The secondary work embrittlement in sheet steels

Increasing requirements for cold forming properties have led to the develop ment of interstitial free (IF) steels. The excellent deep drawability of IF steels results from extra low carbon and nitrogen contents (< 50ppm) in ad dition to titanium and niobium microalloying for stabilising the interstiti al elements. After cold work, a secondary operation may lead to embrittleme nt, often via intergranular fracture. This so called secondary work embritt lement phenomenon has been analysed using several methods. of which the dee p drawing of cups as primary work is the most common method. The influence of impurities on grain boundaries is observed by means of surface analytic tools, e.g. by Auger electron spectroscopy, The main influence is mechanica lly the primary work and the kind of secondary loading, From the metallurgi cal viewpoint, grain boundary weakening elements, especially phosphorus, an d grain boundary strengthening elements, e.g. Boron and free carbon, have a strong effect on secondary work embrittlement.