Electric arc furnace

Some machines use heat to melt metal.

This machine uses a bright spark to get hot. The spark is called an arc. It can melt metal very fast.

Electricity flows through the metal. This makes the metal very hot. It turns the metal into liquid.

This liquid can become steel. Steel is used to make many things. It is very strong.

Do you like big machines?

An electric arc furnace uses electricity to melt metal.

It is a very powerful tool. Some furnaces are small. They might only melt a few grams. Other furnaces are huge. They can hold 400 tonnes of metal!

Inside the furnace, there is a container called a hearth. This part is lined with special bricks. These bricks protect the furnace from the heat. Large rods called electrodes hang from the roof. The electricity flows from these rods to the metal. This creates an electric arc. An arc is a bright, hot spark. This spark can reach 3,500 degrees Celsius. The heat melts the metal into a liquid bath.

When the metal is ready, the furnace tilts. This process is called tapping. The liquid steel pours out of a spout.

It flows into a large bucket called a ladle. This steel can be used to make wires, rods, or bars. It is a very fast way to make steel.

An electric arc furnace is a powerful machine used to melt metal.

These tools come in many different sizes. Some are very small and only melt a few dozen grams. Scientists use these tiny ones in research labs. Other furnaces are huge and can hold 400 tonnes of material.

Large industrial units are used to make steel. This machine is a vital part of making the metal we use every day.

The furnace works by using electricity to create intense heat. It has a main body called a shell and a bottom called a hearth.

The hearth is lined with special bricks that can stand high heat. Large graphite electrodes hang down from the roof. An electric arc forms between the electrode and the metal. This arc is a bright, glowing spark. It can reach temperatures of 3,500 degrees Celsius. The heat from the arc and the electricity melting through the metal turns the solid scrap into a liquid bath.

People have been trying to melt iron with electricity for a long time. Vasily Vladimirovich Petrov showed this was possible in 1803. Later, Sir Humphry Davy did an experiment in 1810. In 1878, Sir William Siemens took out patents for arc-type furnaces.

The first successful, working furnace was made by James Burgess Readman. He lived in Edinburgh, Scotland, and built it in 1888. His furnace was used to create phosphorus.

Modern steelmaking uses many different types of these machines. Paul Héroult from France helped develop more advanced versions. In the United States, the Sanderson brothers built the first one in Syracuse, New York.

A company called Nucor used these furnaces to grow very fast starting in 1969. Today, a mid-sized furnace might produce 80 tonnes of liquid steel in about 50 minutes.

Some massive furnaces in Japan can even handle 420 tonnes at once.

You can think of an electric arc furnace like a giant, high-tech melting pot. Instead of using a fire, it uses a bolt of electricity to do the work.

When the metal is liquid, the furnace tilts to pour it out. This step is called tapping. The liquid steel flows into a large container called a ladle. This steel is then used to make many things. It becomes the wires, rods, and bars found in our homes and buildings.

An electric arc furnace, often called an EAF, is a powerful industrial tool used to melt materials.

It works by using an electric arc to generate intense heat. This process allows manufacturers to turn solid scrap metal into liquid steel. These machines are vital for modern steelmaking and come in many different sizes. Small units used by dentists or in research labs might only hold a few dozen grams.

Industrial furnaces are much larger. Some hold about one tonne for making cast iron. The largest units can hold up to 400 tonnes for secondary steelmaking.

The furnace is built with several specific parts. It has a shell, which includes the sidewalls and a lower steel bowl. The bottom of this bowl is called the hearth. The hearth is lined with refractory brick to protect the shell from extreme heat.

Above the hearth is a retractable roof. This roof supports the electrodes, which are long rods made of graphite. In many large furnaces, the shell is water-cooled to manage the heat. The electrodes are often moved by a positioning system using electric winches or hydraulic cylinders.

To melt the metal, the furnace uses a process involving an electric arc. The arc forms between the graphite electrodes and the material inside, known as the charge.

As electricity passes through the charge, it creates immense heat. The electric arc itself can reach temperatures of approximately 3,500 degrees Celsius. This heat comes from both the electric current and the radiant energy of the arc. The electrodes often glow white-hot during this stage. To keep the temperature even, modern plants may use oxygen-fuel burners in the sidewalls. They might also inject oxygen and carbon into the furnace to add chemical energy.

History shows that many scientists worked to perfect this technology. In 1803, Vasily Vladimirovich Petrov demonstrated that an electric arc could melt metal. Sir Humphry Davy conducted an experimental demonstration in 1810. Later, Sir William Siemens took out patents for arc-type furnaces between 1878 and 1879.

The first successful, operational furnace was invented by James Burgess Readman in Edinburgh, Scotland, in 1888. His machine was used to create phosphorus. Paul Héroult from France later developed more advanced furnaces. In the United States, the Sanderson brothers installed the first electric arc furnace in Syracuse, New York.

Efficiency and scale are very important in modern steelmaking. A mid-sized modern furnace might produce 80 tonnes of liquid steel in about 50 minutes.

This includes the time from when cold scrap is added to when the steel is poured. For comparison, a massive DC furnace in Japan can have a tap weight of 420 tonnes. These large machines use many transformers to reach huge power levels. Melting one tonne of scrap steel requires about 440 kilowatt-hours of energy. This is much more efficient than some other global steel production methods.

There are different ways to manage the liquid steel once it is melted. One method is called tapping, which is when the furnace tilts to pour the metal out.

Some furnaces use an eccentric bottom tap-hole, or EBT, to help with this. This taphole is located in the narrow "nose" of the egg-shaped hearth. It is filled with refractory sand, such as olivine, when the furnace is closed. This method helps reduce the amount of nitrogen and slag that enters the liquid steel. Other designs, like the Stassano furnace, might rotate to mix the molten bath.

Electric arc furnaces have changed how the world produces metal. In the past, "electric steel" was a specialty product for things like spring steel. During World War II, these furnaces were used widely to produce alloy steels. In 1969, a company called Nucor used a mini-mill with an EAF to enter the steel market. Mini-mills are much cheaper to build than integrated steel mills. It costs about US$140–200 per ton of capacity to build a mini-mill. In contrast, an integrated mill costs about US$1,000 per ton. This allowed smaller companies to compete with giant steelmakers. Today, EAFs are used globally to produce many types of steel products.