Carbon steel flanges are used for connecting pipes, pipe fittings, and equipment in pipeline systems across industries such as power, petroleum refining, chemical, offshore engineering, and shipbuilding. This dataset includes primary raw materials, auxiliary materials, energy inputs, and waste outputs from the production process; however, infrastructure such as production equipment and facility construction are excluded from the system boundary. The life cycle inventory is compiled from data sourced from multiple references. The manufacturing process of carbon steel flanges includes procedures such as casting, cutting, drilling, turning, chamfering, grinding, and assembly.