Stainless steels are enhanced by the addition of elements such as chromium, nickel, molybdenum and nitrogen to increase their corrosion resistance for specific environments. According to the metallographic organization, stainless steel can be roughly divided into three types: austenitic stainless steel (non-magnetic), ferritic stainless steel (strongly magnetic) and martensitic stainless steel (strongly magnetic).
Among the austenitic stainless steels, 303 stainless steel is commonly used in CNC machining due to its high sulfur content which makes it easy to cut, but this also results in reduced corrosion resistance. On the other hand, 304 and 316 stainless steels harden significantly during the cutting process and have poor thermal conductivity, leading to a buildup of heat generated during the cutting process and increased tool wear. Therefore, choosing the right tool and setting the right cutting parameters is critical.
Common ferritic stainless steels include 430, 439 and 444, which are prone to edge chipping and chip adhesion during cutting, so it is necessary to avoid these problems by choosing tools with TiN/TiCN coatings or ceramic tools.
Martensitic stainless steels are the hardest (HRC 50-60) and most wear-resistant of the stainless steels. Common types include 410, 420 and 440C, which are commonly used in the manufacture of bearings and cutting tools. During machining, attention should be paid to tool wear. It is best to choose high hardness tools and use a low speed cutting strategy.
