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Edition #150, May 15, 2011
A Million Angry Bumblebees
Photographer: Kevin N. Tomasic
Photo by Kevin N. Tomasic
A Million Angry Bumblebees
A million angry bumblebees, yes that‘s the best way to describe the sound of an electric arc furnace as it reduces scrap metal into a fresh heat of molten steel. The electric arc furnace is today’s preferred method for making steel since it skips mining iron ore, baking coke, smelting the iron ore in a blast furnace and finally refining the iron in a basic oxygen furnace. All you need do is load the steel scrap in and strike the arc.
Basically an electric arc furnace is a big steel kettle that tilts over to tap its load of steel. On the top of this kettle is a lid that swings to the side to allow filling of the furnace with a “charge” of scrap. In the lid are three graphite (really big pencil lead) electrodes that are attached to moveable arms so that they can receive electric current and be driven into and out of the furnace. Watching the furnace work is fascinating-the electrodes glow red/orange, move up and down in their holders and the electrical tethers dangle and dance all the while as smoke and flames pour out of the top of the lid. It’s not a smooth process, it moves in fits and starts--everything is shuddering as sparks rain down everywhere and the furnace crackles with energy. You watch your step here and never turn your back on this machine.
My first introduction to an electric arc furnace was on a spring morning at the Babcock and Wilcox plant in Koppel, PA. I was on a site visit with a small group of contractors and, as we walked through the mill, I could hear that angry bee sound coming from a building ahead on my left. We finally got next to the building; I looked inside and WHAM—it looked like I was staring into the sun! I stood transfixed for a few seconds till finally one of the B&W guys said, “That’s the arc furnace, something ain’t it?” It was at that point that I began to wonder if I really should be in the industrial field with all its noise and dirt and danger, but I stayed. I stayed because, despite my fears, the sheer power emanating from the furnace was kind of exhilarating.
I recall standing on a bluff in Oakland, looking down across the Monongahela River at J&L Steel’s Pittsburgh Works. On the Southside, J&L had two 300 ton arc furnaces, some of the biggest in the world and they were running their last campaign in 1984 to make steel for slabs going to Weirton Steel. You couldn’t see those beasts owing to the mill buildings surrounding them, but you could hear them and their buzzing song all the way across the “Mon”. Even half a mile away you knew they were there.
An electric arc furnace shell has two main openings in its lower section--the pouring/casting spout and the slag door usually directly across from the spout. The slag door allows access to the furnace during operation for such things as lancing the bath, sampling the heat, refractory repair and slag removal. The slag door figured into one of the most amazing things I’ve seen in my 20 plus years in visiting melt shops and foundries. The arc furnace in this particular steel foundry had just been tapped and was returned to level position. There was some problem with the furnace, so the slag door was opened and a worker moved next to the opening in “silvers” (protective clothing). As he stood there in the heat, the furnace was tilted over to 30 degrees. From his small platform (perch may be a better description) he leaned over to inspect the inside of the furnace. To this day I don’t know how he survived that ride or what he was looking for. It was scary to watch a man take such a chance.
The picture shown here is of the tapping of a 25 ton arc furnace at National Roll. This old girl, built by Swindell-Dressler in Pittsburgh some 50 odd years ago is typical of her era. The controls are manual and the panelboard features a single huge light bulb, a bulb that glows brighter as more power is given to the furnace. It looks like nothing so much as the controls on an old carny ride. To tap the furnace, a ladle is suspended below the pouring spout and the furnace is slowly tipped over. Once the molten steel starts to flow, a slow dance begins between the craneman working the crane (from which the ladle is suspended) and the furnace tender. You don’t simply “let it fly”. No, the spout is kept right at the ladle lip until the furnace is fully tipped and the ladle is at the bottom of the pouring pit. Once the furnace is emptied it is tipped back up and goes to sleep until the next heat is needed. The buzzing is gone and all is quiet except for the growl of the crane taking the ladle away.
In the predawn, tomorrow morning, the lid will be moved aside and another load of scrap will be set into the furnace. The arc will be struck, the bees will buzz their mad tune and four hours later the crane and ladle will be back for another load of molten steel.
Kevin N. Tomasic
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