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Table 1. Chemical composition of St.20 steel (wt.%)

Table 1 Chemical composition of St.20 steel (wt.%)

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Fig. 1. Position of Charpy specimens and hardness measurements in the in the vicinity of the "window" type, hydrogen damage fractur«
Fig. 1. Position of Charpy specimens and hardness measurements in the in the vicinity of the "window" type, hydrogen damage fractur«
Fig. 2. Variation of the Vickers hardness (HV5) as a function of the distance (x) from the edge of the fracture Mechanical characteristics of material in the vicinity of the "window" type, hydrogen damage fracture indicated < noticeable embrittlement of material. Yield strength (398 MPa) was significantly higher than minimum standarc value (216 MPa - GOST 1050-88), and it is close to the minimum standard value for tensile strength (min. 42( MPa). Tensile strength was 481 MPa, while deformation characteristic, expressed by elongation (A=13.8 %), was much lower than standard recommended one (Ayjn=24 %), which is an indication of a significant increase of! material brittleness.
Fig. 2. Variation of the Vickers hardness (HV5) as a function of the distance (x) from the edge of the fracture Mechanical characteristics of material in the vicinity of the "window" type, hydrogen damage fracture indicated < noticeable embrittlement of material. Yield strength (398 MPa) was significantly higher than minimum standarc value (216 MPa - GOST 1050-88), and it is close to the minimum standard value for tensile strength (min. 42( MPa). Tensile strength was 481 MPa, while deformation characteristic, expressed by elongation (A=13.8 %), was much lower than standard recommended one (Ayjn=24 %), which is an indication of a significant increase of! material brittleness.
Fig. 3. (a) Variation of the impact strength (KC Vor.) and its crack propagation component (KCVp) and crack initiation component (KCV)) of a Charpy specimens, as a function of the specimens hardness (hydrogen concentration); (b-e) SEM fractographs of the fracture surfaces of particular Charpy specimens tested Simultaneous appearance of HELP and HEDE mechanisms is further (1989). The initial dominant activity of HELP is followed by a negligib supported in a model proposed by Jokl et al. e drop in the impact strength (KCV or.) and its component of crack propagation energy (KCVp) and steady value of crack initiation component (KCV)), Fig. 3(a) — hardness: 150-165, and decreases with increasing in hydrogen concentration (hardness). Relatively sudden manifestation of HEDE mechanism, on reaching a critical value of hyd rogen concentration, is followed by a sharp ductile—brittle fracture transition, Fig. 3(a). This drop is not only due to cohesive strength decline, which may not be significant, but also due to a noticeable reduction in the appearance of hydrogen-enhanced local plasticity. Expressed observations are consistent with a model of the simultaneous effects of H ELP and HEDE [Gerberich at al., 2009].
Fig. 3. (a) Variation of the impact strength (KC Vor.) and its crack propagation component (KCVp) and crack initiation component (KCV)) of a Charpy specimens, as a function of the specimens hardness (hydrogen concentration); (b-e) SEM fractographs of the fracture surfaces of particular Charpy specimens tested Simultaneous appearance of HELP and HEDE mechanisms is further (1989). The initial dominant activity of HELP is followed by a negligib supported in a model proposed by Jokl et al. e drop in the impact strength (KCV or.) and its component of crack propagation energy (KCVp) and steady value of crack initiation component (KCV)), Fig. 3(a) — hardness: 150-165, and decreases with increasing in hydrogen concentration (hardness). Relatively sudden manifestation of HEDE mechanism, on reaching a critical value of hyd rogen concentration, is followed by a sharp ductile—brittle fracture transition, Fig. 3(a). This drop is not only due to cohesive strength decline, which may not be significant, but also due to a noticeable reduction in the appearance of hydrogen-enhanced local plasticity. Expressed observations are consistent with a model of the simultaneous effects of H ELP and HEDE [Gerberich at al., 2009].
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Materials EngineeringMetallurgical EngineeringMechanical EngineeringMaterials ScienceMechanical Behavior Of MaterialsHydrogen StorageFracture MechanicsMetallurgical Failure AnalysisMetallurgy and Materials EngineeringBoiler Tube Failure
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