Titanium alloys are known for their excellent strength-to-weight ratio, high corrosion resistance, and biocompatibility, which make them popular materials in various industries, including aerospace, medical, and automotive. However, titanium alloys are also known to be prone to combustion when machined, especially when CNC machined.
The reason why titanium alloys are easy to catch fire during CNC machining is due to a phenomenon called adiabatic shear localization. This occurs when the machining process generates heat that is not able to dissipate quickly enough, causing the material in the immediate vicinity of the cutting tool to rapidly heat up and deform. The high deformation causes the material to become highly localized and thin, creating a condition known as shear bands. These shear bands become so thin that they heat up to a point where they can ignite and catch fire.
Additionally, titanium alloys have a low thermal conductivity, which means that they do not dissipate heat very quickly, making them more susceptible to adiabatic shear localization. Furthermore, titanium alloys have a low thermal expansion coefficient, which can cause the material to expand and contract rapidly during machining, creating internal stresses that can increase the likelihood of combustion.
To prevent combustion during CNC machining of titanium alloys, it is important to use proper machining techniques and cooling methods. These may include using cutting tools with proper geometry and coatings, using high-pressure coolant to dissipate heat, and minimizing the cutting forces and speeds to reduce the heat generated during machining.