티타늄 합금의 열전도율이 매우 낮기 때문에 티타늄 합금 가공이 어렵습니다. 칩과 절삭 공구 사이의 짧은 접촉 길이와 결합되어 절삭 열 발산에 도움이 되지 않습니다. 결과적으로 절삭날 부위의 온도는 45강 절삭 온도의 약 2배 이상 높다. 또한 공구 마모도 심합니다. 한편, 티타늄 합금과 공구 재료 사이의 강한 화학적 친화성은 공구 재료의 Ti, Co, C와 같은 원소와 결합하기 쉽게 만들어 고온에서 접착 마모를 악화시킵니다. 반면, 티타늄 합금은 공기 중의 산소 및 질소와 반응하여 단단하고 부서지기 쉬운 표면층을 쉽게 형성하여 공구 마모를 악화시킵니다.

Table 1: Selection of Tool Geometric Parameters for Turning Titanium Alloys

Tool material	Front Rake Angle	Back Rake Angle	Cutting Edge Inclination Angle	Main Clearance Angle	Secondary Clearance Angle	Chamfer Width (mm)	Chamfer Front Angle	Cutting Edge Radius (mm)
Carbide lathe	5~10	10~15	0~10	45~75	15	0.05~0.3	0.10~0	0.5~1.5

Machining amount

The cutting speed for turning titanium alloys should not be too high, and the cutting depth can be relatively large, while the feed rate should be appropriate. A feed rate that is too large can cause burning of the cutting edge, while a feed rate that is too small results in rapid wear of the cutting edge when processing the hardened layer. When turning titanium alloys, rust-proof emulsion or extreme-pressure emulsion can be used for cooling and lubrication. The recommended cutting parameters for turning titanium alloys are as shown in

Table 2: Selection of Cutting Parameters for Turning Titanium Alloys

Feed (mm)	cutting speed(mm)
0.08~0.12	87~69
0.13~0.17	71~59
0.16~0.24	62~51
0.25~0.30	53~47
0.33~0.44	48~41
0.45~0.65	42~34

Note: Conditions for the use of this table: Tool material YG8, workpiece material TC4, tool geometric angles front rake angle = 5°, back rake angle = 10°, main clearance angle = 75°, secondary clearance angle = 15°, cutting edge radius = 0.5mm, turning depth = 1mm, dry turning. If using cutting fluid, the turning speed in the table can be appropriately increased.

Machining parameters

Machining Temp.

When turning titanium alloys, the cutting temperature is high, and tool durability is low. Among the cutting parameters, cutting speed has the most significant impact on cutting temperature. Therefore, efforts should be made to ensure that the cutting temperature generated at the selected cutting speed is within the optimal range. The recommended cutting temperature for turning titanium alloys with high-speed steel tools is approximately 480°C to 540°C, while for hard alloy tools, it is around 650°C to 750°C.

Cutting speed Vc

The cutting speed has the most significant impact on tool durability, and it is preferable to operate the tool at the optimal cutting speed with minimal relative wear. When turning titanium alloys of different grades, the cutting speed should be adjusted appropriately due to significant differences in strength. The turning depth also has a certain influence on the cutting speed, and the magnitude of the cutting speed should be determined based on different turning depths.

Feed rate

The feed rate has a relatively small impact on tool durability. While ensuring the machining surface roughness, a larger feed rate can be chosen, typically ranging from f=0.1 to 0.3 mm/r. If the feed rate is too small, the tool may cut within the hardened layer, increasing tool wear. Additionally, extremely thin chips are prone to spontaneous combustion at high cutting temperatures, so a feed rate below f<0.05 mm/r is not allowed.

Cutting depth (ap) has the least impact on tool durability. A larger cutting depth is generally chosen to avoid cutting within the hardened layer, reducing tool wear. It also increases the working length of the cutting edge, promoting heat dissipation. Typically, ap is set at 1 to 5 mm.