Steel is a conductor of electricity. This metallic alloy is primarily composed of iron combined with a small amount of carbon and often other elements. While steel effectively conducts electricity, its performance is significantly lower compared to common electrical materials like copper or aluminum.
Defining Electrical Conductivity and Resistivity
The ability of any material to allow the passage of electric charge is quantified by two related properties: electrical conductivity and electrical resistivity. Electrical conductivity measures how easily current can flow through a material. Resistivity, which is the reciprocal of conductivity, measures how strongly a material opposes the flow of electric current.
Materials are broadly categorized based on their resistivity. Conductors, like metals, have low resistivity and allow charge to flow easily. Insulators, such as rubber or glass, have high resistivity and strongly resist the movement of charge.
Resistivity is an intrinsic property used as the standard metric for comparison. The international standard sets pure copper at 100% conductivity; steel typically falls within a much lower range, indicating its relative inefficiency.
The Mechanism: Why Steel is a Conductor
Steel conducts electricity due to its metallic structure. Iron, the main component, forms a crystalline lattice where the outer electrons are not bound to single atoms but are shared and delocalized across the entire structure. These delocalized electrons, often called a “sea of free electrons,” move freely throughout the metal. When voltage is applied, it creates an electric field that pushes these mobile electrons in a single direction, constituting an electric current.
In steel, the presence of carbon and other elements disrupts the crystalline arrangement. These disruptions cause moving electrons to collide more frequently with the lattice atoms, slowing their progress. This is the microscopic cause of electrical resistance, making steel a less efficient conductor than purer metals like copper.
How Different Steel Alloys Affect Conductivity
The electrical properties of steel depend heavily on its specific alloy composition. Steel is a family of alloys created by adding elements like nickel, manganese, or chromium to the base iron-carbon mixture. These added elements primarily determine the final conductivity. Adding alloying elements generally reduces electrical conductivity by increasing the material’s resistivity.
These foreign atoms create imperfections in the iron crystal structure, which increases the scattering of the free electrons moving through the lattice. The more the electron path is disrupted, the higher the resistance becomes.
For example, common carbon steel has better conductivity than highly alloyed stainless steel. Stainless steel contains significant amounts of chromium, which greatly increases its resistance to corrosion but also severely hinders electron flow. The resistivity of some stainless steels can be up to 40 times higher than that of copper, making them particularly poor conductors compared to other metals.
Practical Applications and Considerations
Steel’s conductive properties are utilized in numerous applications where its strength and low cost are prioritized over high electrical efficiency. One common use is in electrical grounding systems, where its mechanical strength and availability make it an effective, reliable path for safely dissipating fault current into the earth. Structural steel components, like the frames of buildings or transmission towers, inherently act as conductors and are often integrated into the grounding system.
Steel’s strength is also utilized in power transmission lines, although not as the primary conductor. Aluminum conductor steel-reinforced cables use a central steel core to provide the necessary tensile strength to span long distances between towers. The actual electrical current is carried by the surrounding aluminum strands, which are far more conductive than steel.
Despite being a conductor, steel is rarely used for standard electrical wiring in homes or electronics because of its high resistivity compared to copper. When current flows through a high-resistance material like steel, a greater amount of electrical energy is converted into heat. This inefficiency leads to substantial energy loss and can cause problematic heat generation in a circuit. For applications that require efficient power delivery, materials like copper remain the preferred choice due to their superior conductivity.