Iron and Steel Slag
What is Steel and Iron Slag?
Steel slag (Steel Slag) and iron slag (Iron Slag) are among the most important by-products of the steelmaking industry, which gained economic and environmental importance in the 20th century with the development of the steel industry. Steel production, due to the need for high-quality steel, is always accompanied by the generation of waste materials, and slag has become a valuable source of minerals and industrial applications, gaining significant importance. A precise understanding of steel slag is essential for various industries such as cement, road construction, agriculture, and chemical industries.
What is Steel Slag?
Steel slag is a non-metallic solid or semi-solid material produced as a by-product in the steel production process. This material consists of metallic impurities and metal oxides that are separated from the molten metal to produce pure steel.
Main Characteristics of Steel Slag:
- Color: Usually light to dark gray
- Structure: Brittle and crystalline, but some types can be glassy
- Density: Less than steel, so it floats on the surface of molten steel
- Chemical Composition: CaO, SiO₂, Al₂O₃, MgO, FeO, and other elements
Important Note: Slag is not merely waste; it is also recognized as a valuable source of minerals and industrial materials.
Steel Slag Production Process
In the Blast Furnace (Blast Furnace + BOF)
In this method, iron and steel are produced from iron ore and coke:
- Iron ore, coke, and lime are fed into the blast furnace.
- The iron ore is reduced, and impurities combine with lime.
- The impurities separate as molten slag and float on the molten metal.
- After cooling, the slag turns into solid pieces or powder.
In the Electric Arc Furnace (Electric Arc Furnace, EAF)
This method is mainly used for recycling steel scrap:
- Steel scrap is heated in the furnace.
- Impurities rise to the surface of the melt by adding lime and other chemical materials.
- The produced slag contains metal oxides and lime, which is later collected and processed.
Important Production Characteristics of Slag
- Temperature: Usually between 1400 to 1600 degrees Celsius
- Slag Percentage: Approximately 10 to 15% of the produced steel weight
- Chemical Composition: Dependent on the type of steel and raw materials
Chemical Composition of Steel Slag
Steel slag consists of various metal oxides that can be divided into three main categories:
| Component | Approximate Percentage | Role |
|———–|————————-|——|
| CaO | 30–60% | Neutralizing acids, increasing alkalinity |
| SiO₂ | 20–30% | Forming glass and hard structure |
| Al₂O₃ | 5–10% | Improving mechanical strength |
| MgO | 3–10% | Controlling volume and preventing cracking |
| FeO | 5–15% | Residual iron |
| Other Elements | 1–5% | MnO, TiO₂, etc. |
Note: The exact composition varies depending on the type of steel (carbon, alloy) and production method.
Types of Steel Slag
Blast Furnace Slag
- Produced from iron ore and lime
- Applications in cement and road construction
Electric Arc Furnace Slag (EAF Slag)
- Result of melting steel scrap
- Hard and resistant, suitable for road construction and high-strength concrete
Acidic and Basic Steelmaking Slag
- Acidic: High SiO₂, less used in the cement industry
- Basic: High CaO, very suitable for cement and agriculture
Industrial Applications of Steel Slag
Cement Industry
- Partial replacement of cement clinker (up to 30–40%)
- Reducing energy consumption and CO₂ emissions
- Producing high-strength and slow-setting cements
Road Construction and Railway Substructure
- As aggregate or road base
- Increasing road durability and strength
- Use in asphalt and lightweight concrete
- Use as railway ballast
Agriculture
- Amending acidic soils due to CaO and MgO
- Increasing soil pH and better plant growth
- Providing nutrients such as calcium and magnesium
Other Industries
- Producing high-strength concrete and self-compacting concrete
- Filler in plastic industries, coatings, and rock wool
- Producing absorbent materials and filters
Main Consuming Countries
- Countries with active cement industries: China, India, Europe
- Developed countries with recycling programs and green road construction
- Greater application in road construction, civil infrastructure, and alternative cements
Advantages and Challenges of Using Steel Slag
Advantages
- Reducing environmental pollutants
- A source of useful minerals
- Reducing energy consumption in cement and concrete
- Increasing the durability and strength of structures
Challenges
- Need for processing and grinding before use
- Controlling chemical composition to prevent corrosion or unwanted reactions
- Proper transportation and storage
Steel slag is a high-value economic and industrial by-product. With proper management, it can be used as a source of minerals, soil conditioner, cement substitute, and raw material in road construction and concrete. The highest production and consumption occur in countries with advanced steel and cement industries. The future of this product is very bright, with a focus on sustainable development and industrial recycling.
As a pioneer in the global supply of this product, along with its business partners in Iran, India, and Russia, Vahab International Trading Holding is ready to supply all grades of steel and iron slag in various particle sizes.
For more information, analysis, and pricing, please contact us through the communication channels on the “Contact Us” page.