the technology’s inventors. Researchers at AmpSci are working to further develop the technology for widespread commercial deployment to the specialty metals industry.