Hauv Pickling Kab Siv Mixed HNO₃-HF Acids ntawm 50℃, Yuav Tsum Tau Txais Titanium Qib 2 Cov Cuab Yeej Cua Sov Ntau npaum li cas yuav raug tshuaj xyuas rau Intergranular Attack Tom qab 5000 Sijhawm Ua Haujlwm?
Tso lus
Mixed nitric -hydrofluoric acid daws yog siv nyob rau hauv stainless hlau thiab titanium alloy pickling kab kom tshem tawm oxide nplai thiab deg impurities. Cov qauv tsim muaj xws li 10-20% HNO3 thiab 1-5% HF ntawm 40-60 degree. Titanium Qib 2 feem ntau yog siv rau lub tshuab tso cua sov hauv cov kab no vim nws tsim cov txheej txheem tsis zoo hauv nitric acid. Tab sis lub xub ntiag ntawm hydrofluoric acid (HF) pib hloov cov txheej txheem ntawm corrosion. HF tawm tsam titanium los ntawm dissolving cov zaj duab xis passive li soluble hexafluorotitanate (TiF6 2- ). HF tuaj yeem tua cov ciam teb ua rau muaj kev sib tsoo (IGA). Tsis zoo li kev xeb tsis sib xws, IGA tau ua raws li cov ciam teb nrog cov kev hloov pauv me ntsis ntawm qhov chaw kom txog thaum cov nplej raug txiav thiab poob. Raws li qhov ntsuas IGA nkag mus tom qab 5,000 teev ntawm kev pabcuam hauv cov kab sib xyaw HNO3-HF pickling, daim ntawv tshaj tawm cov sijhawm tshuaj xyuas rau Qib 2 titanium rhaub raj.
Mechanism of Grain Boundary Attack hauv HF-muaj Acids
Mixed HNO3-HF acids yog oxidizing thiab feem ntau yuav passivate titanium tab sis HF tsim ib tug compound nrog titanium ions thiab tiv thaiv zaj duab xis tsim. Corrosion mechanism hloov mus rau active dissolution. Tus nqi ntawm kev sib cais nce ntawm cov ciam teb nplej vim yog cov hauv qab no: cais cov impurities (hlau, carbon, oxygen) ntawm cov ciam teb; nce strain zog ntawm grain ciam teb; thiab nyiam tawm tsam ntawm cov kev taw qhia crystallographic.
Rau Qib 2 titanium (kev lag luam ntshiab, cov ntsiab lus tsis tshua muaj alloying), cov qoob loo ciam teb yog me ntsis ntau dua li cov nplej sab hauv. Tus nqi ntawm grain ciam sib cais yog 3-10 npaug ntau dua li qhov dav dav corrosion ntawm 50℃thiab HF concentrations siab tshaj 0.5%. Tom qab raug ntev, ib lub raj uas zoo nkaus li me ntsis etched ntawm qhov chaw tuaj yeem muaj 50-100 µm sib sib zog nqus grain ciam grooves. Thaum cov grooves ncav cuag qhov tob txaus (feem ntau 30-50% ntawm phab ntsa tuab), cov nplej tuaj yeem poob tawm thiab cov pits uas sai sai perforate lub raj.
Mixed HNO₃-HF IGA Kev Nkag Siab
Cov ntaub ntawv ntau ntawm IGA nkag mus yog tau los ntawm kev tswj immersion kuaj ntawm Qib 2 titanium specimens (annealed, grain loj 20-40 µm) nyob rau hauv pickling acid formulations ntawm 50 degree. Cov qauv nthuav tawm tau raug hla ntu thiab qhov siab tshaj plaws ntawm cov ciam teb nres tau ntsuas metallographically.
Tus nqi corrosion feem ntau yog 0.3-0.5 hli / xyoo hauv 15% HNO₃ + 3% HF ntawm 50℃(nruab nrab stainless hlau pickling da dej). Lub IGA nkag mus ntawm tus nqi ntawm 1.5-2.5 hli txhua xyoo - 5 zaug sai dua. Tom qab 5,000 teev (txog 7 lub hlis ntawm kev ua haujlwm tas mus li) qhov ntsuas IGA nkag mus yog 0.9-1.4 hli. Rau tus qauv 1.65 hli phab ntsa raj no siv rau 55-85% ntawm phab ntsa noj los ntawm IGA, piv txwv li lub raj muaj kev pheej hmoo siab ntawm cov nplej poob thiab perforation.
The usual corrosion rate for 10% HNO3 + 1% HF (less aggressive, utilized for titanium alloy pickling) is 0.08-0.12 mm/year. IGA penetration rate is 0.3-0.5 mm/year . IGA penetration is 0.17-0.29 mm after 5,000 hrs, or around 10-18% of a 1.65 mm wall. It's important but not urgent."
Tus nqi corrosion dav dav hauv 20% HNO₃ + 5% HF (siab siab -throughput pickling) yog 0.8-1.2 mm / xyoo thaum IGA nkag mus yog 4-6 mm / xyoo. Txhua qhov ua tau ntawm phab ntsa tuab yuav ua tiav los ntawm IGA nkag mus ntawm 2.3-3.4 hli tom qab 2000-3000 teev tom qab 5000 teev.
Teeb tsa Kev Tshawb Fawb Lub Sij Hawm
Kev tshuaj xyuas zaus yog raws li 30% IGA nkag mus ntawm phab ntsa tuab, thaum lub sijhawm qhov kev pheej hmoo ntawm cov nplej poob siab. Rau 1.65 hli phab ntsa raj, 30% sib npaug 0.5 hli IGA qhov tob.
Raws li cov saum toj no IGA nkag mus, lub sij hawm rau 0.5 hli IGA qhov tob yog:
Rau 15% HNO3 + 3% HF 0.5 mm/(1.5-2.5 mm/yr)=0.2-0.33 xyoo=1,750-2,900 hr. Pom zoo tshuaj xyuas ntawm 2000 teev (kwv yees . 3 hli).
Rau 10% HNO₃ + 1% HF: 0.5 mm/(0.3-0.5 mm/yr)=1.0-1.67 xyoo=8,800-14,600 h 8,000 teev (ib ncig 11 lub hlis) OK rau kev tshuaj xyuas
IGA nkag mus yog twb 0.9-1.4 hli (55-85% phab ntsa) rau ib lub raj uas tau ua hauj lwm 5,000 teev nyob rau hauv 15/3 da dej. Tshem lub raj los ntawm kev pabcuam tam sim, txawm tias nws zoo li sab nraud. Rau 10/1 da dej, 5,000 teev yog 0.17-0.29 mm IGA. Nyob rau ntawm lub sijhawm tshuaj xyuas yuav tsum tau ua los ntsuas qhov tseeb nkag mus thiab kwv yees lub neej tseem tshuav.
Daim ntawv thov Matrix Tshuaj ntsuam xyuas ncua sij hawm
Kev sib xyaw ntawm Pickling Acids Kub Tus Nqi Ntawm Kev Nkag Siab (mm / xyoo) ntawm Qib 2 IGATime rau 30% Phab Ntsa Nkag (1.65mm raj) Kev tshuaj xyuas thawj zaug pom zoo tshuaj xyuas txoj kev
10% HNO3 + 1% HF 50℃0.3-0.5 8,800-14,600 teev 5,000-6,000 teev Ultrasound phab ntsa ntsuas + metallographic replication
10% HNO3 + 2% HF 50℃0.8-1.2 3,700-5,500 teev 3,000-4,000 teev Ultrasonic + eddy tam sim no 15% HNO3 + 3% HF 50℃1.5-2.5 1,750-2,900 teev Ultrasonic 2,000 teev IGsonic feem ntau
20% HNO₃ + 5% HF 50℃4.0-6.0 700-1,100 teev 500 teev Tsis pom zoo rau Qib 2; siv qib 7 lossis Hastelloy
Ib qho muaj pes tsawg leeg ntawm 60℃(piv rau 50 degree) 60℃2-3x tus nqi ntawm 50℃2-3 lub sij hawm txo nyob rau hauv intervalAdjust raws li xav tau raws li saum toj no IGA Detection Inspection Methods
Grain ciam teb quab yuam tsis tsim ib tug du, parallel phab ntsa poob, yog li cov pa ultrasonic thickness ntsuas feem ntau tsis tsim nyog rau IGA. Lub teeb liab ultrasonic tuaj yeem cuam tshuam los ntawm qhov tob tshaj plaws ntawm ciam teb grooves, tab sis cov nplej nruab nrab tseem tuaj yeem txuas nrog. Kev nyeem ntawv tuab ntawm 1.2 hli (cim mus rau qhov tob tshaj plaws) yuav tshwm sim nrog cov nplej uas yuav ua rau ntawm 0.8 hli tiag tiag phab ntsa.
Ntau txoj hauv kev vam khom muaj xws li:
Metallographic replication: Ib ntu ntawm cov polished thiab etched tube nto yog replicated ntawm cellulose acetate thiab grain ciam teb nres tuaj yeem kuaj xyuas hauv qab lub tshuab ntsuas qhov tsis tau txiav lub raj. Replicas tuaj yeem ntes IGA qhov tob ntawm 20-30 µm thiab ntiav.
Kev ntsuas tam sim no Eddy High zaus eddy tam sim no (100-500 kHz) rhiab rau cov ciam teb tsis tu ncua thiab tuaj yeem siv los qhia qhov hnyav ntawm IGA hla lub raj nplaim.
Kev txiav thiab ntsuas ncaj qha. Rau cov ntawv thov tseem ceeb, lub tshuab cua sov raug tshem tawm ntawm lub sijhawm tsim nyog thiab hla ntu ntawm ntau qhov chaw (cov ntu ncaj nraim, khoov, vuam) raug txiav thiab qhov tob IGA ntsuas hauv qab metallograph. Qhov no muab cov ntaub ntawv tseem ceeb rau kev kwv yees ntawm lub neej seem.
Kev tshuaj xyuas ntawm titanium qib 2 cua sov raj rau cov kab pickling nrog sib tov ntawm 15% HNO3 + 3% HF ntawm 50℃yog xav tau tom qab 2000 teev (txog 3 lub hlis ua haujlwm tas li). Feem ntau, tom qab 5,000 teev, IGA nkag mus yuav yog 55-85% ntawm phab ntsa 1.65 hli thiab lub raj yuav tsum tau hloov. Rau qhov tsawg dua 10% HNO3 + 1% HF formulations, kuaj tom qab 5,000 teev yog tsim nyog. Metallographic replication yuav tsum tau siv los txiav txim qhov tob ntawm IGA. Kev hloov pauv yuav tsum tau ua thaum IGA qhov tob tshaj 0.5 hli. Titanium Qib 2 tsis qhia rau cov kua qaub uas HF> 3% lossis kub> 50 degree. Qib 7 (2-3 zaug muaj zog IGA tsis kam) lossis Hastelloy C-276 yuav tsum tau muab. Nug rau cov tubing annealed nrog nplua nplej loj (ASTM 7-8, 20-25 µm) thaum yuav vim nws muaj qis IGA tus nqi dua li cov khoom ntxhib-grained.
