Yuav ua li cas Intermetallic Ti₂Fe Particle Loj Distribution nyob rau qib 2 Titanium rhaub Tube Correlate nrog rau qhov ntom ntawm pits nyob rau hauv kub Aluminium Sulfate tov ntawm 80 degree?

In the Grade 2 titanium, iron is present as an impurity up to 0.20–0.30 wt% and forms intermetallic Ti2Fe particles. These particles are cathodic against the surrounding alpha-titanium matrix. In hot aluminum sulfate (Al2(SO4)3) solution at 80°C-commonly used in water treatment and paper manufacturing-the cathodic Ti2Fe particles form galvanic cells. These galvanic cells initiate pitting at the particle-matrix interface. The size distribution of these particles (number per unit area, average and maximum diameter) is closely correlated to the pitting density. greater pit densities are achieved by larger particles (>5 µm) and greater particle densities (>500 particles/mm²). Cov khoom me me < 2 µm thiab qis dua < 200 particles / mm2 qhia qhov qis dua pitting susceptibility kom lub neej ntawm lub rhaub yog foreseeable.

Mechanism ntawm Ti2Fe-induced Pitting nyob rau hauv Aluminium Sulfate

Lub galvanic tam sim no ntom ntom rau Ti2Fe particle ntawm ntug ntawm ib qho particle yog 10-100 μA / cm2, uas yog txaus los yaj cov titanium matrix uas nyob ib sab. Kub aluminium sulphate ntawm 80℃muab cov yeeb yaj kiab uas tsis muaj zog. Thaum pib lub qhov, qhov siab ntawm sulfate thiab kub kub pab qhov nthuav dav ntawm lub qhov. Pit density has a power law relationship with particle density: pit density ≈ 0.1 (particle density)0.7. Nws yog ib qho tseem ceeb rau kev tswj hwm kev faib tawm ntawm Ti$_2$ Fe hais los ntawm kev xaiv cov khoom tsim nyog thiab kev kho cua sov kom pitting yuav raug kwv yees thiab txo qis hauv kev pabcuam txhuas sulfate. cov khoom ntau dua ua rau cov khub niam txiv galvanic ntau dua thiab ua rau lub qhov pib nrawm dua.

Quantitative Correlation ntawm Pitting Ceev thiab Particles

Tswj kev tshawb nrhiav metallographic thiab kev kuaj corrosion ntawm 10% Al 2 (SO 4) 3 ntawm 80℃rau 500 teev tau qhia cov kev sib raug zoo hauv qab no rau Qib 2 titanium raj. Cov qauv nrog Ti 2 Fe particle ntom<100 particles per mm 2 and average particle size <2 µm show pitting densities of 5-20 pits per cm 2 with maximum pit depths of 20-50 µm. This is a good performance for 5 years or longer with 1.5 mm wall thickness. Particle density of 100 to 300 particles/mm2 and average size of 2 to 4 μm produces pitting density of 30 to 80 pits/cm2 and pit depths of 50 to 120 μm, which is marginal for 2 to 3 years of service. 300–600 particles per square millimeter with a size of 3–5 µm result in a pitting density of 100–250 pits per square centimeter and depths of 100–200 µm, which are considered a high pitting risk. But any density above 600 particles per square millimeter with particle sizes larger than 5 µm leads to a pitting density bigger than 300 pits per square centimeter and depths bigger than 200 µm, which is not acceptable for any long term service.

Cov nyhuv ntawm cov ntsiab lus hlau thiab kev kho cua sov ntawm Particle Distribution

Kev faib tawm ntawm Ti2Fe hais yog tswj los ntawm cov hlau concentration thiab thermal ua keeb kwm. Qib 1 titanium, tov annealed (700 degree, dej quench), nrog 0.05-0.08 wt% hlau, muaj particle ntom ntawm tsawg dua 50 particles / mm2 thiab particle loj ntawm tsawg dua 1 µm. Qib 2 nrog 0.12 wt% hlau hauv lub zeb-annealed xeev (700 degree, cua txias) nthuav tawm qhov ceev ntawm 80-150 particles ib mm2 thiab qhov loj ntawm 1-2 µm. Hom Qib 2 nrog 0.20 wt% hlau hauv lub zeb-annealed mob muaj qhov ceev ntawm 200-400 particles/mm2 thiab qhov loj ntawm 2-4 mm. High-hlau Qib 2 (0.25 wt%) nyob rau hauv cov xwm txheej raws li kos mus txog qhov ceev ntawm 400-700 particles / mm2 thiab qhov loj ntawm 3-6 μm. Beta annealing (qeeb txias los ntawm saum toj 900 degree) txawm tias txo qhov ntom ntom tsim qhov tseem ceeb pitting qhov chaw ntawm coarse hais 5-10 µm.

Kev Pabcuam Aluminium Sulfate Haum Particle Distribution

Cov lus hauv qab no qhia tau hais tias qhov siab tshaj plaws particle tsis tau ntawm Ti2Fe rau Qib 2 titanium hlab hauv 10% aluminium sulfate ntawm 80℃rau lub neej kev pab cuam thiab qhov siab tshaj plaws qhov tob.

Kev Pabcuam Lub Neej (xyoo) Max Qhov tob (mm) Max Ti2Fe Particle Density (particles / mm2) Max Qhov Nruab Nrab Qhov Loj (µm) Kev pom zoo kho cua sov
5 0.15 <150 <2 Solution annealed (700°C, water quench)
5 0.30 150-250 2-3 Mill annealed (700 deg C, cua txias)
3 0.30 250–400 3–4 Mill annealed + pickled 2 0.50 400–600 4–5 As-kos (tsis pom zoo)<1 >0.50 >600 >5 Tsis tsim nyog rau Qib 2 Engineering Beyond Particle Distribution Control

Qib titanium tuaj yeem raug xaiv los tshem tawm Ti2Fe cov khoom kom tiav. Txoj kev daws teeb meem -annealed xeev nrog cov ntsiab lus hlau tsawg dua 0.08 wt% rau Qib 1 qhia qhov qis tshaj pitting ceev. Qib 7 (palladium-stabilized) yog piv rau Qib 2 hauv cov ntsiab lus hlau, tab sis tus cwj pwm galvanic tau hloov, txo qhov ntom ntawm pitting los ntawm 50-70% rau tib qhov sib txawv. Hauv qib 12, molybdenum thiab npib tsib xee yog tam sim no uas tsim cov intermetallic sib txawv uas tsis tshua muaj cathodic dua Ti 2 Fe. Lub phab ntsa tuab tso cai rau lub qhov nkag mus rau qhov siab ntev . 2.0 hli thickness nrog nruab nrab pitting (80 pits / cm^2, 100 µm tob) tuaj yeem kav 5-8 xyoo, 1.2 hli thickness tsis ua ntej. Nto tiav cuam tshuam rau qhov pib. Electropolishing tshem tawm cov txheej txheej saum npoo uas muaj nyob hauv Ti2Fe hais, txo cov khoom siv zoo.

Paub Specification

Rau qib 2 titanium rhaub hauv kub aluminium sulfate tov ntawm 80 degree, qhia qhov siab tshaj plaws hlau concentration ntawm 0.15 wt% thiab tov -annealed mob (700℃± 10 degree, dej quench). Metallographic tshuaj xyuas ntawm ib qho piv txwv ntawm 500 × magnification. Daim ntawv pov thawj tias Ti₂Fe particle ntom yog tsawg dua 250 particles ib square millimeter thiab tsis muaj qhov loj dua 5 microns hauv txoj kab uas hla. Rau cov ntawv thov tseem ceeb uas pitting tsis tuaj yeem tso cai, siv Qib 1 titanium lossis Qib 7 titanium. Kev soj ntsuam tuaj. Rapid Pitting Test. Submerge tus qauv daim coupon hauv 10% Al2 (SO4) 3 ntawm 80℃rau 168 teev thiab tshuaj xyuas hauv qab 50 × magnification. Tshem tawm ntau yog tias qhov tob tob tshaj 50 pits ib square centimeter. Tus kws tshaj lij tswj xyuas qhov loj me me ntawm Ti 2 Fe raws li qhov ntsuas tsis zoo kom txo qis pitting ceev thiab kom paub tseeb tias qhov ntsuas kub ntawm lub neej hauv kub aluminium sulfate siv.