This paper describes the effects of free nitrogen (nitrogen not bound to nitride forming elements) and drawing schedule mainly on the tensile properties of patented and cold drawn high carbon steel wires. The results obtained are as follows.
The deleterious effect of nitrogen upon the reduction of area at tensile fracture, which is apparent in the as-patented steels, gradually diminishes with the reduction by drawing and becomes negligibly small above about 60 to 70% reduction. The tensile properties of the heavily cold drawn wires are determined not by the free nitrogen level but rather by the wire drawing condition. The important role of the drawing condition on the wire strength properties is discussed in terms of the progress of the strain aging during drawing.
The tensile-fractured steels were examined using a scanning electron microscope and it was found that in the as patented steels, the fracture pass was mainly along the proeutectoid ferrite or the pearlite boundaries and that in the heavily cold drawn ones, small voids elongated along the wire axis direction were dominant in the early stage of fracture. These fracture characteristics are discussed in relation to the tensile ductility.
