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Foundry coke is used mainly in cupola furnaces to melt scrap or pig iron into molten iron for castings. It supplies heat as it burns and contributes carbon to the melt. “Metallurgical coke” is a broader category: foundry coke and blast-furnace coke are different grades designed for different furnaces and jobs, so they should not be assumed interchangeable.
What is foundry coke used for?
Foundry coke is used chiefly in cupola furnaces, where it helps melt scrap iron or pig iron to make molten iron for casting. The United States International Trade Commission describes it as a material used in cupola furnaces to produce molten iron. That iron can be cast into products such as automobile engines, pipes, fittings, and municipal castings. USITC staff report (2023)
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Its two jobs in a cupola
- Fuel: Coke combustion provides heat for melting the metal charge.
- Carbon source: Coke carbon contributes to the molten iron’s chemistry.
This describes cupola use; it does not mean that every foundry uses coke or that foundry coke is used in every type of metal-casting furnace.
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How foundry coke differs from blast-furnace coke
“Metallurgical coke” is commonly used as an umbrella term for coke used in metallurgical furnaces. The USITC identifies foundry coke, blast-furnace coke, and industrial coke (including coke breeze) as subgroups with differing sizes, shapes, and chemical properties. USITC staff report (2023)
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| Comparison | Foundry coke | Blast-furnace coke |
|---|---|---|
| Main furnace | Cupola furnace | Ironmaking blast furnace |
| Main functions | Provides heat and carbon for the cupola melt | Acts as fuel and reductant, and helps keep the furnace burden permeable to rising gas |
| Size and consistency | Often supplied as larger, relatively uniform lumps; exact commercial sizes vary | Selected for the requirements of blast-furnace operation |
| Strength | Needs to suit cupola charging, handling, and operating conditions | Needs to withstand loads in the blast-furnace burden |
| Chemistry | Buyers may assess ash, sulfur, fixed carbon, and other properties against their process specification | Specified chemistry depends on the furnace and plant requirements |
The blast-furnace functions are described by the Ministry of Steel, Government of India. IUPAC defines metallurgical coke generally as a high-strength, macroporous carbon material made by carbonizing coal or coal blends, and notes the need for strength under blast-furnace loads. IUPAC Gold Book
Why lump size and strength matter
Coke has to perform in a particular furnace, not just meet a broad label. Lump size and uniformity affect how the charge behaves; strength and abrasion resistance matter during handling and in the furnace. Ash, sulfur, moisture, volatile matter, and other chemical properties may also matter to a buyer’s process. The relevant limits come from the furnace requirements and the specific supplier grade.
For example, Asmet lists foundry coke sizes of 60×130 mm, 90×250 mm, and 130×250 mm, alongside example limits for moisture, ash, volatile matter, and sulfur. These are supplier product examples, not universal foundry-coke standards; Asmet says its published information is guidance and that specifications may be modified. Asmet foundry coke
Are foundry coke and blast-furnace coke interchangeable?
Not automatically. The grades are associated with different furnace uses and can differ in physical and chemical characteristics. A piece of coke being large enough does not by itself establish that it has the strength, consistency, or chemistry required for cupola service. The European Commission’s 2000 decision, for example, noted that oversized blast-furnace coke generally had lower strength and was not destined for the cupola uses considered in that trade investigation. European Commission Decision 2000/273/EC
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Size thresholds also depend on the context in which they were defined. The USITC’s 2023 staff report defined foundry coke for its review as larger than 100 mm, with at least half retained on a 100-mm sieve. The European Commission used a threshold of more than 80 mm in its 2000 investigation. Neither figure is a universal purchasing rule. Follow the foundry’s process specification and confirm the grade’s suitability with the supplier. USITC staff report (2023); European Commission Decision 2000/273/EC
What to check when specifying or buying foundry coke
- Furnace and application: Confirm that the material is intended for the cupola process and iron charge in question.
- Size range and distribution: Request the supplier’s current grade range and clarify how the size is measured; do not rely on a generic cutoff.
- Physical performance: Check the required strength and abrasion resistance for charging, handling, and furnace operation.
- Chemical limits: Compare ash, sulfur, moisture, volatile matter, and any other specified parameters with the plant’s requirements.
- Current specification: Obtain the supplier’s applicable product specification and confirm that it matches the foundry’s operating requirements.
How much foundry coke is produced?
A USITC publication issued in 2001 estimated that foundry coke accounted for 5 to 7 percent of annual U.S. metallurgical coke production, based on historical industry conditions and production data from 1995–1999. That is a historical U.S. estimate, not a current global production share. USITC, Foundry Coke: A Review of the Industries in the United States and China (2001)
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