Nyob rau hauv dab tsi tshwj xeeb kev sib xyaw ntawm Residual Stress los ntawm dabtsi yog khoov (R / D=2) thiab Hydrogen Charging tam sim no ceev nyob rau hauv Cathodically tiv thaiv Seawater ntawm 15℃Puas yog 316L rhaub Sheath tsim qeeb Hydrogen Cracking Tom qab 5 xyoos
Tso lus
Hydrogen embrittlement risk nyob rau hauv marine cathodic tiv thaiv systems: Ntev -lub sij hawm xav txog
The residual tensile stress associated with manufacturing (especially bends) coupled with hydrogen charging from the cathodic protection (CP) system may lead to delayed hydrogen cracking (DHC) after long service (5 + years). 316L stainless steel sheathed electric heating tubes installed in seawater with CP-such as on offshore platforms, shipboard heaters, or coastal structures. At the bend outer radius (R/D = 2), residual tensile stresses usually range from 200-400 MPa (60-120% of yield). Hydrogen evolution occurs at cathodic protection potentials of -900 to -1,050 mV vs. Ag/AgCl. The hydrogen charging current density (iH) is related to the CP current density. No DHC occurs after 5 years at a critical i H of around 0.5-1.0 mA/cm 2 (CP potential of about -950 to -1,000 mV at 15°C). CP ≈ -1,000 to -1,050 mV) after 3-5 years. DHC is initiated at iH = 1-2 mA/cm2 Cracking is seen after 1-2 years for i_H >3 mA/cm 2 (CP < -1,050 mV). Daim ntawv no kwv yees qhov pib ua ke ntawm cov kev ntxhov siab seem thiab hydrogen them tam sim no ceev rau 5-xyoo DHC-dawb lub neej hauv 316L.
Rephrase kab lus
Rov qab mus rau qhov qub kab lus
Luam kab lus
Tsis muaj tswv yim
Mechanism ntawm ncua hydrogen cracking induced los ntawm residual kev nyuaj siab
Hydrogen txo qis lub zog cohesive ntawm cov ciam teb nplej thiab ua kom yooj yim quasi -cleavage fracture. Lub sijhawm tawg ntawm qhov pib incubation yog inversely proportional rau cov ntsiab lus hydrogen thiab rau kev siv kev ntxhov siab. Tom qab incubation (hli mus rau xyoo), tawg pib thiab propagates rau perforation.
DHC 5 xyoo Residual Stress -Charging Tam sim no Thresholds Quantified
Lub sijhawm pib DHC hauv qab no tau txiav txim siab los ntawm kev tswj hwm cathodic them ntawm 316L U- khoov cov qauv (khoov rau R / D=2, sab nrauv fiber ntau ≈ 8-10%, residual stress ≈ 250-350 MPa) hauv cov dej hiav txwv hluavtaws (15℃CP 0, vary ae 8) siv tam sim no pH mus txog 5 xyoos (43,800 teev).
Applied CP Potential (mV versus Ag/AgCl) Hydrogen Charging Current Density (mA/cm2) Residual Stress at Khoov Outer Radius (MPa) DHC Initiation Lub Sijhawm (xyoo) Lub Sijhawm Ua Haujlwm Tom Qab Pib (xyoo) 5-Xyoo Failure Risk Tag Nrho Kev Pom Zoo rau 30 / 5-Xyoo<0.1 <200 >10 >10 None Yes -900 to -950 0.1-0.5 200-300 >10 >10 Tsis muaj Yes Xus
-950 rau -1, 000 0.5-1.0 250-350 5-10 2-5 Tsawg OK
-1,000 rau -1,025 1.0-1.5 300-350 3-5 1-3 Nruab nrab Marginal
Tsis pom zoo heev Tsis muaj (316L tsis haum)
Khoov residual stress cuam tshuam los ntawm kev ua haujlwm txias ua ntej
Kev ua haujlwm txias ua ntej hauv cov tubing ua rau muaj kev ntxhov siab ntau ntxiv hauv kev khoov.
Kev Ua Haujlwm Txias Ua Ntej ntawm Txoj Kev Ncaj Ncees (%) Kev Nyuaj Siab Ntawm R/D=2 Khoov Sab Nraud Sab Nraud (MPa) Pom Zoo Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij rau 5 Xyoo Lub Neej (mV vs. Ag/AgCl) Tsis muaj 10-20 250-300 -98030 350-450 -900
