Cutting solutions for titanium alloy structural parts

The main factors affecting the machining of titanium alloy weakly rigid structure are: machine rigidity, tool selection, process parameters, effective cooling and so on. In the process of processing, the effect of various factors, the interaction influence, the accumulation of deformation errors lead to the machining of weak rigid structural parts out of tolerance, processing deformation is difficult to control.

1. Selection of machine tools
Machine tool-jig tool system The rigidity is better, the gap between the parts of the machine tool should be adjusted well, the radial runout of the spindle should be small, and the machine tool should be used as far as possible.

2. Selection of cutting tools
The improvement of cutting productivity is mainly the result of the development and application of new tool materials. In the past few decades, the cutting tool has had a great development, including carbide coating, ceramics, cubic boron nitride, polycrystalline diamond. These are effective for processing cast iron, steel and superalloys. However, no tool can improve the machinability of titanium alloy, because the cutting tool material of titanium alloy requires very important properties, which include: 1) good thermal hardness to resist high stress; 2) Good thermal conductivity to reduce thermal gradient and thermal shock; 3) Good chemical inertness to reduce the tendency of chemical reaction with titanium; 4) Good toughness and fatigue resistance to adapt to the chip segmentation process. In almost all titanium alloy cutting processes, tungsten carbide (WC/co) cemented carbide tools are considered to be the best performance. Some tests show that the wear rate of all cemented carbide coated tools is greater than that of uncoated tools. Although the quality of ceramic tools has been improved and more and more used for machining hard-to-cut materials, especially those superalloys (such as nickel-based superalloys), but because of their poor thermal conductivity, low fracture toughness and reaction with titanium, they have not replaced cemented carbide and high-speed steel. Superhard cutting tool materials (cubic boron nitride and polycrystalline diamond) show good performance because of their low wear rate when cutting titanium alloys.

The main problem in the milling process of titanium alloy weakly rigid structural parts is the milling deformation of thin walls. Because the elastic modulus of titanium alloy is low, and the cutting force is relatively large, the thin wall is easily deformed by the milling force in the milling process, and the result is that the actual thickness of the thin wall after processing is greater than the theoretical thickness. The solution to this problem should be as far as possible to reduce the thin wall in the milling process from the direction of the direction of the machined surface to cause the thin wall to deform the tool.

3. Cutting fluid
Titanium alloy has high strength, oxidation resistance, high temperature resistance, etc., which not only meets the requirements of high performance, but also brings a lot of problems to the cutting process. When cutting titanium alloy, in order to reduce the cutting temperature, a large amount of cooling-based cutting fluid should be poured into the cutting area to take away the heat of the blade and wash away the chips to reduce the cutting force.

Therefore, the requirements for cutting fluid are large thermal conductivity, large heat capacity, fast flow rate and large flow rate. The best way to cool is high pressure cooling method, cutting fluid flow is not less than 15 ~ 20L/min. There are three types of cutting fluids commonly used, namely water or alkaline solution, water-based soluble oil solution and non-water soluble oil solution.