Precision machining in aerospace industry has high requirements on materials. In order to meet the particularity of aviation equipment and the impact of aerospace environment, titanium alloy, a special material, is commonly used in aerospace industry.
The weight of titanium alloy is small, which determines its small mass, high hardness and thermal strength, high temperature resistance, seawater resistance, acid and alkali corrosion and a series of excellent physical and mechanical properties, so that it can be used in whatever environment.In addition, the deformation coefficient of titanium alloy is very small, so it is widely used in aerospace, aviation, shipping, petroleum, chemical industry and other industries.Because titanium alloy has different properties from ordinary materials, it is very difficult to be processed accurately.Due to the small deformation coefficient of titanium alloy materials, high cutting temperature, high tip stress, serious hardening, in the cutting process tool easy to wear and edge breakage, it is difficult to ensure the quality of cutting.
So how do you cut it?
Titanium alloy has small thermal conductivity, high cutting temperature, large tool wear and low durability. Therefore, tungsten and cobalt carbide tools with small chemical affinity with titanium, high thermal conductivity, high strength and small grain size should be selected.In the process of turning processing of titanium alloy, the chip breaker is one of the most difficult problems in processing, especially the processing of pure titanium, in order to achieve chip breaker, cutting parts can be made perfect arc grinding roll groove, the former light after deep, narrow after wide before discharging, makes it easier to chip to avoid scraps winding on the surface, causing surface scratch.
The cutting deformation coefficient of titanium alloy is small, the contact area between cutter and chip is small, and the cutting temperature is high.In order to reduce the generation of cutting heat, the selected carbide turning tool front Angle should not be too large (generally take 5-8°);Due to the high hardness of titanium alloy, in order to increase the impact strength of turning tools, it is not suitable to choose a large turning tool back Angle (generally 5°).In order to strengthen the strength of the tip part, improve the heat dissipation condition and improve the impact resistance of the cutter, the negative edge Angle with larger absolute value is adopted.In the process of processing, reasonable control of cutting speed, not too fast, and the use of titanium alloy special cutting liquid cooling, can effectively improve the life of the tool, and select a reasonable amount of feed.
Drilling in aerospace industry is more common, while titanium alloy drilling is more difficult, often in the process of burning and breaking phenomenon, mainly due to the drill bit grinding, chip removal is not timely, poor cooling and poor rigidity of the process system and other reasons.According to the diameter of the bit, grind the narrow transverse edge, the width is generally 0.5mm, in order to reduce the axial force and vibration caused by the resistance.At the same time, at a distance of 5-8mm from the tip of the bit, the bit blade belt should be sharpened narrow (leaving about 0.5mm), which is conducive to bit chip removal.Correct sharpening geometry and symmetry between the two cutting edges prevents the bit from cutting only one side of the blade.If the cutting force is all concentrated on one side, the drill bit will wear out prematurely or even slip and cause edge breakage.Always keep the blade sharp, when the blade is blunt, should immediately stop drilling, re-sharpening the drill bit.If forced drilling with a blunted bit continues, the bit will soon burn and anneal from the high friction temperature, causing the bit to die.It also thickens the hardened layer of the workpiece, which increases the difficulty of re-drilling and the number of times of grinding the bit.According to the requirements of drilling depth, the length of the drill bit should be shortened as far as possible, and the thickness of the drilling core should be increased to increase the rigidity, so as to prevent the edge breakage caused by jitter during drilling.Practice has proved that, with respect to the drill bit of 15, 150mm is longer than 195mm life, so the selection of the appropriate length is very important.
Through the above two commonly used processing methods, the processing of titanium alloy is relatively difficult, but the correct processing can still be processed into good precision parts and titanium alloy parts of aerospace equipment.