Comparison of Machinability of Difficult-to-Cut Metal Materials
With the increasing demand for cutting performance and the development of new cutting tools and processing technologies, cutting operations are becoming more and more complex. With the continuous updating of industrial materials, the hardness and toughness of cutting materials have also been continuously improved, making it more and more difficult to cut. Difficult to cut metals are those that are difficult to cut and prone to failure when machining ordinary metals, such as high-strength structural steels, stainless steels, titanium alloys and other materials with high hardness and high toughness. Among them, titanium alloys have the most difficult cutting performance, making them a major scientific research problem.
Difficult-to-cut metals refer to those metals or alloys that have poor machinability and tend to fail when machined with ordinary cutting tools and ordinary cutting process parameters. It is usually required to modify or optimize the cutting process parameters, such as cutting speed, feed rate and tool geometry to complete the cutting task. Failure mayinclude wear, chipping, crushing, plastic deformation of the cutting edge, impossible roughness, poor surface integrity and bad surface quality. In addition, difficult-to-cut metals usually require high cutting temperatures, which may further aggravate wear and accelerate tool failure．
The machinability of difficult-to-cut metals mainly depends on the physical and mechanical properties of the materials, the applied cutting parameters, the cutting tool material and its geometry. Material properties such as hardness and strain hardening coefficient have a direct influence on the machinability. In general, difficult-to-cut metals tend to be harder and have higher strain hardening coefficients than easily machinable metals, which increases the cutting forces and cutting temperatures and thus imposes high demands on the tool material and geometry. The applied cutting parameters, such as the cutting speed, feed rate, cutting depth and cutting fluid, also have a great influence on the machinability of difficult-to-cut metals.
It is well known that the machinability of metals is greatly affected by the cutting tool material and its geometry. High-speed steel (HSS) tools are the most widely used tools for cutting difficult-to-cut metals due to their good resistance to abrasive wear and thermal shock. Ceramics and cermets are also increasingly used as cutting tools due to their high hardness, wear resistance and thermal stability. In addition, the cutting edge geometry of these tools also affects the machinability of difficult-to-cut metals, especially the rake angle and relief angle. A large rake angle is beneficial to improving the cutting performance, while a large relief angle is beneficial to improving the tool life.
In conclusion, difficult-to-cut metals have poor machinability and require special cutting tools, cutting processes and parameters to complete the cutting task. The machinability of difficult-to-cut metals is mainly determined by material properties, cutting parameters, cutting tool materials and their geometries. Therefore, the selection of cutting tools and parameters is critical in order to achieve the required cutting performance and quality.
