Titanium alloy has become an ideal material for aircraft and engine because of its high strength, mechanical property and good corrosion resistance. But because of its poor machinability, it has largely restricted its application for a long time. With the development of processing technology in recent years, the manufacturing of titanium alloy parts have been widely used in aircraft engine compressor, engine hood, exhaust device manufacturing and plane beam frame structure of the frame member.
1.Properties of titanium alloys
Titanium alloys have the following advantages over ordinary alloy steels:
Higher than the strength: titanium alloy density is only 4.5g/cm3, much smaller than the iron, and its strength is similar to ordinary carbon steel.
Good mechanical properties: titanium alloy melting point is 1660 degrees, higher than iron, with higher thermal strength, can work at less than 550 degrees Celsius, at the same time at low temperatures usually show good toughness.
Good corrosion resistance: under the temperature of 550 degrees, the compact oxide film is easy to form on the surface of titanium alloy, so it is not easy to be further oxidized, and has higher corrosion resistance to atmosphere, sea water, steam, and some acid, alkali and salt medium.
On the other hand, the machinability of titanium alloys is poor. The main reason for: Poor thermal conductivity, resulting in high cutting temperature, reducing tool durability.
2.Cutting process of titanium alloy
Titanium alloy turning is easy to obtain better surface roughness, but the work hardening is not serious, but the cutting temperature is high and the tool wear is fast.
Milling of titanium alloy is more difficult than turning, because milling is interrupted cutting, and the chip is easy to bond with the blade. When the blade of the stick cuts into the workpiece again, the chip is knocked away and a small piece of cutting material is removed to form a chipping edge, which greatly reduces the durability of the tool.
The common problem of grinding titanium alloy parts is that the chip causes the grinding wheel blockage and the surface burn of parts.
The drilling of titanium alloy is difficult, and the phenomenon of burning and cutting is often appeared in the process of machining.This is mainly due to the poor grinding of drill bits, poor chip removal, poor cooling and poor process system rigidity.
When the titanium alloy is reaming, the tool wear is not serious, and hard alloy and high-speed steel reamer can be used.
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