In the high-speed rail industry, rotary files may be used in the following aspects:

1. Component manufacturing: In the manufacturing process of high-speed rail, rotary files can be used to grind and trim metal parts to ensure the precise fit and smooth surface of the parts.

2. Maintenance and repair: After a period of operation, high-speed rail requires regular maintenance and repair. Rotary files can be used to remove rust, wear, and damage, and repair parts.

3. Surface treatment: Before painting, rotary files can be used to grind the metal surface of the train to ensure the adhesion and uniformity of the coating.

4. Post-welding treatment: Welding slag and uneven surfaces may be generated during welding. Rotary files can be used to clean welds and grind welding areas to improve welding quality.

5. Precision machining: On parts that require precision machining, rotary files can be used to remove burrs and sharp edges to ensure the accuracy and safety of the parts.

6. Decoration and detail processing: Rotary files can be used for grinding and polishing the decorative parts and details of the EMU to improve the appearance quality of the EMU.

7. Emergency repair: In an emergency, rotary files can quickly make temporary repairs to the damaged parts of the EMU to ensure that the EMU can continue to operate.

The use of rotary files requires professional operating skills and safety measures to prevent accidental injuries and equipment damage. In the high-speed rail EMU industry, these tools are usually operated by professionally trained technicians.