Effects of Working under Cooling upon the Properties of Heat-Affected Zone of High Tension Steel (Ist Report)

On Hardness Mainly

Abstract

From the experimental rerults that the applied stress in cooling of steel promotes the Ar' transformation, it was investigated what are the effects of tensille stress under cooling upon the synthetic heat-affected zone of 80 kg/mm² high tension steel. The results may be summarized as follows.
(i) It was shown that hardness decreased considerably when the stress was applied in the cooling process of Ar' transformation range and its decreasion rate rose in proportion to the stress. For example, when the stress was 19.6 kg/mm², the hardness decreased by the amount of Hv 60.
On the other hand, the stress applied in austenite range had little effect on hardness.
(ii) Stress applied in Ar' transformation range resulted in an increase of elongation and re-duction of area of HAZ accompanied by a decrease of hardness and the formation of ferrite aad bainite was observed to be by the stress.