Preheating Effect on the Critical Rupture Stress of Nodular Graphite Cast Iron Welds : Study on the Weld Cracking of Nodular Graphite Cast Iron (Report 2)

概要

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This paper describes the preheating effect for preventing cracking of heat-affected zone of nodular graphite cast iron (FCD 500) by means of the implant cracking test. The apparatus for the test, dimensions of the smoothed test specimens and DFC NiFe (55%Ni-Fe) electrodes used for the present study are the same as in the first report. Weld heat input is 21, 000 Joules/cm. When preheating temperature was made higher, the critical rupture stress of the cracking increased : It amounted to about 90% of the tensile strength of base metal with preheating at 573K and 723K, while it showed only about a half of that strength without preheating. In case of preheating at 573K and 723K, the implant specimens were fractured in the unmixed zone which had ledeburite structure. By studying the CCT diagram of cast iron used for the present work, the critical cooling time from 1073K to 773K, was found to be about twelve seconds, when the troostite structure appeared at the partially melted zone and true heat-affected zone. In the present work, this condition was obtained with prcheating at 573K.
社団法人溶接学会の論文
1991-04-01