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Free Cutting Steel Round 11SMn30+C
11SMn30 is a free-machining steel with low carbon content. The term free-machining implies that the analysis is tailored to promote machinability at the expense of other properties. The material can be machined at high speeds and it is short-chipping, which expediates processing in unmanned machines. The principal addition promoting machinability is sulphur, 0.3%, but a high phosphorous content can also contribute. In addition, the high level of machinability is further enhanced by cold drawing. 11SMn30 +C offers a lead-free alternative should one wish to mitigate contamination by lead in the workplace.
11SMn30 +C is standardised in SS-EN 10077 - 3. The (discontinued) SS-designation is 1912. The base steel 11SMn30 does not have very high strength but yield and tensile strengths are enhanced somewhat via cold drawing. The minimum prescribed level of yield strength varies depending on diameter over the range 440 - 245 MPa. The interval for tensile strength decreases and the minimum allowed elongation in a tensile test increases somewhat as the bar diameter increases. There is no guarantee for impact toughness.
The diameter tolerance for 11SMn30 +C as cold-drawn rounds is good, h9 as defined in
ISO 286 - 2 or better. Furthermore, straightness is considerably better than what is typical for hot-rolled round bars and the maximum height of arc is 0.001 times bar length. Straightness as a property is important for processing in bar-feed machines.
The weldability of 11SMn30 is limited as a consequence of the high sulphur content.
If the application requires that the part has a wear-resistant surface, 11SMn30 +C can be case hardened.