Stainless steel milling
The machinability of stainless steels differs, depending on alloying elements, heat treatment and manufacturing process (forged, cast, etc.)
Material Classification: P5.x
Ferritic and annealed martensitic stainless steels have a machinability that is comparable to low alloyed steels, and therefore, the recommendations for steel milling can be used.
Thermal cracks due to cutting fluid
Edge chipping on the insert.
Burr formation and bad surface finish.
Austenitic and duplex stainless
Material Classification: M1.x, M2.x and M3.x
- The dominant wear criteria when milling austenitic and duplex stainless steels are: chipping on the edges due to thermal cracks, notch wear and built-up edge/smearing.
- On the component, burr formation and surface finish problems are the main issues.
Suitable cutters and inserts
- Most CoroMill cutters can be used in austenitic and duplex stainless steel simply by choosing a dedicated insert geometry and grade.
- In face milling, CoroMill 245 and CoroMill 300 are more suitable than CoroMill 345 and CoroMill 200, due to the more positive cutter geometry.
- Use cutters with round inserts or small lead angles to minimize notch wear.
- Use positive insert geometries (-ML, -WL).
- GC2030 (PVD) is the first choice.
- GC2040 (MT-CVD) is the complementary grade for tough conditions and cast stainless steel, where abrasive wear dominates.
- GC1030 (PVD) is the universal choice for mixed production (ISO P, M and S)
- If thermal cracks appear, change to a harder/more wear resistant grade, i.e. from GC2040 to GC2030.
- For CoroMill Plura, grade GC1630 is the basic choice and GC1640 is a complementary choice if there is increased demand for toughness and an internal cutting fluid supply is needed.
- Use high cutting speeds (vc = 492-820 ft/min) to avoid built-up edge.
- In roughing, always run dry, without cutting fluid, to minimize problems with thermal cracks.
- In finishing, cutting fluid, or preferably mist coolant/minimal lubrication, is
sometimes necessary to improve the surface finish. There are fewer problems with thermal cracks in finish milling, because the heat generated in the cutting zone is lower.
- With a cermet grade, CT530, sufficient surface finish can be obtained without cutting fluid.
- A feed, fz, that is too low can cause higher insert wear because the edge is cutting in the deformation hardened zone.
CoroMill® indexable insert cutters