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By Sally Zhang | 09 March 2023 | 0 Comments

What tools are needed to process titanium on a lathe?

Titanium alloy processing brings great challenges to cutting tools
Various properties of titanium make it an attractive material for parts, but many of these properties also affect its machinability. Titanium alloys commonly used in industry are two-phase titanium alloys, that is, (α+β) titanium alloys, and Grade 5 is commonly used in aero-engine fuel accessories, and Grade 5 is a typical representative of this type of alloy. Titanium alloy materials have high hardness, poor cutting performance, and are prone to work hardening, which brings difficulties to cutting. Zuudee BYD Titanium has done in-depth research and gained some experience for parts made of Grade 5 materials in titanium alloys, especially the turning process.
First of all, the elastic modulus of titanium alloy is small, among which the elastic modulus E=110GPa of Grade 5 is about half of that of steel, and its thermal conductivity is low, so the elastic deformation of the workpiece caused by the cutting force is large. Higher and more concentrated cutting forces are produced in the medium. In this way, vibrations are likely to occur, resulting in tremors during cutting and reducing the accuracy of the workpiece, so the rigidity of the processing system must be improved.
Secondly, the local high temperature generated during the cutting process of titanium alloy makes it easy for titanium to absorb oxygen and nitrogen in the atmosphere, thus forming a hard and brittle outer skin. This will cause work hardening on the machined surface of the workpiece, and the work hardening speed is fast, causing serious scratches on the surface of the tool, which is prone to chipping during the cutting process.
In addition, the physical and chemical properties of the titanium alloy material itself make it have a high affinity with the workpiece during cutting, and the tool is prone to sticking when the tool contacts the workpiece during cutting, which increases the friction between the tool and the workpiece, resulting in a large amount of cutting heat. The resulting large amount of cutting heat cannot be dissipated through chips in time, which greatly reduces the service life of the tool. Therefore, the tool for processing titanium alloy must have high hot hardness.
Titanium alloy processing is a systematic project
In the aero-engine fuel control system manufactured by Zuudee BYD Titanium, titanium alloy parts are mainly small shaft parts, and turning is the main processing method.
Titanium alloy processing here can be regarded as a systematic project, which needs to be considered from multiple perspectives such as processing equipment, cutting tools, cutting parameters, and coolant. As far as processing equipment is concerned, titanium alloy processing requires machine tools with good processing performance and sufficient cooling. Therefore, CNC lathes with high processing precision are selected for processing equipment. The vibration of the spindle is extremely small during processing and the processing stability is good.
The tool material used for titanium alloy processing should have good hardness and wear resistance, excellent heat resistance, high strength and toughness at high temperatures, and certain impact resistance and damage resistance. Tools that meet the above requirements include: ceramic tools, coated carbide tools, cubic boron nitride tools (CBN) and diamond-like tools (PCD), etc. Among them, coated carbide tools are cheap, have good thermal conductivity and high hardness, and perform well in terms of red hardness and toughness, although they are better than ceramics, cubic boron nitride tools (CBN), and diamond-like tools. The heat resistance and chemical stability are poorer, but it has higher impact resistance and damage resistance than ceramic and diamond-like tools. Therefore, it has become the tool of choice for processing titanium alloys.
In terms of turning parameters, titanium alloy processing also requires more consideration. Such as the setting of cutting speed, too high cutting speed will cause the cutting heat to rise, the cutting edge of the tool will be overheated, the bonding phenomenon will be serious, the tool wear will be aggravated, and the service life of the tool will be shortened; at the same time, the surface layer of the titanium alloy workpiece will be cracked or oxidized, It affects the mechanical properties of the workpiece, so it is necessary to select an appropriate lower cutting speed to reduce the processing cost and ensure the processing quality while ensuring a greater tool durability. The second is the setting of the cutting depth. Because the titanium alloy workpiece must be pre-heated before processing, there is a layer of oxide layer on the surface of the workpiece. In order to improve the durability of the tool, a relatively large cutting depth should be used, which can directly cut into the titanium alloy body without oxidation. The metal layer increases the service life of the tool. Another parameter setting that needs to be considered is the feed rate. The size of the feed rate has little effect on the cutting temperature. Under the premise of ensuring the processing efficiency, it is reasonable to reduce the cutting speed and increase the feed rate. Cutting method.
In order to ensure the processing quality and improve the durability of the tool, the use of coolant should also be considered. For example, to fully cool the processing area, the coolant can not only effectively reduce the cutting temperature, but also reduce the bonding phenomenon of the tool during cutting, and improve the quality of the cutting tool. efficiency and prolong tool life.
Carbide-coated tools improve machining
For rotating parts such as a screw plug part, the maximum outer diameter is φ33.8, the material is Grade 5, and the raw material is φ30 bar. Parts are finished in one turning operation. In order to ensure the processing accuracy of the parts, the processing equipment uses imported CNC lathes. The spindle speed is up to 6000 rpm, the spindle runout is less than 2μm, the spindle vibration is very small during processing, and the processing stability is good. The coolant can be sprayed from 3 directions and the cooling is sufficient. .
Due to its excellent performance, the utilization rate of titanium alloy in the aerospace industry at home and abroad is increasing year by year. However, due to the high processing cost, low processing efficiency, and low tool durability, the application level has been relatively hindered. Through The above analysis of titanium alloy cutting performance, reasonable selection of cutting tools and processing parameters have effectively solved the problem of low tool durability in turning titanium alloy parts. Practice has proved that CNC lathes and carbide-coated tools are sharp tools for processing titanium alloys. Products from well-known companies are a wise choice in the selection of turning tools.

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