Effect of Residual Stress and Strain-Induced α′-Martensite on Delayed Cracking of Metastable Austenitic Stainless Steels

Papula, Suvi; Talonen, Juho; Hänninen, Hannu

doi:10.1007/s11661-013-2090-3

Cited by 31 publications

(40 citation statements)

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“…According to our earlier study, residual stresses in Swift cups of a stable austenitic stainless steel were markedly lower. 10) Tangential residual stresses in α'-martensite and austenite phases of the test materials, measured with X-ray diffraction from the Swift cups at drawing ratio 1.8, are presented in Figs. 3(a)-3(c).…”

Section: Resultsmentioning

confidence: 99%

“…On the contrary, steel 301 was highly susceptible to delayed cracking. Although the presence of α'-martensite is necessary for delayed cracking to occur, 10) there was no direct correlation between the volume fraction of α'-martensite and cracking susceptibility. During deep drawing, substantial residual stresses were introduced in the studied stainless steels due to inhomogeneous distribution of plastic strain and the martensitic transformation.…”

Section: Discussionmentioning

confidence: 99%

“…The effect of residual stress on the magnetic properties (Villari effect) was taken into account by correction factors experimentally defined for each material. 10) Residual stresses in deep-drawn cups were measured with X-ray diffraction, by the sin 2 Ψ (multi-angle) method, using XStress3000 diffractometer. The measurements were done separately for each phase, employing Cr-Kα -radiation for the α'-martensite phase and Mn-Kα -radiation for the austenite phase.…”

Section: Methodsmentioning

confidence: 99%

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Delayed Cracking of Metastable Austenitic Stainless Steels after Deep Drawing

et al. 2015

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Delayed Cracking of Metastable Austenitic Stainless Steels after Deep Drawing

et al. 2015

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“…It was selected as a test material because it allows studies of delayed cracking in a practicable time scale. According to Swift cup forming tests, the limiting drawing ratio of 204Cu steel with respect to delayed cracking is very low, and cracks appear in the deep drawn cups already with drawing ratio of 1.5 . Crack initiation in the Swift cups of this material occurs relatively shortly within a few hours from deep drawing.…”

Section: Methodsmentioning

confidence: 96%

“…In this study, the kinetics of delayed cracking phenomenon is studied in a low‐Ni austenitic stainless steel 204Cu, which is a material very prone to this type of cracking, using a specially designed constant load tensile testing arrangement. The effect of applied stress, α′‐martensite content and hydrogen content are systematically examined and their relative importance is discussed.…”

Section: Introductionmentioning

confidence: 99%

Delayed cracking of low‐nickel austenitic stainless steel studied with constant load tensile testing

Papula

Talonen

Hänninen

2015

Fatigue Fract Eng Mat Struct

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A B S T R A C T Delayed cracking in unstable low-Ni austenitic stainless steel 204Cu was studied by constant load tensile testing. The developed testing arrangement enabled a systematical examination on the effect of applied stress, strain-induced α′-martensite and internal hydrogen content on time to fracture. Volume fraction of strain-induced α′-martensite was shown to affect cracking kinetics, except at a very high stress level. Hydrogen content had a marked effect on time to fracture, also at the highest applied stress level. When hydrogen content was reduced by annealing, delayed cracking kinetics and susceptibility were suppressed, and cracking required a considerably higher stress level. The apparent critical hydrogen content, below which delayed cracking was not observed, was about 0.85 wppm. According to scanning electron microscope and electron backscattering diffraction examination, fracture mechanism in the constant load test specimens was mainly transgranular quasi-cleavage, and cracking propagated along α′-martensite.Keywords constant load testing; hydrogen; hydrogen-induced delayed cracking; stainless steel; strain-induced α′-martensite; stress ratio.N O M E N C L A T U R E EBSD = electron backscattering diffraction LDR = limiting drawing ratio SFE = stacking fault energy TDS = thermal desorption spectroscopy I N T R O D U C T I O NDelayed cracking can occur in formed metallic components under static stress, applied or residual, below the yield strength of the material. It is a problem concerning high-strength steels and also some metastable austenitic stainless steels. Cracks may appear in successfully formed components after days or even months from forming, such as deep drawing. Metastable austenitic stainless steels, in which austenite is partly transformed to martensite under plastic strain, possess an excellent combination of strength and elongation, as the formation of strain-induced martensite increases work hardening of the material. Because of their high energy-absorbing capacity, metastable austenitic stainless steels have become attractive materials to be used, for example, in automotive crash-relevant structures. Nickel accounts for a significant percentage of the raw material cost of conventional austenitic stainless steels.Therefore, low-Ni austenitic stainless steels, in which nickel alloying is partly substituted with manganese and nitrogen, have become increasingly popular. They exhibit as good or even better mechanical properties than their nickel-alloyed counterparts, but are generally more susceptible to delayed cracking than the Fe-Cr-Ni austenitic stainless steels, if they experience strain-induced martensitic transformation during forming. This has been one of the important factors limiting increasing use of low-Ni austenitic stainless steels in many potential applications. Delayed cracking of metastable austenitic stainless steels is related to coexistence of solute hydrogen, straininduced α′-martensite and residual tensile stresses. 1-3 Crack initiation and growth are cont...

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Effect of Inclusions and Precipitates on Hydrogen Embrittlement of Mn‐Alloyed Austenitic Stainless Steels

Pulkkinen

Papula

Todoshchenko

et al. 2013

steel research int.

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The aim of this study was to characterize the inclusions and precipitates of the six austenitic stainless steel test materials by the INCA analysis program as well as to examine the capability of inclusions and precipitates to act as hydrogen traps by utilizing the thermal desorption spectroscopy (TDS). Especially, the hydrogen trapping capability of nano‐sized Nb‐precipitates of the steel 204Cu/Nb was of interest. On the INCA results it was noticed that the average sizes of the inclusions as well as the distribution and the amount of the oxide inclusions were about the same in all test materials. In comparison to the other grades, the distribution of inclusions and precipitates was significantly different in the niobium‐alloyed 204Cu/Nb steel containing a large number of small micro‐ and nano‐sized niobium precipitates. In the TDS study, it was observed that the TDS spectra of 201B, 204Cu, and 204Cu/Nb were similar, although the inclusion and precipitation distribution of these steels differs considerably between the materials. Thus, it was assumed that the nano‐sized Nb‐precipitates or other inclusions were not able to trap sufficiently hydrogen to their interface, which would result in a better resistance against delayed cracking.

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Effect of Residual Stress and Strain-Induced α′-Martensite on Delayed Cracking of Metastable Austenitic Stainless Steels

Cited by 31 publications

References 28 publications

Delayed Cracking of Metastable Austenitic Stainless Steels after Deep Drawing

Delayed Cracking of Metastable Austenitic Stainless Steels after Deep Drawing

Delayed cracking of low‐nickel austenitic stainless steel studied with constant load tensile testing

Effect of Inclusions and Precipitates on Hydrogen Embrittlement of Mn‐Alloyed Austenitic Stainless Steels

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