U. S. Steel Tubular Products, Inc. U. S. Steel Tubular Products, Inc.
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Electric Arc Furnace
Lone Star Steel has two electric furnaces with a combined annual melting capacity of approximately 490,000 ingot tons. Electric Arc Furnaces (EAF) offer several advantages including a low capital cost investment, flexibility, efficiency, and no contamination from fuel or other agents. Steel from the furnaces is converted into hot rolled strip, specialty tubing, oil country tubular goods (OCTG), line pipe products and other industrial products. The chemistry of each heat of steel is purpose formulated to meet the requirements of the final product.

Each heat of steel uses approximately 136,000 pounds of scrap generated from two sources, internal generated scrap from mill operations and purchased scrap. Each furnace requires 34,500 volts of primary power and 500 volts at 44,000 amperes of secondary power to begin the melting process.

Lone Star uses scrap to initiate the steel making process. The scrap is loaded into a bucket and hoisted into a position over the furnace for charging. Once the scrap has been dumped into the furnace, three electrodes are lowered into the scrap and a charge is delivered to create molten metal.

As the scrap turns to molten steel, the non-metallic portion rises to the top, forming a layer called slag. This slag, while not used to make products, serves as a protective coat over the molten steel preventing oxidation of the surface metal, removes oxidizable contaminants, protects the furnace refractories, and is the primary means by which sulfur and phosphorous are removed from the molten steel. The slag is removed from the molten steel by tilting the furnace about 10 degrees backward. The slag is then converted to other industrial products such as concrete, roofing granules, and soil treatments.
After the steel is melted, the molten metal is tapped into a ladle for further chemical refinement. The whole process from charging to tapping takes less than two hours.

Once the heat has been tapped, the ladle is transported to the teeming bay where further chemistry refinements are conducted. If specified in the melt practice, Lone Star will inject chemical additions into the molten metal for proper refining of the steel. Additionally, bulk additions can be added to the steel.

Controls and tests performed throughout the process include:

  • Temperature checks using disposable pyrometers
  • Carbon checks based on the solidification temperature
  • Carbon and Sulfur checks using pin samples sent to the Technical Center
  • Spectrometer tests for residual elements.