MechTech has recently taken a tour of South Africa’s Columbus Stainless plant, producer of stainless steel flat products, Middelburg. At the starting point of the stainless steelmaking process is stainless scrap. “We also make stainless steel by melting carbon steel scrap – sourced from within SA – and then blending that with chrome and nickel as required,” says Lucien Matthews, the company’s CEO.
From the EAF (electric arc furnace), the molten metal is transferred to one of two 100 t Argon-Oxygen Decarburisers (AODs). There, by blowing oxygen, argon and nitrogen into the molten steel, the stainless steel is refined.
Once the melt in the AOD is ready it is tapped into a ladle and transported to Columbus’ continuous casting machine. “The slabs go through a surface grinding process to remove any possible surface defects and they can be cut to lengths of between 4 and 12 m. This is our first saleable product,” Matthews adds.
The hot rolling process begins at the reheat furnace, the hot rolled products are softened (annealed) and de-scaled (pickled with acids) to produce a No. 1 finish product. Cold rolling of the No. 1 coils takes place on one of four Sendzimer mills (Z-mills), which produce smooth, shiny finished, cold rolled stainless steel.
