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Analysis of performance characteristics and processing characteristics of 1 titanium alloy
1. 1 Titanium alloy performance characteristics Titanium alloy is to add alloying elements in industrial pure titanium to increase the strength of titanium. Titanium alloys can be divided into three types: gorge alloy, bismuth alloy and bis-bismuth alloy. C1+ bismuth alloy, such as TC4 (Ti-6A1 - 4V), this titanium alloy is composed of kanqing phase. The alloy is stable in structure, high temperature deformation property, toughness and plasticity, and can be quenched and aging treated to strengthen the alloy. It is an important raw material for the aviation industry. The performance characteristics of titanium alloy are mainly manifested in:
a) High specific strength. Titanium alloy has a low density (4.4 kg/m 3 ) and is light in weight, but its specific strength is greater than that of ultra-high strength steel.
b) High heat strength. Titanium good thermal stability, at a (300 ℃) 500 ℃, its strength is about 10 times higher than that of aluminum alloy.
c] chemically active. Titanium has a large chemical activity and generates a strong chemical reaction with 0, N, CO, water vapor, etc. in the air, and forms a TiC and TiN hardened layer on the surface of the titanium alloy.
d) Poor thermal conductivity. Titanium alloy has poor thermal conductivity. The thermal conductivity of titanium alloy TC4 at 20 °C is X=16.8 W/m•°C, and the thermal conductivity is 0.036 cal/(cm•:•°C).
1. 2 titanium alloy processing characteristics analysis Because titanium alloy has low thermal conductivity, only steel 114, aluminum 1113, copper 1125, so the heat dissipation is slow, which is not conducive to heat balance, especially in the process of drilling and tapping, heat dissipation The cooling effect is very poor, high temperature is formed in the cutting zone, and the rebound is large after processing, which causes the torque of the drill bit and the tap to increase, the cutting edge wears fast, and the durability is lowered. At the same time, since the deformation coefficient of titanium alloy is less than or close to 1, this is a remarkable feature in the processing of titanium alloy. Therefore, the distance of the sliding friction of the chips on the rake face is increased, and the tool wear is accelerated. In addition, the titanium alloy has high chemical activity, is processed under high temperature and high pressure, reacts with the tool material, forms a solution, and diffuses into an alloy, which causes a sticky tool, and the chips are not easily removed, and the bit is bitten and the bit is broken.
2Drilling of titanium alloy Through the analysis of the processing characteristics of titanium alloy, the factors affecting the drilling process of titanium alloy are understood, that is, during the machining process and the problems such as burning knife, broken drill and fast tool wear are prone to occur. Therefore, the research focused on the bit material, the geometric parameters of the drill bit, the amount of drilling and the coolant, and solved this problem well.
2.1 Bit material The bit material should meet the following requirements:
a) Sufficient hardness. The hardness of the drill bit and tap must be greater than the hardness of the titanium alloy.
b) Sufficient strength and toughness. Because the drill bit and tap are subjected to large torsional forces and cutting forces when machining titanium alloys. Therefore, there must be sufficient strength and toughness. [next]
C) Sufficient wear resistance. Due to the good toughness of the titanium alloy and the sharpness of the cutting edge during machining, the tool material must have sufficient resistance to wear to reduce work hardening.
d) Tool materials have a poor affinity with titanium alloys. Due to the high chemical activity of the titanium alloy, the affinity of the tool material and the titanium alloy is required to be poor, so as to avoid the formation of a solution and diffusion into an alloy, resulting in sticking and breaking.
In summary, after testing and analysis of drill bits and taps made of commonly used cutting tool materials W18C 2V, cemented carbide (YG8), W6Mo5C 2V3Al, W12C 2V4Mo and W2Mo9C 2VV8, the results show that the material is made of W2Mo9Cr4VCo8. When the drill bit and the tap are processed with titanium alloy, the cutting edge is sharp, the wear is small, and the efficiency is significantly improved, which is an ideal cutting tool material.
W 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 The metal element is drilled. The main function of the drill is to enhance the effect of secondary hardening, improve the hardness of red hardness and heat treatment, and at the same time, have good heat dissipation. Therefore, high-speed steel containing drill has high cutting ability.
2. 2 Changing the geometric parameters of the drill bit The processing characteristics of the titanium alloy determine the standard twist drill bit when drilling titanium alloy. There are many problems, the main performance:
a) The drill tip angle 2T is small, the cutting edge is long, and the cut chips are wide, so the bit torque is large and the axial resistance is also large. At the same time, the chips are curled into a spiral shape, the space occupied by the chips is also large, and the chip removal is not smooth, which affects the cooling.
b) Drill core thickness sword, the drill bit is subjected to large torque and axial resistance due to the drilling of titanium alloy. If the thickness of the core is small, the bit strength is low and the bit is easily broken. Drill helix angle,
C) The helix angle directly affects the rake angle of the main cutting edge. If the helix angle is large, the cutting edge is sharp and the cutting is light, otherwise it will cause work hardening.
d) The back angle of the outer edge of the drill bit is small, affecting the rake angle of the cutting edge at the core.
2. 2. 1 increase the drill tip angle 2T
a) The apex angle of the drill bit determines the chip width and the size of the drill front angle. When the drill diameter and the feed amount are constant, the apex angle 2 is increased, the cutting width is narrowed, and the load on the unit cutting edge is reduced. At the same time, the cutting edge angle at the outer circumference of the drill bit is reduced, which reduces the wear speed of the cutting edge angle, and is advantageous for heat dissipation and durability.
b) The apex angle has a great influence on the rake angle. When the apex angle is equal to 900, the main section is an axial section, and the anterior angle is the helix angle at a certain point. Therefore, increasing the vertex angle 2T is advantageous for improving the cutting conditions at the core. The apex angle affects the direction in which the chips flow out. When the apex angle is large, the degree of chip curling into a spiral is reduced, and it is relatively straight, and it is easy to eliminate, that is, the chip discharging performance is improved.
Through the analysis and test, when the titanium alloy is processed, the top angle of the drill bit is increased by 2T, and the range of 2T is 1350 to 1400. The results show that the drilling effect is good.
2. 2. 2 Select the appropriate drill helix angle a) The drill helix angle barrier affects the increase and decrease of the rake angle of the main cutting edge. It does increase, the rake angle also increases, the cutting is light, the chipping is easy, and the torque and axial force are also small. Where D is the drill diameter: P is the spiral groove lead.
b) As seen from the above equation, the points on the cutting edge do change. It is the largest near the outer circle, the front angle is also the largest, the cutting edge is sharp, and the cutting performance is good. It is the smallest near the core and the cutting performance is poor. It will be ground into a circular shape to improve the cutting conditions.
With the increase, the cutting edge strength is weakened, the wear is fast, and even the cutting edge burns out. Therefore, it is reasonable to choose to be suitable for titanium alloy drilling. [next]
Increase the helix angle of the drill bit by analyzing the test
2. 2. 3 Increase the thickness of the core Because the drill bit is subjected to large torque and radial resistance during drilling of titanium alloy, especially for small-diameter drills, it is easy to break, so the thickness of the core is increased to increase the strength of the drill bit. The thickness of the core is generally: where D is the diameter of the drill.
2. 2.4 Increasing the outer edge of the drill bit The back angle of the cutting edge of the drill bit is not equal. The closer to the center, the larger the back angle. Therefore, the marking and requirements of the rear corner of the drill bit are all the outer edge of the drill bit. The standard is subject to change.
Since the cutting surface is a helicoid, the cutting speed at any point on the cutting edge is a spiral. As can be seen from the development of Fig. 5, the actual back angle A is smaller. The size is calculated by the following formula: In the Sgo two fhrD formula, f is the amount of the drill: D is the diameter of the drill at this point.
It can be seen from the above formula that the amount of the cutter increases, the closer the point on the cutting edge is to the center, the larger the corner angle, and the smaller the actual back angle of the drill bit. This requires an unequal back angle v, which gradually increases toward the core. In order to be suitable for titanium alloy processing, the summed back angles are shown in Table 3. Increasing the relief angle at the outer edge of the drill bit can make the transverse edge sharply improve the cutting performance. In particular, there is a significant improvement in the drilling process at the core.
2. 2. 5 drill bit processed into inverted cone x
The drill bit is processed into an inverted cone to reduce the friction between the rib belt and the hole wall, so that the torque of the drill bit is reduced. The angle of the reverse cone is shown in Table 4. After the analysis and test, the drilled diamond is processed according to the above geometric parameters, and the effect is good. Raise around 40$
2. 3 Drilling dosage The performance characteristics of titanium alloy require low turning when drilling titanium alloy, and the feed rate should be moderate. Table 5 is for drilling a drilled titanium alloy.
Effect: My unit drilled on titanium alloy (4.2, (D5, (D8, 012, (D23 hole, one drilling efficiency is significantly improved than standard twist drill. For example: drilling diameter (4.2, deep) 18. Drill a hole about 4 2 about 25 drills. One hole, sharpen once; the diameter of the hole is CD5, the depth is 18. Drill a hole about 4 2 about 25 drills. One hole, sharpening once; Drilling diameter (D8, depth 20), drilling a hole about 8 2 about 1822 holes, sharpening once; drilling diameter 12, deep 20., drilling a hole about two shakes about 15 full. Hole, sharpening once: Drilling diameter (D23, depth 24.), drilling a hole about 24 2 about 1015 holes, sharpening once.
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When drilling and tapping titanium alloys, it is best not to use hydrogen-containing coolant to avoid toxic substances and cause hydrogen embrittlement. When shallow hole drilling, electroless available cutting fluid which composition is: sebacic acid Y%} 10%, triethanolamine Y%} 10%, glycerol Y%} 10%, boric acid Y%} 10%, sodium nitrite 3%}5%%, the rest is water.
When drilling deep holes with N32 machine oil plus kerosene, West had a ratio of 3: 15, may also be sulfurized cutting fluid.
3 Tapping processing of titanium alloy Titanium alloy tapping processing, especially small hole tapping processing is very difficult. The main reason is that due to the low thermal conductivity of the titanium alloy, during the tapping process, the cutting zone forms a high temperature, which causes the titanium alloy to thermally expand. In addition, the titanium alloy is rebounded after processing, the hole wall is squeezed, and even the tooth type is stuck. The tap cannot be rotated, otherwise the tap will be broken.
After a large number of analytical tests, the problem was solved mainly by improving the tap structure and selecting a suitable titanium alloy tool material. [next]
3. 1 tap material The tap material is the same as the drill material.
3. 2 tap structure The standard tap is formed by one-time cutting, the cutting amount is large, the torque is also large, and the tap is difficult to rotate after thermal expansion and rebound of the hole wall. In order to solve this problem, the structural form of the tap is improved, and the primary cutting process of the standard tap is divided into the work, II, and II three-cone cutting. At the same time, the tap is processed into a skipping type, which solves the chip breaking well. The problem is that the cutting is light, the effect is very good, the efficiency is greatly improved, and the cooling effect is also improved.
The structural form of the M5 jumper tap, see Figure 6, the geometric parameters of the jumper tap, see Table 6, the technical conditions of the tap: a) the hardness of the cutting part HRC62-64, the rest of the HRC32-42; b) the width of the tooth 2 The hole bottom hole design along the threaded toothed shovel can be enlarged according to the characteristics of the titanium alloy. After the thread tolerance position and accuracy level are determined, under the condition that the tolerance meets the tolerance level of the internal thread diameter D1, the diameter of the bottom hole of the thread is appropriately increased, and the contraction amount of the bottom hole of the thread after cooling can offset the increase of this part. The machined thread meets the design accuracy requirements. Due to the different grades of titanium alloy, different forging heat treatment methods, different structural forms, etc., the amount of thread base L is also increased, and it is determined according to the specific conditions.
3.4 Coolant The coolant used in the titanium alloy filament is the same as the coolant used in the drilling process.
4 Conclusion Through the analysis of the characteristics of titanium alloy, the key problems in the drilling and tapping process of titanium alloy are solved, and good results are obtained. The following conclusions are drawn:
[1) Drills and taps of W2Mo9C II 4Vo8 material are suitable for titanium alloy processing;
[2] Improve the geometric parameters of the drill bit, which can significantly improve the processing efficiency of titanium alloy parts;
[3] Improved tap structure, which can significantly improve the processing effect of titanium alloy parts;
[4) Formulate a coolant suitable for titanium alloy processing to extend the life of the cutting tool.
Process Analysis and Research of Titanium Alloy Drilling and Tapping
Titanium alloy of light weight materials, the density is 4.4 kg eight 3, high strength, a metal material is important in the field of aerospace. However, its processing performance is poor, especially the efficiency of drilling and tapping is very low, which greatly restricts the processing quality and production efficiency of titanium alloy parts in the product. Here, the specific characteristics of titanium alloy materials and their cutting characteristics in drilling and tapping are analyzed. In particular, the tool materials, tool structure and tool geometry parameters have been repeatedly studied and tested, and corresponding measures have been taken. The problem solved in the process of titanium alloy drilling and tapping is solved.