Understanding Materials and Steel Production: From Raw to Refined
1. Materials: Origin and Classification
Materials can be broadly classified into raw materials and produced materials.
- Raw materials: Natural materials gathered from nature.
- Produced materials: Materials obtained after subjecting raw materials to appropriate transformations.
Material Composition
- Metallic: Metal acts as a basic component.
- Ferrous metals: Steel, cast iron, soft iron.
- Non-ferrous metals: Light metals, heavy metal alloys.
- Non-metallic: Metal is not a basic component.
- Natural: Silk, wood, quartz.
- Synthetic: Concrete, plastic, glass.
- Assistants: Complements, lubricants, insecticides.
2. Ferrous Materials
Ferrous materials are those whose main component is iron.
Iron Ores
- Magnetite: A mixture of iron oxides.
- Red hematite: Iron oxide (III).
- Siderite: Carbonate of iron (III).
- Limonite: Iron hydroxide (III).
- Pyrite: Iron sulfide mixed with copper compounds.
3. Obtaining Iron: The Blast Furnace
The blast furnace is a complex installation whose main objective is to obtain cast iron. The central body, called the blast furnace, consists of two truncated cones placed with one another and united at their wider bases. The interior wall is built of refractory brick, and the exterior is steel. Between the two are cooling channels. The top of the blast furnace is called the mouth and consists of two hoppers.
The material is introduced inside the furnace in alternating layers:
- Layer of iron ore mixture.
- Layer of coking coal.
- Layer of fluxing material.
The tank heating occurs first. The widest part is called the belly, where the fusion process of iron and slag occurs. Under the belly are the nozzles, which inject the air required for combustion. This air comes from facilities called heat reclaimers. The bottom is called the hearth.
The removal of slag and iron is carried out through two holes located at the bottom:
- Slag notch: The extracted supernatant slag.
- Tap hole: For extracting the cast iron.
4. Steel Products
Steel products are the various products obtained from iron ore.
Classification
- Sweet iron: Iron with a carbon content less than 0.1%.
- Cast iron: Material obtained directly from the blast furnace.
Impurities in Cast Iron
- Gray cast iron: Obtained when the silicon content is high.
- White cast iron: Obtained when the manganese content is high.
Refinement: Reducing the carbon content and modifying the composition of other elements present in the cast iron.
5. Steels
Steel is an alloy of iron and carbon.
Types of Steel Based on Alloying Elements
- Carbon: Increases hardness and resistance.
- Silicon: Improves elasticity and magnetic conductivity.
- Manganese: Enhances hardness and wear resistance.
- Chromium: Provides hardness, resistance to heat and friction.
- Nickel: Increases tenacity, tensile strength, and corrosion resistance.
- Molybdenum: Enhances hardness and wear resistance.
- Tungsten: Improves tenacity, corrosion resistance, and heat resistance.
Types of Steel Based on Alloy Proportion
- Non-alloy: Alloying elements do not exceed 1%.
- Low-alloy: Alloying elements between 1% and 5%.
- High-alloy: Alloying elements greater than 5%.
6. Processes for Manufacturing Steel
The Bessemer Converter and Thomas
Phases
- Filling
- Blowing
- Emptying
LD Converter
Phases
- Filling
- Refining
- Emptying
The Siemens-Martin Furnace
A large reverberatory furnace.
The Electric Furnace
Types
- Electric-arc furnace
- Induction furnace
7. Treatment of Casting
Ingot casting process: Casting consists of pouring the liquid inside a mold called an ingot mold.
Continuous casting: This consists of pouring molten material on bottomless molds with a movable section, which is the way to get the product.
7.1 Types of Steel Facilities
- Integrated steelworks: Partial reduction of iron ore.
- Non-integrated steelworks: They do not have blast furnaces and produce material from scrap.
8. Types of Commercial Steel
- Building steels (F1)
- Special steels (F2)
- Stainless steels (F3)
- Tool steels (F5)