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Electric Arc Furnace: the Héroult Series-Arc Steel Furnace (Stansfield, 1914)
Héroult's steel furnace: a tilting hearth like an open-hearth furnace, lined with dolomite, with two carbon electrodes coming down through the roof. The current goes down one electrode, arcs into the slag, passes through the molten steel and arcs back up the other, so the heat goes straight into the metal.
Result: an electric steel furnace about 7 x 4 ft inside for a 3 ton charge, run at about 350 kW and 110 V.
Source: A. Stansfield, The Electric Furnace, 2nd ed. (1914), pp. 115-116, 214-216. Unknown: case and tilting gear details, electrode size. Picture: a drawn diagram (Fig. 93 is blank in the scan).
Expert
Unknown
Instructions
1
1
Build the case and lining
Build the case and lining
Build the furnace in a steel case on a tilting mounting, about 7 x 4 ft inside, with charging doors at the ends. Line it with dolomite bricks and crushed dolomite; dolomite or magnesite on the hearth, which allows strongly basic slags. Ours: mild steel plate. Not given: the case and tilting gear, the bricks' making.
Materials for this step:
Mild Steel Plate1 case
Dolomite (Magnesian Limestone)1 lining and crushed dolomite
Magnesite Blocks1 hearth, if magnesiteTools needed:
Arc Welder
Trowel
Unknown Dimensions2
2
Make the removable roof
Make the removable roof
Make the roof of silica brick, covered with steel plates and given eyes so it can be lifted off. Between the two electrode holes use bronze plates instead of steel, because steel there would raise the inductance of the AC circuit. Fit water jackets round each electrode hole for a close fit, so less heat escapes and the electrodes do not burn in the air. Ours: copper tube for the water jackets. Silica brick has no head here.
Materials for this step:
Unknown Material1 silica brickMild Steel Plate1 roof plates
Bronze Sheet1 plates between electrodes
Copper Tube1 water jacketsTools needed:
Arc Welder
Drill Press
Water3
3
Hang the electrodes
Hang the electrodes
Use two vertical carbon electrodes, square in section. Carry each in a holder on an arm supported by the furnace itself, so its height does not change when the furnace tilts: four contact pieces round the electrode, drawn tight by a steel strap and a screw in the arm, with the cable bolted to them. Raise and lower each electrode separately, by a regulator controlled by the voltage between it and the metal. Not given: electrode size, the regulator's build.
Materials for this step:
Carbon Electrode2 electrodes
Unknown Metal1 holders, arms, contact piecesTools needed:
Drill Press4
4
Melt and refine a charge
Melt and refine a charge
Charge steel scrap with some iron ore and lime. Keep each electrode a little above the slag, leaving room for its arc. Regulate the current by hand while the scrap melts, then switch to automatic; full power only after about an hour. Pour off the slag and make a second, then a third, with lime and a little sand and fluorspar, before the final additions. At La Praz this took about 350 kW at 110 V: 5 hours for 1.25 tons of low-carbon steel, 8 hours for 2.33 tons of high-carbon steel. Not given: the electric supply.
Tools needed:
WaterMaterials
8- 1 roof platesPlaceholder
- 1 lining and crushed dolomitePlaceholder
- 1 hearth, if magnesitePlaceholder
- 1 silica brickPlaceholder
- 1 plates between electrodesPlaceholder
- 1 water jacketsPlaceholder
- 2 electrodesPlaceholder
- 1 holders, arms, contact piecesPlaceholder
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