Steelworks: Developments in Lquid Steelmaking Processes

The function of steelmaking processes is to produce a steel at the required temperature and composition, ready to be cast and solidified into a semi-finished product, from the raw materials (blast furnace iron), scrap and pre-reduced ore.

If we try to summarize in a few lines the evolution of the world's steel industry, since the momentous inventions of Bessemer, Martin and Siemens, Thomas, and Héroult, in the second half of the 19th century, we can distinguish four main periods.

• Until 1950: continuous improvement of these inventions in the technological and metallurgical fields, without them being called into question.

• From 1950 to 1980 :

  • numerous new technologies based on the use of pure oxygen, eventually giving way only to the pure oxygen converter, with its variants;

  • at the same time: significant development of the electric furnace, benefiting from technological improvements and the availability of scrap due to the closure of the Martin furnace; then the disappearance of Thomas and Bessemer converters, as well as Martin furnaces, at least in modern industrialized countries; and finally the emergence and expansion of a highly diversified ladle metallurgy industry.

• From 1980 to 2015:

  • stability in manufacturing processes, which continue to be perfected;

  • widespread development of ladle metallurgy to meet productivity requirements and ever-increasing demands on steel quality;

  • for certain very pure steels (very low phosphorus content), addition of a reactor for initial phosphorus removal upstream of conventional refining.

• From 2015 :

  • pre-projects for the conversion of cast-iron plants to a low-CO ₂ blast furnace;

  • or replacement of the cast-iron plant by an electric (green electricity) process supplied with pre-reduced (reduced to hydrogen) and scrap metal, increasingly sophisticated in quality and size.

This article traces the birth and evolution of steelmaking processes and technologies, describing the technical features that have underpinned their performance and industrial development.