At SeAH - the only producer of stainless-steel pipes and tubes in South Korea - ABB ArcSave was installed on a 70t EAF that was struggling with significant skull build-up, which could be as much as 1000 mm thick. The SeAH EAF has a 72MVA transformer with four-lance manipulator, injecting O2, alumix and C. Three oxyfuel burners provide additional energy input to melt a 90%-scrap feedstock plus 10% of ferroalloy.
As at Outokumpu Stainless, BGS with three porous plugs had proved ineffective, leaving the company to drill out its skulls with its refractory removal machine and lift them out of the furnace by crane. To say this was a difficult and time-consuming effort is to put it mildly. Following the installation of ABB ArcSave, bottom skull formation was reduced to less than 200mm, as a result of the homogenising impact of EMS on furnace temperature. This reduced skull thickness, brought multiple operating benefits, including:
• Easier scrap bucket charging.
• Better melt bath level control.
• Improved tap weight hit ratio.
• Higher scrap and ferroalloy yield.
• Lower maintenance requirements on the furnace refractory.
The electromagnetic stirring created by ArcSave provides complete and precisely-controlled mixing of the whole furnace melt.
Energy savings of by 3-4%, were also seen at SeAH, while power-on time fell by 4-5%. Perhaps most impressive, however, was the 70-80% reduction in the cost of scrap handling that was achieved due to an improved ability to melt larger bundles of scrap and whole rejected ingots (up to 4 tons). Before the installation of ABB EAF-EMS, the SeAH EAF could only handle smaller charges to ensure full melt in one heat2.
Tap weight hit ratio increased by 24% with ArcSave