INFLUENCE OF PREHEATING OF SLAB ON PROPERTIES OF 3S SHEET. (Part 3)

EFFECTS OF PREHEATING TEMPERATURE AND IRON CONTENT

Abstract

Synopsis
It was previously reported that a remarkable grain growth and "Orang Peel" by deep drawing take place in the annealed sheet of 3S alloy rolled from un-preheated slab, but the preheating of slab is very effective to prevent these unfavourable defects.
In this paper, the authors further investigated the effects of preheating temperature and iron content on the grain size and the mechanical properties of 3S sheet.
It was found that the very fine grain could be obtained by the final annealing at 450°C in air furnace if its slab were preheated at 550°C or 575°C for 24 hours, but it is not necessary to preheat at higher temperature such as 600°C. When it was preheated at 625°, the more striking grain growth took place rather than that in the case of un-preheated slab.
Furthermore, it was ascertained that the final annealing of 3S sheet rolled from preheated slab should be carried out at higher temperature than 450°C in order to get the finer grain when its content of iron is low as 0.2%.
On the other hand, when its content is comparatively high as 0.6%, its grain became to be fine even at 350°C and very fine at 400-450°C corresponding to the fine grain of 2S sheet.