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4 reasons and 7 countermeasures for difficult processing of titanium alloys

Titanium alloy, with its unique advantages, occupies an important position in aviation, aerospace, medical and other fields. In the past two years, it has also risen in the 3C consumer electronics field and is used in the body and structural components of many popular high-end smartphones.
Titanium alloy has the advantages of lightweight, high strength, and excellent texture, which can help improve the appearance design of smartphones and significantly reduce the weight of the body. It is expected to become an innovative trend in consumer electronics materials. However, the difficulty in processing titanium alloys has always plagued engineering and technical personnel.
Difficulties in titanium alloy processing
1. Temperature concentration
Most titanium alloys have extremely low thermal conductivity, only 1/7 of steel, 1/16 of aluminum, and 1/25 of copper. Therefore, the heat generated during the cutting process is not easily dissipated, but rather concentrated in the cutting area. The temperature of the cutting edge can rise to 1000 ℃, causing rapid wear and cracking of the tool, as well as the generation of chips, shortening the tool life.
The high cutting temperature is concentrated at the tip of the tool, making it difficult to dissipate heat and making the tool vulnerable. High temperature also damages the surface integrity of titanium alloy parts, reduces their geometric accuracy, and causes work hardening, seriously reducing their fatigue strength.
2. Elastic deformation
The elastic modulus of titanium alloy is relatively low, for example, the elastic modulus of TC4 is only 110Gpa, while that of 45 steel is 210Gpa, and the elastic modulus of stainless steel such as 303, 304, 316 is also around 200Gpa. When processing titanium alloys, elastic deformation is prone to occur, especially when processing thin-walled or ring-shaped parts. Thin walled parts undergo local deformation beyond the elastic range during processing, resulting in plastic deformation and a significant increase in the strength and hardness of the cutting point material.
Cutting pressure causes elastic deformation and rebound of the workpiece, increasing the friction between the tool and the workpiece, generating additional heat, and exacerbating the problem of poor thermal conductivity of titanium alloys.
3. Strong affinity
Titanium alloy has a good affinity and is prone to forming long and continuous chips during turning and drilling processes, which can entangle the tool and hinder its function. When the cutting depth is too large, it is easy to cause sticking, burning or fracture of the tool.
The affinity advantage is valuable in many fields, such as in ion pumps where titanium is used as the cathode plate. When titanium atoms are sputtered onto the inner wall of the anode tube, they can adsorb gas molecules, creating an ultra-high vacuum environment.
4. Vibration
The elasticity of titanium alloy may be advantageous in part performance, but it becomes the main cause of vibration during cutting process. The vibration generated by processing titanium alloy is 10 times that of steel. Due to the concentration of cutting heat in the cutting area, serrated chips are generated, resulting in fluctuations in cutting power.
Countermeasures for difficult processing of titanium alloys
1. Cooling
Use coolant to reduce cutting high temperatures. 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 used, such as using liquid nitrogen (-180 ℃) or liquid CO2 (-76 ℃) as cutting fluid, which can effectively reduce the temperature in the cutting zone, improve the surface quality of the machining, and extend the tool life.
2. Choose the appropriate tool
Choosing appropriate cutting tools can significantly improve machining efficiency. Due to the fact that the heat of titanium alloys mainly relies on the cutting edge and coolant to dissipate, rather than being discharged through chips like steel, the small parts of the cutting edge need to withstand great thermal and mechanical stress. Keeping the cutting edge sharp can reduce cutting force.
In addition, the use of polishing groove grinding technology and high positive angle rotatable blades also helps to reduce cutting pressure.
When necessary, coated cutting tools can also be used to reduce the viscosity of the alloy and crush excessively long chips. This not only reduces friction during the chip removal process, but also helps control the heat generated during the machining process.
3. Constant feed or increasing feed rate
Titanium alloys are prone to hardening during the machining process, meaning that their hardness increases during cutting, which accelerates tool wear. Therefore, maintaining a constant feed rate is crucial for reducing work hardening to *.
Of course, if the equipment performance allows, you can try increasing the feed rate. This can reduce the time the tool stays in the machining area, thereby reducing the chance of heat accumulation and work hardening.
4. Reduce cutting speed
Control heat release and use steel cutting speed of 1/3 or lower for titanium alloy processing.
5. Replace cutting tools according to the process
When processing titanium alloys, the lifespan of ceramic, titanium carbide, and titanium nitride coated cutting tools is relatively short. Usually, for large-scale processing of titanium alloys, hard steel cutting tools are *; For small batch processing, high-speed hard alloy cutting tools are more suitable.
At present, ultrasonic machining technology is being developed with the aim of extending the service life of cutting tools by reducing the contact time between the tool and the workpiece.
6. Using 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 cutting.
7. Regular cleaning
Regularly clean processing equipment and cutting tools to prevent debris from depositing and affecting processing efficiency.

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