Estimation of Cracking Susceptibility of Nodular Graphite Cast Iron by the Implant Test : Study on the Weld Cracking of Nodular Graphite Cast Iron (Report 1)

概要

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A study on the cracking susceptibility of nodular graphite cast iron by means of the implant test at different heat inputs is described. Most of the implant specimens were 6 mm in diameter and made without notching. Weld heat inputs, with the use of 4 mm diameter DFCNiFe type electrode (55%AV£V), were changed as 1.8, 2.1 and 2.4 kJ/mm with 1.67 mm/sec travel speed and 50 mm bead length. After welding, when the temperature of the HAZ cooled to about 673K, the load was applied. The implant specimens were fractured at about 373K, which was below the Ms temperature of I he cast iron used. In the heat input range of the present study, when the heat input was increased, the lower critical stress of fracture slightly increased; but it went up to only below one half of the strength of the base metal. The implant specimens were fractured at the part of the martensite structure wit/ the highest micro-vickers hardness number, about 900. The fracture surface consisted of mainly intergranular fracture with partly quasi-cleavge fracture mode.
社団法人溶接学会の論文
1986-04-01