Kev puas tsuaj impurities hauv Titanium cov ntaub ntawv

Titanium thiab nws cov alloys muaj npe nrov rau lawv cov purity siab thiab biocompatibility, tab sis lawv tuaj yeem muaj cov kab mob tsis zoo (xws li hydrogen, phosphorus, thiab sulfur) uas yuav tsum tau tswj nruj me ntsis hauv kev lag luam - tus qauv txwv. Ntau theem ntawm cov impurities no, tshwj xeeb tshaj yog hydrogen, tuaj yeem ua rau cov khoom siv kho tshuab thiab kev nyab xeeb ntawm kev pabcuam. Hauv qab no yog cov ncauj lus kom ntxaws txog lawv cov ntsiab lus txwv thiab cov kev pheej hmoo cuam tshuam:

1. Cov ntsiab lus txwv tsis pub muaj kev phom sij tseem ceeb hauv cov khoom siv titanium

Qhov tso cai kom muaj zog ntawm hydrogen (H), phosphorus (P), thiab sulfur (S) hauv titanium yog txhais los ntawm cov qauv thoob ntiaj teb xws liASTM B 348 Cov Lus Qhia Tshwj Xeeb(rau titanium thiab titanium alloy tuav),ASTM B265(rau cov ntawv titanium / daim hlau), thiabTIAB SA 4928(aerospace-qib Ti-6Al-4V). Cov kev txwv sib txawv los ntawm qib titanium (kev lag luam ntshiab titanium vs. titanium alloys) thiab cov ntawv thov (kev lag luam vs. aerospace / kho mob):

(1) Hydrogen (H)

Hydrogen yog qhov tseem ceeb tshaj plaws kev puas tsuaj impurity nyob rau hauv titanium vim nws muaj zog cuam tshuam rau ductility thiab toughness. Nws qhov siab tshaj plaws tso cai cov ntsiab lus yog nruj me ntsis tswj:

Kev lag luam ntshiab titanium (Qib 1/2/3/4): Rau kev siv dav hauv kev lag luam, cov ntsiab lus hydrogen yuav tsum tsis pub tshaj0.015 wt% (150 ppm); rau siab -kev kho mob purity- qib ntshiab titanium (piv txwv li, Qib 2 rau kev cog qoob loo), qhov txwv tau nruj rau0.010 wt% (100 ppm)los xyuas kom meej biocompatibility thiab kev nyab xeeb ntawm cov qauv.

Titanium alloys (piv txwv li, Qib 5 / Ti-6Al-4V): Rau aerospace- cov khoom qib, cov ntsiab lus hydrogen yog capped ntawm0.012 wt% (120 ppm)(rau AMS 4928); rau kev lag luam-qib Ti-6Al-4V, qhov kev txwv yog me ntsis so rau0.015 wt% (150 ppm), tab sis nws yuav tsum yog hauv qab no0.008 wt% (80 ppm)rau cov khoom tseem ceeb (piv txwv li, aircraft engine qhov chaw) los tiv thaiv hydrogen embrittlement.

(2) Phosphorus (P)

Phosphorus yog ib qho qis -toxicity impurity nyob rau hauv titanium, tab sis cov qib siab tuaj yeem sib cais ntawm cov ciam teb nplej thiab txo cov hlau ductility thiab qaug zog. Nws cov ntsiab lus txwv tsis pub tsawg dua piv rau hydrogen:

Kev lag luam ntshiab titanium: Cov ntsiab lus phosphorus siab tshaj plaws yog feem ntau0.04 wt% (400 ppm)thoob plaws txhua qib (ASTM B348).

Titanium alloys (Ti-6Al-4V): Aerospace thiab qib kho mob txwv phosphorus rau0.015 wt% (150 ppm); qib kev lag luam tso cai mus txog0.03 wt% (300 ppm).

(3) Sulfur (S)

Sulfur forms brittle sulfide inclusions (piv txwv li, TiS, Ti₂S) nyob rau hauv titanium, uas ua raws li kev ntxhov siab concentration ntsiab lus thiab pib tawg nyob rau hauv load. Nws cov ntsiab lus yog nruj me ntsis txwv kom tsis txhob embrittlement:

Kev lag luam ntshiab titanium: Cov ntsiab lus sulfur yuav tsum tsawg dua lossis sib npaug0.015 wt% (150 ppm)(ASTM B265) .

Titanium alloys (Ti-6Al-4V): Rau kev siv aerospace, qhov txwv yog0.010 wt% (100 ppm); rau industrial siv, nws tuaj yeem ua rau0.02 wt% (200 ppm).

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2. Hydrogen embrittlement tshwm sim los ntawm ntau cov ntsiab lus hydrogen

Hydrogen embrittlement (HE) yog hom kev puas tsuaj loj rau cov khoom siv titanium, tshwm sim los ntawm hydrogen ntau tshaj qhov chaw nyab xeeb. Nws mechanism thiab cov kev cuam tshuam yog raws li nram no:

(1) Mechanism ntawm Hydrogen Embrittlement hauv Titanium

Titanium muaj kev sib raug zoo rau hydrogen, uas tuaj yeem nkag mus rau cov khoom siv los ntawm ntau txoj hauv kev:

Smelting thiab ua: Hydrogen absorption thaum lub tshuab nqus tsev arc remelting (VAR) yog tias lub tshuab cua sov tsis raug tswj xyuas kom zoo, lossis thaum ua haujlwm kub hauv qhov chaw ntub dej.

Kev pabcuam ib puag ncig: Hydrogen pickup los ntawm corrosive media (xws li, aqueous solutions, acids, los yog hydrogen-}muaj gases) los ntawm cov tshuaj tiv thaiv nto, los yog los ntawm cov txheej txheem electrochemical (xws li, cathodic tiv thaiv hauv marine applications).

Ib zaug hauv titanium matrix, hydrogen coj txawv raws li qhov kub thiab txias:

Nyob rau hauv chav tsev kub thiab qis hydrogen theem (<50 ppm), hydrogen dissolves interstitially in the titanium lattice without causing harm.

Thaum cov ntsiab lus hydrogen ntau tshaj ~ 100 ppm, nws precipitates li nkigtitanium hydride (TiH₂)raws li cov ciam teb lossis hauv -theem. TiH₂ muaj cov qauv siv lead ua tetragonal nrog lub siab hardness thiab tsis tshua muaj ductility, uas cuam tshuam qhov txuas ntxiv ntawm titanium matrix.

Nyob rau hauv txhua yam kev nyuaj siab, hydride theem ua raws li qhov chaw tawg nucleation. Raws li kev ntxhov siab nce ntxiv, cov kab nrib pleb no nthuav tawm sai sai raws li hydride- matrix interfaces, ua rau tam sim ntawd, nkig tawg (txawm tias nyob rau theem kev ntxhov siab zoo hauv qab cov khoom siv zog).

(2) Kev cuam tshuam ntawm Hydrogen Embrittlement

Poob ductility thiab toughness: Titanium nrog ntau cov hydrogen qhia tau hais tias qhov poob qis hauv elongation thiab txo qhov chaw. Piv txwv li, annealed Ti-6Al-4V nrog 200 ppm hydrogen muaj qhov elongation ntawm 5-8% xwb (qis los ntawm 10-15% rau cov khoom siv hydrogen tsawg), thiab nws cov pob txha toughness (KIC) txo los ntawm 30-40%.

Kev puas tsuaj structural tsis ua haujlwm: Hydrogen embrittlement feem ntau tshwm sim yam tsis tau ceeb toom ua ntej (tsis muaj cov yas deformation), ua rau nws muaj kev phom sij tshwj xeeb rau kev nyab xeeb - cov khoom tseem ceeb. Hauv kev siv aerospace, hydride-induced cracking tau ua rau tsis ua haujlwm ntawm cov khoom siv hauv av thiab cov cav ntoo hauv qhov xwm txheej hnyav.

Txo qaug zog lub neej: Hydrogen accelerates qaug zog tawg kev loj hlob los ntawm kev txhawb kev tsim cov hydrides ntawm cov lus qhia tawg. Lub zog qaug zog ntawm Ti-6Al-4V nrog 150 ppm hydrogen yog txo los ntawm 25-30% piv rau cov khoom siv hydrogen tsawg, ua rau tsis ua hauj lwm ntxov nyob rau hauv cyclic loading.

(3) Kev tiv thaiv thiab txo qis ntawm Hydrogen embrittlement

Txhawm rau zam kom tsis txhob muaj hydrogen embrittlement, cov tuam txhab tsim khoom thiab kawg - cov neeg siv tau txais cov kev ntsuas hauv qab no:

Kev tswj cov txheej txheem nruj: Ua kom qis-hydrogen huab cua thaum smelting thiab kho cua sov; siv qhuav, dehumidified gases rau kub ua hauj lwm thiab vuam.

Tshaj tawm - ua degassing: Rau cov khoom siv titanium nrog cov ntsiab lus hydrogen siab, ua lub tshuab nqus tsev ntawm 600-700℃rau ob peb teev kom diffuse hydrogen tawm ntawm matrix (txo hydrogen rau<50 ppm).

Kev tswj hwm ib puag ncig: Tsis txhob nthuav tawm cov khoom titanium rau hydrogen- cov xov xwm nplua nuj lossis corrosive yam tsis muaj kev tiv thaiv zoo (xws li, coatings lossis inhibitors); saib xyuas cov ntsiab lus hydrogen ib ntus rau qhov tseem ceeb ntawm cov txheej txheem xws li kub rho tawm lossis inert gas fusion.

Kev puas tsuaj impurities hauv titanium cov ntaub ntawv