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Air-cooled high alloy electric arc furnace (EAF) and stainless steel slag (AOD)

What Are High Alloy and Stainless Steel Slags?

High alloy and stainless steel slags are by-products of the manufacture of these steels by either the electric arc furnace process (EAF) or the argon oxygen decarburisation (AOD) process.

Production and Processing

An EAF produces steel by the melting of recycled steel scrap, using heat generated by an arc, created by a large electric current. The slag is formed through the addition of lime, which is added to remove non-essential elements from the steel. The slag has a lower density than steel and therefore floats on top of the molten steel. Once the steel has been tapped into a ladle, the slag is either poured from the furnace onto the floor where it is cooled and removed for further processing, or into slag pots where specially designed vehicles are used to transport the slag to purpose built lagoons. Here it is tipped and cooled prior to onward processing.

The AOD process is a secondary steel making process for the refinement and manufacture of different grades of stainless steels in a ladle furnace. This process produces a slag that is then further treated to prevent dusting of the aggregate.

Both these slags are removed and tipped into pits where they are air cooled with the assistance of water. Once cooled the excavated slag is processed through a metal recovery facility where entrapped steel is removed.

Following this process the slag is treated very similarly to virgin aggregates and is crushed and screened into size fractions and stockpiled.

Due to the presence of free (uncombined) lime (calcium and magnesium oxide) and depending on the final end use of the EAF slag, the stockpiles may be weathered for a designated time period in controlled areas. Weathered slag is tested to check the expansion properties of the material as identified in BS EN 1744-1 to meet the requirements of its end use

Typical Chemical Properties

Compound

Typical value

High Alloy

AOD

Fe2O3

27

1

CaO

30

53

SiO2

15

26

MgO

8

6

Al2O3

6

2

Typical Physical Properties

Property

Typical value

High Alloy

AOD

Relative Density (SSD)

3.40

2.98

Water Absorption

1.8

1.75

Magnesium Sulfate Soundness

1.0

1.0

Los Angeles

14

17

Aggregate Abrasion Value

3.0

2.8

Polished Stone Value

63

63

Applications

  • Aggregates for Asphalt
  • Aggregates for surfacing dressing
  • Hydraulic Bound Mixes
  • Filter media

Standards and Specifications Applicable to the Use of Metalliferous Slag Aggregates

For further information concerning the standards and specifications applicable to Slag Aggregates refer to: http://www.mineralproducts.org/prod_agg01.htm

For case studies applicable to the use of slag aggregates refer to: http://www.mineralproducts.org/prod_agg01.htm

For more information contact Martin Bridges

Please note this website is maintained to provide information and guidance on UK issues, products and applications of those products.

 
 

For more information on aggregates, please contact (info@mineralproducts.org) or phone us on 020 7963 8000

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