Free Cutting Steel Round 36SMnPb14+C
36SMnPb14 is a free-machining steel with medium 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. In comparison with 11SMnPb30, the machinability-enhancing additions of sulphur and lead are lower since the higher carbon content also promotes machinability. The positive influence of lead for machinability derives from its low melting point whereby the particles of lead in the steel melt in the vicinity of the cutting edge thereby contributing locally to lubrication. The high level of machinability is further enhanced by cold drawing.
36SMnPb14 +C is standardised in SS-EN 10077 - 3. The (discontinued) SS-designation is 1957 - 04. The base steel 36SMnPb14 has better strength than 11SMnPb30 and yield and tensile strengths are enhanced further via cold drawing. The minimum prescribed level of yield strength varies depending on diameter over the range 550 - 360 MPa. The interval for tensile strength decreases and the minimum allowed elongation in a tensile test increases somewhat as the bar diameter increases.
The diameter tolerance for 36SMnPb14 +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 11SMnPb30 is extremely limited as a consequence of the high levels of sulphur and lead.
Should the application require that the part has a wear-resistant surface, 36SMnPb14 +C can be induction hardened. Furthermore, and if necessary, the base strength can be increased significantly via quenching and tempering.