Characteristics of Titanium Alloy Cutting Processing

The series of physical and chemical properties of titanium alloys pose many difficulties in the machining of titanium alloys.

(1) The thermal conductivity of titanium alloys is very low, and the heat generated during cutting is difficult to dissipate. The machining process of titanium alloys is a nonlinear large-strain process, which generates a large amount of heat. The high heat generated during processing cannot be effectively diffused. At the same time, the cutting edge of the tool and the contact length of the chip are short, causing a large amount of heat to accumulate on the cutting edge, resulting in a sharp increase in temperature, softening of the tool edge, and accelerated tool wear.

(2) The chemical properties of titanium alloys are significant. On the one hand, at high temperatures, titanium alloys easily react with the tool material, accelerating the formation of the crescent groove. However, the cutting process of titanium alloys is basically carried out at high temperatures. On the other hand, at higher cutting temperatures, titanium alloys are prone to chemical reactions with oxygen and nitrogen in the air, forming a brittle and hard outer layer. In addition, the plastic deformation of the machined surface of the workpiece during the cutting process also causes surface hardening, which is called cold hardening. Cold hardening not only reduces the fatigue strength of titanium alloy parts but also accelerates tool wear, which is an important characteristic when cutting titanium alloys.

(3) The deformation coefficient is small. This is a significant characteristic of titanium alloy cutting processing, with a deformation coefficient less than or close to 1. During the machining process, the contact area between the chip and the rake face is too large, and the sliding distance of the chip on the rake face is too long, greatly increasing tool wear and also raising the temperature in the cutting zone.

(4) The tool is prone to wear. After the blank undergoes processes such as stamping, forging, and hot rolling, an uneven hard and brittle outer layer is formed, which easily causes chipping. Therefore, removing the hard layer becomes the most difficult process in the cutting of titanium alloys. In addition, due to the strong chemical affinity of titanium alloys to tool materials, it is prone to cutting temperature being high and the cutting force being large per unit area, and adhesive wear is likely to occur on the tool.

The main reason hindering the wide use of titanium alloy cutting processing is the high cost of titanium alloy processing. Because titanium alloy materials are expensive and processing is very difficult, the requirements for cutting tools for titanium alloy processing are much higher than those for ordinary materials. Especially in high-speed cutting processing and fine processing, the requirements for the tools are very high. However, the final cutting amount of titanium alloy is not high, and the processing cost is too high. In China, the domesticization degree of high-performance special machine tools and cutting tools is relatively low, and the selection of cutting parameters in the titanium alloy cutting process is also unreasonable, seriously restricting the improvement of China's titanium alloy cutting processing level. In the end, the basic theory and process specifications for high-speed cutting of titanium alloys are not perfect, resulting in high-performance machine tools and cutting tools being unable to fully exert their efficiency, which restricts the further development and application of titanium alloy high-speed cutting technology. Therefore, in-depth research on the mechanism of high-speed cutting of titanium alloys and optimization of process parameters are one of the main measures to improve the processing technology level of titanium alloys.