ナンコウ ノ バウシンガ コウカ ト カコウ コウカ (ヤキナマシザイ ト ツブジョウカザイ ノ ヒカク)

For the purpose of examining of the effect of microstructure on the Bauschinger effect and the relation between the Bauschinger effect and the work hardening, experiments were carried out on a mild steel in tension-compression and reverse torsion tests. The annealed steel is composed of the alternate layers of ferrites and pearlites along the rolling axis, which is called the ferrite band structure. The pearlites of specimen are spheroidized and dispersed uniformiy in the ferrite matrix by tempering. The influence of the distribution of second phase particles on the development of the Bauschinger effect was examined on comparing the reverse loading curves of the annealed and the spheroidized. The transient softening of the Bauschinger effect in the annealed steel is larger in reverse torsion than in tension-compression. On the other hand, the Bauschinger effect in the spheroidized steel is much the same in both cases. Hence the ferrite band structure has an effect on the development of the Bauschinger effect. As it can be considered that the work hardening of spheroidized steel depends on the dispersed cementites, the dispersion hardening theory proposed by Fisher et.al. applies to the experimental results and the quantitative relation between the Bauschinger effect and the work hardening is obtained. It was shown that the permanent softening of the Bauschinger effect corresponds to the work hardening