Refining of stainless steels

Over the past half-century, stainless steel refining techniques have evolved considerably, both technically (control of chemical composition, control of inclusionary state, etc.) and economically. A major technological leap had already been made in the 1930s with the Perrin decarburization and desulfurization process. The second technological leap forward came with reduced-pressure refining processes in the early 1970s (the AOD process and its derivatives). These gave us excellent control over decarburization and desulphurization, while considerably reducing the cost of the refining operation. With the VOD process and its derivatives (early 1980s), lowering the partial pressure of CO by means of vacuum, obtaining very low carbon, sulfur and nitrogen contents paved the way for ferritic grades with high chromium content (Cr ≈ 30%) and austenoferritic grades.

Since these major developments, we have mainly seen variants geared towards economic aspects, in particular savings in gas and raw materials (chromium and molybdenum). Finally, the refining capacity of a steel mill, which was around 500,000 tonnes per year in 1990, has been doubled in ten years, corresponding in fact to the doubling – over the same period – of stainless steel consumption worldwide.