to its material control and handling, as well. According to Gene Muratore, Rio Tinto Iron and Titanium Amer- ica, Chicago, charge materials should be handled minimally from the time they are brought into the metalcasting facility and charged into the furnace. “Do you have adequate, well- defined storage bins?” Gene Muratore asked. “If the charge is in piles touch- ing each other, you are losing money on one hand and quality on the other.” When Benton Foundry installed
new 4-ton furnaces in the 1980s, it sunk its first set of standardized bins for each type of scrap into its floor. More have been added as melting capacity has increased. Te bins keep material separated for better quality control and save space. “If you take a load of pig iron and
put it on the ground, it doesn’t take up a lot of feet, whereas bushings prob- ably take up four times as many cubic feet,” Brown said. When charge materials are selected
and added to the furnace, the charge weight vs. the tap weight should be calculated and addressed. “Tree things can happen, the
charge turns into metal, slag or a gas,” Muratore said. “Weighing your charge vs. the tap give you control over the material. Tree percent melt loss cor- relates to close to 3% scrap. You lost the metal somewhere.” Te crane used to grab charge
material from the bins at Benton Foundry is sensored to track the weight of each load.
Ferrous Melting Considerations As with aluminum melting equip-
ment, the care and maintenance of steel and iron melting furnaces affect the quality and efficiency of the melt depart- ment. According to Muratore, metal- casting facilities that are benchmarking their melting practices should consider how ergonomically and efficiently slag is removed from the furnace, temperatures are taken, and alloy additions are made. “Newer furnaces have options like
backslagging. Furnaces tilt backward so you can drag the slag off,” he said. “They also make automatic slagging equipment.” World-class facilities should have
Furnaces should be well sealed with a tight-fitting cover to keep out air, which can cause oxidation in the melt and lead to slag.
an efficient means of replacing a spent lining, Muratore said. Digging out the old lining in a coreless furnace is laborious, but equipment suppliers have created pusher systems to push the lining out, saving six hours of labor for two or three people. Proper dust collection and electri-
cal efficiency also signify a well-run melting department. Many modern furnaces have built-in dust collection systems or fume hoods. If the furnaces don’t have built-in dust collection, a system should be in place for the entire melt department, and the air pressure within the area must be prop- erly engineered and monitored for best dust collection performance. In many cases the dust or fume col-
lection system can be tied into a means of heating the building to cut electri- cal or gas bills. Newer low frequency furnaces also increase energy efficiency. “If the furnace runs at a lower
frequency, the material can melt more quickly and changes to the melt can be made more quickly,” Muratore said. “It
can handle alternate charge sizes—in the past you might have been lim- ited to a charge size, but with lower frequency you might be able to melt larger chunks. It makes charge mate- rial selection more broad.” Although Benton Foundry’s
furnaces operate at a low frequency already, it found a way to further improve its electric efficiency through electricity management and control. The company puts limits on electric usage by each department throughout the month. It also works with the electric company to cut back electricity usage during peak demand times. “Typically, we’ll get a call or an email asking us to shed [power],” Brown said. “Those events are usu- ally five to 15 minutes long. We choose to shed off of two furnaces. We are pouring out of one furnace while heating up in the other, so no electricity goes into the heating furnace, but we continue to pour out of the other.”
April 2012 MODERN CASTING | 21
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