Simple Solutions That Work! Issue 5

Contact: Dean Vander Jagt [email protected] 49 Hydrogen produced by the com- bustion of natural gas becomes absorbed in the melt. Much of the hydrogen has to be removed by an energy consuming degassing process or it will come out of solu- tionduringcasting solidificationcre- ating bubble defects in the castings. ELECTRIC RADIENT HEAT ABOVE THE MELT As with gas, electric radiant heat above the melt contributes signifi- cantly to the creation of surface oxides. Attempting to heat through a layer of oxides, compoundedwith thedistance limitationof radiant heat in anything less than a full furnace, results in the inability to maintain casting temperature in the dip-well, thus delaying casting production, cooling the tool, and wastes a lot of energy. Many of the drawbacks of electric heat above the melt are the same as gas heat above the melt but to a lesser extent. Electric heating above the melt has the advantage of not adding as much hydrogen into the melt and often does not require de-gassing. Electric heating is normally less able to recover temperature in the dip- well as quickly after cleaning as gas fired furnaces. ELECTRIC IMMERSIONHEAT The advantage of having immer- sion heat below the surface of the melt reduces the surface tempera- ture of the melt so few oxides on or in themelt are created and very little hydrogen is absorbed into the melt. Intervals between cleanings can be extended savingenergy and increas- ing casting production. Strategically positioning a heater just before the arch that leads to thedip- well provides precise casting tem- perature control in the dip-well. This saves energy, reduces refractory degradation, improvesmetal quality, and is critical whenusingpneumatic or electro-magnetic dosing pumps. Installing a filter between this heater and other heaters in the bath pro- vides the opportunity to improve casting quality even more. Temperature recovery time in thedip well aftercleaning is typicallyreduced by 75% thereby saving energy and increasing casting production. The interval betweenrefractory relin- ing of immersion heated furnaces is typically double that of roof heated furnaces. Understanding oxide reduction will save your facility money, energy, maintenance,downtime,andprovide bettermelt qualitywhileyouarepro- ducing more and better castings. Understanding oxide reduction will save your facility money, energy,maintenance, downtime, andprovide bettermelt qualitywhile you are producingmore and better castings.