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, before declining and finally disappearing around 1980.

  Indeed, from 1945 onwards, the growing demand for sheets and wires requiring cold-forming properties (stamping, wire drawing) raised the issue of nitrogen, which is responsible for metal ageing far more than phosphorus.

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