Why do we think titanium alloy is a difficult material to work? Because of the lack of deep understanding of its processing mechanism and phenomenon.
1. Physical phenomena of titanium processing
The cutting force of titanium alloy is only moderately higher than that of steel of the same hardness, but the physical phenomenon of titanium alloy processing is much more complicated than that of steel processing, so that titanium alloy processing confronts great difficulties.
Most titanium alloys have meager thermal conductivity, 1/7 of that of steel and 1/16 of that of aluminum. Therefore, in the process of cutting of titanium alloy heat will not quickly passed to the artifact or taken away by chip, and agglomeration in cutting area, the temperature can be as high as 1 000 ℃ above, make the cutter blade quickly wear, cracks, and generate the devolop tumor, rapid wear of the blade, and make the cutting area produces more heat and further shorten the life of cutting tools.
The high temperature generated in the process of Metal Laser Cutting Service service ruins the surface integrity of titanium alloy parts, which leads to the decline of the geometric accuracy of parts and the phenomenon of work hardening which severely lowers the fatigue strength.
The elasticity of titanium alloy may be beneficial to the performance of parts, but the elastic deformation of the workpiece is an important cause of vibration during cutting. The cutting pressure causes the "elastic" workpiece to move away from the tool and rebound, hence causing greater friction between the tool and the workpiece than the cutting action. The friction process will likewise generate heat, aggravating the poor thermal conductivity of titanium alloy.
This problem is even more severe when processing thin wall or ring deformable parts. It is not easy to process titanium alloy thin wall parts to the predicted dimensional accuracy. Because when the workpiece material is moved by the tool, the local deformation of the thin wall has moved beyond the elastic range and the plastic deformation is generated, the strength and hardness of the material at the cutting point rise substantially. At this point, machining at the previously calculated cutting speed becomes too steep, further leading to severe tool wear.
"Warm" titanium alloy is hard to process "the main culprit"!
2 processing titanium alloy technological know-how
On the basis of understanding the mechanism of titanium alloy processing, coupled with previous experience, the main technological know-how of titanium alloy processing is as follows:
(1) The blade with positive angular geometry is used to decrease the cutting force, cutting heat and workpiece deformation.
(2) maintain steady feed to prevent hardening of the workpiece, in the cutting process to always be in the feed state, milling radial tool A E should be 30% of the radius.
3. Resolve the problems of titanium processing from the blade
The blade groove wear in titanium alloy machining is the local wear in the back and front along the cutting depth direction, which is usually caused by the hardening layer left by the preceding machining. The chemical reaction and diffusion between the tool and the workpiece material at the processing temperature over 800℃ is also one of the reasons for the formation of groove wear. Because in the process of machining, titanium molecules of the workpiece accumulate in the front of the blade, under high pressure and high temperature "welding" to the blade, forming a chip tumor. When the lumps are removed from the blade, they take away the carbide coating of the blade. Consequently, titanium alloy processing needs special blade materials and geometry.
4. Suitable for titanium machining tool structure
The focus of titanium alloy processing is heat, a large number of high-pressure cutting fluid to timely and precise injection on the cutting edge, can rapidly eliminate the heat. There is a unique structure of milling cutter for titanium alloy machining on the market.