| Abstract |
Clean steels were "invented" in the middle of the 20th century, at a time when steels started to be produced en masse and when it was understood that quality should also be addressed as a special and important issue, both in terms of the strategy of the sector and as a major research topic for the science and technology that accompanies the industry. The series of Clean Steel conferences, launched in Hungary in 1970 and organized every 4 years since then, with Paul Tardy in the organizing committee or in the lead, have been providing important time markers of this evolution. Since then, major progress was made by the introduction in most steel shops of secondary or ladle metallurgy, which was invented in the process, while steel cleanliness was defined precisely in standards and textbooks. The discoveries of pioneers have become state-of-the art and, today, a steady state situation has been reached, where research continues in using new tools and methods to refine the topic, while new comers, mainly from the BRIC countries, are contributing their understanding of the topic to the international steel community. The distinction between special steels and carbon steels got blurred in this historical process, as similar secondary metallurgy tools were used for making both kinds of steels and, in essence, steel ceased to be a simple commodity and most steels became special to some extend. Clean steels have thus not become much more sophisticated recently, but rather much more common and mainstream. The expression "clean steel" stems from a vision of the purity of the metal in terms of minor elements, which had been controlled until then only at the margin compared to the major elements, iron, carbon, silicon and manganese. This is today a somewhat passeed vision as metallurgy has become a much more holistic and systemic technology, whereby steels are defined in terms of global composition, of distribution of phases, including the minor phases that are known as non-metallic inclusions, of microstructures and, more often than not, in terms of applications and properties in service. Moreover, steels have time extensions, which are discussed as life cycle or value chain and are thus embedded in the anthroposphere and its intersection with the biosphere and the geosphere. This emphasizes the fact that steels are made from raw materials, primary and secondary - thus including scrap from recycling -, that they are transformed into artifacts that participate to the life of society and eventually are disposed of at end of life to feed back into the circular economy. This holistic vision is what we call "environmental metallurgy". It is linked to clean steel production and constitutes another dimension of the cleanliness of steel. Plenary presentation to the 9th International Conference on Clean Steel; 8-10 September 2015; Budapest; Hungary |