[bodhiandpysics1]

This isn't true. First the terminology is a bit weird. Steel is an alloy of iron and carbon. This fact was not known until the 19th century! Classial "wrought iron" (whih has a carbon content under 2%) has a similiar composition to what is now called mild steel (it has somewhat different physical properties because wrought iron has inclusions of slag because of how its made). Classical steel has a somewhat higher carbon content. Pig iron (or cast iron) has an even higher carbon content, and is the product of a blast furnace. Steel could be made in a number of ways. The process of creating wrought iron naturally produces some higher carbon steel, which could be removed. This is how japanese swordmaking works (they take higher carbon steel, and low carbon steel, and pound the together). The finery process, invented in china, but heavilly used in europe, involved taking pig iron, and slowly oxidizing it to remove carbon. For armor, case hardening involves baking wrought iron in carbon to cause the surface to become steel. The cementation process from early modern europe involved doing this, and then folding the steel to produce uniform metal. Indian steelmaking didn't involve pig iron, since india didn't use blast furnaces.