1. Commercially Pure (CP) Titanium Qib 3 thiab 4 yog txhais los ntawm lawv cov pa oxygen thiab hlau ntxiv. Cov ntsiab lus interstitial no txhais tau li cas ncaj qha rau lawv cov khoom siv kho tshuab, thiab dab tsi yog qhov kev lag luam tseem ceeb ntawm - tawm ntawm lub zog siab dua thiab kev tsim khoom?
Cov khoom siv hluav taws xob ntawm Kev Lag Luam Pure (CP) Titanium yog tswj hwm tsis yog los ntawm kev sib xyaw ua ke hauv kev txiav txim siab ib txwm muaj, tab sis los ntawm kev sib xyaw ntawm cov ntsiab lus sib txawv - feem ntau Oxygen (O) thiab thib ob Iron (Fe). Cov atoms me me no haum rau hauv qhov chaw nruab nrab ntawm cov titanium atoms loj dua hauv cov iav siv lead ua, tsim cov lattice strain.
Qib 3 (UNS R50500): Muaj cov pa oxygen thiab hlau qis dua. Nws suav hais tias yog qhov nruab nrab -lub zog CP titanium.
Qib 4 (UNS R50700): Muaj cov ntsiab lus siab tshaj plaws ntawm cov pa oxygen thiab hlau ntawm CP qib, ua rau nws muaj zog tshaj plaws.
Direct Translation rau Mechanical Properties:
Cov ntsiab lus interstitial nce ntxiv ua raws li cov khoom muaj zog - kev daws teeb meem. Raws li cov pa oxygen thiab hlau nce los ntawm Gr3 mus rau Gr4:
Tensile thiab Yield Strength nce: Lub lattice strain tshwm sim los ntawm interstitials impedes lub zog ntawm dislocations (tsis xws luag nyob rau hauv lub crystal qauv), ua rau nws nyuaj rau cov hlau deform plastically. Qhov no ua rau muaj zog dua.
Ductility thiab Fracture Toughness Txo: Qhov no yog kev lag luam tseem ceeb -tawm. Tib lub lattice strain uas muab lub zog kuj txo cov khoom muaj peev xwm ua rau cov yas deformation ua ntej tawg. Yog li ntawd, Qib 4 muaj lub zog ntau dua tab sis qis dua ductility (elongation) thiab cuam tshuam toughness piv rau Qib 3.
Fabricability Trade-tawm:
Qhov kev txo qis hauv ductility cuam tshuam ncaj qha rau fabricability:
Qib 3 yog kev zam txim ntau dua rau kev khoov txias, flaring, thiab lwm yam kev ua haujlwm. Nws cov ductility siab dua tso cai rau nws tiv taus ntau deformation yam tsis muaj cracking.
Qib 4, thaum tseem tsim tau, yuav tsum tau ceev faj ntau dua thaum tsim khoom. Cov txheej txheem zoo li kev khoov txias yuav xav tau qhov khoov radii loj dua, thiab muaj kev pheej hmoo siab dua ntawm kev tawg thaum ua haujlwm cov khoom hnyav. Nws feem ntau tau txais txiaj ntsig los ntawm cov txheej txheem kub sib sau rau cov duab nyuaj.
Hauv cov ntsiab lus: Xaiv Qib 3 rau cov ntawv thov uas xav tau kev tsim kho kom zoo thiab muaj zog; xaiv Qib 4 thaum xav tau lub zog siab tshaj plaws los ntawm CP titanium thiab cov txheej txheem tsim khoom tuaj yeem ua kom haum nws qhov qis dua.
2. Rau cov kav dej txias dej hiav txwv, CP Titanium (Gr2/Gr3) feem ntau xaiv los ntawm cov hlau tsis muaj steel. Dab tsi yog cov cuab yeej siv hluav taws xob tseem ceeb uas ua rau titanium zoo tiv thaiv pitting thiab crevice corrosion hauv chlorides, txawm tias qhov kub siab?
Cov cuab yeej tseem ceeb yog titanium tsis tshua muaj siab ua haujlwm rau hauv zos corrosion, uas tau tsav los ntawm qhov xwm txheej ntawm nws cov yeeb yaj kiab passive.
Cov zaj duab xis Passive: Thaum raug huab cua los yog noo noo, titanium tam sim ntawd tsim ib tug ntom, adherent, thiab nruam tiv thaiv txheej ntawm Titanium Dioxide (TiO₂). Cov oxide zaj duab xis no tshwj xeeb ruaj khov thiab tsis yooj yim soluble hauv ntau qhov chaw, suav nrog chloride- nplua nuj brines.
Kev puas tsuaj muaj peev xwm (Pitting Potential): Hauv cov ntsiab lus electrochemical, txhua cov hlau muaj tus yam ntxwv "pitting peev" (E_pit) nyob rau hauv ib puag ncig muab. Pitting corrosion pib thaum lub peev xwm siv tau tshaj qhov nqi no. Titanium lub peev xwm pitting nyob rau hauv cov tshuaj chloride yog siab heev, feem ntau saum lub peev xwm rau decomposition dej (oxygen evolution). Qhov no txhais tau hais tias nyob rau hauv feem ntau cov tswv yim, aerated seawater daim ntaub ntawv, lub electrochemical muaj peev xwm yeej tsis ncav cuag ib theem siab txaus los rhuav tshem TiO₂ zaj duab xis.
Repassivation: Txawm hais tias cov yeeb yaj kiab raug puas tsuaj (piv txwv li, los ntawm khawb lossis abrasive particle), nws hloov kho yuav luag tam sim ntawd nyob rau hauv lub xub ntiag ntawm dej los yog huab cua, kho qhov ua txhaum cai ua ntej muaj kev cuam tshuam loj tuaj yeem tshwm sim.
Qhov kev coj cwj pwm no zoo sib xws nrog cov hlau tsis muaj steel. Thaum cov hlau tsis muaj steel kuj tsim ib zaj duab xis passive (Cr₂O₃), nws muaj kev cuam tshuam los ntawm cov tshuaj chloride ions ntawm qhov qis dua, ua rau pitting thiab crevice corrosion, tshwj xeeb tshaj yog nyob rau hauv sov, stagnation seawater. Titanium's impervious oxide zaj duab xis ua rau nws "mus- mus" cov khoom siv rau kev pabcuam dej hiav txwv, cov khoom siv hluav taws xob, thiab cov ntawv thov nyob sab ntug dej uas cov hlau tsis huv yuav ua tsis tiav.
3. Ti-6Al-4V (Qib 5) piping yog teev rau siab -siab aerospace systems. Ob -theem microstructural Cheebtsam yog dab tsi (alpha thiab beta), thiab qhov microstructure no muab lub zog-rau-hnyav piv thiab qaug zog piv rau qib CP li cas?
Qib 5 yog ib qho alpha-beta alloy, txhais tau tias nws cov microstructure ntawm chav tsev kub muaj qhov sib xyaw ntawm ob theem:
Alpha ( ) Theem: Lub hexagonal kaw -packed (HCP) siv lead ua qauv. Cov theem no ruaj khov, muab kev nkag siab zoo, thiab txiav txim siab cov alloy lub hauv paus zog thiab corrosion kuj.
Beta ( ) Phase: Lub cev -centered cubic (BCC) crystal structure. Cov theem no muab kev txhim kho ductility, formability, thiab, qhov tseem ceeb, muaj peev xwm ntxiv dag zog rau cov hlau los ntawm kev kho cua sov.
Superior Strength - rau - Qhov hnyav piv:
Qhov sib ntxiv ntawm 6% Txhuas (ib qho alpha stabilizer) thiab 4% Vanadium (ib qho beta stabilizer) tsim cov tshuaj muaj zog ntau dua li qhov sib xyaw ua kom muaj zog hauv CP titanium.
Qhov tseem ceeb tshaj, Qib 5 tuaj yeem ua kom sov-kho (kev daws teeb meem thiab hnub nyoog). Cov txheej txheem no precipitates fine particles ntawm lub alpha theem nyob rau hauv lub beta theem matrix, tsim immense sab hauv obstacles rau dislocation txav. Cov nag lossis daus no tuaj yeem txhawb nqa lub zog tensile ntawm Qib 5 mus rau ntau dua 1000 MPa, piv rau qhov siab tshaj plaws ntawm ~ 550 MPa rau Qib 4 CP titanium.
Qhov kev loj hlob ntawm lub zog tseem ceeb no tau ua tiav nrog tsuas yog qhov tsawg kawg nkaus ntawm qhov ceev. Qhov tshwm sim muaj zog - rau - qhov hnyav piv yog qhov siab tshaj plaws ntawm peb qib, ua rau nws zoo tagnrho rau qhov hnyav - qhov tseem ceeb ntawm aerospace hydraulic kab thiab roj tshuab.
Enhanced Fatigue Performance:
Kev qaug zog tsis ua haujlwm tshwm sim los ntawm cyclic loading. Qhov zoo, dispersed ob -theem microstructure ntawm lub tshav kub kom zoo- kho Qib 5 yeeb nkab yog qhov zoo heev ntawm:
Kev ntes micro- tawg: Qhov cuam tshuam ntawm cov theem alpha thiab beta tuaj yeem ua rau tsis pom lossis nres qhov tawg tawg.
Kev faib tawm kev ntxhov siab: Kev sib xyaw ua ke ntawm lub zog muaj zog, nkig ntau dua (alpha) nrog lub zog, ntau dua ductile theem (beta) tsim kom muaj kev sib xyaw ua ke -zoo li cov qauv uas zoo dua tiv thaiv kev ntxhov siab.
CP titanium, nrog rau nws ib zaug -theem (tag nrho alpha) microstructure, muaj kev qaug zog zoo tab sis tsis tuaj yeem ua kom zoo, zoo -grained alpha-beta qauv ntawm Qib 5 rau qhov xav tau siab tshaj plaws - daim ntawv thov kev qaug zog.
4. Vuam yog ib qho tseem ceeb ntawm kev sib koom ua ke rau titanium piping. Dab tsi yog qhov tseem ceeb tshaj plaws uas yuav tsum tau ua thaum lub sij hawm vuam ntawm txhua qib titanium, thiab dab tsi tshwj xeeb tshwm sim yog tias qhov yuav tsum tau ua tsis tau?
Qhov tseem ceeb tshaj plaws uas yuav tsum tau muaj yog kev siv qhov nruj heev thiab siab -purity inert gas shielding system los tiv thaiv lub pas dej molten weld thiab cov cua sov uas nyob ib sab- cuam tshuam cheeb tsam (HAZ) los ntawm huab cua paug.
Titanium muaj kev sib raug zoo heev rau cov pa oxygen, nitrogen, thiab hydrogen, tshwj xeeb tshaj yog nyob rau qhov kub siab tshaj 500℃(930℃F). Yog tias tsis muaj kev tiv thaiv, nws yuav nkag siab nqus cov ntsiab lus ntawm huab cua.
Qhov tshwj xeeb tsis xws luag: Embrittlement
Kev nqus ntawm cov ntsiab lus interstitial no ua rau muaj kev cuam tshuam loj heev ntawm kev sib koom ua ke, uas tshwm sim raws li:
Oxygen thiab Nitrogen Contamination: Cov ntsiab lus no dissolve interstitially nyob rau hauv titanium lattice, ua rau kom muaj zog thiab muaj kev puas tsuaj loj ntawm ductility thiab toughness. Cov hlau vuam thiab cov HAZ tsis muaj xim (uas zoo li xiav, ntshav, lossis dawb) ua tawv thiab tawv.
Hydrogen Contamination: Hydrogen tuaj yeem ua rau tsim cov nkig hydrides nyob rau hauv lub microstructure, ntxiv txo cov pob txha toughness thiab muaj peev xwm ua rau ncua sij hawm Cracking los yog hnub tom qab vuam.
Kev tiv thaiv kev tiv thaiv:
Qhov no yuav tsum muaj kev tiv thaiv kev tiv thaiv kom nruj dua li cov hlau tsis muaj steel:
Primary Shielding: High -purity Argon (los yog Helium / Argon mix) los ntawm vuam teeb.
Trailing Shielding: Lub sijhawm ntev ntawm cov pa roj inert tshaj qhov kub, ua kom cov hlua khi kom ruaj khov kom txog thaum nws txias hauv qab ~ 400 degree.
Back Purging: Sab hauv ntawm cov yeeb nkab yuav tsum tau purged nrog argon los tiv thaiv cov hauv paus hniav ntawm oxidizing. Lub purity ntawm cov huab cua sab hauv feem ntau raug txheeb xyuas nrog lub ntsuas pa oxygen ua ntej vuam pib.
Ib qho kev sib txuas uas qhia tau tias muaj kev hloov xim dhau ntawm lub teeb straw xim yog suav tias muaj feem cuam tshuam thiab tuaj yeem raug tsis lees paub, vim tias cov xim tsis zoo qhia txog kev tsim oxide thiab cov khoom sib txuam.
5. Hauv kev lag luam kev lag luam tshuaj, kev txiav txim siab yuav tsum tau txiav txim siab ntawm CP Qib 4 thiab Qib 5 cov kav dej los tuav cov dej kub, oxidizing acid. Dab tsi yog qhov tseem ceeb ntawm cov khoom tiv thaiv corrosion sib txawv ntawm ob, thiab vim li cas cov qib "tsis muaj zog" CP yog qhov kev xaiv zoo dua?
Cov cuab yeej tseem ceeb sib txawv yog qhov kev tiv thaiv corrosion dav dav hauv oxidizing media, thiab Kev Lag Luam Pure (CP) titanium feem ntau ua tau zoo dua qib 5 hauv cov cheeb tsam tshwj xeeb.
Qhov laj thawj: Galvanic Corrosion hauv Microstructure
CP Titanium (Qib 1-4): Muaj ib theem (alpha) microstructure. Nws yog homogeneous, nrog rau tag nrho cov nplej muaj tib lub peev xwm electrochemical. Qhov no homogeneity txhawb cov tsim ntawm ib tug uniform, ruaj khov TiO₂ passive zaj duab xis.
Qib 5 (Ti-6Al-4V): Muaj ob-phase (alpha-beta) microstructure. Cov theem alpha thiab beta muaj cov tshuaj sib txawv me ntsis thiab, yog li ntawd, me ntsis txawv electrochemical muaj peev xwm. Qhov no tsim muaj kev pheej hmoo ntawm micro-galvanic corrosion nyob rau hauv weld HAZ los yog hauv paus hlau nyob rau hauv tej yam kev mob.
Nyob rau hauv lub zog oxidizing acid (xws li, nitric acid, chromic acid), lub peev xwm yog tsav mus rau ib cheeb tsam uas TiO₂ zaj duab xis yog ruaj khov. Rau homogeneous CP titanium, qhov no ua rau zoo heev, tsis sib xws passivity. Txawm li cas los xij, hauv Qib 5, qhov tsawg dua - theem beta muaj txiaj ntsig tuaj yeem raug xaiv tawm tsam ntawm alpha- beta ciam teb, ua rau muaj kev cuam tshuam zoo dua. Cov txhuas hauv Qib 5 kuj tuaj yeem txo nws cov corrosion kuj hauv qee cov alkalis.
Yog vim li cas qhov "tsis muaj zog" CP Qib feem ntau yog qhov kev xaiv zoo dua:
Thaum Qib 5 muaj zog dua, nws lub zog tsis yog ib txwm yog qhov yuav tsum tau ua rau cov yeeb nkab nyob ruaj ruaj. Rau cov txheej txheem tshuaj yeeb dej caw tuav kub, oxidizing acids, qhov kev txhawj xeeb tseem ceeb yog kev tiv thaiv corrosion tsis zoo thiab ntev - lub sij hawm kev ncaj ncees. CP Qib 4 muab cov cuab yeej muaj zog txaus rau feem ntau cov ntawv siv kav dej thiab muaj kev ua tau zoo dua, muaj peev xwm ua tau zoo dua, thiab txhim khu kev tiv thaiv corrosion nyob rau hauv cov cheeb tsam tshwj xeeb vim nws cov microstructural homogeneity.
Kev Taw Qhia Kev Xaiv: Rau qhov tsis yog -oxidizing lossis txo cov kua qaub, ob qho tib si yuav ua tau tsis zoo. Tab sis rau oxidizing ib puag ncig, CP Qib 4 feem ntau yog qhov corrosion ntau dua -resistant thiab yog li kev xaiv zoo dua. Qib 5 yog tshwj tseg rau cov ntawv thov uas nws lub zog zoo tshaj - rau - qhov hnyav piv thiab qaug zog ua haujlwm yog qhov tsim nyog, xws li hauv siab - siab lossis vibrating systems, muab nws cov kev ua tau zoo corrosion hauv cov txheej txheem tshwj xeeb raug txheeb xyuas.
