API TR 934-F PART 2-2017 Literature Review of Fracture Mechanics Cbased Experimental Data for Internal Hydrogen-assisted Cracking of Vanadium-modified 2 Cr-1Mo Steel (First Edition.pdf

1、Literature Review of Fracture Mechanicsbased Experimental Data for Internal Hydrogen-assisted Cracking of Vanadium-modified2Cr-1Mo SteelAPI TECHNICAL REPORT 934-F, PART 2FIRST EDITION, AUGUST 2017Literature Review of Fracture Mechanicsbased Experimental Data for Internal Hydrogen-assisted Cracking o

2、f Vanadium-modified2Cr-1Mo SteelDownstream SegmentAPI TECHNICAL REPORT 934-F, PART 2FIRST EDITION, AUGUST 2017Prepared under contract for API by:Dr. Richard P. GangloffEmeritus Ferman W. Perry Professor of Materials Science and EngineeringDepartment of Materials Science and EngineeringSchool of Engi

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13、et, NW, Washington, DC 20005.Copyright 2017 American Petroleum InstituteForewordNothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither sh

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17、published annually by API, 1220 L Street, NW, Washington, DC 20005.Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, DC 20005, standardsapi.org.iiiContentsPage1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1 Initial Experimentation;

19、19852000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2 Improved Experimental Characterization of IHAC; 2000present. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182.3 Hydrogen Solubility, Diffusivity, and Tra

20、pping in V-modified Cr-Mo Steel . . . . . . . . . . . . . . . . . . . . . . . . . 262.4 Hydrogen Embrittlement of Cr-Mo and Cr-Mo-V Steels in H2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34vExecutive SummaryLiterature data colle

22、ctively suggest that V-modified 2Cr-1Mo base plate and weld metal each exhibit improved resistance to Internal Hydrogen-assisted Cracking (IHAC) compared to modern 2Cr-1Mo steel, where each steel is typified by modern-low J-factor or low XB, and thus minimal temper embrittlement. IHAC in petrochemic

23、al applications typically involves H charging of the steel during elevated temperature exposure in high-pressure H2, followed by stressing at near-ambient temperatures. For V-modified Cr-Mo, the slow-rising-displacement threshold stress intensity (KIH) is a significant fraction of the H-free plane s

24、train fracture toughness; however, V-modified steels are not immune to IHAC for this conservatively aggressive loading mode. This good IHAC resistance is attributed to beneficial H interaction with nano-scale vanadium carbide trap sites, but the details of this complex H trapping behavior are neithe

25、r quantified nor fully understood. No single study of IHAC in 2Cr-1Mo-0.25V base plate or weld metal is sufficiently comprehensive and quantitative to support fracture-mechanics modeling of pressure vessel fitness for service or a minimum pressurization temperature. Uncertainties in the existing dat

26、a base are associated with:a) the challenge in detecting KIHin the midst of substantial crack tip plastic deformation; b) slow crack growth rates typical of reversible H-trap interaction; c) the lack of experimental results for very slow loading rates, weld metal, and stressing temperatures from -25

27、 C to 200 C; d) demonstration of H retention during an IHAC experiment; e) lack of understanding of the fundamental mechanism by which H trapping at VXCYprecipitates reduces susceptibility to IHAC; and f) the effect of low-temperature H charging. All KIHdata for conventional and V-modified Cr-Mo ste

28、el reflect H charging followed by rising-displacement loading in moist air. A novel-deleterious interaction of IHAC and Hydrogen Environment-assisted Cracking (HEAC) for stressing of H precharged specimens in H2may occur, but is not supported by sufficient published data for Cr-Mo and Cr-Mo-V steels

29、. H precharging, with stressing in moist air, or stressing in high-pressure H2, without H precharging, are both capable of producing substantial H embrittlement in conventional Cr-Mo steel. Preliminary data show that V-modified Cr-Mo (without H precharging) is susceptible to HEAC in high-pressure H2

30、, conforming with the behavior of other low- to moderate-strength alloy steels, and apparently less affected by H trapping at vanadium carbides. KIHvalues for uncharged 2Cr-1Mo-0.25V base plate stressed in high-pressure H2are substantially less than the thresholds typical of IHAC. The HEAC susceptib

31、ility of V-modified Cr-Mo should be considered in pressure vessel fitness-for-service modeling. The ongoing laboratory study, commissioned by API Task Group 934F on Heavy Wall Pressure Vessel MPT, is addressing these uncertainties for 2Cr-1Mo-0.25V weld metal and base plate. Literature results obtai

32、ned after about 2002 are sufficiently accurate and detailed to provide important comparisons with these newly emerging laboratory data. The result will be a strong characterization of the IHAC susceptibility of V-modified Cr-Mo steels.Literature Review of Fracture Mechanicsbased Experimental Data fo

33、r Internal Hydrogen-assisted Cracking of Vanadium-modified 21/4Cr-1Mo Steel 1 Background Between 1980 and 1990, researchers in Japan, France, and the United States determined that bainitic 2Cr-1Mo steels (UNS K21590) exhibited unexpectedly low-threshold K stress intensity levels (KIH) for the onset

34、of Internal Hydrogen Assisted Cracking (IHAC). Much of this work was sponsored by the American Petroleum Institute and the Materials Properties Council (MPC). Such cracking was observed for compact tension specimens that were fatigue precracked, precharged with atomic hydrogen (H) through elevated t

35、emperature exposure in high pressure H2, and stressed under slow-rising crack mouth opening displacement (CMOD). The threshold for IHAC under static displacement loading was very high, as is expected for this moderate-strength steel. While this class of Cr-Mo pressure vessel steels is clearly suscep

36、tible to significant IHAC under these conditions, initial data were uncertain for several reasons: lack of a standardized experimental method; detection of the onset of crack growth during rising CMOD was not rigorous; plasticity during loading complicated crack-growth detection and elastic stress i

37、ntensity factor analysis; variables including actual loading rate in terms of dK/dt and H loss during testing were either not controlled or not reported; high variability in KIHmeasurement both for a single laboratory and across groups; the mechanism for the deleterious effect of rising CMOD on IHAC

38、 was not elucidated; and much of this work was presented as hard copy associated with API-MPC committee presentations, or in conference proceedings, and was not published in peer-reviewed journals. Between 1994 and 2000, a joint industry program (JIP) was conducted, including five laboratories in Ja

39、pan, France, and the United States, to develop a rigorous-standard test method for measurement of KIH, as well as crack-growth rate (da/dt) versus elastic-plastic stress intensity (KJ) and the threshold for the arrest of IHAC (KTH) 1,2. This method was then applied to develop a strong data base for

40、IHAC of 12 heats of 2Cr-1Mo base plate and weld metal, with impurity composition (and degree of temper embrittlement) being a primary variable, as well as retained H concentration and applied dK/dt 2. Figure 1 provides a collection of results from this work, plotted as KIHversus total-dissolved H co

41、ncentration for several low-impurity (J-factor 150 55 0.43 0.22 0.07 / 4.2 4.4 2.25Cr-1Mo-V treat. B ref. gaseous 231 221 257 248 124 131 232 227 / 150 0.25 0.18 / 4.4 A516 gde70 ref. NACE 163 11 301 26 492 75 195 51 / 50 0.85 0.06 / 1.1 SE 500 ref. NACE 378 35 615 63 791 133 297 90 / 80 0.85 0.13 /

42、 1.1 Figure 11 (after Coudreuse et al. 12) Figures 11 and 12 demonstrate that the threshold stress intensity for the onset of IHAC is much higher for the V-modified steel, which is precharged at elevated temperature in H2, compared to conventional Cr-Mo base plate. For the Cr-Mo base plate, both KIH

43、and the J-R curve for the H-charged case are substantially lowered compared to that characteristic of the V-modified steel. In fact, H cracking in the V-modified steel shows essentially identical first-initiation “toughnesses” with and without H charging. The J-R curve is lowered somewhat by H prech

44、arging for the 2Cr-1Mo-0.25V steel. This enhanced threshold is in spite of the fact that the measured-bulk H concentration for this constant charging condition was almost twice as high for 2Cr-1Mo-0.25V, consistent with the data shown in Figure 4. This result is tempered by the fact that a single, r

45、elatively rapid dK/dt was employed and the precharged H concentration was moderate (4 wppm). LITERATURE REVIEW OF FRACTURE MECHANICSBASED EXPERIMENTAL DATA FOR INTERNAL HYDROGEN-ASSISTED CRACKING OF VANADIUM-MODIFIED 21/4CR-1MO STEEL 13 Figure 12 (after Coudreuse et al. 12; replotted in 16) Coudreus

46、e et al. examined the effect of the loading rate on IHAC in Cr-Mo-V steel, with the results presented in Figure 13 for crack mouth opening displacement rates of 0.005, 0.05, and 0.5 mm/min for the V-modified steel 12. These three grip-displacement rates correspond to initial-applied dK/dt levels of

47、48, 480, and 4,800 MPam/h (0.013, 0.13, and 1.3 MPam/s). The extensive results shown in Figure 14 for conventional Cr-Mo steel establish that KIHis loading rateindependent for dK/dt up to 0.4 MPam/s and perhaps higher (equivalent to an approximate dCMOD/dt value of 0.15 mm/min shown by the vertical

48、arrow in Figure 13) 2. However, since the mobility of H in the V-modified steel is 100 or more times slower compared to Cr-Mo, the loading rates examined by Coudreuse et al. (Figure 13) may not be sufficiently slow to adequately characterize the IHAC resistance of this steel. 14 API TECHNICAL REPORT

49、 934-F, PART 2 Figure 13 (after Coudreuse et al. 12; replotted in 16) Figure 14 (after Gangloff 2) LITERATURE REVIEW OF FRACTURE MECHANICSBASED EXPERIMENTAL DATA FOR INTERNAL HYDROGEN-ASSISTED CRACKING OF VANADIUM-MODIFIED 21/4CR-1MO STEEL 15 This study by Coudreuse and co-workers is notable in that the effect of the H charging source and charging temperature was investigated 12,15,16. As tabulated in Figure 11, and plotted in Figures 15 and 16, H precharging in NACE solution at 23 C promoted IHAC in this heat of 2Cr-1Mo-0.25