2007 Volume 47 Issue 3 Pages 486-492
The effect of aluminum content during the annealing of interstitial free high strength steel (IF-HSS) containing Mn, P, Ti and Nb was investigated. The resulting mechanical properties were evaluated and recorded. The results showed that a super formable high strength IF steel with an r-value equal to or higher than 2.3 can be obtained by Al additions. One of the interesting observations of this investigation was the change of precipitation behavior with aluminum content. Aluminum has the effect of improving the formability, especially the drawability, of the IF-HSS when more than 0.10 wt% Al is added. Texture analysis showed that the ‹111›//ND fiber (γ-fiber) was intensified, and ‹110›//RD (α-fiber) was weakened, with an increase of aluminum content. These benefits appear to result from the change of precipitation behavior with the increase of aluminum content. It was confirmed thorough the SANS analysis that the size of the precipitates in the sample with higher aluminum content was larger and their number was much fewer than in the sample with lower aluminum content. It appears that the high aluminum in IF-HSS containing Mn, P, Ti and Nb strengthened the scavenging effect of Ti or Nb and thus purifies the iron matrix.