First of all, the chemical composition of steel is very important. The higher the alloy composition of steel, the harder it is to process. As the carbon content increases, the metal cutting performance decreases.
Second, the structure of the 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.
Third, hardness is an important factor affecting metal cutting performance. The general rule is that the harder the steel, the harder it is to process. High speed steel (HSS) can be used to process materials up to 330-400HB; high speed steel + titanium nitride (TiN) coatings can process materials up to 45HRC; for materials with hardness 65-70HRC, Carbide, ceramic, cermet and cubic boron nitride (CBN) are used.
Fourth, non-metallic inclusions generally have an adverse effect on tool life. For example, Al2O3 (alumina), which is a pure ceramic, has a strong abrasiveness.
Fifth, the last one is residual stress, which can cause metal cutting performance problems. It is often recommended to perform a stress relief process after roughing.