This is not entirely impossible. Modern "differential hardening" creates a similar effect in high-end Japanese Katana (the Hamon line). However, the legends of Fuladh al Haami suggest a macro effect—a blade that never needed a whetstone.
But if you ask a bladesmith who has handled a genuine 10th-century Persian Shamshir : They will show you the strange red hue of the steel, the way it rings like a bell for thirty seconds after being tapped, and the fact that it has not rusted in 1,100 years. They will then whisper: "Fuladh al Haami." Fuladh al Haami remains the ultimate "MacGuffin" of the metallurgical world—a treasure that bridges the gap between hard science and romantic fantasy. Whether it was a specific batch of hypereutectoid steel or a purely mythological construct, the keyword resonates because humanity craves the perfect object. fuladh al haami
If you ask a historian: Yes, but metaphorical. The legend was used to sell expensive swords. This is not entirely impossible
In the 20th century, scientists discovered that certain ancient Indian and Sri Lankan steels (Wootz) containing high levels of phosphorus exhibited an anomaly. When forged correctly, they did not need to be reheated as frequently as conventional steel; the chemical exothermic reaction during hammering kept the metal "alive." But if you ask a bladesmith who has
We live in an age of stainless steel and ceramic blades, yet we have never replicated the supposed warmth of the Ardent Steel. Perhaps that is for the best. In a world of disposable commodities, a sword that never cools and never dulls belongs to the realm of legend.
Medieval texts describe a test: A sheet of the finest silk was draped over a stack of 50 brass coins. A blade of ordinary Damascus steel would cut 10 coins. A blade of Fuladh al Haami was said to cut the silk, all 50 coins, and the stone table beneath—without losing its edge. Beyond physics, Fuladh al Haami occupies a massive space in Islamic Alchemy (Kimiya). The alchemist Jabir ibn Hayyan (Geber) theorized that metals were composed of "Sulfur" (the principle of combustibility) and "Mercury" (the principle of ductility).