Abstract
With eight varieties of samples taken from the hot-rolled high carbon steel strips containing 0.47-1.38% carbon, the effect of annealing temperature and the holding time on their hardness and structure was studied.
1) There was found a distinct relationship between the hardness and the structure, and when the structure was spheroidized the hardness value became minimum.
2) In hyper-eutectoid steels, the temperature to develop the minimum hardness was higher as the carbon content increased. And the minimum hardness value obtained was almost invariable being independent from the holding time.
3) In eutectoid and hypo-eutectoid steels, the temperature to develop the minimum hardness was lower as the holding time increased and the minimum hardness value obtained became low as the holding time increased.
4) The temperature to develop the minimum hardness value in each holding time was enhanced as the carbon content increased.
