Abstract
In this investigation the various notch-fracture toughness values were studied and evaluated for the electron beam (EB)-weld metals of structural high strength steels (HT50 and 80) by means of deep notch, crack opening displacement (COD) and Charpy impact tests, and furthermore the mutual relations between them were discussed.
The remarkable conclusions are as follows.
(1) The notch-fracture toughness of EB-weld metals showed lower value than that for base metal in general, and it tended to be lowered with an increase of weld heat input regardless of the difference in the method of notch toughness test.
(2) The peculiar phenomenons that the fracture path of test specimen differs at a specific testing temperature were commonly observed in all notch toughness tests adopted in this investigation, especially in the narrow-fused and hardenable EB-weld metal of 10 KJ/cm weld heat input. In general such specific temperature was called “Fracture path transition temperature, TF” in this report.
(3) The toughness values of EB-weld metal were distinctly affected by the difference in fracture path of specimen in Charpy impact test, however they have no relation with such “fracture path transition” in deep notch and COD tests.
(4) The fracture toughness for the EB-weld metal of HT80 steel is in general superior to that for HT50 weld metal from the results for three types of toughness test adopted. Especially it showed higher value than the toughness for conventional arc weld metal in deep notch and COD tests.
