1) Overspeed cutting characteristics and scope of application Ultra-high-speed machining is a breakthrough in the understanding of traditional cutting in the cutting principle. The cutting mechanism is different from conventional cutting. Ultra-high-speed cutting has its own characteristics and application range.
a. The temperature rise of the workpiece is small to reduce the thermal deformation of the workpiece. In the ultra-high-speed cutting, although the heat generated is much, the cutting heat is cut away from the workpiece by the cutting speed, more than 90% of the cutting heat is carried away by the chip, and the heat transferred to the workpiece Very small, the workpiece accumulates very little heat, so the workpiece temperature rise does not exceed 3 °C during cutting.
b. Low cutting force Due to high cutting speed, the shear deformation zone is narrowed, the shear angle is increased, the deformation coefficient is reduced, and the chip outflow speed is fast, so that the cutting deformation is reduced, and the cutting force is lower than the conventional cutting force. 30% to 90%, tool durability increased by 70%, especially suitable for processing thin-walled workpieces with poor rigidity.
c. The material removal rate is high. The surface quality is high. When the high-speed cutting is performed, the feed rate can be increased by 5 to 10 times with the increase of the cutting speed. Thus, the material removal rate per unit time can be increased by 3 to 5 times. In addition, as the cutting speed increases, the chips can be quickly cut away from the workpiece, so the stress remaining on the surface is small. Due to the increase of the cutting point temperature, the height of the surface of the workpiece will be significantly reduced or even completely disappeared.
2) Ultra-high-speed cutting titanium alloy ultra-high-speed cutting titanium alloy is to improve the processing performance under the action of high strain rate response, thereby obtaining high processing quality. The speed of ultra-high speed cutting of titanium alloy is generally controlled in the range of 150 to 1000 m/min.
In addition to the cutting speed, the key technology of ultra-high-speed cutting titanium alloy is the tool spindle unit and feed unit manufacturing technology, machine tool support and auxiliary unit manufacturing technology, processing and testing technology and many other factors. This paper focuses on the tool materials that have great influence on tool durability, machining efficiency and machining quality during ultra-high speed cutting of titanium alloy, in order to find the best match between tool and titanium alloy.
a. Ultra-high-speed cutting tool material Because the speed of ultra-high-speed cutting is several times or even ten times higher than the conventional cutting speed, the cutting temperature is very high, so the ultra-high-speed cutting puts higher requirements on the tool material. Tool materials should have high heat resistance, thermal shock resistance, good high temperature mechanical properties and high reliability. At present, the tool materials for ultra-high speed cutting at home and abroad mainly include: coated cemented carbide, TiC (N) based hard alloy, ceramic cutter, polycrystalline diamond PCD and cubic boron nitride.
The coated cemented carbide tool coating tool is coated on the toughness of the body, and one or more layers of wear-resistant refractory compound are applied to make the tool have high toughness and high hardness and resistance. Abrasive, coated tool life is 2 to 5 times higher than uncoated tools.
Polycrystalline diamond cutters Natural diamond cutters are fragile due to their nature and are prone to cracking along the crystal plane of the crystal, resulting in large chipping. In many cases, polycrystalline diamond (PCD) has been replaced. PCD is a catalyst that is added to graphite as a raw material and sintered at high temperature and high pressure. It has good thermal conductivity and wear resistance and high hardness.
Polycrystalline Cubic Boron Nitride Tools Polycrystalline Cubic Boron Nitride (PCBN) is a polycrystalline material that combines fine cubic boron nitride (CBN) materials through a bonding phase at high temperatures and pressures. PCBN tools have the advantages of CBN. It is also easier to manufacture than CBN, so PCBN has been developed very quickly. PCBN has high thermal stability, can withstand cutting temperatures above 1200 °C, and has high hardness and high wear resistance.
b. Requirements for tool materials of titanium alloy According to the processing characteristics of titanium alloy materials, the tool materials should have high resistance to high strength, high hardness, good toughness, good heat hardness, good wear resistance and good heat dissipation.
In addition to the above, since the tool material containing titanium is easily compatible with the titanium alloy at a high temperature, the tool material of titanium should never be used.
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