Who makes grain-oriented electrical steel & amorphous cores for AI data centers

The core of a transformer is a stack of thin steel or amorphous-alloy laminations that carries the magnetic flux linking the primary and secondary windings; the grade of that material sets the transformer's efficiency and, increasingly, how long it takes to build one. Grain-oriented electrical steel (GOES) is the standard material for larger power and distribution transformers; amorphous alloy cores are used where no-load losses matter most. This sits directly upstream of every transformer in the power chain — utility and substation transformers, unit substations and pad-mounted transformers feeding the building, and the smaller transformers inside power distribution equipment (Layer 6). Production is concentrated among a small number of specialty steel mills that run dedicated GOES lines, and a shift toward amorphous cores draws on an even narrower alloy-supply base. Utilities and data-center developers have been buying transformers years ahead of need, and the taxonomy identifies GOES supply itself — not transformer manufacturing capacity — as the binding constraint behind those lead times. For investors, the questions are mill capacity additions (GOES lines are slow and capital-intensive to build), the pace of qualification for new suppliers, and exposure to Cleveland-Cliffs, named in the taxonomy as the sole US GOES producer, versus the larger number of international mills.