Boston Metal, a Bill Gates-backed start-up based in Boston (unsurprisingly), has announced that it has raised $50 million in its pursuit to decarbonize the steel industry. As one of the largest and hardest to decarbonize contributors towards global warming, breakthroughs from such companies could result in the largest transformation of steelmaking in the past 3,000 years. The company, which spun out of an MIT lab in 2012, initially offered up $60 million through this recent funding round, according to a filing with the Securities and Exchange Commission, but has so far only managed to hit $10 million short of target, coming from eight unnamed investors. This builds on previous investment from Bill Gates’ Breakthrough Energy Ventures, as well as Prelude…