Interesting facts about Sulphur in steel

Produces the most pronounced segregation of all steel accompanying elements. Iron sulphide, leads to red shortness or hot shortness, as the low melting point sulphide eutectics surround the grains in reticular fashion, so that only slight cohesion of the latter occurs and during hot forming the grain boundaries tend to break down. This is further increased by the action of oxygen. As sulphur possesses a considerable affinity for manganese, it is combined in the form of Mn sulphide, as this is the least dangerous of all existing inclusions, being present distributed in point form in the steel. Toughness in transverse direction is reduced significantly by S. S is added intentionally to steels for automatic machining up to 0.4%, as the friction on the tool cutting edge reduced by the lubrication action permits increased life between workpiece and tool. In addition, short chips occur when free-cutting steels are machined. S increases susceptibility to welding cracks.