Electromagnetic stirring, as a means of mobilizing metallurgical melts to achieve higher quality and more effective output, was invented by Dr Ludwig Dreyfus at ABB (then ASEA) in the 1930s. The “stirrer”, or EMS, is positioned outside the furnace and creates a traveling magnetic field that moves the melt, resulting in more consistent temperatures throughout the molten metal, and accelerated slag-metal reactions.
In 2015, after several iterations and versions of the EMS had been created for various different applications and furnaces, ABB launched ArcSave. A fully customizable application of the technology for electric arc furnaces (EAFs), it allows controlled stirring intensity, duration and direction for each process step scrap heating, homogenization, melting of alloys, decarburization, de-slagging and tapping in either stainless, carbon or special steel production.
“We couldn’t afford any mistakes in the first ArcSave installation, since the new technology and EAF modification represented a big investment by the customer,” says Hongliang Yang, R&D Team Leader at ABB Metallurgy. “We undertook extra research, and ran and re-ran simulations to be sure the solution would work, and that it could deliver a return on investment within 6-12 months. Our customer’s faith was justified and their experience provided an undeniable proof point for ABB’s new ArcSave technology!”
“By pushing the carbon-oxygen reaction closer to its equilibrium,” says Yang, “ArcSave results in higher steel yield from scrap, improving productivity by 5-7 per cent and reducing energy consumption by 3-5 per cent.” Safer tapping: A more homogenous temperature in the entire melt gives a higher free EBT opening frequency, reducing tapping delays and allowing smoother, more reliable EAF operation. In addition, the flow pattern induced by ArcSave in the melt bath delays vortex formation, resulting in less carryover slag in the tap ladle.
in Sweden produces 500,000 tonnes of stainless steel each year using around 90 per cent scrap, and partnered with ABB to improve the efficiency of its 90-ton EAF. Using ArcSave, it was able to achieve 3-4 percent lower energy use; 6-8 percent enhanced furnace productivity; and a 70 percent increase in tap temperature hit ratio. Says an Outokumpu metallurgist, “We solved our bottom skull problem using ArcSave. The result is smoother, more predictable EAF operations at lower cost.”