The chemical composition of steel is very important. The higher the alloy composition of steel, the more difficult it is to process. As the carbon content increases, the metal cutting performance decreases.
The structure of steel is also very important for metal cutting performance. Different structures include: forged, cast, extruded, rolled, and machined. Forgings and castings have very difficult to machine surfaces.
Hardness is an important factor affecting metal cutting performance. The general rule is that the harder steel is, the harder it is to process.
High-speed steel (HSS) can be used to process materials with hardness up to 330-400HB; high-speed steel + titanium nitride (TiN) coating can process materials with hardness up to 45HRC; and for materials with hardness of 65-70HRC, it must be Use carbide, ceramics, cermets, and cubic boron nitride (CBN).
Non-metallic inclusions generally have a negative effect on tool life. For example, Al2O3 (alumina), which is pure ceramic, has strong abrasive properties.
The last one is residual stress, which can cause metal cutting performance problems. It is often recommended to perform stress relief after roughing.