The thermal conductivity of titanium alloy is very poor, and the contact length of the chip and the tool is very short, which is not conducive to the export of cutting heat, so that the temperature of the cutting edge area is high, about twice as high as that of the cutting 45 steel. In addition, tool wear is also very serious, on the one hand, titanium alloy and tool material chemical affinity is strong, easy and tool materials in the Ti, Co, C and other elements bonding, high temperature aggravates the bonding wear; On the other hand, titanium alloy is easy to combine with oxygen and nitrogen in the air to form a hard and brittle surface, which aggravates tool wear. In addition, because the chip and the cutting tool front face contact length is only 1/3~1/4 of the cutting steel, resulting in cutting force concentrated near the cutting edge, the tool is easy to collapse. Therefore, the cutting tool material of titanium alloy, such as the use of high speed steel, it is appropriate to use cobalt, aluminum or high vanadium high speed steel.
In order to improve the cutting edge strength and heat dissipation ability, it is advisable to choose smaller rake Angle and blade Angle. Due to the large elastic recovery of the machined surface in the cutting of titanium alloy, the rear Angle should be a larger value. The tool tip should be circular transition edge, cutting edge is not allowed to have burr, small notch or crack and other defects, the roughness of the cutter surface should be within RA0.2μm, in order to ensure smooth chip removal and avoid chipping edge.
In order to improve production efficiency, cemented carbide tools should be used as much as possible, but fine grain tungsten-cobalt cemented carbide with high strength and low affinity with titanium alloy and good thermal conductivity should be selected. The speed of turning titanium alloy should not be too high, the amount of cutting tool can be large, the amount of feed should be appropriate. Feed is too large, will cause cutting edge burn loss; If the feed is too small, the cutting edge will wear too fast when working the hardened layer. When turning titanium alloy, antirust emulsion or extreme pressure emulsion can be used for cooling and lubrication. Tool material YG8, workpiece material TC4, tool geometric Angle raceway =5°, back Angle =10°, main Angle =75°, deputy Angle =15°, tip radius =0.5mm, cutting depth =1mm, dry cutting.
