Steel Manufacturing Processes: Techniques and Methods

Steel Production by Carbonization

Carburization: Steel with less than 0.2% carbon is placed in boxes surrounded by charcoal accelerators, sealed with mud, and heated in an oven at 950°C. The piece remains in the oven until the carbon penetrates the surface; thicker pieces require longer heating times.

Decarburization Methods

Puddling: A rarely used method to remove impurities. Cast iron and iron ore are introduced into special rotating ovens where burning carbon is removed to reach the desired carbon level.

Liquid State Processing

Crucible Steel: Iron, mineral smelting, scrap carbide, and high-carbon alloys are processed to remove silicon, manganese, and carbon, resulting in high-quality steel.

Converter: A vessel made of sheet metal with a refractory lining. The bottom is perforated to allow air entry from compressors.

LD Converter: Instead of blowing air through the liquid mass, oxygen is injected via a lance onto the surface.

Siemens-Martin Process: Utilizes scrap in reverberatory furnaces. Its key characteristic is the recovery of combustion gases. The operation relies on inversion valves and specialized components.

Electric Oven Processing

Electric Furnace: Offers high thermal efficiency and is capable of producing pure, high-quality steel products.

Steel Casting and Solidification

Cast Steel: Once in a liquid state, the steel is removed from the oven and transferred via a ladle to fill molds. After the steel solidifies, the ingot is removed from the mold.

Vacuum Casting: Gas presence in liquid steel reduces its resistance. To obtain steel low in nitrogen and hydrogen, the ladle is placed in a chamber under a vacuum of 60-70 mmHg for 10 minutes. This process removes gases, resulting in more resistant steel with fewer pores.

Rolling and Finishing

Lamination: Cold ingots are heated in equalizing furnaces and extracted to pass through a rolling train. This occurs in stages:

• Blooming Mill: Large ingots are reduced into smaller sizes.
• Billet Mill: Produces intermediate shapes.
• Finishing Mill: Driven by electric motors, cylinders give the steel its final shape.

Continuous Casting: A modern process that eliminates the ingot casting stage by passing the molten steel directly to the rolling mill, saving both heat and time.