The "stelmorized wire" is a product achieved by rod coming from steel mill and directly cold-drawn. The "patented wire", instead, results from rod which, before drawing, between two drawing cycles or after drawing, is subjected to a heat treatment called patenting. In order to understand these treatments, we have to specify that steel consists fundamentally in a iron-carbon alloy. The patenting, a treatment characteristic of steel wire, can be defined as an interrupted hardening. The steel wire is subjected to a temperature of 900-950 deg C and immersed in a bath of lead or fused salt, at 500-550 deg C. This way, the structure acquisred by steel shows good mechanical properties, highlighted by high tensile strength and ductility. The Stelmor process, instead, is carried out in air. After the patenting treatment, the wire has to be prepared for the following drawing operations. The drawing consists in a reduction in section of the product. During h drawing, as a consequence of the cold plastic deformation, the wire undergoes remarkable transformation of its mechanical features: increase in specific tensile strength and elastic limit, decrease in breaking lengthening and breaking necking. In practice, the operator has to consider these changes and, on the basis of the project data, plan the drawing cycle, which has anyhow to respect plant limits (type of equipment at disposal) and physical limits (utmost admitted reductions in section).
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