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The Groupe CB refractory division serving high-temperature industries
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TRB's contribution
to the relining of ArcelorMittal's
blast furnace n°4
TRB, the Groupe CB refractory division, designs, manufactures and implements refractory solutions for high-temperature industries. With nearly 80 years of expertise, TRB supports its customers in the steel, cement and foundry sectors, thanks to its integrated skills ranging from design office and laboratory to workshops and field teams.
Among its long-standing partners, ArcelorMittal is one of the world's leading steelmakers, and Europe's largest, with annual production of over 65 million tonnes. Its Dunkirk site, the largest in France, has three blast furnaces with a total capacity of around 7 million tonnes per year. Blast furnace no. 4 alone can produce up to 10,500 tonnes of cast iron per day, making this facility a strategic tool for European steel supply.
The role of the blast furnace
in steelmaking
Steel production begins with the production of cast iron in a blast furnace. Iron ore, coke and fluxes are fed into the furnace, then heated to very high temperatures by injecting hot air through tuyères.
This chemical and thermal process produces liquid pig iron and slag. The cast iron is then refined in converters to obtain steel, while the slag is cooled and recycled, notably in the cement sector.
The blast furnace is therefore at the heart of the steelmaking chain, and the refractory infrastructures that ensure the pouring, channelling and cooling of products are essential to its safety and performance.
The TRB interventions on ArcelorMittal's
BF No.4
This major project, which began in April 2025, mobilized TRB teams to supply and install over 2,000 tonnes of refractory materials in critical areas of the blast furnace.
Complete relining of the casting floor
The taphole floor is the area where molten iron and slag flow out of the blast furnace. Exposed to extreme temperatures and intense wear, it is a central component of the facility.
As part of this relining project, TRB teams installed a safety layer and a wear layer, comprising approximately 350 tons of refractory concrete and precast blocks. These materials were manufactured at TRB’s facilities in Nesles (Hauts-de-France).
Nozzle floor
Tuyeres are the nozzles through which hot air is injected into the blast furnace. They are arranged in a ring at the base of the vessel. To protect this critical area and facilitate maintenance operations in complete safety, the floor around this equipment has been lined with a 10 cm thick by 1.50 m wide layer of refractory concrete.
Slag granulation basins, North & South
During the production of cast iron, the slag is cooled by water granulation so that it can later be reused as a raw material in cement. TRB renovated the granulation basins using troweled Densit concrete, a solution developed by our partner PA Technologies. This abrasion-resistant material had already proven its worth and was chosen once again for its reliability.
Slag Channels, North & South
The gutters are used to evacuate cast iron and liquid slag from the blast furnace to the pits or processing facilities. TRB has used refractory concretes specially designed to withstand temperatures in excess of 1,000°C, guaranteeing the durability and safety of these drainage channels.
Slag pit walls
The pits receive liquid slag and are subjected to extreme conditions. TRB installed prefabricated refractory blocks. Already baked and ready to use, these blocks save considerable time compared with cast-in-place concrete, and offer greater outdoor resistance.
Results and outlook
This major project illustrates the ability of the CB Group's refractory sector to mobilize all its skills. Over 2,000 tonnes of TRB products were installed on schedule, with the blast furnace safely restarted in July and zero accidents recorded over the period.
Over and above the technical results, this achievement testifies to the renewed confidence of ArcelorMittal and confirms TRB's role as a strategic partner to the steel industry. It also illustrates the importance of innovative, durable refractory solutions, capable of withstanding extreme temperatures in excess of 1,500°C, and contributing to the performance of the steel industry and all industrial sectors using refractory products.
The relining of blast furnace no. 4 is continuing, and TRB is proud to continue supporting ArcelorMittal in the next stages of this major operation.