The 864-strong workforce at ThyssenKrupp Steel Europe’s BOF meltshop in Duisburg-Bruckhausen had special cause to celebrate: On August 25 at 11.51 o’clock they produced the 150 millionth metric ton of crude steel – enough in theory to build 15,000 Eiffel Towers.
“We’re proud that our plant and the team have reached this milestone,” says Heinz Liebig, head of crude steel production at ThyssenKrupp Steel Europe in Duisburg. “After all, our core meltshop equipment dates from 1969, making it 41 years old. But by continuously upgrading we have kept it state-of-the-art, in particular with regard to meeting environmental standards.” Two 380 ton capacity converters form the basis for steelmaking at Bruckhausen. The meltshop was one of the first to be equipped with converter gas and dust recirculation systems. “Our facility in Bruckhausen is one of the few oxygen steelmaking shops able to produce high-silicon electrical steels as well as the usual carbon steels,” adds Liebig. “Per year, more than three million tons of molten steel are cast into up to 2.6 meter wide slabs on the continuous caster and then cut to the lengths and widths required by customers.” The meltshop has also been supplying crude steel to the company’s casting/rolling line for the past 11 years.
The hot metal from the blast furnace is delivered to the Bruckhausen BOF meltshop in torpedo ladles and then processed in several steps to produce steel of the required quality. Here’s a simplified version of what happens: Pig iron still contains impurities such as silicon, sulfur and phosphorus. These are removed by oxidation in the converter by top-blowing oxygen through a water-cooled lance. This process, which generates temperatures of 2,500 degrees Celsius, is known as “refining”. To cool the boiling steel – a converter holds around 380 metric tons – steel scrap is added in quantities of ten to 30 percent of the overall heat weight. The actual blowing process lasts around 20 minutes. When it is tapped into a pouring ladle, the molten steel still has a temperature of 1,650 to 1,750 degrees Celsius. Alloying agents can also be added during tapping. Due to the high quality requirements for the properties of the steel, it has to undergo post-treatment, referred to as secondary metallurgy.
60 percent of the molten steel is cast into slabs on the continuous casters. These slabs are supplied to customers of ThyssenKrupp Steel Europe for processing on their rolling mills. 40 percent of the molten steel is supplied to the casting/rolling line.