What is Electric Arc Furnace?

What is Electric Arc Furnace?

What is Electric Arc Furnace? The Electric arc furnace steelmaking process uses electricity as its energy source.  Electric arc furnace (EAF) steelmaking primarily utilizes electric arc heat, reaching temperatures as high as 4000℃ in the arc zone. The smelting process generally consists of a melting phase, an oxidation phase, and a reduction phase. Within the furnace, both oxidizing and reducing atmospheres can be created, resulting in highly efficient dephosphorization and desulfurization.

Types of Electric Arc  Furnaces

Types of electric furnaces include arc furnaces, induction furnaces, electroslag furnaces, electron beam furnaces, and consumable electrode arc furnaces. 
Typically, EAF steelmaking is produced using basic oxygen arc furnaces.  Steelmaking EAF is commonly used to produce carbon structural steel, tool steel, and alloy steel. These steels are of high quality and uniform performance. 

At the same carbon content, EAF steelmaking exhibits superior strength and plasticity compared to open hearth furnace steel.

EAF steelmaking primarily uses scrap from similar steel grades as raw material, though sponge iron can replace some of the scrap. Chemical composition and alloy element content are adjusted by adding ferroalloys.
Steelmaking with scrap as the raw material in EAFs requires less capital investment than the blast furnace-converter method. 

Additionally, advancements in direct reduction have provided metallized pellets to replace most scrap in EAFs, significantly promoting EAF steelmaking. 

Currently, there are about 1,400 large EAFs worldwide, with ongoing development towards larger capacities, higher power, and automation through electronic computer control. The largest EAFs have capacities of up to 400 tons. 

In foreign countries, EAFs larger than 150 tons are almost exclusively used for producing plain steel, with many nations' EAF steel output comprising 60–80% low-carbon steel. Due to limitations in electricity and scrap availability, China mainly uses EAFs for producing steel and alloy steel.

Short Process Steelmaking Technology

Short process technology refers to processes that deviate from the traditional long process (also known as conventional processes), which includes the blast furnace—converter—continuous casting (or mold casting) route. The short process in EAFs is represented by the early 1990s American EAF—thin slab continuous casting process. 
Since its introduction, this process has garnered significant attention within the steel industry. Compact EAF short processes are a typical example. 

Compared to traditional processes, EAF short processes offer several advantages:

1. Investment is more than halved compared to the blast furnace—converter route. For instance, the actual costs of the EAF thin slab short process in countries like the United States and Japan are about a quarter of those for traditional processes.Production costs are lower, and labor productivity is higher. Steel conglomerates typically consume around 23 kJ/t of energy per ton of steel from ironmaking through hot rolling coil production, whereas EAF steel plants using scrap as raw material in short processes consume nearly 10 kJ/t, reducing energy consumption by approximately 60%.

2. With annual scrap production exceeding 300 million tons, the development of EAF short processes plays a crucial role in promoting environmental protection, recycling scrap, and purifying the environment in metallurgical plants. 

3. As a result, developed countries prioritize the development of compact EAF short processes. In recent years, although China's EAF process development has received attention, the expansion of EAF short processes should be cautious and appropriately managed to avoid recklessness, given the current lack of advantages in electricity and scrap resources, meaning no cost advantage. 

Larger capacity furnaces offer higher thermal efficiency, reducing electricity consumption per ton of steel while also significantly lowering average equipment investment per ton of steel, thus reducing steel costs and improving labor productivity.

For example, a furnace with a capacity of 320 tons has a productivity more than 100 times higher than a small furnace of 1.5 tons. In certain special cases requiring large volumes of molten steel, only large-capacity arc furnaces can meet the demands. 

Many countries adopt large-capacity arc furnaces; currently, there are over 30 EAFs with capacities exceeding 180 tons, the largest being 400 tons. Baosteel's arc furnace in China has the largest capacity at 150 tons.