Analysis of melting steel with arc furnace Arc melting is an important part of metallurgical production and melting steel with an arc furnace (EAF) is the most popular method of steelmaking. The high electric potential of the electrodes used in arc furnaces make it possible to quickly melt and mix the metals with high speeds. This usually leads to improved quality and higher yields than conventional melting processes.
Arc furnaces are typically used for melting scrap materials or a combination of scrap and other alloying elements. This process is popularly used for melts of stainless steels, heat-resistant steels, low-alloy steels, and other specialty alloys. In electric arc furnaces (EAFs), a large quantity of steel scrap or ferrous alloy is heated to temperatures high enough to melt the scrap, which is then poured into a steel shell. The electrodes are then used to arc melt the material in the shell.
The first step in the EAF process is the charging of the furnace, which is typically done by a computerized remote-controlled crane system. During the charging process, the furnace charge must be prepared in accordance with the pre-charging program, generally requiring the correct scrap selection, level of purity and correct quantity of materials. The correct combination of scrap and other alloys allow for better mixing and melting of the scrap.
The next step in the EAF process is the melting of the charge under high levels of electric current. Three main types of power sources are commonly used in EAFs: Rectifiers, Alternators and Inverters. Rectifiers are commonly used with medium to small-size EAFs and require direct current at high levels of power. Alternators are most often used in large-scale medium to large-size EAFs and require alternating current at high levels of power. Inverters are used with small to medium-size EAFs and can convert direct current to alternating current. The level of the power is determined by the size of the furnace, the amount of steel being melted and the rate of melting for the particular batch.
The power source feeds the electrodes, which are held in place by a deep well structure. The electrodes are lowered into the steel shell and allow an electrical arc to form between the electrodes and the shell. The arc is regulated to allow the charge to reach its melting point, usually between 2700 and 3000 degrees Celsius. The heat of the arc creates a convective motion that agitates and mixes the charge.
Once the desired temperature is reached, the slag layer forms on top of the molten steel bath, which acts as an insulator to protect the charge from oxidation. The slag can also have a special composition in order to ensure the desired chemical composition of the finished steel. As the carbon content decreases, the melting point of the steel decreases, thus speeding up the melting process. In order to achieve the steels desired chemical composition, additional alloying elements are added to the charge and mixed into the steel.
After the steel and iron materials have been melted and all of the required alloying elements added, the charge is then tapped from the shell into a ladle. This process, known as tapping, requires specialized tapping machines and requires the furnace door to be opened, which allows oxygen to enter the furnace and oxidize the molten steel, preventing proper tapping. Therefore, a flux and/or a deoxidizer agent (such as copper and aluminum) are added to the charge before tapping to protect it from oxidation.
In conclusion, arc furnace melting of steel involves a number of steps that must be strictly adhered to in order to ensure the correct chemical composition and quality of the finished product. The temperature and rate of melting, treatments with fluxing materials, and proper alloying are all important factors that must be taken into account. If everything is done correctly, then the finished product should be of a high standard and yield a higher quality steel product.
