A New Evaluation Method of Hydrogen Embrittlement Fracture for High Strength Steel by Local Approach

Abstract

An evaluation method for hydrogen embrittlement (HE) susceptibility for ultra high strength steel was studied. The study showed that the evaluation results obtained by the method were independent of the stress concentration factor and the dimension of the specimen. A commercial 0.40C-0.24Si-0.81Mn-1.03Cr-0.16Mo (mass%) steel with a tensile strength of 1 400 MPa was used. The Local Approach, which was originally used for the evaluation of brittle fracture property, was applied to evaluate the HE susceptibility. The method was modified to consider the effect of hydrogen content to evaluate the HE susceptibility. The critical HE data, which were required in the modified Local Approach, were obtained by the stepwise test in which the stress increasing process and the stress holding process were alternatively repeated until the specimen fractured. The dimensions of the specimen used in the stepwise test consisted of a diameter of 10 mm and a stress concentration factor of 4.9. To evaluate the HE susceptibility for specimens with other dimensions, a critical hydrogen content for failure called Hc, which represents the maximum hydrogen content among the unfracture specimens on the HE test with constant loading, was used. It was found that the HE susceptibility could be evaluated by the modified Local Approach considering hydrogen content distribution in the specimens and that the probability of the HE fracture on the components could be designed by using the evaluation results.

Effect of Uniform Distribution of Fine Cementite on Hydrogen Embrittlement of Low Carbon Martensitic Steel Plates

“…The maximum peak 1 hydrogen content which does not cause hydrogen embrittlement failure is defined as 'critical hydrogen content for hydrogen embrittlement' [Hc]. 3,9) The critical hydrogen content correlates with the tensile strength irrespective of the heating rate to the tempering temperature. The It should be noted that time to fracture also correlates with the tensile strength irrespective of the heating rate to the tempering temperature.…”

Evaluation of Hydrogen Embrittlement for High Strength Steel Sheets

“…Mechanical properties of the steel used. [16][17][18][19][20] иииииииииииииииииииииииииииииииииииииии( 2 )…”

Weibull Model for Hydrogen-induced Fracture of High Strength Steel

“…With focusing on this local approach, a development of a new estimation method of hydrogen-induced unstable fracture in brittle manner has been advanced taking the deterioration of materials due to hydrogen into consideration. 4) This new approach is successful for predicting the occurrence of delayed fracture for components with various stress concentration factors and hydrogen contents, whereas the method for determining the material parameters with respect to hydrogen-induced deterioration of materials has not been necessarily established.…”

“…1,2) Moreover, the methods taking not only the local stress but also the local diffusible hydrogen content in the components into consideration have also been proposed. 3,4) However, for the more accurate evaluation of the time dependent hydrogen-induced fracture with statistical scatter and for transferable evaluation of that dependent on the shape and size of the components and loading condition, a new evaluation model is required to be proposed.…”