Optimization of an Electromagnetic Technology in ArcelorMittal Gent for Improving Products Quality in Steel Industry

Abstract

A multi-mode electromagnetic stirring technology (MM-EMS) delivered by Danieli-Rotelec Company has been implemented in ArcelorMittal Gent CC2. This solution is able to control the liquid steel flows in CC mould by braking, accelerating or stirring them through the use of three different modes: EMLS, EMLA and EMRS. This paper presents the methodology followed in order to optimize the working of this new technology for improving the quality of products in terms of slivers defects. Different tools were developed and used by ArcelorMittal Maizières R&D to reach this objective: Numerical simulation with MagnetoHydroDynamics (MHD) tool to simulate the fluid flows in mould under the influence of magnetic fields, Submeniscus Velocity Control (SVC) tool to directly measure the liquid steel flows in the mould and finally some quality investigation tool like Automatic Surface Inspection System to detect defects directly on coils and qualify quality of products. Numerical and experimental approaches were associated to finally deliver to ArcelorMittal Gent steelplant an optimized actuator efficient for reducing defects in slabs and improving the final quality of products.

Electromagnetic Forces in Continuous Casting of Steel Slabs

“…Firstly, the average velocity near the top surface depends on the measured torque, which can be related to the drag force applied by the steel moving past the rod, averaged over time and length of the rod [39,50]. The Submeniscus Velocity Control (SVC) device is an example commercial implementation of this method [51]. Secondly, a more sophisticated method is to measure the shedding frequency of the Kármán vortices forming behind the rod, based on the frequency of the time-varying deflections, [52][53][54] as shown in Figure 2a.…”

“…The strength and direction of the force depends on the magnet orientation, the applied current, and the effective frequency of the phase shift. Three types of horizontally-moving magnetic fields near the nozzle ports are EMLA [16,32,33,40,51,56,121], EMLS [16,32,33,40,51,56,122], and EMRS [16,32,33,40,51] or M-EMS [123,124]. Alternatively, EMC applies vertically-moving magnetic fields near the meniscus [36][37][38].…”

“…Alternatively, when surface flow is too fast, EMLS can slow down the jets in order to decrease surface velocity, surface profile variations, level fluctuations, and associated quality problems such as slag entrainment [32]. However, excessive magnetic field strength may lead to a single-roll pattern in the mold when argon gas fraction is high [51,122].…”

“…Moving field effects on flow stability in the mold region have received less previous study [39,51,56,75], compared to that of static fields. Feedback control systems have been implemented in a few commercial operations with EMLS and EMLA, adjusting the magnetic field strength according to the current "F-value" [105], which is an estimate of surface flow strength based on SEN geometry, mold width, and casting speed [51,75]. This system is reported to maintain stable surface level in the mold [51,75].…”

“…Feedback control systems have been implemented in a few commercial operations with EMLS and EMLA, adjusting the magnetic field strength according to the current "F-value" [105], which is an estimate of surface flow strength based on SEN geometry, mold width, and casting speed [51,75]. This system is reported to maintain stable surface level in the mold [51,75]. For this to be effective, the EMLS and EMLA fields should be located just below the nozzle ports [51,75] and the flow pattern should be double-roll [16].…”