Author :
Najafi- Zadeh, A.,Jonas, J.,Yue, S
Abstract :
Multipass torsion tests were used to investigate the warm-rolling behavior of three interstitial free (IF) steels containing Ti and/or Nb. All the tests were carried out at a strain rate of 2s . and the samples were water-quenched immediately after particular passes. Whereas the finishing passes were always executed in the single-phase ferrite region, the roughing passes were applied either in the austenite phase (hot/warm-rolling) or in the ferrite region (warm/warm-rolling). In the former case, the temperature of the first roughing pass was 1260 C, while it was 850 C for the warm/warm method. It is shown that dynamic recrystalization occurs to a degree that depends on the composition of the steel and the finishing temperature. Although the finish-rolling loads for warm-rolling (in the ferrite region) are no higher than for conventional strip-rolling in the austenite region, the ultrafine ferrite grain sizes of 1 to 2 m that are produced by warm-rolling are an order of magnitude finer than those resulting from conventional processing .
