5. Converter evolution since 1950

5.1 Bessemer and Thomas converters

By 1950, the Bessemer converter was no longer in operation, due to a lack of ore resources with very low phosphorus content.

The Thomas process, on the other hand, thanks to phosphorous ore deposits, mainly in Lorraine and Sweden, saw its production grow until 1960, when it peaked at 45 million tonnes a year. It then declined and finally disappeared around 1980.

Indeed, from 1945 onwards, the growth in demand for sheet and wire requiring cold forming properties (stamping, wire drawing) raised the problem of nitrogen, which is responsible for metal ageing, much more than that of phosphorus.

In order to meet the new requirements, the Thomas process received a number of improvements....