Lean and sustainable metal production

The sintering and blast furnance processes have been characterized during the last years by a progressive adaptation of the quality of the iron ores and by the implementation of new technologies (hot air/waste gas recirculation in sintering, high rate of carbon injection at BF) for boosting their productivity and comply with more and more stringent environmental regulations. This evolution needed to redefine the key performances indices (KPIs) associated to the raw materials for a better compliance of their quality with the new operating conditions. For supporting this evolution, enhanced characterization techniques have been developed inside the CRM laboratories notably for reaching a more precise assessment of the mineralogical phases present in the sintered iron ore.

In the blast furnance area, the MOGADOR model has been adapted to better predict the behaviour of the alkali components and their zones of concentration all along the blast furnace height and periphery. The next step of this upgrading will include the carbonates, silicates, zinc and cyanides components.

The sintering pilot installation has been adapted to simulate the injection of high temperature fumes in the sintering process, through the introduction of a combustion chamber able to operate with different alternative fuels with lower carbon footprint.

Various melting furnances are available in order to cast ingots with specific requirements. (500 grams, 35 kg, 80 kg, 300 kg and 1 ton of capacity). A very precise control of the chemical composition of the steel can be achieved. Various mould sections are available in different materials and a specific casting simulator has been also developed for the late addition of metallic alloying powder during the casting process.

A pilot continuous caster is also available in order to develop new processes or new products in the casting and solidification field. This machine is fully vertical with a length of 3.9 meters and product sections of 430x115 mm, 250x110 mm and 150x150 mm and a casting range from 0.8 to 1.5 m/min. The caster is fed by the induction melting furnance of 1 ton of capacity and an heated tundish ensuring a very good control of the casting superheat and of the steel flow rate. A very large range of steel grades can be cast with a very good control of the steel composition.

During the hot and cold rolling, the application of a lubricant is a key element to reduce the friction between the roll and the strip and consequently decrease the rolling forces with a very positive impact on the length of the rolling campaigns and the reduction of the strip surface defects. The processing of more and more hard steel grades needs to further enhance the performances and reliability of the lubrication system. In order to better support its industrial members and to cover the different types of existing installations, a new full scale versatile simulator has been built. It can operate with different nozzles and emulsions and is particularly useful to evaluate the mixing conditions and the clogging behaviour after long term trials. This will help the mill operators to defi ne more precise guidelines on how to restrict the clogging issues and to improve the maintenance and rinsing instructions.

With the objective to better appraise and simulate the oxidation phenomena occurring on metallic products when processed at high temperature, a new furnance has been acquired in 2017 in the frame of the MPC partnership between OCAS & CRM at Gent. Especially designed for loading/ downloading large sample at high temperature, the equipment comprises an electrically heated chamber with a pneumatic lift door and a gas injection unit involving a humidifier. The furnance can operate at a temperature up to 1350°C with the possibility to inject N2 & O2 in a strictly controlled way and to vary the dew point between -7°C and +60°C.

Concerning the galvanization process, a major industrial target is to run the lines at higher speed. In this prospect, a key aspect is the improvement of the hardware and more especially the bearings in order to reach a smoother rotation of the immersed rolls whilst keeping a good strip surface quality and a low maintenance cost. A new concept of bearings is tested by CRM, based on the separation of the bearing and tightening functions. A dedicated simulator has been built to test this concept. A conventional high temperature bearing is placed on the top of a tight chamber containing liquid zinc. By increasing the pressure inside this chamber, the liquid zinc can rise until it makes contact with the upper part where the bearing is fi xed. This upper part is drilled for letting the rotating roll shaft penetrating in the sealed chamber. The cooling of the shaft with water leads to solidify zinc inside the bearing opening and to assure by this way the sealing of the chamber simulating the zinc pot.

The development of the patented stabilisation system aiming to reduce the vibration of the moving strip as it emerges from the galvanising bath has been pursued through pilot line campaigns. Thanks to several improvements introduced during the last year such as a more constant behaviour during the transitory phases (start-up phase, slow-down and weld passage more open-space let to the operators for the top bath skimming, fi ner tuning of the pass-line), a better damping effect is obtained leading to a more homogeneous control of the strip vibrations.