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www.kiswire.com In addition, the addition of Vanadium will remove nitrogen from solid solution as V(C,N). Nitrogen in solid solution contributes to strain aging during wire drawing, resulting in reduced ductility of the finished wire. Higher ductility, usually measured by the wire torsion test, is reported using vanadium micro alloyed steels in direct drawn wire applications. Again, vanadium changes the nitrogen from an undesirable element to an integral part of the alloy system. Strain Age Strain ageing is associated with strain that results from plastic deformation which is more commonly known as cold working. Steel is an alloy of iron and carbon and contains other alloying elements which provide it with specific performance characteristics. Severe cold working of steel causes the migration of carbon atoms in the iron crystals and the segregation of these atoms at dislocations in the steel causes a reduction in ductility of the steel. The ageing process is a function of temperature and time and occurs very slowly at ambient temperature but very rapidly at the 450-460°C temperatures of the galvanising process. Severe cold working of steel can be caused by hole punching in thicker sections, tight radius bending or rebending. It should be noted that it is not the hot dip galvanising that is the cause of accelerating the strain ageing of the steel, but the heat of the process, so strain age embrittlement can be induced in any severely cold worked steel by heating and the tendency to embrittlement by strain ageing will always be present and its manifestation will simply be a matter of time. Avoiding Strain Age Embrittlement To avoid the risk of strain aging embitterment, the following design criteria should be followed : • use a bend radius of 3 times the diameter of the steel wire • avoid cold strain. Bend and/or work the steel hot. When galvanizing, anneal at 650-815 degrees Celsius It is these two effects, the increased strength and reduction in ductility and toughness from cold strain followed by an additional strength increase and toughness loss through aging, that are the primary elements in strain aging. Technical Data Sheet 9