Titanium alloy has a small modulus of elasticity and a small thermal conductivity coefficient. It is a typical difficult-to-machine material, especially for deep groove cutting. Figure 1 shows an example of machining a deep groove with a width of 4mm, a depth of 30mm, and a length of 300mm on a titanium alloy part.
For ordinary materials (such as 45 steel), high-speed steel (W18Cr4V) saw blade milling cutters (φ120×φ40×4, 60 teeth) are often used to process the above-mentioned deep grooves, and they are sufficiently cooled to obtain good milling results. But for the titanium alloy TC4 material, when using the above saw blade milling cutter to cut a blind groove with a depth of 30mm, a new blade will wear out when the first or second workpiece is processed, and its cutting edge will become blunt. When grinding, the extrusion in front of the cutting edge will increase significantly, and the metal deformation in the cutting zone will also increase. At the same time, the clearance angle of the tool will continue to decrease after wear, thereby increasing the friction between the back of the tool and the machined surface. The cutting heat increases, causing the cutting temperature to rise sharply. When processing the third part, the tips on both sides of the cutter teeth were obviously burnt, especially the back of the cutter teeth and the chip pockets are stuck with titanium chips, indicating that severe extrusion occurred during the cutting process. This is because in addition to the small thermal conductivity coefficient of titanium alloy and the large friction coefficient between titanium alloy material and tool material, the cutting temperature rises rapidly, and there is also difficulty in chip removal due to insufficient chip flutes. For the sharpening of the above-mentioned worn blades, the burnt tip needs to be completely ground, and the diameter of the blade should be 3-4mm. In this way, the number of sharpening of a tool will be greatly reduced, so that the teeth of the blade can contain chips. The slot becomes smaller. Practice shows that the blade after such sharpening can only process one part at most. For this reason, in the research, the new insert was tried to jump teeth to increase the chip space of the milling cutter. The result was that this method can increase the life of the cutter by about 3 times, and each insert can process 5 parts. This tool can meet the needs of scientific research and trial production, but it cannot meet the requirements of mass production.
We use the method of skipping the teeth of the saw blade milling cutter, which can significantly improve the life of the saw blade milling cutter for milling titanium alloy TC4. This method can reduce the friction between the tool and the titanium alloy material and increase the chip holding space, but the potential of this method is limited. From the perspective of production efficiency and cost, cemented carbide (YG15) welding tools and high-speed steel (W6Mo5Cr4V2Al) welding tools should be designed.
Carbide welding tools and high-speed steel welding tools are used to test the grooving of the above-mentioned workpieces (the cutting conditions are the same). The high-speed steel welding tools can process 6 parts, while the YD15 welding tools can process 30 parts. Comprehensive saw blade milling cutter and skipped tooth saw blade milling cutter, the cutting amount is ap=7mm, f=0.3mm/r, v=26m/min. Relationship.
It can be seen from Figure 3 that in the deep groove milling of titanium alloy, the wear of the tool is mainly related to the tool material. For the difficult-to-machine material of titanium alloy, fine-grained cemented carbide materials should be preferentially selected, which can greatly improve its processing efficiency. And processing quality. In addition, the structure of the cutting part of the tool is also very important. It is necessary to consider the large chip space of the teeth and the selection of a reasonable number of teeth to improve processing efficiency. Therefore, we choose 4-tooth or 6-tooth cemented carbide welded slot milling cutters to meet the requirements for batch processing of titanium alloy deep grooves.
Experiments show that for titanium alloy deep groove milling, the use of skipped tooth saw blade milling cutters can increase the tool life by 3 times compared with conventional saw blade milling cutters; the use of YD15 cemented carbide welding milling cutters can significantly increase tool life.