Hot hours at Europe’s largest steel location
Engineering | People at thyssenkrupp | How is steel, the most versatile material in the world, made? We were able to experience the blending beds, fires and giant boilers of our steel production plant in the north of Duisburg with all our senses.
Our world relies on steel. From the construction and automotive business to the tattoo needles or the grill at home, without the famous alloy of iron and carbon, our everyday life would be inconceivable. This is also reflected in the figures. In 2016, for example, steel manufacturers produced an incredible 1.6 billion tons of the material worldwide, with a rising trend. However, most of us are unaware of how much work is involved in producing steel.
Hence, that was a good enough reason for us to take a closer look at it – after all, thyssenkrupp operates Europe’s largest steel site in Duisburg. A unique opportunity to understand the fascinating effect steel still has on the people of the Ruhr area today.
At dusk, the steel-influenced north of Duisburg reveals an industrial romance that is unparalleled.
The early bird catches the steel
Wednesday morning, 7:30 am. It’s time. The blaring of the alarm clock woke me up. I got ready in a jiffy. Have I packed everything? Did I have my camera? After all, we need it to introduce you to the impressive world of steel on the blog. You can count your lucky stars. For security reasons, photographs in the factory are actually not permitted. However, we managed to get the clearance needed. Hurray!
After a little odyssey by train and bus, our visitor group arrived at the station “Thyssen administration, Duisburg” punctually at 10 am. Okay, the name isn’t updated, but oh well…sometimes the mills of transport companies grind a little slower.
Theory before hut fun
Inside the visitor center, we got a taste of what is to come. At the beginning, we were taken through an exhibition which brought us closer to the eventful history of the all-round material steel – with some unusual exhibits such as a meteorite. And in our own 300-degree cinema, we learnt everything about the raw ore’s journey through the plant and the later areas of application fields of the finished steel. Exciting! We were hooked – and finally want to get into the hut!
But, again, safety first: Before we started on our journey, each of us were given a stylish helmet. This is understandable, because occupational safety is a top priority at thyssenkrupp. And with all the suspended load weighing several tons on the factory premises, we had to be extra careful. Our tour guide also explained: Always stay behind the yellow line! In order not to miss his anecdotes and explanations in the deafeningly loud environment, we were all provided headsets.
With us now having been equipped, we set off to our shuttle bus to witness the incredible dimensions of the place. The thyssenkrupp steel mill in the north of Duisburg is almost five times the size of Monaco – and employs as many people as living in a small German town. Together, they form more than 30,000 tons of pig iron every day.
The story of a group who went forth to learn what sintering was
The first stop of our bus trip immediately left our group breathless: the company’s own harbour with its countless cranes, imposing freighters and kilometer-long quay walls. 23 million tons of raw materials – but above all iron ore, the basis of all steel – go ashore here every year. The goods shipped from Rotterdam to Duisburg are first stored on an area of 22 football pitches before being sintered. Wait… sintered? Pardon?
A few minutes later, we were enlightened. On an area of several hundred square meters, one of the six blending beds of the site appears on our right. A massive drum is constantly making its way through 140,000 tons of mixed ore. This mass, carefully mixed with other ingredients, forms the basis for all further steps on the way to steel. The mixture is then transported to the sintering plant, which cakes it together into piece-shaped sinter. All right, but why doesn’t the ore just end up in the oven in the first place? Our guide explained that “sintering” and premixing with other materials are crucial for the production of good pig iron. And only through that, sintering pig iron can be produced in the blast furnace, which can then be optimally processed into steel.
From our shuttle bus we repeatedly see strange shiny grey castors. Only later we do get to know that these are the finished steel coils that go to the customers.
Rush Hour at the blast furnace
After a hot-steaming dip, four strange and torpedo-shaped railway wagons, and countless trucks with full load later, we turned into a parking lot. A complex network of multi-colored tubes at the nearby plant complex is the harbinger of the first highlight of our journey: the blast furnace “Schwelgern 1”, reverently called “Black Giant” by insiders. Every day, together with three other industrial monuments, it melts ore, coke and many additives at up to 2,000 degrees into almost 30,000 tons of pig iron. All right, now it’s getting hot!
Sparks, heat and sensations
We entered the tapping hall. This is where a huge, compressed air-driven “plug” regularly releases the so-called tap hole at the foot of the blast furnace. But first, there is the quiet before the firestorm. Several smelters sat together, and it almost looked as if their jobs were not as exhausting as we had expected.
But then everything happened very quickly: A siren belted out and one of the “men of steel” put on his silver protective clothing which included a mirrored mask, grabbed a long stick and stood ready for the black giant when it turned its inside out. In the midst of wild flying sparks, he took a sample of the pig iron, which was only a few centimeters away and glowed bright red at up to 1,600 degrees Celsius. As soon as the sample cooled down, the expert drew a quick conclusion about the quality of his product with his trained eye. Impressive! And we quickly realized that the jobs at the blast furnace are among the most demanding in steel-making.
At the foot of the blast furnace, an employee carries out the so-called “tapping”.
The rest of the glowing mass, however, runs through a channel into the so-called “fox”. Due to the different density of both materials, the double drain separates the valuable pig iron from slag residues. But anyone who thinks that slag is a waste material is wrong! The cooled slag is granulated and processed into granulated blast furnace slag, which is important for cement production, among other things.
At the end of the fox, the still extremely hot pig iron runs over a hole in the ground into one of the torpedo cars we had seen before. thyssenkrupp also plans to continue using the metallurgical gases generated during the process and convert them into a chemical raw material. In this way, the CO2 is to be sensibly recycled. We left the tapping hall in amazement and took the bus to our next stop. What more could there possibly be?!
Scenes as in „Blade Runner“
A few bridges and meters later, we arrived at the oxygen steel plant – the very place, where for the very first time, we were using the term steel instead of iron. Because the pig iron from the blast furnace contains undesirable components such as carbon, silicon, sulphur or phosphorus – everything must go. While the sulphur is already separated in advance, a lot of heat is needed for the rest, besides oxygen. More than 2,500 degrees in the focal spot – that is the hottest spot – to be precise.
In the “OX1”, this is done in two converters, each holding 380 tons of liquid crude steel. And after we crossed a small labyrinth of corridors, we could see the proud boilers at “refining”, as the steelworkers call it. Up to 30 percent steel scrap is added to the boiling crude steel so that it reaches about 1,700 degrees at the end of refining. This is not only quite creative but also very energy efficient.
Huge systems of cranes on the ceiling move the steel ladles from one end of the hall to the other before they empty their glowing contents like a roaring volcano into massive converters. This industrial charm, the steam, the noise – we absorbed every impression and felt the heat of the liquid fire on our faces as they moved past us in steel pans just a few meters away.
As with baking cakes, certain ingredients are added to the iron to create very specific alloys – depending on which customers the steel is intended for. To stay in the picture: Not everyone likes every cake dough. The molten steel is then cast into an apparently endless box-shaped strand, hardened and finally cut into slabs. These then move on.
By the way: In Europe alone, the steel industry produces 2,500 different steel grades to meet the variety of applications. After all, the steel for a solid bridge girder has to meet completely different requirements than the ultra-thin sheet for a can of peanuts. And there are always new variants – up to 30 per year. One innovative example is e-mobility as the megatrend demands new ideas in order to further increase the range of electrically powered vehicles.
Because form is vital
The slabs are therefore ready and slowly cool down in the warehouse. But how do the thick plates turn into the oversized coils we’ve seen all over the site? To get to the bottom of the mystery, we visit the penultimate stop on the tour: the hot strip mill, whose red façade already clearly differs from the blue-colored cold strip mill in the neighborhood. Here the steel is finally brought into shape. How does it work? With a lot of pressure!
When the steel waltzes
Our first impression of the hot strip hall: This thing really stretches. And this is necessary, because the massive slabs are rolled along the several hundred meters long production line from 20 to 30 centimeters thickness to up to 0.8 millimeters. And this is how it works: In a special furnace, the steel blocks, which have cooled down in the meantime, are reheated to around 1,250 degrees Celsius. The red-hot slab is then freed from the scale layer formed in the furnace, pre-rolled to a thickness of around 25 to 40 millimeters and trimmed at the beginning and end.
What we saw on site is the “finishing line”. Under enormous pressure, seven rolling stands reduce the individual steel plates piece by piece to long strips, which are cooled down with water and finally wound up to the known coils. We twitched several times because the steel shoots through the complex roller system at up to 72 km/h. thyssenkrupp then delivers the finished coil to its customers. That’s why almost every steel product in our lives has already seen a hot strip mill from the inside, from the body panel of a car to the washing machine to the paint pot.
Still flattered by steam, we left the hot strip mill. But before we opened the door to the outside, a robot made us smile: With its laser arm, the funny colleague provided each coil with its own serial number and then disappeared again behind a wall, remarkably elegantly. Mission accomplished: The steel is finished… well, at least in the coarse form of a hot strip – the simplest form thyssenkrupp sells to its customers. And our journey through the Duisburg-Bruckhausen steel mill came to an end. Nevertheless, at the end of the hot strip mill, the steel we usually find in our everyday lives has only made half of its journey. One more reason for us to come back here someday soon.
Some like it thinner, coated or galvanized
As said before, 0.8 millimeters are still not thin enough for some steels. And so, the coils are often refined again in the cold strip mill and rolled to 0.12 millimeters at room temperature. The packaging industry is pleased. And the automotive industry, architects or civil engineers are happy about corrosion-resistant steels, excellent paintability or stylish coatings for facades.
Everyone should have experienced this!
Talking or writing about steel is one thing. However, the metamorphosis from raw ore into the ultra-modern steel of our daily lives brings this fascination to a completely new level. Experiencing a steel mill live makes connections and processes clearer and more tangible, teaches you a lot about the history and significance of steel and lets you immediately feel that the hard work of hundreds of experts is in every piece of this diverse material. And one more thing, it is unbelievably fun!
If you would like to see the thyssenkrupp steelworkers in action for yourself, you can find all the information you need for your own factory tour with friends, family or colleagues here. Our conclusion: definitely worth a trip to Duisburg!