The Secrets Behind the Technology of High-Speed Train Wheels

The Steering Principle of High-Speed Trains:

The operation of train wheels can be described as a smaller "cart" carrying a larger one. Unlike cars, trains do not have a steering wheel, so how do they move forward or even make turns? This is primarily done by the bogie. When the train enters a curve at a certain speed, the outer wheel of the front wheelset makes contact with the inner side of the outer rail, generating a guiding force through the pressure between them. This guiding force creates a moment that causes the bogie to turn relative to the track.

A bogie is essentially a "cart" made up of a frame and two pairs of wheels. The train carriage rests on this "cart," allowing a certain degree of turning. Each train carriage has two such "carts" underneath, supporting the entire train as it speeds along the tracks. However, since the bogies are installed underneath the carriage, they are usually not easily visible.

Development and Production of High-Speed Train Wheels:

High-speed train wheels involve more than 50 key technologies in their development and production, making them highly technical and difficult products to manufacture. As the train runs at speeds exceeding 300 km/h, intense friction occurs between the wheels and the rails, with the wheel surface temperature rising above 1000 degrees Celsius. This extreme heat can cause surface defects on the wheels, leading to increased vibration during operation and impacting the safety of the train.

Furthermore, each high-speed train carriage weighs over 50 tons, with most of the weight borne by the wheels. On average, a pair of wheels has to endure a repetitive pressure of over ten tons. Therefore, high-speed train wheels must meet multiple requirements such as high strength, toughness, wear resistance, resistance to heat cracking, fatigue resistance, and peeling resistance. Currently, only a few countries worldwide have mastered this technology. Even China, with its rapidly developing high-speed rail industry, initially had to rely on importing high-speed train wheels.

Material Requirements for High-Speed Train Wheels:

How do we ensure that high-speed train wheels can withstand high temperatures while not deforming when cooling down after stopping? While this sounds simple, achieving it is quite challenging. High-speed train wheels involve numerous bearings and small parts with intricate designs, requiring extremely high precision in manufacturing.

Each high-speed train carriage weighs about 60 tons, and the wheels must endure heavy loads while rotating at high speeds, leading to rapid wear. Generally, high-speed train wheels undergo inspections every 48 hours or 4,000 kilometers and are typically maintained every night. The raw material used for manufacturing high-speed train wheels is a special type of steel, which China initially could not produce and had to import at a high cost. After years of independent research and development, China now has two types of domestically produced high-speed train wheels for its Fuxing series.

The Strict Requirements of High-Speed Train Wheel Manufacturing:

High-speed train wheels must support high-speed operation and withstand the workload of traveling thousands of kilometers daily, which leaves little room for defects. Even a flaw as small as 0.2 mm can cause damage or cracks, posing potential safety hazards. Therefore, manufacturing high-speed train wheels requires precision comparable to that of making precision instruments. These wheels need exceptional strength, toughness, and stability at both low and high temperatures.

The raw material for high-speed train wheels must be a special type of steel with a high level of purity, free from metallic impurities. For example, the hydrogen content must be below two parts per million. After complex forging and multiple processes, the wheel blanks undergo ultrasonic inspection, magnetic particle testing to check for magnetism and insulation, static balancing, hardness testing, and other stringent inspections before they can be considered finished products.

High-Speed Train Wheelsets and Their Market Demand:

Wheelsets of high-speed trains are subject to severe wear and tear, requiring mandatory inspection after 1.2 million kilometers and replacement at around 2.4 million kilometers. This means there is a significant market demand for high-speed train wheels and wheelsets. Countries that have mastered this technology have long profited from sales over the years. China, out of necessity, has also imported high-speed wheelsets at high costs for maintenance and replacement. It is reported that a pair of imported high-speed train wheels costs over 600,000 RMB. For example, the G105 train from Beijing South to Shanghai Hongqiao runs about 3,042 kilometers daily, which means the wheels need to be replaced roughly every two years. China's annual spending on importing these wheels amounts to over 2 billion RMB.