Effect of Nonmetallic Inclusions on Hydrogen Assisted Cracking

概要

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Laboratory heats of HSLA steel containing different volume fractions of MnS inclusions have been investigated. Three-point bending test has been performed using hydrogen charged specimens in order to determine the critical stress intensity (K_<TH>) and the crack propagation rate for hydrogen assisted cracking (HAC). The suppressive effect of inclusions on the HAC initiation and propagation was found. Hydrogen diffusivity diminished with an increase in inclusions. Hence, it is concluded that the reduction of hydrogen concentration at the crack tip and the delay of hydrogen diffusion to the crack tip due to hydrogen trapping of inclusions account for the above effects of inclusions on HAC. Weld cold cracking is a kind of HAC which occurs principally in heat affected zone. Inclusions can, therefore, influence the sensibility to weld cold cracking. Thus weld cold cracking test has been performed using a modified implant test. The critical stress for crack initiation rose with the sulphur and the inclusion content of steels.
社団法人溶接学会の論文
1988-04-01