Countermeasures for the Difficult Machining of Titanium Alloys

1.Cooling
Use coolant to reduce the high temperature during cutting. Generally, non-soluble oil coolant is suitable for low-speed heavy-duty cutting, while soluble cutting coolant is suitable for high-speed cutting.

In addition, low-temperature cutting methods can be employed, such as using liquid nitrogen (-180℃) or liquid CO2 (-76℃) as cutting fluids. This can effectively reduce the temperature in the cutting zone, improve the surface quality of the processed parts, and extend the tool life.

2. Select the appropriate cutting tool.
The selection of appropriate cutting tools can significantly enhance processing efficiency. As the heat of titanium alloys is mainly dissipated through the cutting edge and coolant rather than being expelled through chips as in steel, a small part of the cutting edge has to endure extreme thermal and mechanical stress. Keeping the cutting edge sharp can reduce cutting force.

In addition, the grinding technology with polished grooves and high positive angle indexable inserts also help to reduce cutting pressure.

When necessary, coated tools can also be used to reduce the stickiness of the alloy and break up excessively long chips. This not only reduces the friction during chip removal but also helps to control the heat generated during the machining process.

3. Constant feed or increased feed rate
Titanium alloys tend to harden during processing, meaning that their hardness increases during cutting, which accelerates tool wear. Therefore, maintaining a constant feed rate is crucial for minimizing work hardening.

Of course, if the performance of the equipment permits, it is possible to try increasing the feed rate. Doing so can reduce the time the tool stays in the processing area, thereby reducing the chances of heat accumulation and work hardening.

4. Reduce the cutting speed
Control the heat release and process titanium alloys at a cutting speed of one-third or less of that used for steel.

5. Change tools according to the process.
When processing titanium alloys, the lifespan of ceramic, titanium carbide and titanium nitride coated tools is relatively short. Generally, for large-scale titanium alloy processing, hard steel tools are the first choice; while for small-scale processing, high-speed hard alloy tools are more suitable.

Currently, ultrasonic processing technology is under development, with the aim of extending the tool's service life by reducing the contact time between the tool and the workpiece.

6. Use high-rigidity machine tools
High-rigidity machine tools are crucial for the successful processing of titanium alloys. The ideal titanium alloy milling machine must be rigid, with a spindle capable of operating at low speeds and high torques to absorb vibrations and reduce chatter during the cutting process.

7. Regular cleaning
Regularly clean the processing equipment and tools to prevent debris from accumulating and affecting the processing results.