A steel rail is a load-bearing and guiding element in a railroad or tramway track. The individual pieces are bolted or welded together to form a continuous line supporting the wheels of a railcar. The cross section or profile of a rail segment varies with time and application area.
The two groups of modern railroad elements commonly used in rail specification guides include trains and trams. A train rail profile is an asymmetrical I-beam with a wide flat bottom suitable for railroad tracks. The wheels rest on the top of the rail and the rim extends down the inside of the rail. A slotted head is characteristic of the tram track section. In this configuration, the wheel rim is located in a groove in the rail head.
Railroads have shaped the course of history and industry by changing the way people and goods are transported. The emergence of the mass market in the United States had a major impact on the construction of railroad networks connecting rural areas to distant urban centers. In the era of industrialization and the rise of the mass market, track design and manufacturing no longer used wood, cast iron or wrought iron. Steel alloys have replaced other materials for the production of medium and heavy-duty structures.
Engineering innovations, advances in metallurgical technology and improvements in steel manufacturing processes have standardized the available rail grades. Conformity varies by geographic region. The United States, United Kingdom, European Union, Russia, China and India have each developed separate standards. Each standard grade is designed to meet specific load-bearing, mechanical and operational characteristics. Units of measure vary from one region to another between metric and imperial, with imperial units still in use in the U.S. and U.K.
Guideways for high speed travel are precision engineered. They contain long sections that are fused and rigorously tested. With the correct geometry and microstructure, this enables trains to run at speeds of over 350 km/h.
Urban centers catering to congested traffic have curved sections and fluctuating gradients. The mechanical characteristics of the device were chosen to withstand the characteristic stresses consistent with the area. Conditions involving rapid acceleration and deceleration require components that can resist tension and stretch. For tightly curved sections, lubricants help reduce mechanical wear on the track. Oil or grease dispensers are placed along the track in areas where high friction is expected.
Coastal and marine conditions require special attention to corrosion. Galvanizing prevents rusting while protective coatings and polished finishes are combined with recommended standard grade steel elements to minimize maintenance and repair costs.
Steel rail products are used for a wide range of transportation functions and fall into the following categories.
Public transportation - passenger railroads, underground railroads, trams.
Freight and logistics - bulk material transportation.
Cranes, fixed rail lifting equipment for short distance and high load transportation.
Graded steel is the main material used in the manufacturing process of rails. There are many operational and safety issues as the components are susceptible to crushing cracks or spalling. Testing existing structures for potential weaknesses requires continuous effort. To this end, automated testers that rely on induction magnetic fields, ultrasound or a combination of both can help detect dangerous cracks and flakes.
The chemical composition of steel alloys used for heavy and light components is balanced to produce material strength, flexibility, wear resistance and temperature variation. The stiffness of steel can be improved by creating alloys of carbon, silicon, phosphorus and manganese. This changes the microstructure of the alloy, which in turn changes its mechanical properties. While superior tensile strength and stiffness can withstand greater loads and speeds, they may have a higher susceptibility to low temperature embrittlement and fracture.
Considerations when selecting a rail product are determined by the following factors.
Increased weight and speed of the load resulting in higher forces applied to the rail
Expected levels of wear, abrasion and failure for testing and maintenance
Industry standards contain comprehensive specifications and region-specific data for matching desired characteristics to available standard grades. Compatibility with existing infrastructure and ease of maintenance are essential when evaluating long-term operating costs.
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