Optimization of the strain aging resistance in aluminum killed steels produced by continuous annealing

The influence of manganese, boron and carbon content and of the coiling temperature on the strain aging resistance of continuous annealed Al killed steels was investigated, using five different steel compositions and three coiling temperatures. The material was produced and processed in laboratory and the continuous annealing cycle was performed using a thermomechanical simulation machine. In boron added steels, it was found that the coiling temperature has no influence on the strain aging resistance. On the other hand, in boron free steels of similar composition, coiling temperatures equal to or higher than 720 °C were required to reduce the amount of nitrogen in solid solution at room temperature after the overaging treatment and thus to increase the aging resistance. However, an increase in the Mn content of the boron free steels produced the same results observed in boron added steels. This effect is discussed in terms of the influence of the Mn content on the kinetics of AlN precipitation in these steels.