Tipping Slag

Slag is the mineral residue left over once iron has been extracted from ore in the blast furnace. It forms as limestone flux reacts with the impurities in the iron ore burden, drawing them away from the metal and floating to the surface of the molten iron as a separate liquid layer. That liquid is tapped off through its own notch in the furnace. Slag also forms in the basic oxygen steelmaking vessel, where it is poured off after the steel has been tapped. The photograph shows one of those pours: flames and sparks shooting from the tapping hole on the side of the vessel as it tilts, the liquid bright orange and lit from within. Thick white smoke rises through the gantry above, and a dark slag pot sits in the foreground. The surrounding darkness throws the heat into full contrast. Port Kembla Steelworks has been producing iron this way since No. 1 blast furnace was blown in on 29 August 1928. That furnace, designed by Freyn Engineering of Chicago with an 800 tonnes per day capacity, was described at commissioning as the largest and best equipped in the British Empire. It was lit by Emily Hoskins, widow of Charles Hoskins, the man whose ambition and land purchase made the site possible. Charles died in February 1926, before construction was complete. The furnace carried Emily's name. Five more blast furnaces followed over the next seven decades. No. 5 was blown in during May 1972 and is currently operating, scheduled for retirement by 2030. No. 6, with a 7,200 tonnes per day capacity, is undergoing a $1.15 billion reline that is expected to keep it running for a further 20 years. The steelworks has never fully gone dark. The slag pour in this 2016 photograph is not a dramatic exception in the life of Port Kembla Steelworks. It is the ordinary physical reality of integrated steelmaking, repeated across every shift, at a site that has been doing exactly this since 1928. The smoke, the heat and the orange light are what the work looks like from the outside.