Riding the rails isn’t as popular as it was 100 years ago, but trains still play a crucial role in a number of industries, including transportation, manufacturing, and logistics. Trains have come a long way from their steam and iron origins, and aluminum has had a lot to do with the modernization of the railway industry.
Aluminum’s History in Railcars
The earliest locomotives were largely made from a combination of cast iron and wood. In particular the steam boilers were made from iron, meaning the parts would often suffer from severe corrosion and rust because of the amount of hot water that was necessary to power the trains. However, although the use of aluminum in the railway industry did not become prevalent until the last 50 years, even some of the earliest trains featured aluminum.
As far as we know, the first example of aluminum being used in a train dates back to 1894. A special lightweight car was built by the New York, New Haven, and Hartford Railroad that used aluminum seat frames, a technologically advanced endeavor at the time. In the 1930s, experiments were made with building all-aluminum railway cars, for either freight or passengers. For example, the Chicago World’s Fair in 1933 featured the world’s first main-line, aluminum passenger cars on display.
While experiments would continue for the next several decades, and certain specific uses of aluminum took off, it wasn’t until the 1960’s that aluminum use became widespread in the industry. By the 1980’s, aluminum was a go-to choice for all manner of railway applications, in particular, urban metro systems and high-speed trains.
The Advantages of Aluminum
Just as for comparable industries, such as aerospace and automotive, aluminum offers a number of clear benefits that have made it popular in the railway industry. The transition from the cast iron of early locomotives has gotten to the point where today many of the load-bearing elements of the train are made solely of aluminum, not to mention the carriage bodies.
The most important advantage of course is aluminum’s extremely high strength-to-weight ratio. Many of the greatest advancements in aluminum alloys came about as a result of innovations in the aerospace industry, where the premium on developing low weight materials is tremendous. The efficiency of railways, which depends greatly on lowering the amount of friction by reducing the weight of the vehicles, increased immediately with the extensive use of aluminum.
Another prominent benefit of aluminum alloys is their tremendous corrosion resistance. Aluminum’s natural passivation process (in which a thin aluminum oxide layer forms when the metal is exposed to oxygen) reduces the possibility of further oxidation, and the protection can be increased by anodizing the metal. This means that aluminum is one of the most corrosive resistant metals available, an important consideration for the durability of trains, which often have 30-year or longer lifecycles.
Aluminum also possesses high formability and is aesthetically pleasing, an critical factor for modern passenger cars. Because it can be easily worked into any conceivable shape and any excess material is fully recyclable, the production is also more efficient when compared to other materials.
Recent advances in aluminum alloys have led to many cutting edge applications for aluminum that are continuing to transform the railroad industry. For example, engineers have developed an aluminum foam that is being used to build high-speed train cars and is twenty percent lighter than fiberglass, yet still extremely strong.
Uses of Aluminum in the Railway Industry
Aluminum is pervasive in both freight and passenger trains. For the former, the low weight of aluminum allows for larger payloads to be shipped. One example of an application that has innovated the industry is the use of internally-stiffened, hollow extrusions that are used in the moveable side walls of freight cars. When compared to steel walls, aluminum walls can be made with fewer parts, making them both easier to build and lighter, and allowing a single worker to manipulate the wall, further reducing the labor involved.
These days, passenger cars are frequently made with single aluminum extrusions that are the full length of the car, in some cases 75 feet long. The individual parts are welded together and reinforced with horizontal members around the doors and windows. With fewer parts required and a simplified assembly process, the manufacturing is more efficient than steel and the finished product is lighter, cheaper, and more aerodynamic.
Aluminum’s versatility has also allowed train manufacturers to meet the latest demands of the industry. Many trains are designed to be tilting, which allows them to lean into curves, meaning higher speeds can be achieved. Trains are also being designed to generate electricity while braking, and aluminum technology enables extremely low axle weight without sacrificing structural integrity or safety. Additionally, issues such as sustainability and environmental protection are being taken into consideration more often and aluminum alloys are allowing manufacturers to better address these needs.
Which Alloys Will You Find in Trains
The characteristics that are most sought after in aluminum alloys include a light weight, ease of fabrication, mechanical strength, weldability, corrosion resistance, and how they take to heat treatment. The alloys that best match these characteristics fall into the 5xxx and 6xxx families. The sheet metals most commonly used are 5052, 5083, 5086, 5454, and 6061. For extrusion purposes, 5083, 6061, and 7005 are widespread. When welding, 5356 or 5556 are used as filler.
Even in the most advanced high-speed trains, the above alloys will be used, in addition to 7075 alloy, which is most commonly found in the aerospace industry. Because of the great diversity of alloys, aluminum can meet just about any of the challenges posed by the railroad industry.
Summary
Of course, this also means that knowing exactly what kind of alloy is needed for a particular application can be difficult. At Clinton Aluminum, our knowledgeable representatives are dedicated to helping our clients find the right alloy for any job. We pride ourselves on being your technical resource partner, with a strong commitment to service, value, and education.
Resources:
