While many might wonder if railroad spikes are made of iron, modern railway systems primarily rely on steel spikes. This common question stems from the historical use of iron in early railway construction. As railway technology advanced and trains became heavier and faster, the demands on track components increased. This necessitated a shift to a more robust material: steel.
The Material Evolution of Railroad Spikes
Early railroad spikes, first used in 1832 by Robert Livingston Stevens, were made from wrought iron. These initial spikes were simple, nail-like pieces designed to secure rails to wooden ties. Wrought iron, known for its malleability and ductility, was suitable for the lighter loads and slower speeds of early trains. It was relatively easy to produce and shape with blacksmithing techniques.
As the railway system expanded and trains became larger and heavier, wrought iron’s limitations became apparent. It exhibits lower tensile strength and is more susceptible to fatigue under repeated stresses from passing trains compared to steel. This could lead to spikes bending or breaking, compromising track stability. Advancements in steel production during the late 19th and early 20th centuries, such as the Bessemer process and open-hearth furnaces, made steel more accessible and cost-effective, leading to its widespread adoption. Steel gradually replaced wrought iron as the preferred material for railroad components, including spikes, due to its enhanced mechanical properties.
Why Steel is the Ideal Choice
Steel, particularly carbon steel, is the material of choice for modern railroad spikes due to its mechanical properties that contribute to track safety and longevity. Carbon steel offers a balance of strength, ductility, and cost-effectiveness, important for components enduring dynamic loads from trains. Different types of carbon steel, such as Q235 and Q345, are commonly used, providing varying levels of strength and performance.
One property is steel’s high tensile strength, its ability to resist pulling forces without breaking. This strength is fundamental for securely fastening rails to ties, preventing lateral movement and maintaining track gauge. Steel also possesses ductility, meaning it can deform under stress without fracturing. This property helps prevent brittle failure under dynamic loads and repeated impacts from trains, allowing the spike to bend rather than snap.
Steel offers good hardness and wear resistance, enabling spikes to withstand constant vibration and environmental exposure without degradation. Its resilience to repeated stress cycles, known as fatigue resistance, also prevents material degradation over time. While low-carbon steel spikes are common, higher carbon steel varieties are used in demanding applications, offering increased resistance to wear and bending. Steel’s relative abundance and ease of production contribute to its cost-effectiveness, making it an economically viable material for railway infrastructure.