The manufacture of “green steel” moved one step closer to reality Friday as Massachusetts-based Boston Metal announced a $120 million investment from the world’s second-largest steelmaker, ArcelorMittal. Boston Metal will use the injection of funds to expand production at a pilot plant in Woburn, near Boston, and help launch commercial production in Brazil. The company uses renewable electricity to convert iron ore into steel. Steel is one of the world’s dirtiest heavy industries. Three-quarters of world production uses a traditional method that burns through train loads of coal to heat the furnaces and drive the reaction that releases pure iron...