Machining stainless steels

Stainless steels are alloys with the element iron (Fe) as the major constituent and with a minimum of 12% chromium. Their machinability differs depending on their alloying elements, heat treatment and manufacturing processes (forged, cast, etc.), although machinability-improved versions of all groups of stainless steels exist.

Typical of stainless steels is their generally low carbon content (C ≤ 0.05 %). Various additions of nickel (Ni), chromium (Cr), molybdenum (Mo), niobium (Nb) and titanium (Ti) supply different characteristics, such as resistance to corrosion and strength at high temperatures. Different conditions, such as ferritic, martensitic, austenitic and austenitic-ferritic (duplex), create a large range of materials. Chrome combines with oxygen (O) to create a passivating layer of Cr2O3 on the surface of the steel, which provides a non-corrosive property to the material.

In general, machinability of stainless steel decreases with a higher alloy content, but free-machining or machinability-improved materials are available in all groups of stainless steels.  For instance, sulfur (S) can be added to improve machinability.

When machining any kind of stainless steel, the tools’ cutting edges are exposed to a great deal of heat, notch wear and built-up edge. The material tends to create long chips;  machining involves high cutting forces and a tendency to a built-up edge. This influences the type of coating that can best be applied to increase tool lifetime and machining performance.

Ionbond engineers would be happy to discuss your application and help determine the most appropriate coating.

Application examples