Steel Sheets US Steel Producer Preserves with Technology from Germany

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For the efficient and precise processing of huge steel sheets in a challenging project environment, a leading US steel producer relies on a preservation line from Rösler.

In the middle of a greenfield site in an industrial park in the USA, one of the largest steel producers in North America has erected a gigantic rolling mill for steel sheets.

This sets new standards in terms of the size of the rolled and processed sheets there and is one of the most powerful steel plants in the North American region. In addition to particularly thick and large-format, freshly rolled steel sheets, the company offers surface treatment of the rolled products as an additional service to its major customers in the oil and offshore industry, which is becoming increasingly important in the industry. This is specifically implemented with a preservation line of the type KON 47/3-HD in rolling mill design by Rösler Oberflächentechnik GmbH.

Gigantic Steel Sheets Require the Highest Precision and Maximum Power

With a length of around 75 meters (approx. 246 ft), an abrasive throughput of 3.7 tons per minute, and a production volume of 122,000 tons per year, the preservation line designed and manufactured by Rösler Oberflächentechnik GmbH for the American steel producer is a real powerhouse. It has to be, as the sheets processed here are of enormous dimensions. Depending on the rolling thickness of the slab, i.e., the raw steel block, they can be up to 4,300 millimeters wide (approx. 169 inches), 18,000 millimeters long (approx. 708 inches), and a maximum of 203 millimeters thick (approx. 7.9 inches). "That was precisely the challenge for us: to be able to blast such large and heavy plates with a maximum weight of over 45 tons, an extremely robust plant is needed, which is extremely powerful but at the same time works precisely and reliably achieves the required purity level of 2.5 SA. Combined with a fairly tight schedule, this was an exciting and ambitious project for us," says Marcus Witter, Global Sales Expert at Rösler.

Preservation Line Offers Additional Value

The location of the Rösler plant at the end of the process chain already indicates its special status within the rolling mill: the Rösler preservation line does not offer standard processing, but an optional additional service that is gaining importance for more and more intermediaries and end customers. The customer has the choice between a freshly rolled sheet or an already blasted and/or coated sheet. “Depending on what happens with the sheet, this can be a very attractive added value. For example, if sheets have long shipping routes and may experience initial corrosion spots. In this case, it makes sense to blast and apply corrosion protection before shipping. At the same time, the customer saves one or two process steps in their own production, as they can directly cut and weld the sheet without having to remove the weldable primer beforehand,” explains Marcus Witter, Global Sales Expert at Rösler. The plant uses solvent-based primers, as are also required in the shipbuilding and offshore sectors. Solvent-based paints are also sometimes used in traditional steel construction. Due to the increasing demands on environmental protection, Rösler preservation lines are also capable of processing water-based paints.

Efficiency and Cost-Effectiveness

The heart of the Rösler preservation line is a roller conveyor blasting machine. Preceding it are a blow-off unit that prevents the introduction of contamination, as well as a preheater. This preheater has a maximum operating temperature of 260 degrees celsius (approx. 500 °F) and is very efficiently heated with two gas burners in recirculation mode. Here, the sheets are heated to the optimal operating temperature for subsequent coating. They then pass over a short intermediate roller conveyor into the blasting machine, which is equipped with ten Gamma 400G turbines, each with 30 kilowatts. The turbines can be selectively and automatically switched off depending on the sheet width. This increases efficiency, reduces wear, and thus lowers operating costs.

Specifically for automatic sheet width detection, the system was equipped with an improved abrasive return and distribution system to ensure consistent abrasive distribution with optimal cleaning performance even with the selective shutdown of individual turbines. To withstand the weight of 7 tons per running meter and an abrasive throughput of 3.7 tons per minute even under full load and continuous operation, the blasting chamber is entirely made of 8 mm (approx. 0.3 inches) manganese steel and additionally equipped with replaceable manganese steel plates with a thickness of 8 mm (approx. 0.3 inches).

After blasting, the sheet is automatically cleaned using an integrated cleaning station, so it is free of abrasive and dust when transported to the automatic painting system. There, the two-component paint is applied using the airless process. Sensors detect the sheet size and width as well as the sheet's transport speed, thereby minimizing unnecessary overspray, which means the dispersion of paint in the air, and ensuring more efficiency and lower paint consumption. In the final state, the painted sheet must have a dry film thickness of 15 to 25 µm.

Once the sheet is painted, it goes into the paint dryer heated to around 60 degrees celsius (approx. 140 °F). The sheet passes through this on a special chain conveyor to ensure that the paint on the underside of the sheet is not damaged and no visible defects occur. A thermal afterburner ensures that the solvent-laden exhaust air from the painting system and the dryer is cleaned, and that the plant's emission limits are safely met.

Successful Commissioning Despite Challenging Assembly Conditions and Time Pressure

Since the end of 2023, the Rösler preservation line has been in operation, running reliably and continuously. The installation of the preservation line was a real challenge due to the tight schedule for the construction of the entire rolling mill. While the preservation line was already being set up, construction work on the hall continued at full speed to complete the roof, exterior walls, and other necessary installations. "This made the installation of the system a real challenge, but we wanted to support our client in meeting their tight schedule. This was only possible through direct daily communication between the project teams on both sides, which from our view went very pleasantly and constructively and ultimately led to mutual success," says Marcus Witter from Rösler.

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