The abundance of Ti in the earth's crust is 0.56% (mass fraction, the same below), ranking 9th among all the elements, and 4th among the metals that can be used as structural materials, second only to Al, Fe, Mg, and its reserves are more than the sum of the reserves of common metals Cu, Pb, and Zn. China is rich in titanium resources, the reserves of the world's first. Titanium alloy has low density, high specific strength and stiffness, good corrosion resistance, high temperature mechanical properties, fatigue resistance and creep properties, and excellent overall performance, and is a new type of structural material with great potential for development and application prospects.
Titanium screws" titanium alloy physical and mechanical properties of the cutting process has brought greater difficulty
Cutting characteristics of titanium alloy material: some physical and mechanical properties of titanium alloy make cutting and processing more difficult. Titanium alloy cutting deformation coefficient is small, making the chip in the front tool surface sliding friction distance increases, accelerating tool wear. Titanium alloy thermal conductivity is small, the heat generated during cutting is not easily transmitted, concentrated in a small area near the cutting edge. Titanium alloy modulus of elasticity is small, processing in the role of radial force is easy to produce bending deformation, causing vibration, increase tool wear and affect the accuracy of the parts. Due to the strong chemical affinity of titanium alloy to the tool material, the tool is prone to adhesive wear under the conditions of high cutting temperature and high cutting force per unit area.
Based on the understanding of the mechanism of titanium alloy machining and the previous experience, the main process know-how for machining titanium alloy is as follows.
(1) Use inserts with positive angle type geometry to reduce cutting forces, cutting heat and deformation of the workpiece.
The physical and mechanical properties of "titanium screws" titanium alloy make cutting more difficult
(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 feed ae 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 the workpiece surface from denaturing and tool damage due to high temperature.
(4) Keep the blade edge sharp, dull tools are the cause of heat build-up and wear, which can easily lead to tool failure.
(5) Machine titanium alloys in their softest state possible, as hardening makes the material more difficult to machine and heat treatment increases the strength of the material and increases the wear of the insert.
The physical and mechanical properties of titanium alloy "titanium screws" make cutting more difficult
(6) Use a large tip radius or chamfer cut to bring as much of the cutting edge into the cut as possible. This reduces the cutting force and heat at each point and prevents local breakage. In milling titanium alloy, each cutting parameter cutting speed has the greatest effect on tool life vc, radial draft (milling depth) ae the second.