"If the MCD inserts would be appropriate for machining titanium or not" This is the question that a customer who placed an order for MCD tool asked us this week.
Nowadays, titanium alloy is known as a strategic metal material that leads mankind to the space age with its excellent comprehensive mechanical properties, low density and good corrosion resistance. It is not only widely used in the aerospace and military fields, but also gradually penetrates into all aspects of economic life.
1) The high cost of titanium alloy processing is the main reason that hinders its widespread use. Seeking a high-efficiency and low-cost processing method has become a hot spot in titanium alloy research today.
2) The physical and chemical properties of titanium alloy itself bring difficulties to cutting. The groove wear of the insert during titanium alloy processing is the local wear of the back and front along the cutting depth direction. It is often caused by the hardened layer left by the previous processing. The chemical reaction and diffusion of the tool and the workpiece material at a processing temperature of more than 800℃ is also one of the reasons for the formation of groove wear. Because during the processing, the titanium molecules of the workpiece accumulate in front of the cutting edge and "weld" to the edge under high pressure and high temperature to form a built-up edge. When the built-up edge is peeled off from the blade, the carbide coating of the blade is taken away.
3) The ideal tool material for titanium alloy must have high hot hardness, good toughness, wear resistance, high thermal conductivity and low chemical activity. When milling, the tool should also have good impact resistance.
1) Use inserts with positive angle geometry to reduce cutting force, cutting heat and deformation of the workpiece.
2) Maintain constant feed to avoid hardening of the workpiece. The tool should always be in feed state during the cutting process. The radial cutting amount a e should be 30% of the radius during milling.
3) Use high-pressure and high-flow cutting fluid to ensure the thermal stability of the machining process and prevent surface degeneration of the workpiece and tool damage due to excessive temperature.
4) Keep the inserts edge sharp. Blunt tools are the cause of heat accumulation and wear, which can easily lead to tool failure.
5) PCD superhard tools should be processed in the soft state of titanium alloy as much as possible, because the material becomes more difficult to process after hardening, and heat treatment increases the strength of the material and increases the wear of the blade.
6) Use a large tip radius or chamfer to cut in, and put as much edge as possible into the cutting. This can reduce the cutting force and heat at each point and prevent local damage. When milling titanium alloy, the cutting speed has the greatest impact on the tool life among all cutting parameters, and the radial cutting depth (milling depth) is second.
1) Cutting speed: Cutting speed is an important factor affecting edge temperature. Too high cutting speed will lead to inserts overheating, severe edge adhesion and diffusion wear, frequent tool re-grinding, shortening tool life, and on the contrary, cracking or oxidation of the surface layer of titanium alloy workpieces, affecting its mechanical properties. Therefore, under the premise of ensuring greater tool durability, appropriate cutting speed should be selected to reduce costs and ensure processing quality.
2) Feed depth and feed amount: The change in feed amount has little effect on the change in temperature, so reducing the cutting speed and increasing the feed amount is a reasonable cutting method. According to the situation of the oxide layer and the subcutaneous pore layer, a large cutting depth can directly cut into the unoxidized metal layer of the substrate, thereby increasing the life of the tool.
3) Tool geometry: When cutting titanium alloy, selecting geometric parameters such as rake angle and back angle that are suitable for the processing method and properly treating the tool tip will have an important impact on cutting efficiency and tool life. In order to improve heat dissipation conditions and enhance the cutting edge during turning, the rake angle is generally 5°~9°; in order to overcome the friction caused by rebound, the back angle of the tool body is generally 10°~15°; when drilling, shorten the drill length, increase the thickness of the drill core and the amount of guide cone, and the durability of the drill can be increased several times.
4) Clamping force of the fixture: Titanium alloy is easy to deform, and the clamping force should not be too large. Especially in the finishing process, a certain auxiliary support can be selected.
5) Cutting fluid: Cutting fluid is an indispensable process lubricant in titanium alloy processing. Cutting fluid can not only effectively reduce the cutting temperature and reduce the heat generated by the tool and cutting friction, but also act as a lubricant in the cutting process, reduce the adhesion of titanium alloy chips and tool surface, improve efficiency, reduce costs, and extend the life of the tool. Cutting fluids containing chlorine or other halogen elements and sulfur should not be used, as such cutting fluids will have an adverse effect on the mechanical properties of titanium alloys.
