Optimizing continuous annealing of interstitial-free steels for improving deep drawability

The crystallographic textures and the resulting plastic anisotropy of five interstitial-free (IF) steels with different carbon equivalents and Nb and Ti microalloying content have been investigated. The steels were industrial ly hot rolled, cold rolled, annealed, and finally hot-dip galvanized. An al ternative heat treatment of the cold rolled samples was conducted in labora tory scale using parameters close to those in industry-scale continuous ann ealing lines. The anisotropy parameters were both measured and predicted on the basis of the measured texture data. The calculated values were correct ed by using functions that were fitted to the experimental data. It was fou nd that for a given hot and cold rolling state even minor changes in the an nealing conditions can improve the anisotropy parameter (r) over bar by up to 13 pct. Increase in recrystallization texture and improvement of the res ulting anisotropy parameters are discussed in terms of partial transformati on of ferrite to austenite in the intercritical regime.