Study of Reheat Cracking in Weldment (Report 2) : Relation Between Cracking Susceptibility and Some Properties of HAZ at High Temperature

概要

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Occurrence of reheat cracking is promoted by the presence of elements which show a precipitation hardening phenomenon. It might be natural to consider that the secondary hardening phenomenon, during stress relief heat treatment, is a factor controlling the tendency of the cracking behaviours. Investigations have shown that Nb-Mo type 80kg/mm^2 class high tensile strength steel-precipitation hardening steelhas very low susceptibility to the cracking comparing to T-1 type steel. Therefore it is necessary to reconsider the relations between cracking susceptibility and secondary hardening phenomenon. In this study, this phenomenon was examined by measuring the hardness and strength at high temperature of HAZ. The conclusions obtained from the investigation were as follows ; (1) There is no relationship between the secondary precipitation hardening and the susceptibility to the cracking. (2) When the strength of HAZ at high temperature is high, the susceptibility to the cracking is low and when the strength is low, the susceptibility is high. Boundary strength of HAZ at high temperature is one of the main factors influencing the cracking.
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