As we all know, precision machining in the aerospace industry has very high requirements for materials. Of course, one side is to meet the particularity of aviation equipment, and more importantly, it is due to the environmental impact of aerospace. Because of the special environmental impact, the general materials on the market certainly cannot meet the needs of the environment, and some special materials are bound to be used as substitutes. Today, I will introduce to you a more commonly used material, that is, titanium alloy, especially in aerospace, it is more common. Why is this material used more? It has something to do with its characteristics.

Titanium alloy, its small specific gravity determines its small mass, high strength and thermal strength, hardness and high temperature resistance, and a series of excellent physical and mechanical properties such as resistance to seawater and acid and alkali corrosion, which determines that it can be used in any environment. Another point is that the deformation coefficient is very small, so it has been widely used in aerospace, aviation, shipbuilding, petroleum, chemical and other industries.

Precisely because titanium alloy has the above differences from ordinary materials, it also determines that it is very difficult to process precision machining. Many machining factories are unwilling to process this material, and do not know how to process this material. To this end, Suien Lubricant has been communicating with some titanium alloy processing customers for a long time, and has sorted out some small tips to share with you!

Due to the small deformation coefficient, high cutting temperature, large tip stress and severe work hardening of titanium alloy, the tool is easy to wear and chip during cutting, and the cutting quality is difficult to guarantee. So how to do cutting?

When cutting titanium alloy, the cutting force is not large, the work hardening is not serious, and it is easy to obtain a better surface finish. However, the thermal conductivity of titanium alloy is small, the cutting temperature is high, the tool wear is large, and the tool durability is low. The tool should be selected from tungsten-cobalt cemented carbide tools with small chemical affinity with titanium, high thermal conductivity, high strength, and small grain size, such as YG8, YG3 and other tools. In the turning process of titanium alloy, chip breaking is a difficult problem in processing, especially in the processing of pure titanium. In order to achieve the purpose of chip breaking, the cutting part can be ground into a full arc chip groove, shallow in front and deep in the back, narrow in front and wide in the back, so that the chips are easy to discharge outward, so that the chips will not be entangled on the surface of the workpiece, causing scratches on the surface of the workpiece.

The cutting deformation coefficient of titanium alloy is small, the contact area between the tool and the chip is small, and the cutting temperature is high. In order to reduce the generation of cutting heat, ① the front angle of the turning tool should not be too large. The front angle of the carbide turning tool is generally 5-8 degrees. Due to the high hardness of titanium alloy, in order to increase the impact strength of the turning tool, the back angle of the turning tool should not be too large, generally 5°. In order to strengthen the strength of the tip part, improve the heat dissipation conditions, and improve the impact resistance of the tool, a negative edge inclination angle with a large absolute value is adopted.

Control the reasonable cutting speed, which should not be too fast, and use titanium alloy special cutting fluid for cooling during the processing process, which can effectively improve the tool durability and select a reasonable feed rate.

Drilling is also commonly used. Drilling of titanium alloy is more difficult, and burning and breaking of drills often occur during the processing. The main reasons are poor grinding of the drill bit, untimely chip removal, poor cooling, and poor rigidity of the process system. Depending on the diameter of the drill bit, the narrow transverse edge is generally 0.5mm wide to reduce the axial force and reduce the vibration caused by resistance. At the same time, the drill bit edge band is narrowed at 5-8mm from the tip of the drill bit, leaving about 0.5mm, which is conducive to chip removal of the drill bit. The geometric shape must be sharpened correctly, and the two cutting edges must be kept symmetrical, so as to prevent the drill bit from cutting with only one edge, and the cutting force is concentrated on one side, causing premature wear of the drill bit, and even causing chipping due to slipping. Always keep the blade sharp. When the blade becomes blunt, stop drilling immediately and re-sharpen the drill bit. If you continue to force cutting with a blunt drill bit, the drill bit will soon burn and anneal due to high friction temperature, causing the drill bit to be scrapped. At the same time, the hardened layer of the workpiece is thickened, which increases the difficulty of re-drilling and the number of times the drill bit needs to be sharpened in the future. According to the drilling depth requirements, the drill bit length should be shortened as much as possible, and the drill core thickness should be increased to increase rigidity to prevent chipping due to shaking during drilling. Practice has proved that the life of a φ15 drill bit with a length of 150 is longer than that of a drill bit with a length of 195. Therefore, the selection of length is also very important.
Judging from the two common processing methods mentioned above, the processing of titanium alloys is relatively difficult, but after good processing, good precision parts can still be processed, such as titanium alloy parts for aerospace equipment.