Yuav ua li cas 316 Stainless Hlau Sheath Phab Ntsa Thickness cuam tshuam cov kev ntxhov siab seem tom qab Swaging thiab nws cuam tshuam rau Corrosion Fatigue Lub neej nyob rau hauv Marine Environments?

Corrosion qaug zog yog ib qho tshwj xeeb tsis ua haujlwm rau cov tshuab hluav taws xob immersion heaters teev los ntawm marine engineers rau offshore platforms, shipboard systems thiab coastal industrial nroj tsuag thaum cyclic mechanical load thiab chloride corrosion ua ke. Corrosion qaug zog ua rau tawg pib ntawm ntau qhov kev ntxhov siab amplitudes thiab lub voj voog luv luv dua li kev qaug zog hauv huab cua lossis ntshiab corrosion hauv qhov chaw zoo li qub. Cov residual stresses generated los ntawm swaging (uas compacts lub magnesium oxide rwb thaiv tsev nyob ib ncig ntawm lub resistor hlau) cuam tshuam nrog kev pab cuam stresses thiab leeb los yog retard tawg tsim nyob ntawm seb lawv kos npe rau thiab loj. Tsab ntawv xov xwm no qhia txog qhov cuam tshuam ntawm cov phab ntsa thickness ntawm qhov kev faib tawm ntawm qhov seem ntawm kev ntxhov siab tom qab swaging thiab cov nyhuv ntawm cov residual stresses ntawm corrosion qaug zog lub neej nyob rau hauv ib puag ncig marine.

Tsim cov kev ntxhov siab nyob hauv Swaging ntawm 316 Sheaths
When a 316 stainless steel tube is swaged from a bigger to a smaller diameter around the MgO filled core, a specific pattern of residual stress is induced. Residual stresses on the outside surface of the sheath are compressive due to the inward hammering of the swaging dies on the material, and tensile on the inner surface due to the outward push of the compressed MgO during elastic springback. The amplitude of these residual strains is dependent on the wall thickness compared to the diameter reduction. In the case of a thin-walled sheath with wall thickness below 1.0 mm, the swaging force penetrates almost the entire wall thickness, which leads to strong compressive stresses at the outer surface (often from -200 to -300 MPa) and moderate tensile stresses at the inner surface (from +50 to +100 MPa). For a thick-walled sheath (>1.8 hli) lub zog swaging yog absorbed feem ntau nyob rau hauv txheej txheej thiab loj compressive stresses tsuas yog tsim nyob ze ntawm lub sab nrauv, lub sab hauv txheej tsis cuam tshuam. Lub tensile stresses ntawm lub puab nto kuj raug txo vim yog tsis tiav compaction ntawm MgO. X-ray diffraction kev tshawb fawb ntawm cov kev ntxhov siab nyob hauv swaged 316 sheaths validate qhov kev sib raug zoo. Rau lub 0.9 hli phab ntsa sheath lub nto compressive kev nyuaj siab yog -280 MPa. 1.5 hli phab ntsa sheath yog -180 MPa. 2.0 hli phab ntsa sheath qhia tsuas yog -120 MPa. Lub thinner sheath muaj ntau qhov kev nyuab siab compressive nyob rau sab nrauv qhov twg corrosion qaug zog tawg feem ntau tsim.

Lub luag hauj lwm ntawm Residual Compressive Stress nyob rau hauv Retarding Corrosion Fatigue Crack Initiation
Lub cyclic tensile stress thiab corrosive electrolyte uas muaj chlorides ua rau corrosion qaug zog tawg pib hauv 316 stainless hlau. Qhov tawg pib ntawm qhov chaw nto los yog suav nrog qhov uas cov txheej txheem tiv thaiv tsis tau ua tiav. Yog hais tias qhov seem ntawm compressive kev nyuaj siab nyob rau ntawm qhov chaw, qhov kev siv cyclic tensile kev nyuaj siab yuav tsum kov yeej qhov compression no los tsim net nro ntawm qhov tawg. Qhov no ua rau muaj kev ntxhov siab ntau ntxiv kom pib qhov tawg. Yog hais tias qhov seem seem compression yog -280 MPa, thiab cov kev siv cyclic kev nyuaj siab yog +200 MPa, ces lub vas ntawm qhov chaw yog -80 MPa. Qhov no tseem yog compressive thiab tsis tuaj yeem pib qaug zog tawg. Net nro tsuas yog muaj yog tias qhov kev ntxhov siab cyclic siab dua +280 MPa. Nyob rau hauv kev sib piv, 2.0 hli sheath uas tsuas yog -120 MPa ntawm nto compression yog nyob rau hauv net nro thaum lub thov kev nyuaj siab yog ntau tshaj +120 MPa, ib tug deb ntawm qhov pib. Corrosion fatigue tests hauv cov dej hiav txwv hluavtaws ntawm 60 ° C validate cov nyhuv no. Cov qauv nrog cov phab ntsa tuab ntawm 0.9 hli thiab cov seem seem compression txhawb nqa 10 lab cycles ntawm 250 MPa siv alternating kev ntxhov siab yam tsis muaj qhov pib tawg. Nyob rau tib daim ntawv thov load, cov qauv nrog me ntsis residual compression thiab 2.0 hli phab ntsa thickness ua tsis tau tejyam tom qab 2 lab cycles. Lub thinner sheath yielded tsib zaug ntau dua corrosion qaug zog lub neej txawm tias txo cov phab ntsa tuab.

Ua lag luam-Tawm ntawm Cov Kev Pab Cuam Tshuam Kev Nyuaj Siab thiab Phab Ntsa Thickness Margin
Nyias-walled sheaths muaj qhov zoo ntawm corrosion qaug zog tab sis qhov no yuav tsum sib npaug tiv thaiv cov khoom siv qis dua yuav tsum pib tawg. Lub 0.9 hli sheath nrog ntau qhov seem seem compression tuaj yeem tiv thaiv kev pib tawg rau ntau lab lub voj voog. Txawm li cas los xij, txhua qhov tawg, uas tau kov yeej qhov kev ntxhov siab seem, xws li los ntawm lub qhov dej loj lossis lub sijhawm hloov pauv, tsuas yog 0.9 hli ntawm cov khoom siv los nthuav tawm ua ntej perforation. Lub 2.0 hli sheath nrog tsawg seem compression yuav ua rau ib tug tawg nyob rau hauv tsawg cycles, tab sis lub tawg yuav tsum propagate 2.0 hli los ua tsis ua hauj lwm. Tag nrho lub neej rau kev ua tsis tiav=Kev pib lub neej + Kev nthuav tawm lub neej Corrosion qaug zog kuaj hauv cov dej ntsev ntawm 60 ° C nyob rau hauv ib qho kev sib hloov beam apparatus muab tag nrho cov voj voog hauv qab no kom tsis ua hauj lwm rau 10 hli txheej kab 316 sheaths ntawm 200 MPa alternating stress. Lub 0.8 hli sheath tau txais tag nrho ntawm 12 lab lub voj voog, 11.5 lab rau kev pib thiab 0.5 lab rau kev nthuav tawm. Lub 1.2 hli sheath tiv taus 8 lab lub voj voog, 7 lab rau kev pib thiab 1 lab rau kev nthuav tawm. Lub 1.6 hli sheath tiv taus 5 lab lub voj voog (3 lab rau kev pib thiab 2 lab rau kev nthuav tawm). Lub 2.0 hli sheath khiav rau 3.5 lab cycles, ntawm uas 1.5 lab yog rau pib thiab 2 lab rau propagation. Qhov nyias nyias-walled sheath muaj qhov seem seem ntau tshaj plaws thiab lub neej ntev tshaj plaws, txawm tias qhov kev nthuav tawm me me.

Marine Environment Corrosion Fatigue Life Selection Matrix
Cov lus hauv qab no qhia tau hais tias pom zoo 316 sheath phab ntsa thicknesses rau hluav taws xob immersion heaters nyob rau hauv marine kev pab cuam nyob ntawm kwv yees cyclic stress amplitude thiab tsim nyog kev pab cuam lub neej. Cov txiaj ntsig yog rau kev raug dej hiav txwv tsis tu ncua los yog dej brackish ntawm 30-60 ° C thiab tseem rau cov txheej txheem swaging ib txwm tsis muaj kev tshaj tawm -swage annealing.

Kev Cia Siab Cyclic Stress Amplitude Yuav Tsum Muaj Kev Pabcuam Lub Neej Pom Zoo Pom Zoo 316 Sheath Phab Ntsa Thickness Dominant Failure Mode Design Rationale
Tsawg, qis dua 50 MPaOver 10 xyoo 1.2 - 1.6 mm Corrosion nyob rau hauv crevicesThickness uas tau tsav los ntawm corrosion pub, residual kev nyuaj siab tau txais txiaj ntsig tsawg dua
Nruab Nrab, 50 - 150 MPa 5 - 10 xyoo 1.0 - 1.2 hli Corrosion qaug zog pibThin phab ntsa muab siab seem compression los tiv thaiv kev tawg
Nruab nrab, 50 mus rau 150 Mpa10 xyoo lossis ntau dua 1.4 - 1.6 mm nrog post-swage annealing Propagation los ntawm keeb kwm Annealing txo kom zoo dua los ntawm kev ntxhov siab seem; siv lub thickness
Siab, 150 - 250 MPa 3 - 5 xyoo 0.8 - 1.0 mm Corrosion qaug zog pib Txais kev pab cuam luv luv, qhov siab tshaj qhov seem compression tseem ceeb
High, 150 – 250 MPa>5 xyoo 316 Tsis tauOverload lossis ceev tawg Hloov nrog Incoloy 825 lossis titanium
Kev hloov pauv nrog ntau qhov nyiaj ntau dhauTxhua qhov kev pabcuam lub neej 1.6 - 2.0 mm Propag. tom qab npaj txhij txog crackThickness margin tiv thaiv cov xwm txheej tsis tau pom dua
Nyob rau hauv daim ntawv thov uas cyclic stresses induced los ntawm kev co, thermal expansion cycling los yog siab hloov, nws yog ib qho tseem ceeb kom muaj peev xwm ntsuas los yog kwv yees qhov kev ntxhov siab amplitude. Thaum tsis muaj kev ntsuas, qhov kev ntxhov siab me ntsis ntawm 100 MPa yog qhov ua tau zoo. Hauv cov xwm txheej no, phab ntsa thickness ntawm 1.2 hli muab qhov kev pom zoo ntawm qhov zoo ntawm qhov seem ntawm kev ntxhov siab thiab cov npoo rau kev nthuav tawm. Cov kws tshaj lij yuav tsum xav txog kev pom zoo rau kev tshaj tawm -swage annealing rau tuab-cov ntaub thaiv phab ntsa siv rau hauv siab - daim ntawv thov mus ncig. Annealing ntawm 1050℃tshem tawm tag nrho cov residual stresses thiab yog li cov corrosion fatigue pab ntawm nyias phab ntsa, tab sis kuj lub tensile residual stresses nyob rau hauv lub puab nto uas yuav ua rau tawg propagation. Ib qho annealed 1.6 mm sheath muaj ib tug zoo xws li tag nrho cov qaug zog lub neej mus rau ib tug uas tsis yog -annealed 1.2 mm sheath, muab ib tug alternate txoj kev mus cuag lub neej ntev kev pab cuam yam tsis muaj kev cia siab rau ntawm nyias phab ntsa. Qhov kev xaiv ntawm cov phab ntsa nyias nrog cov kev ntxhov siab ntau dhau los yog cov phab ntsa tuab nrog annealing yog nyob ntawm kev tsim muaj peev xwm thiab tus nqi. Rau feem ntau cov ntawv thov dej hiav txwv uas muaj kev vibration tab sis tsis hnyav, ib txwm swaging yuav muaj kev txhim khu kev txhim khu kev ua haujlwm tsis muaj kev ua haujlwm ntxiv yog tias phab ntsa thickness nyob rau hauv thaj tsam ntawm 1.2 txog 1.4 hli.