52 kg rails are commonly used in railway track construction. They have a mass of 52 kilograms per meter and are typically made of high-grade steel. Some properties of 52 kg rails include:

• Strength: 52 kg rails have a high tensile strength, which allows them to support the weight of trains and resist deformation.
• Durability: These rails are designed to withstand the wear and tear of heavy train traffic and are resistant to corrosion.
• Flexibility: Rails are designed to be flexible, so that they can accommodate slight movement and shifting of the track without breaking.
• Compatibility: 52 kg rails are compatible with other standard railway components, such as sleepers and fasteners, and are widely used in many countries around the world.
• Wear resistance: 52 kg rails have a relatively low coefficient of friction and are designed to have a hard surface to reduce wear and prolong their lifespan.
• Fatigue resistance: These rails are also designed to resist the cyclic loading caused by passing trains, which can lead to fatigue failure over time.
• Thermal properties: Rails expand and contract with changes in temperature, so they are manufactured to have a specific coefficient of thermal expansion to prevent buckling or other issues.
• Rail profile: The shape of the rail head is a standard profile, and the rail foot is parallel to the rail head, this is to ensure that the wheel is guided correctly and wear is minimized.

It’s also important to note that rail standards can vary between countries and regions. For example, the AREMA (American Railway Engineering and Maintenance-of-Way Association) specifies different standards for rail properties in North America, while the UIC (International Union of Railways) sets standards for European rail systems.

It’s important to note that the properties of the rail might vary depending on the manufacturing process and the grades of steel used.