Simple Solutions That Work! Issue 6

This family-owned foundry had noticed unexpected “lining growth” in the 500 lb coreless induction furnace, at the rate of 25 mm (1-inch) per day. As shown above, a 2-inch thick layer of build-up occurred in 2 days of operation. There were attempts made to mechanically remove the build-up with a chipping hammer but the concern of damaging the lining prevented this to be a viable option. This became an emergency situation due to the rapid reduction of the furnace capacity and resulting loss of production. A piece of the build-up was analyzed and found to be a combination 2MnO·SiO2, tephroite, and 2FeO·SiO2, fayalite. Actual build-up chemistry was found to be: 69.4% SiO2, 11.2% FeO, 6.7% MnO, 6.6% Al2O3, 2.7% CaO, and 1.7% MgO. It should be noted that the FeO and MnO levels were higher than normal. Superheating the molten metal bath at the end of the heat was attempted to remove the build- up but did not work. However, success was achieved when continuous Redux EF40 (Patent 7,618,473B1), fluoride-free flux additions to the charge (1 lb flux per ton of metal) were done. The foundry was able to reestablish the furnace capacity without any damage/wear to the domestic silica working lining. It was later found that a recent change to a different “pig iron” coincided with the change in the sponge-like foamy black slag within the furnace. The slag change was attributed to the amount of FeO in the charge, i.e. from the condition of the pig iron. The foundry continued to use the pig iron but did modify the charge to keep the build-up manageable. This included the continuous use of flux. Initially, the foundry could barely continue to melt through 3 days of operation. Afterwards, they returned to their normal two week production cycle. There was no longer any doubt about the effectiveness of the flux and any potential damage to the working lining. Currently, mild fluxes like Redux EF40 can enhance lining life in ferrous induction applications while preventing insoluble build-up deposition. Many case histories in coreless induction furnaces, channel induction furnaces, press pouring furnaces and ladles applications, have proven to be successful. Now ferrous foundries do not need to fear FLUXES, just use them properly, as prescribed by the manufacturer. Contact: ROD NARO [email protected] 25