Credited to Luxembourg. The universal beam mill was invented by Henry Grey in the United States and the beam is often called the Bethlehem beam there. Luxembourg's claim is only to the first industrial production, at Differdange in 1902.
How it began
Henry Grey invented and patented a universal beam mill in 1896 while working for a steel mill in Duluth, Minnesota. Engineers and mill owners in the United States were skeptical of the method, and Grey could not find an American mill willing to put it into full-scale production. The Differdange (Differdingen) iron and steel works in Luxembourg took it up, and in 1902 became the first producer of the modern wide-flange beam. The design is therefore American, and the first working production was in Luxembourg.
Before it existed
Builders used I-beams, a shape developed in 1849 by the French inventor Alphonse Halbou, rolled with narrow flanges. Where a larger or stiffer member was needed, beams were built up by riveting plates and L-shaped angle sections together, which took labor and added weight.
How it works
A universal mill uses sets of both horizontal and vertical rollers at the same time. The horizontal rolls work the web, the flat middle of the beam, while the vertical rolls press the outer faces of the flanges, so that a wide, deep section can be formed from a single piece of steel. A second set of finishing rollers then shapes the tips of the flanges and completes the beam.
How it spread
Charles Schwab brought the Grey process to Bethlehem Steel, which in 1907 became the first mill in the United States to begin production with the new rolling method. Bethlehem improved on several of the technologies pioneered in Luxembourg, raised production volumes and made its Bethlehem beams with a more consistent flange thickness than the beams first produced at Differdange.
What changed first
The Differdange mill went on to roll larger and more efficient shapes. By 1911 it had produced the first beam one meter deep, and in that year it turned out 15,000 tons of Grey beams per month and shifted its focus to this single product, a sign of how quickly demand for the new shape had grown.
What lasted
Wide-flange sections became the standard members of steel building frames, used in gravity columns, transfer trusses and girders and as steel elements inside large concrete structures. An engineering history of the shape links it to the tallest and largest structures built since, and notes that heavy high-strength sections are still specified for the columns of new supertall towers.
