Bulat steel
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Bulat is a type of steel alloy developed by Pavel Petrovich Anosov in 1838, when he completed ten years of study into the nature of Damascus steel swords and eventually managed to duplicate the qualities of that metal. Bulat is a Russian translation of the Persian word pulad, meaning steel. Bulat became popular in weapons manufacturing, notably cannons, until the Bessemer process was able to make the same quality steels for far less money.
Anosov had entered the Saint Petersburg Mine Cadet School in 1810, where a Damascus steel sword was stored in a display case. He became enchanted with the sword, and was filled with stories of them slashing through their European counterparts. In November 1817 he was sent to the factories of Zlatoust mining region in the southern Urals, where he was soon promoted to the inspector of the "weapon decoration department".
Here he again came into contact with Damascus steel of European origin (which was in fact pattern welded steel, and not at all similar), but quickly found that this steel was quite inferior to the original from the Middle East. Anosov had been working with various quenching techniques, and decided to attempt to duplicate Damascus steel with quenching. He eventually developed a methodology that greatly increased the hardness of his steels, although it is clear in retrospect that the original Damascus technique did not use quenching.
Unless quenching is used, carbon steel consists of two components: pure iron, in the form of ferrite, and cementite, a compound of iron and carbon. Cementite is very hard; its hardness is about 640 by the Brinell hardness test, whereas normal ferrite is only 200. In bulat the slow cooling process allowed the cementite to precipitate out into layers, sandwitched between layers of ferrite. The creation of the layering is what leads to the famous patterning of Damascus steel. Cementite is unstable and breaks down between 600-1100°C into ferrite and carbon, so working the hot metal must be done very carefully.