Effect of cold-rolling reductions on planar anisotropy of r-value in cold-rolled high carbon steel sheets

The effect of cold-rolling reductions on the recrystallization texture and planar anisotropy of the r-value (Delta r) in JIS S35C high carbon cold-rolled steel sheets was investigated. When the microstructure contained coarse cementite prior to cold rolling, Delta r was large regardless of the cold-rolling reduction ratio. In particular, Delta r showed its maximum value at 50% cold-rolling reduction with a secondary annealing temperature of 953 K. This is attributed to strong development of 1101 grains, which correspond to the recrystallization texture in the secondary annealing process and are an impediment to planar anisotropy, thereby reducing Delta r. Growth of these {110} grains reached its maximum with 50% cold-rolling reduction. Formation of {110} grains originated in the high dislocation density surrounding cementite grains. The dislocation density was high around coarse cementite. On the other hand, when the microstructure contained fine spheroidized cementite prior to cold rolling, nucleation of {110} grains was extremely slight at 30% and 70% cold-rolling reduction, resulting in minimum values of Delta r. Because dislocation was homogeneously distributed over the matrix by the fine homogeneous cementite distribution, the dislocation density around cementite grains was reduced. As a result, it is thought that these dislocations did not act as nucleation sites for 110 grains.