Raws li kev sib xyaw ua ke ntawm Tensile Residual Stress los ntawm Kos duab thiab Sulfide Inclusion Stringer Length Ua 316 Lub Cua sov Tubing tsis ua haujlwm los ntawm Hydrogen-Induced Cracking hauv Sour Water Service

Hydrogen Embrittlement: Synergistic Effects of Stress thiab Inclusion Morphology

Hydrogen-induced cracking (HIC) yog hom tsis ua hauj lwm rau 316 stainless hlau sheathed hluav taws xob cua sov tub nyob rau hauv cov dej qaub cov kev pab cuam -aqueous ib puag ncig nrog hydrogen sulphide (H2S) concentrations ntau tshaj 10 ppm, feem ntau ntawm oilfield dej kho, geothermal cua sov, thiab refinery txheej txheem. HIC hauv 316 tsis tas yuav tsum tau siv anodic polarisation, tsis zoo li chloride kev nyuaj siab corrosion tawg. HIC tshwm sim thaum atomic hydrogen, tsim los ntawm cov tshuaj tiv thaiv corrosion (Fe + H₂S → FeS + 2H) diffuses rau hauv cov hlau thiab recombines ntawm non{10}}metallic inclusion interfaces, tsim sab hauv siab uas ua rau tawg propagation . Susceptibility rau HIC yog tswj los ntawm ob qhov tsis, qhov loj ntawm tensile residual kev nyuaj siab uas tshwm sim los ntawm raj los yog dabtsi yog khoov thiab qhov ntev thiab orientation ntawm manganese sulphide (MnS) stringer inclusions. HIC pib nyob rau hauv cov dej qaub ntawm 80-100℃ntawm lub lis piam mus rau lub hlis yog hais tias residual tensile stresses surpasses ib ncig ntawm 150 MPa thiab inclusion stringer ntev tshaj 50 µm nyob rau hauv ib tug kev taw qhia perpendicular rau cov kev ntxhov siab. Kab lus no kwv yees cov kev sib txuas tseem ceeb rau HIC tsis ua haujlwm thiab muab cov lus qhia rau cov khoom siv tshwj xeeb rau kev pabcuam qaub.

Hydrogen-Induced Cracking Mechanism ntawm 316 Austenitic Stainless Hlau

316 corrodes rau ferrous sulfide (FeS) thiab atomic hydrogen hauv dej qaub. H2S tshuaj lom cov tshuaj tiv thaiv hydrogen recombination (2H → H2) thiab yog li cov atomic hydrogen nyob ntawm cov hlau saum npoo thiab diffuses rau hauv austenitic lattice. Hydrogen diffuses sai raws li cov ciam teb ntawm grain thiab yog daig ntawm cov tsis yog -metallic inclusions, tshwj xeeb tshaj yog elongated MnS stringers, qhov twg nws yog recombined rau molecular hydrogen. Lub siab sab hauv tuaj yeem siab li 1,000 MPa lossis ntau dua, txaus los ua kom tawg hauv cov matrix ib puag ncig txawm tias tsis muaj kev ntxhov siab sab nraud. Nyob rau hauv lub xub ntiag ntawm ib tug tensile residual kev nyuaj siab, lub pob txha propagates raws lub interface ntawm cov inclusion thiab matrix, txuas cov neeg nyob sib ze inclusions mus rau hauv ib tug nruam nruam channel. Qhov tshwm sim ntawm perforation vim HIC yuav tsum tau coincidence ntawm peb tej yam kev mob: (1) ib qhov chaw ntawm hydrogen (H 2 S concentration saum toj no 10 ppm, pH qis dua 6, los yog ob qho tib si), (2) elongated MnS inclusions orientated perpendicular mus rau lub siab tshaj plaws tensile kev nyuaj siab kev taw qhia, thiab (3) residual tensile kev nyuaj siab saum toj no propximate kev nyuaj siab. 100-150 MPa rau 316).

80℃hauv Sour Water Quantified HIC Initiation Thresholds

Kev soj ntsuam ntawm 316 tubing nrog kev tswj qhov seem ntawm cov kev ntxhov siab thiab ntsuas qhov ntsuas qhov ntev ntawm NACE TM0177 Kev daws A (5% NaCl + 0.5}% acetic acid, sat'd nrog H2S, pH ~ 3.5) tau tsim cov kev sib txuas tseem ceeb rau HIC pib hauv 720 teev (8 hnub).

Residual Tensile Stress (MPa) Maximum MnS Stringer Length (µm) Stringer Orientation Relative to Stress HIC Initiation Time (hours) Crack Depth after 1,000 hours (µm) Time to Perforation (1.5 mm wall) Recommended for Sour Service (H₂S >10 ppm)<50 Any Any No HIC 0 >10 xyoo Yes 50-100<50 No any HIC >10 years 0Yes 50-100 50-100Perpendicular >2,000 <50 >10 xyoo Txais
100-150 <50 Any >2,000 <30 >10 xyoo Txais tau 100-150 50-100 Perpendicular 500-1, 000 50-150 5-10 xyoo Marginal 100-150 100-200 Perpendicular 200-500 150-300 2-5 xyoo Tsis pom zoo
150-200 <50 Any 500-1,000 50-100 5-10 years Marginal 
150-200 50-100 Perpendicular 100-200 200-400 1-3 xyoo Tsis qhia
150-200 100-200 Perpendicular 50-100 400-800 6-18 hli Tsis haum200 50-100 Perpendicular<100 >500 <6 months Not acceptable >200 >100 Perpendicular<50 >800 <3 months Not acceptable
Qhov cuam tshuam ntawm Kev Ua Haujlwm Txias thiab kos duab taw qhia ntawm HIC Susceptibility

Thaum lub sij hawm kev kos duab ntawm 316 tubing, MnS inclusions yog sib npaug zos rau lub raj axis. Qhov siab tshaj plaws tensile residual kev ntxhov siab thaum lub sij hawm kos duab rau lub rhaub dej kub kuj yog axial (raws li lub raj ntev). Yog hais tias cov inclusions yog elongated parallel mus rau lub stressful kev taw qhia, ces qhov tawg yuav tsum propagate raws cov inclusion -matrix interface uas tsis yog perpendicular rau qhov kev nyuaj siab- ua rau tsawg rhiab heev rau HIC. Txawm li cas los xij, kev ua haujlwm dabtsi yog khoov (U-tube creation) tsim cov tensile residual stresses nyob rau hauv lub hoop kev taw qhia ntawm lub sab nraud khoov vojvoog. Tam sim no yog tias daim duab -kev sib koom ua ke yog taw qhia ib txwm rau qhov kev sib tw no, HIC susceptibility yog qhov zoo dua. Cov cua sov yuav tsum tau teev nrog cov raj ncaj qha tshwj xeeb (tsis muaj khoov), lossis nrog khoov kev ntxhov siab tom qab tsim, rau kev pabcuam qaub. Tsis tas li ntawd, steelmaking txheej txheem uas ua rau globular es tsis txhob stringer inclusions (AOD los yog VAR refining raws li tau teev tseg nyob rau hauv tsab xov xwm 24) kuj txwv lub siab tshaj plaws stringer ntev hauv qab no 50 µm, txawm nyob rau tib theem sulfur.

Cov tswv yim tshwj xeeb rau cov cua kub cua sov 316

Rau kev pabcuam hauv cov dej uas muaj H2S ntau tshaj 10 ppm lossis nrog pH qis dua 6.0 ntawm qhov kub thiab txias tshaj 60 degree, cov kev txwv hauv qab no tau pom zoo rau 316 lub tshuab cua sov:

Qhov siab tshaj plaws tensile kev ntxhov siab tom qab txhua qhov kev ua haujlwm: 100 MPa (tsim los ntawm X-ray diffraction lossis los ntawm ASTM G38 U- khoov kuaj tsis muaj qhov tawg tom qab 100 teev hauv NACE TM0177 kua)

Qhov siab tshaj plaws MnS stringer ntev: 50 µm (raws li ASTM E45, txoj kev A, qhov hnyav qis dua lossis sib npaug rau 1.0 rau hom A sulfides)

Qhov siab tshaj plaws sulfur concentration hauv steel: 0.005% (50ppm)

Steelmaking xyaum: AOD refined los yog superior (VAR / ESR nyiam rau cov kev pab cuam tseem ceeb)

Ncej - khoov kev ntxhov siab: 400-450℃rau 1 teev rau txhua qhov khoov vojvoog R / D < 5.0

Hardness: Max 22 HRC (220 HV) rau txo hydrogen absorption

Yog tias ib qho ntawm cov qauv no tsis tuaj yeem ncav cuag, duplex 2205 stainless hlau (uas muaj HIC tiv thaiv ntau dua) lossis Alloy 825 raug pom zoo.

Field Identification ntawm HIC-Induced Failures

Nyob rau hauv HIC hauv 316 lub tshuab cua sov sheaths raug tiaj tus, kauj ruam - cov kab nrib pleb ntse tsim propagating parallel mus rau lub raj axis (yog tias suav nrog axial) lossis circumferential (yog tias hoop kev ntxhov siab ntau dhau). Ntau cov kab nrib pleb sib luag yog qhov raug thiab feem ntau nrog los ntawm blistering ntawm daim tawv nqaij, qhov chaw o nyob qhov twg cov hlau tau distorted los ntawm sab hauv hydrogen siab. Cov pob txha tawg ua rau pom qhov tsis zoo thiab tuaj yeem nthuav tawm "ntses- nplai" lossis " ntaiv" zoo li thaum cov kab nrib pleb tau koom nrog cov hlua uas nyob ib sab. Txoj kev tshawb fawb EDS ntawm cov pob txha tawg qhia pom cov sulfur los ntawm cov thawj MnS suav nrog thiab ntxiv cov sulfur los ntawm cov txheej txheem corrosion. Yog tias cov yam ntxwv no tsis tuaj yeem ua tsis tiav hauv cov cua sov hauv cov dej qaub, ces cov tshuaj chloride SCC lossis pitting yuav tsum tau kuaj xyuas raws li qhov ua tau ua tsis tiav.

Xaus: Kev Tswj Kev Nyuaj Siab thiab suav nrog Morphology rau Sour Service

• For 316 stainless steel encased heaters in sour water service (H2S >10 pH, pH<6, temperature >60 degree), hydrogen-induced cracking tshwm sim thaum tensile residual kev nyuaj siab tshaj 100-150 MPa thiab elongated MnS suav nrog stringers tshaj 50-100 µm nyob rau hauv ntev orientated perpendicular mus rau kev nyuaj siab. Axial residual kev ntxhov siab vim yog kos duab ua ke nrog kev sib luag-rau-axis stringer inclusions tsis tshua muaj teeb meem ntau dua li kev ntxhov siab ntawm hoop residual kev ntxhov siab vim khoov ua rau axially aligned inclusions . 316 sheaths tau teev tseg rau cov kev pabcuam qaub los ntawm cov kws ua haujlwm yuav tsum tswj cov kev ntxhov siab seem (tom qab khoov kev ntxhov siab) thiab suav nrog morphology (OD0 stringing length, low sulp 5). Lub moj khaum uas tau piav qhia ntawm no hais txog qhov kev ntxhov siab seem thiab qhov ntev ntawm kev suav nrog rau lub sijhawm ntsuas HIC pib. Nrog rau lub moj khaum no, tus neeg yuav khoom tuaj yeem xaiv 316 tubing los tiv thaiv hydrogen embrittlement nyob rau hauv cov dej qaub tshaj plaws.