Why Is Titanium So Difficult To Machine

1. The physical phenomenon of titanium processing The cutting force of titanium alloy processing is only slightly higher than that of steel of the same hardness, but the physical phenomenon of processing titanium alloy is much more complex than that of processing steel, which makes the processing of titanium alloy face great difficulties.
The thermal conductivity of most titanium alloys is very low, only 1/7 of steel and 1/16 of aluminum. Therefore, the heat generated in the process of cutting titanium alloy will not be quickly transferred to the workpiece or taken away by the chips, and gathered in the cutting area, the temperature generated can be as high as 1 000 ° C or more, so that the cutting edge of the tool rapidly wear, crack and generate chip tumors, rapid wear of the blade, but also make the cutting area produce more heat, further shorten the life of the tool.
The high temperature generated during the cutting process also destroys the surface integrity of the titanium alloy parts, leading to the reduction of the geometric accuracy of the parts and the work hardening phenomenon that seriously reduces their fatigue strength.
The elasticity of titanium alloy may be beneficial to the performance of parts, but in the cutting process, the elastic deformation of the workpiece is an important cause of vibration. The cutting pressure causes the "elastic" workpiece to leave the tool and rebound, so that the friction between the tool and the workpiece is greater than the cutting action. The friction process also generates heat, which aggravates the problem of poor thermal conductivity of titanium alloys.
This problem is even more serious when processing thin-walled or torus and other easily deformed parts, and it is not an easy task to process thin-walled titanium alloy parts to the expected dimensional accuracy. Because when the workpiece material is pushed away by the tool, the local deformation of the thin wall has exceeded the elastic range and produced plastic deformation, and the strength and hardness of the material at the cutting point have increased significantly. At this time, machining at the previously determined cutting speed becomes too high, further leading to sharp tool wear.
"Heat" is the "culprit" of titanium alloy difficult to process!

2. Processing know-how of titanium alloy On the basis of understanding the processing mechanism of titanium alloy, coupled with previous experience, the main process know-how of processing titanium alloy is as follows:

(1) The blade with positive Angle geometry is used to reduce cutting force, cutting heat and deformation of the workpiece.
(2) Maintain a constant feed to avoid hardening of the workpiece, the tool should always be in the feed state during the cutting process, and the radial cutting amount ae should be 30% of the radius during milling.
(3) The high pressure and large flow cutting fluid is used to ensure the thermal stability of the processing process and prevent the surface denaturation of the workpiece and tool damage due to high temperature.
(4) Keep the edge of the blade sharp, blunt tools are the cause of thermal accumulation and wear, easy to lead to tool failure.
(5) Processing in the softest state of titanium alloy as far as possible, because the material becomes more difficult to process after hardening, heat treatment increases the strength of the material and increases the wear of the blade.
(6) Use a large tip arc radius or chamfer cut, as much as possible into the cutting edge. This reduces the cutting force and heat at every point, preventing local breakage. In milling titanium alloy, the cutting speed has the greatest effect on tool life vc, followed by radial cutting amount (milling depth) ae.

3. Start from the blade to solve the titanium processing problem. The groove wear of the blade in the processing of titanium alloy is the local wear in the back and front along the cutting depth, which is often caused by the hardened layer left by the early processing. The chemical reaction and diffusion between the tool and the workpiece material at the processing temperature of more than 800 ° C is also one of the reasons for the formation of groove wear. Because in the process of processing, the titanium molecules of the workpiece accumulate in the front of the blade, and are "welded" to the blade at high pressure and high temperature, forming a chip tumor. When the chip nodules are removed from the blade, the carbide coating of the blade is taken away, so the machining of titanium alloys requires special blade materials and geometry.

4, suitable for titanium processing tool structure titanium alloy processing focus is heat, a large number of high-pressure cutting fluid to timely and accurate injection to the cutting edge, can quickly remove the heat. There are unique structures of milling cutters on the market specifically for titanium alloy processing.