Titanium Alloy Material Cutting And Machining Technology

Titanium alloy materials are widely used in the aerospace field due to their excellent properties such as high specific strength, low density, corrosion resistance and high temperature resistance. However, due to the characteristics of titanium alloy such as small thermal conductivity, low modulus of elasticity and large chemical activity, it makes titanium alloy materials in the processing of cutting temperature is high, tool wear is serious, etc., which affects the machining efficiency of titanium alloy, so how to improve the cutting efficiency of titanium alloy has always been the urgent need to solve the problem in the aerospace industry.

1 Titanium alloy material characteristics and processing performance

(1) high specific strength: titanium alloy density is small, high strength, its strength is greater than the strength of steel.

(2) poor thermal conductivity: titanium alloy thermal conductivity, thermal conductivity coefficient is small, it is difficult to transfer heat from the chip zone, resulting in higher temperatures of the cutting edge of the tool, the knife has a strong abrasive effect, reducing the tool durability.

(3) active chemical properties: titanium alloy at high temperatures, and the air in the O, N, H and other elements of the chemical reaction to form a work-hardening layer, so that cutting and machining difficulties; at the same time, titanium alloy in the processing of the tool material is easy to produce and affinity, the occurrence of adhesion and diffusion phenomena, resulting in accelerated wear of the tool.

(4) Small modulus of elasticity: the workpiece rebound during cutting processing, easy to cause the tool back face wear and workpiece deformation.

(5) corrosion resistance: below 550 ℃ titanium alloy surface is easy to form a dense oxide film, so it is not easy to be further oxidized, the atmosphere, seawater, steam and some acid, alkali, salt media have a high corrosion resistance [1].

2 Basic principles of cutting titanium alloy material processing

In the machining process, the selected tool material, tool geometry and cutting parameters will affect the efficiency and economy of titanium alloy cutting and processing, the processing principles are as follows.

2.1 Tool material

Tool material is an important factor affecting the cutting process, so as far as possible to choose the hardness of good, wear-resistant tool materials, such as carbide tools, coated tools and high-speed steel tools, etc., Fig. 1 for the carbide tools and coated tools.

2.2 Tool geometry angle

When cutting difficult-to-machine materials, the appropriate tool geometry angle helps to give full play to the cutting performance of the tool and improve cutting efficiency. There are three deformation zones when cutting titanium alloy, as shown in Figure .

(1) Basic deformation zone I: large deformation, cutting force and cutting heat mainly from this region. By keeping the cutting edge sharp and the tip of the knife arc transition, etc., the friction coefficient and cutting temperature during titanium alloy machining are reduced to avoid sticking chips and chipping.

(2) Friction and deformation zone II between chips and front face: it directly affects the wear of the front face of the tool. By choosing a smaller front angle to increase the length of the chip and the front tool face, the front tool face wear is reduced.

(3) The workpiece has been machined surface and the rear face wear deformation zone III: a greater impact on the work hardening and tool rear face wear. By selecting a larger back angle to reduce the friction between the back tool face and the machined surface.

2.3 Cutting parameters

Cutting speed on tool life Large, the higher the cutting speed, the higher the temperature of the cutting edge, so choose low-speed cutting; at the same time, the depth of cut has a smaller impact on tool life, so in the parts and machine tool rigidity allows the conditions, the use of a larger depth of cut.

2.4 Coolant

The heat of the blade can be taken away and flushed away chips, reduce the cutting temperature, effectively improve productivity and improve the surface quality of the processed parts. General cutting fluid has three categories, namely, water or alkaline aqueous solution, water-based soluble oil solution and non-water-soluble oil solution [2].

3 Titanium alloy material cutting process

3.1 Turning

Titanium alloy turning easy to obtain a good surface roughness, work hardening is not serious, but the cutting temperature is high, fast tool wear. For these characteristics of titanium alloy turning should pay attention to the problem: (1) turning parameters try to choose low speed cutting, large depth of cut. For roughing, cutting speed 45 ~ 70 m/min, feed 0.10 ~ 0.15 mm / r; for finishing, cutting speed 80 ~ 100 m / min, feed 0.05 ~ 0.10 mm / r. (2) Finishing clamping force should not be too large, reduce the deformation of the processed parts. (3) After machining, the contour of the part should be machined again according to the route of the last tool travel to eliminate the deformation of the part caused by the cutting force and give way to the tool.

3.2 Milling

Titanium alloy milling is more difficult than turning, because milling is intermittent cutting, and chips are easy to bond with the cutting edge, forming chipping, greatly reducing the durability of the tool. For these characteristics of milling titanium alloy should pay attention to the following issues: (1) generally use the smooth milling, smooth milling when the depth of cut from large to small, the chip from thick to thin, and always the thin side of the side of the back to leave the teeth, the chip is easy to break, improve the tool life. (2) Roughing has a small impact on machining quality, and should choose a large depth of cut, small feed, low speed; finishing should reduce machining deformation, improve surface quality, and use a higher speed and small depth of cut. (3) After machining of titanium alloy, a hardened layer of 0.1 ~ 0.2 mm will be formed on the machined surface, so the secondary depth of cut should be greater than 0.2 mm; roughing reserve unilateral allowance should be greater than 0.2 mm.

4 Conclusion

The paper combines some of the current research results and experience in the production process, mainly from the titanium alloy material properties, cutting tools, cutting parameters and coolant and other aspects of the elaboration, summarizes the titanium alloy turning, milling should usually pay attention to the problems and process measures taken, and I hope that peers can play a certain role in reference.