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How did you get the titanium in your hand (6)? Mechanical processing and precision machining

Now we have obtained titanium alloy plates with specified thickness specifications. Please note that the plates are approximately 1 meter wide, 3-5 meters long, and have different thicknesses ranging from 5mm to 100mm. Next, we need to use machining to perform initial processing, cutting the large board into corresponding shapes for later use or further precision machining. There are various types of mechanical processing techniques for titanium alloy materials, such as electrical discharge machining, milling, turning, grinding, drilling, tapping, etc. The mechanical processing of titanium alloy materials is influenced by important factors such as tool materials, cutting fluids, machining process parameters, and tool geometry parameters, which must be highly valued.
(1) Cutting fluid. In the cutting process of titanium alloy materials, the use of cutting fluid can not only reduce the heat of the cutting edge, but also wash away the chips, thereby reducing the cutting force. It can be seen that the use of cutting fluid must be reasonable in order to improve the surface quality and production efficiency of the machined parts. At present, commonly used cutting fluids include non water soluble oil-based solutions, water-based soluble oil-based solutions, and water or alkaline aqueous solutions.
(2) Tool material. As mentioned earlier, titanium alloy materials have the disadvantages of high hardness, low plasticity, and low thermal conductivity. Therefore, the machining process will inevitably exhibit high cutting temperature and strong cutting force, which will exacerbate tool wear and reduce tool life. It can be seen that the selected tool material must have high wear resistance and strong hardness. At present, commonly used cutting tool materials include high-speed steel grades, hard alloy grades, coated cutting tools (with strong adhesion resistance, oxidation resistance, good wear resistance, etc.), cubic boron nitride cutting tools (with high thermal hardness, high hardness, etc.), and polycrystalline diamond cutting tools (with high hardness, high wear resistance, high thermal conductivity, low friction coefficient, etc.).
(3) Geometric parameters of cutting tools. For the rough machining process of titanium alloy materials, it is recommended to use tools with small front/back angles and high rigidity, such as the rough machining of titanium alloy TC4, with a front angle of 0-3 °. During the precision machining process of titanium alloy materials, it is recommended to use tools with sharp edges, dense teeth, large front/back angles and helix angles, small negative chamfers or no chamfers. For example, in the precision machining of titanium alloy TC4, the front angle should be taken as 8-15 °. If using a boring tool or circular turning tool to process titanium alloy, the front/back angles should be 10-15 ° and 8-14 °, respectively, and the radius of the tool tip arc should be 0.2-0.6mm; if using a threaded turning tool, the front/back angles should be 0 ° and 10 °, respectively; If using a molding tool, the front/rear angles should be set at 5 ° and 10 °, respectively. The design of the drill bit must meet the requirements of smooth chip removal, that is, the helix angle should be set at 25-30 °, the drill bit spiral groove should be polished, and the drill core thickness should be set at 1/4 of the drill bit diameter; According to the actual situation, the cutting edge should be ground to ensure better strength and centering of the drill bit. In addition, the top angle of the drill bit should be set at 135-140 ° and the back angle of the drill bit should be set at 12-15 ° to increase the cutting width and thickness. The design of milling cutters must meet the cutting requirements of titanium alloys. For end mills, the front/back angles are set to 6-8 ° and 6-12 ° respectively, the helix angle is set to 35-40 ° (3 ° for the front section), and the radius of the tool tip arc is set to 0.5-0.6mm. The cutting environment for tapping often maintains a semi closed state, making it difficult for the cutting fluid to flow smoothly to the cutting area, and the lubrication and heat dissipation effects are poor. Additionally, titanium alloy has only a small elastic modulus, which can easily cause the tap to twist or collapse. In response to this situation, optimizing the geometric parameters of tapping is particularly important, that is, the back angle of the cutting cone part is taken as 6-12 °, the front angle is taken as 7-10 °, the cutting cone angle is taken as 5-7 ° 30 ', and the correction tooth profile shovel back angle is taken as 1 °. The design of the reamer must conform to the characteristics of titanium alloy with a small elastic modulus, that is, the front/back angles of the reamer should be 3-5 ° and 10 ° respectively, and the cutting edge width should be 0.15mm.
(4) Cutting process parameters for titanium alloy materials. Process parameters for turning in cases of intermittent cutting and continuous cutting.
During the drilling process of titanium alloy, there are often occurrences of drill breakage and tool burning, which are caused by poor grinding of the drill bit, poor cooling, untimely chip removal, and poor rigidity of the process system.
In response to the above situation, strict control must be exercised over the following aspects:
One is to frequently return the blade and promptly remove the chips, while tracking and observing the color and shape of the chips; The second is to add sufficient chip solution; The third is to fix the drill die and worktable, and at the same time, the guide of the drill die and the machining surface should be as close as possible to shorten the drill bit; The fourth is the manual feed process, and the drill bit inside the hole should move back and forth to avoid dulling the drill bit due to friction between the drilling edge and the machined surface.
Milling requires intermittent cutting, so the milling process often experiences phenomena such as milling cutter edge breakage, cutting and tooth bonding, and severe bonding can even damage the tooth or cause edge breakage. In response to this situation, the forward milling cutting method is adopted because the forward milling cutting is smoother and the cutting path of the tool teeth is shorter. At the same time, the cutting sequence from thick to thin can effectively control the occurrence of cutting adhesion phenomenon. This can not only control the wear of the milling cutter, but also enhance the durability of the tool and reduce the roughness of the machined surface. The cutting cone angle should be as large as possible, and the taper part should have a thread length of 3-4 threads.
In addition, the cutting cone should be ground with a negative inclination angle as much as possible to facilitate chip removal; Use short taps as much as possible to increase the rigidity of the tap; The tapered part of the tap should be as large as possible (compared to the standard value) to control the friction between the workpiece and the tap.
Grinding of titanium alloy often leads to surface burns or wheel blockages due to chip sticking issues. Due to the poor thermal conductivity of titanium alloy, it will exacerbate the temperature rise in the grinding zone, causing the titanium alloy to bond with the abrasive or undergo chemical reactions. This helps to burn the machined surface of the workpiece and reduce the fatigue strength of the part.
The common control method for the above situation is to optimize the grinding process parameters, such as: grinding wheel material - green silicon carbide TL; grinding wheel hardness - ZRI; Grinding wheel speed -10-20m/s; Grinding wheel particle size -60, in addition, the feed rate should be controlled as low as possible, and emulsion should be used for complete cooling. As for tapping of titanium alloy, the jumping tap should be preferred, and the number of teeth should be taken as 2-3.
Precision machining refers to machining with a precision of 10 to 0.1 micrometers and a surface roughness of less than 0.1 micrometers. When we talk about precision machining of titanium alloys, we usually refer to CNC machining. Computer digital control precision machining, CNC machining lathes, CNC machining milling machines, CNC machining boring and milling machines and other precision machined titanium alloy materials can be surface treated and colored, and finally come into your hands, becoming a part of people's daily lives.

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