Overview

Over the decades, the evolution of train manufacturing has been a journey of continuous innovation, driven by the objective of increasing efficiency, safety, and performance. In the early stages of rail transport, trains were manufactured primarily from steel and cast iron materials, which are known for their strength and durability. However, their considerable weight severely limited the potential for achieving faster and more energy-efficient travel. As rail networks expanded and advancements in materials science progressed, a shift occurred toward the manufacturing of trains that are not only reliable but also lighter and more cost-effective.

Currently,  lightweight materials are emerging as a critical element in train manufacturing. The railway industry has embraced lightweight materials as an efficient solution to optimize the overall efficiency and performance of rolling stock. These materials not only reduce the weight of trains but also enhance their durability, performance, and safety.

This paper examines the importance and benefits of lightweight materials in contemporary train manufacturing, addressing the obstacles that impede their integration.

Why Lightweight Material in Train Manufacturing? 

Initially, train manufacturers prioritised the use of materials such as steel and iron, which are renowned for their durability and strength. However, the significant weight of these materials created several challenges, including increased fuel consumption, heightened wear on railway tracks, and limitations in design flexibility. In response to the growing demands for improved speed, energy efficiency, and environmental sustainability within the transportation sector, the railway industry has actively adopted lightweight materials.

Financially Viable: In major manufacturing organisations under Indian Railways such as ICF (Integral Coach Factory), DLW (Diesel Locomotive Works), CLW (Chittaranjan Locomotive Works), RCF (Rail Coach Factory), RWF (Rail Wheel Factory), and DMW (Diesel Loco Modernisation Works), materials alone account for approximately 70% to 80% of the total manufacturing costs. 

Given this proportion, even a 10% reduction in component or structural weight enabled through the use of lightweight materials such as aluminum alloys or composites can lead to a 4% or more reduction in overall manufacturing costs when materials constitute 40% of the total expenditure. 

Energy Efficient: A study by Bombardier Transportation indicates that a weight saving of up to 30% is feasible using lightweight materials, such as aluminium or composites. This weight saving has the potential to reduce energy consumption by 20% or more.

Environmentally Sustainable: The trains, which are manufactured using lightweight materials, are environmentally sustainable because they reduce energy consumption by using less fuel or electricity for operations. Some lightweight materials, like aluminum, are highly recyclable, and they contribute to a circular economy.

Key Lightweight Materials in Train Manufacturing

Aluminum & Aluminum Alloys

• The utilisation of aluminum alloys reduces the net weight of rail passenger cars while simultaneously adhering to stringent safety requirements regarding strength and rigidity. 

• The density of aluminum alloys is approximately one-third that of steel. When considering structural optimisation through material substitution, the overall weight of the railcar body is reduced by up to 50% with the implementation of aluminum. 

•  Additionally, aluminum alloys exhibit superior corrosion resistance compared to steel. This material offers a balanced performance characterized by a light weight, excellent corrosion resistance, favorable formability, high specific strength, and relatively low cost.

Carbon Fiber Reinforced Polymers (CFRP)

• Carbon fiber-reinforced polymers are increasingly becoming a preferred material in the high-speed rail market due to their outstanding strength-to-weight ratio. As per the insights from CRRC (A chinese rolling stock manufacturer), each carbon fibre train can cut down CO2 emissions by about 130 tons per year. 

• The use of CFRP in the structural design of rail vehicles facilitates substantial mass reductions relative to traditional metals, owing to the remarkable specific stiffness and strength associated with CFRP.

•  The development of lightweight bogie frames employing CFRP materials is particularly advantageous for enhancing attributes such as energy efficiency, maximum payload capacity, as well as running dynamics and acoustic performance.

Magnesium Alloys

• According to a report by Semantic Scholar, magnesium alloys possess excellent high strength and damping properties, making them suitable for critical components of high-speed trains. 

• Magnesium alloys are distinguished by their low density, rendering them the lightest structural metal available for practical applications. They offer significant advantages, including high specific strength and specific stiffness, as well as effective electromagnetic shielding.

Global Trends in Lightweight Materials for Train Manufacturing

The World’s First Carbon Fiber Subway Train: CETROVO 1.0

The launching ceremony of CETROVO 1.0

On January 10, 2025, the CETROVO 1.0 train, which was developed collaboratively by CRRC and Qingdao Metro Group, was introduced into regular service on Line 1 of the Qingdao Metro. This rollout is noted for being the first commercial application of carbon fiber composite materials in the main structural load-bearing components of a metro train.

Weight Reduction Metrics of CETROVO 1.0

• Car body: Approximately 25% lighter compared to conventional metal-bodied vehicles.
  
• Bogie structure: The Weight was reduced by about 50%.
  
• Overall train weight: Decreased by around 11%.
  

Energy Efficiency Improvements

• The weight reduction directly contributes to operational efficiency. The CETROVO 1.0’s energy consumption is lowered by approximately 7%.

Environmental Impact

• By improving energy efficiency and reducing mass, each CETROVO 1.0 train is expected to achieve an annual carbon dioxide emission reduction of approximately 130 metric tons as per CRRC’s estimates.

Lightweight Carbon Fiber Composite Heavy-Duty Freight Train

• On 10 September 2024, the world’s first lightweight carbon fiber composite heavy-duty freight train rolled out at the assembly line in Qiqihar. The train was manufactured by the CHN Energy Railway Equipment Company and the CRRC Qiqihar Company.

• The carbon fiber composite material exhibits strength and modulus characteristics that are 3 to 5 times and 1.5 to 1.8 times greater than those of aluminum alloys. 

Application of Aluminum Alloy in  Shinkansen (Bullet Train) 

• Aluminum alloy sheets are being extensively used in the manufacturing of Shinkansen (Bullet Train) and other high-speed railcars to optimize high-speed performance while maintaining a structure that is both lightweight and possesses high strength. 

• The properties of aluminum alloys provide an advantageous balance of reduced weight, elevated strength, excellent corrosion resistance, and relatively low cost, positioning them as an ideal material for high-speed train applications.

The Applications of Lightweight Materials in Indian Train Manufacturing

Aluminium Body for Vande Bharat Trains: A Challenge Yet to Overcome

In the future, Indian Railways intends to enhance the speed capabilities of Vande Bharat Trains to 250 kilometers per hour, with an operational speed of 220 kilometers per hour. However, the challenge of achieving higher speeds while utilising a steel body necessitates the adoption of lightweight materials such as aluminum. In light of this, Indian Railways issued a tender for the procurement of 100 Vande Bharat Trains, in which Alstom emerged as the lowest bidder. Despite this, Indian Railways cancelled the contract, valued at Rs 30000 crore, for the 100 aluminum Vande Bharat Trains due to the high manufacturing cost.

Current Scenario

The tender panel of Indian Railways had proposed a maximum price of Rs 140 crore; however, despite Alstom India’s readiness to finalise the agreement at approximately Rs 145 crore per trainset, an accord could not be reached, which led to the cancellation of the tender. 

However, aluminium is being used on a small scale in the Vande Bharat Project in the following components:

• The engineered aluminium has played a vital role in the Vande Bharat project. This material is employed in essential components, including seats, pantographs, braking systems, luggage carriers, electrical panels, and doors. 

• Specialised aluminium alloys, such as 6063 and 6005, have been utilised due to their superior strength, lightweight characteristics, and corrosion resistance.

Indigenously Manufactured Aluminium Freight Train Rake

• In October 2022, the first indigenously manufactured aluminium goods train rake, developed in collaboration with Besco Limited Wagon Division and Hindalco, flagged off from Bhubaneswar in Odisha by the Railway Minister Ashwini Vaishnaw.

• The Rake is 180 tonnes lighter than traditional steel rakes, resulting in increased speed and reduced power consumption. These rakes save 14,500 tonnes of CO2 emissions, have more carrying capacity, consume less energy and are corrosion-resistant.

Analysing the Feasibility of Lightweight Materials in the Indian Rolling Stock Ecosystem

The use of  Lightweight materials in train manufacturing offers several operational and lifecycle benefits, including reduced energy consumption, better acceleration performance, and lower emissions; however, exposing them to the Indian railway ecosystem is a cumbersome task which comes with financial and technical challenges. This transition necessitates a comprehensive overhaul of existing design, manufacturing, and supply chain frameworks. 

Stainless steel the best fit?

In the late 1990s, Indian Railways adopted the German Linke-Hofmann-Busch (LHB) coach design, using stainless steel as the primary material.  These coaches have demonstrated considerable durability and effectiveness in terms of safety and economic viability.

As a result of their success, Indian Railways transitioned to the complete production of 100% stainless steel coaches across all three coach manufacturing facilities, including:

• Integral Coach Factory (ICF), 
• Rail Coach Factory (RCF), and 
• Modern Coach Factory (MCF). 

Established Stainless Steel Coach Manufacturing Ecosystem

The use of stainless steel coach shells based on the LHB (Linke Hofmann Busch) platform is now well established in India. This manufacturing approach benefits from fully localised production with no dependency on imports for core materials, which enables efficient coach manufacturing.

Domestic Supply Chain and Vendor Development

Over the years, coach manufacturing units have developed a reliable network of domestic vendors who are capable of supplying stainless steel assemblies and components.

Support from Indian Stainless Steel Industry

The growth of this ecosystem further gains strength from the domestic stainless steel industry and allied sectors, which have scaled their capabilities to meet the stringent requirements of modern railway coach production. As a result, coach factories and their vendors are not reliant on imported stainless steel.

Lack of Domestic Expertise in Aluminium Structure

The leading manufacturers of rail and metro coaches in India, including BEML, Alstom, ICF, RCF, and MCF, currently lack experience in the development of aluminum coaches. Moreover, the honeycomb-type box sections, which are essential for the structural integrity and weight efficiency of aluminium-bodied trains, are not fabricated in India, which will create high dependency on imports. 

Environmental Considerations: Stainless Steel vs Aluminium

Stainless Steel offers 100% recyclability with high end-of-life recovery value. In contrast, the production of aluminum involves energy-intensive electrolytic processes, which leads to heightened CO2 emissions that are approximately 5-6 times higher per tonne compared to those associated with stainless steel.

Lifecycle Performance and Maintenance Implications

In terms of structural durability, stainless steel coach shells typically offer a lifecycle exceeding 50 years. Aluminium shells, on the other hand, have a relatively shorter operational life due to fatigue concerns and camber deformation over time.

Conclusion 

The integration of lightweight materials in train manufacturing holds potential for improving the energy efficiency, operational performance, and environmental footprint of railway systems. Materials such as aluminum alloys, CFRPs, and magnesium alloys offer measurable advantages in terms of specific strength, corrosion resistance, and overall mass reduction.

In the Indian context, while stainless steel continues to be the predominant material due to its well-established supply chain and performance in diverse climatic conditions, a gradual transition towards advanced lightweight materials may be necessary to meet the requirements of next-generation rail transport. This transition will depend on factors such as lifecycle cost analysis, manufacturing readiness, and compatibility with Indian Railways’ existing infrastructure.

Technological adaptation will also require capacity building across the industry, including material testing, design standardisation, and development of localized supply chains for composite materials. A phased, application-specific approach may serve as a practical pathway for the broader adoption of lightweight materials in India’s rolling stock ecosystem