Cov ntsiab lus Inclusions li cas (raws li ntsuas los ntawm ASTM E45, Hom A Vs. Hom C) Hauv Qib 2 Titanium Rhaub Tube Correlate Nrog Cov Pitting Ceev Hauv A 0.5% Bromine Solution Ntawm 50 degree?
Tso lus
In Grade 2 titanium, inclusions-primarily Ti₂Fe particles-act as pitting initiation sites. ASTM E45 classifies inclusions by type: Type A (sulfides, rare in titanium), Type B (aluminates), Type C (silicates), and Type D (globular oxides). In titanium, iron-rich inclusions (Type D) are most common and most detrimental. Higher inclusion content correlates directly with higher pitting density in bromine solutions at 50°C. A severe inclusion rating (E45 rating >2) ua rau pitting ceev 5-10 npaug ntau dua li cov khoom siv huv (E45 ntsuam xyuas<1). The correlation follows a power law, with pitting density approximately proportional to the inclusion density raised to the 0.7 power.
Lub Mechanism of Inclusion-Induced Pitting in Bromine Solutions
Hauv 0.5% bromine (Br₂) ntawm 50 degree, cov tshuaj yog oxidizing tab sis tsis muaj zog passivating. Cov cathodic Ti₂Fe cov khoom tsim cov galvanic hlwb nrog cov titanium matrix nyob ib puag ncig. Lub titanium matrix dhau los ua lub anode thiab yaj hauv zos ntawm cov particle-matrix interface. Thaum lub qhov pib pib, bromine (ib qho muaj zog oxidizer) tsav kev nthuav tawm sai. Lub qhov tob tob nce linearly nrog lub sijhawm. Kev suav nrog loj dua 2 µm tshwj xeeb yog kev puas tsuaj vim lawv tsim cov khub niam txiv loj dua. Cov kev sib koom ua ke ua ke tsim cov kab sib tshooj sib tshooj, tsim cov pits loj.
Quantitative Pitting Density raws li Kev Ua Haujlwm ntawm Kev Ntsuas Kev Ntsuas
Kev tswj xyuas hauv 0.5% Br₂ ntawm 50℃tshaj 500 teev tau tsim cov pitting ceev hauv qab no rau Qib 2 titanium raj nrog ntau yam ASTM E45 suav nrog kev ntsuas. Rau kev suav nrog hauv qab 0.5 (ntxuav huv heev, lub tshuab nqus tsev arc remelted), Ti₂Fe particle ntom yog qis dua 50 particles ib mm², pitting ceev yog 5-20 pits ib cm², thiab qhov siab tshaj qhov tob yog 20-50 µm. Rau qhov ntsuas ntawm 0.5-1.0 (huv), particle ntom yog 50-150 ib mm², pitting ceev yog 20-60 pits ib cm², thiab lub qhov tob yog 40-100 µm. Rau qhov ntsuas ntawm 1.0-1.5 (nruab nrab), particle ntom yog 150-300 ib mm², pitting ceev yog 50-150 pits ib cm², thiab lub qhov tob yog 80-180 µm. Rau qhov ntsuas ntawm 1.5-2.0 (nruab nrab mus rau hnyav), particle ntom yog 300-600 ib mm², pitting ceev yog 100-300 pits ib cm², thiab lub qhov tob yog 120-250 µm. For a rating above 2.0 (heavy), the particle density exceeds 600 per mm², the pitting density is 200–500 pits per cm², and the pit depth is 200–400 µm.
Inclusion Type thiab Pitting Severity
Ntau hom kev suav nrog muaj qhov sib txawv pitting hnyav. Hom A suav nrog (sulfides) tsis tshua muaj nyob hauv titanium thiab tsis tshua muaj pitting hnyav (qhov txheeb ze qhov hnyav 0.2). Hom B (aluminates) kuj tsis tshua muaj thiab muaj qhov hnyav (0.3). Hom C (silicates) tshwm sim qee zaus los ntawm crucible contamination thiab muaj mob hnyav (0.6). Hom D (globular oxides, feem ntau Ti₂Fe) muaj nyob rau qib 2 titanium thiab muaj qhov hnyav (1.0). Tag nrho pitting ceev yog kwv yees li ntawm cov nyiaj tau los ntawm txhua hom kev suav nrog qhov hnyav los ntawm nws qhov hnyav.
Inclusion Control Guide for Bromine Service
Cov lus hauv qab no muab qhov siab tshaj plaws tso cai ASTM E45 suav nrog kev ntsuas thiab qhov ntom ntom rau Qib 2 titanium rhaub cov raj hauv 0.5% bromine ntawm 50 degree, raws li qhov xav tau pitting ceev thiab kev pabcuam lub neej.
| Desired Pitting Ceev (pits / cm²) tshaj 5,000 teev | Qhov siab tshaj plaws ASTM E45 Inclusion Rating | Maximum Ti₂Fe Particle Density (particles / mm²) | Pom zoo Melting xyaum | Qhov siab tshaj plaws qhov siab (µm) |
|---|---|---|---|---|
| <20 | <0.5 | <50 | VAR (nqus arc remelted) | 20–50 |
| 20–50 | <1.0 | 50–150 | Ob chav VAR | 40–100 |
| 50–100 | <1.5 | 150–300 | Ib leeg VAR + cov khoom noj kom huv | 80–180 |
| 100–200 | <2.0 | 300–600 | Ib leeg VAR | 120–250 |
| >200 | >2.0 | >600 | Tsis pom zoo rau kev pabcuam Br₂ | >200 |
Engineering Beyond Inclusion Control
Qib titanium cuam tshuam rau tus cwj pwm pitting. Qib 7 (palladium-stabilized) muaj cov ntsiab lus zoo sib xws rau Qib 2 tab sis lub palladium hloov pauv tus cwj pwm galvanic, txo qis pitting ntom ntawm 50-70% rau tib qhov kev faib tawm. Qib 1 muaj cov ntsiab lus hlau qis (0.08% max) thiab feem ntau tsawg dua Ti₂Fe suav nrog. Phab ntsa thickness muab lub qhov nkag nkag; 2.0 hli phab ntsa nrog 100 µm pits muaj 95% ntawm nws phab ntsa. Lub raj nto tiav cuam tshuam rau qhov pib pib; electropolishing tshem tawm cov txheej txheej nyias, nthuav tawm tsawg dua kev suav. Hydrogen annealing ntawm 700℃tuaj yeem spheroidize Ti₂Fe hais, txo lawv cov nam piv thiab pitting hnyav.
Ua ib qho kev qhia tshwj xeeb
Rau lub titanium rhaub raj hauv 0.5% bromine ntawm 50 degree, qhia ib qho ASTM E45 suav nrog qhov ntsuas tsawg dua 1.0 (huv). Yuav tsum tau muab ob npaug rau lub tshuab nqus tsev arc remelted (VAR) kom ua tiav cov ntsiab lus qis. Thov kuaj metallographic ntawm tus neeg sawv cev ntawm tus qauv ntawm 500 × magnification, nrog ntawv pov thawj tias Ti₂Fe particle ntom yog qis dua 150 particles ib mm² thiab hais tias tsis muaj particles tshaj 5 µm inch. Rau cov ntawv thov tseem ceeb, qhia Qib 1 titanium lossis Qib 7 titanium. Thaum lub sij hawm tuaj xyuas, ua ib qho kev sim pitting ceev los ntawm immersing tus qauv daim coupon nyob rau hauv 0.5% Br₂ ntawm 50℃rau 168 teev thiab tshuaj xyuas nyob rau hauv 50 × magnification; tsis lees txais qhov ntau yog tias qhov pitting ceev tshaj 50 pits ib cm². Los ntawm kev tswj cov ntsiab lus suav nrog raws li qhov tsis zoo, tus kws ua haujlwm txo qis pitting ceev hauv kev pabcuam bromine.
