Study of Reheat Cracking in Weldment (Report 1) : Investigations on Testing Methods, Some Characteristics and Factors Contributing to Susceptibility of Reheat Cracking

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Some problems arise when post weld heat treatment is applied, namely toughness and strength decrement, reheat cracking especially in weldment of high tensile steel. This report describes testing method to evaluate the cracking susceptibilities and some characteristics of the cracking. The results obtained are as follows : 1) Cracking susceptibilities can be evaluated quantitatively, easily and precisely by newly developed testing methods. 2) At the tip of crack, voids are observed and some coalesce becoming a small crack. These voids exist on gain boundary which is perpendicular to stress axis and they are round type. 3) The cracking is affected by the existence of notch. There is no effect of heating rate in generally used range and cracks begin to grow at about 550℃. 4) There is tendency that susceptibility decreases with higher preheat temperature and lower strength electrode. 5) Alloying elements, V, Cu, Cr, Mo, Nb and C are unfavourable. But onty Mn is favourable.
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