An electric arc furnace (EAF) is a steelmaking furnace that melts metal using electrical energy from large graphite electrodes. It is the main technology used in scrap-based steelmaking and mini-mills because it can melt high percentages of recycled steel, start and stop quickly, and be located closer to markets. EAFs are different from blast furnace/basic oxygen furnace routes because they do not depend on coke and iron ore for every heat.

In this blog, we explain how the EAF cycle works, why scrap is important, what graphite electrodes do, how off-gas is controlled, and where standard HVAC filtration fits on the plant site.

Key Takeaways

• An electric arc furnace melts mostly scrap steel using electrical energy from graphite electrodes instead of relying on coke and iron ore.
• The EAF process follows a simple cycle: charge the furnace, close it, melt the scrap, refine the steel, tap the molten steel, and remove the slag. This cycle can be repeated multiple times in a day.
• EAFs make high levels of scrap recycling possible and can operate with a lower overall emissions profile when the electricity source is cleaner.
• Off-gas from an EAF is handled by industrial capture systems such as hoods, direct evacuation, and baghouses, not by residential or commercial MERV filters.
• MERV-rated HVAC filters from Filterbuy are for the building areas around the melt shop, such as offices and control rooms, not for the furnace exhaust itself.

How The Eaf Process Works

1. Charge. Scrap steel, sometimes mixed with DRI or HBI to improve chemistry, is loaded into the furnace shell.
2. Close and position. The roof is closed and the three graphite electrodes are lowered through the roof openings.
3. Arc and melt. Power is applied. An electric arc forms between the electrode tips and the charge and melts the scrap.
4. Refine. Oxygen, carbon, and fluxes (often lime) are injected to remove impurities and adjust steel chemistry.
5. Tap. When temperature and composition are on target, the furnace is tilted and liquid steel is poured into a ladle for further treatment or casting.
6. Slag removal. Non-metallic material is skimmed off separately.

This cycle can be repeated several times per day, which is why EAF shops are considered flexible.

Scrap Recycling Benefits

• EAFs can melt large volumes of ferrous scrap and turn them back into new steel products.
• Because scrap is the main input, EAFs reduce dependence on iron ore and coke.
• With cleaner electricity, EAF steel can have a lower overall emissions profile than traditional furnace routes.

Graphite Electrodes And Their Role

EAFs use large graphite electrodes to carry current into the furnace. The arc is formed at the tip of these electrodes. They must tolerate high current, high temperature, and thermal shock. Electrodes are consumed gradually, and operators add electrode sections as the heat progresses.

Operating Temperature

The arc is hotter than the bath, but the molten steel is typically brought to about 1,600°C (about 2,900°F) for tapping, which is suitable for many carbon steels. Operators control temperature so the steel is hot enough for tapping without damaging the refractory or wasting power.

Off-Gas And Dust Control

An operating EAF produces fume and off-gas. Steel plants capture this with:

• direct furnace evacuation (fourth-hole systems)
• canopy or roof hoods for secondary emissions
• large industrial baghouse/dedusting systems

These are heavy-duty industrial systems, not MERV panels. Their job is to capture hot, dust-laden gas, cool it, and filter it before release.

HVAC Filtration For Offices And Control Rooms

Melt shops and EAFs use industrial fume capture, but the offices, control rooms, labs, and support areas on the same site still rely on standard HVAC. Those building systems are typically designed around MERV-rated filters to keep indoor spaces and equipment cleaner in a dusty environment.

Filterbuy offers pleated furnace filters in MERV 8, MERV 11, and MERV 13, in standard and custom sizes, made in the USA with fast shipping.

FAQs

What is an electric arc furnace?

An electric arc furnace is a steelmaking furnace that uses electric arcs from graphite electrodes to melt steel scrap inside a refractory-lined shell.

Why do steelmakers use so much scrap in an EAF?

Because an EAF can melt scrap directly with electrical energy, it does not have to turn iron ore into iron first. That makes it well suited for recycling steel from cars, construction, equipment, and industrial scrap.

How is an EAF different from a blast furnace or basic oxygen furnace?

Blast furnace and BOF routes depend on iron ore, coke, and hot metal. An EAF can run mostly on scrap and electricity, and it can start and stop more easily.

What do graphite electrodes do?

They carry the electric current into the furnace. The arc that forms at the tips of the electrodes is the main heat source that melts the scrap.

How hot does an EAF run?

Steel is usually tapped at about 1,600°C (about 2,900°F), which is hot enough for many carbon steels.

Why does an EAF need off-gas and dust control?

Melting scrap creates fumes and hot off-gas. Plants capture this with hoods, direct evacuation, and baghouses so dust and fumes do not enter the shop air.

Can MERV filters be used on the furnace exhaust?

No. Furnace off-gas is handled by heavy industrial systems. MERV filters are for the building HVAC that serves offices, control rooms, and other support areas on the same site.

Why is an EAF considered lower impact in some cases?

When it runs on cleaner electricity and uses clean scrap, the process can have lower overall emissions than a route that must reduce iron ore and burn coke.

What gets done after tapping?

The liquid steel is sent to a ladle for further refining or to casting, depending on the grade being produced.

Why would a company still need standard HVAC filters near an EAF?

Because people still work in offices, labs, and control rooms near the melt shop. Those spaces use normal HVAC equipment, and MERV-rated filters help keep those areas cleaner.