Koj tau ua kom paub tseeb tias cov khoom siv tau ua raws li qhov tshwj xeeb.Tam sim no, xyuas kom tseeb tias koj tau ua cov kauj ruam los tiv thaiv cov khoom no hauv cov xwm txheej uas koj cov neeg siv khoom xav tau.#basic
Passivation tseem yog cov kauj ruam tseem ceeb hauv kev ua kom qhov yooj yim corrosion kuj ntawm stainless machined qhov chaw thiab cov rooj sib txoos.Nws tuaj yeem ua rau qhov sib txawv ntawm kev ua haujlwm txaus siab thiab tsis ua haujlwm ntxov ntxov.Ua tsis tau zoo, passivation tuaj yeem ua rau corrosion.
Passivation yog ib txoj hauv kev tom qab kev tsim khoom uas ua rau kom muaj kev tiv thaiv corrosion ntawm cov hlau tsis muaj steel hlau uas tsim cov khoom ua haujlwm.
Tsis muaj kev pom zoo dav dav ntawm cov txheej txheem meej ntawm kev ua haujlwm passivation li cas.Tab sis nws yog qhov tseeb tias muaj cov yeeb yaj kiab tiv thaiv oxide nyob rau saum npoo ntawm passivated stainless hlau.Cov zaj duab xis pom tsis pom tau xav tias nyias nyias, tsawg dua 0.0000001 nti tuab, txog 1/100,000th thickness ntawm tib neeg cov plaub hau!
Ib qho huv, tshiab tshiab, polished los yog pickled stainless hlau ib feem yuav tau txais cov oxide zaj duab xis vim nws raug rau atmospheric oxygen. Nyob rau hauv cov xwm txheej zoo, cov txheej txheem oxide tiv thaiv no npog tag nrho cov chaw ntawm qhov chaw.
Hauv kev xyaum, txawm li cas los xij, cov khoom paug xws li khw av lossis cov khoom siv hlau los ntawm cov cuab yeej txiav tuaj yeem hloov mus rau qhov chaw ntawm cov hlau tsis huv thaum lub sijhawm ua haujlwm.
Thaum lub sij hawm machining, cov khoom siv hlau dawb tuaj yeem hnav tawm ntawm lub cuab yeej thiab hloov mus rau qhov chaw ntawm cov hlau tsis muaj steel workpiece. Qee zaum, txheej nyias ntawm xeb tuaj yeem tshwm rau ntawm ib feem.Qhov no yog qhov tseeb corrosion ntawm cov hlau los ntawm cov cuab yeej, tsis yog lub hauv paus hlau. Qee zaus, crevices ntawm embedded steel hais los ntawm cov cuab yeej txiav los yog lawv cov khoom corrosion tuaj yeem ua rau nws tus kheej erosion.
Ib yam li ntawd, cov khoom me me ntawm cov khw ferrous av tuaj yeem ua raws li qhov chaw ntawm qhov chaw.Txawm tias cov hlau yuav zoo li ci ntsa iab nyob rau hauv lub xeev machined, tom qab raug rau huab cua, cov khoom tsis pom ntawm cov hlau dawb tuaj yeem ua rau nto rusting.
Tawm sulfides kuj yog ib qho teeb meem.Lawv los ntawm kev ntxiv cov sulfur rau stainless hlau los txhim kho machinability.Sulfides ua rau cov hlau muaj peev xwm tsim chips thaum lub sij hawm machining, uas tuaj yeem ua tiav sloughed tawm ntawm cov cuab yeej txiav.Tshwj tsis yog cov khoom raug passivated, sulfides tuaj yeem dhau los ua qhov pib ntawm qhov corrosion ntawm cov khoom tsim.
Nyob rau hauv ob qho tib si, passivation yog yuav tsum tau ua kom lub ntuj corrosion kuj ntawm stainless hlau.Nws tshem tawm cov kab mob, xws li ferrous khw av hais thiab hlau hais nyob rau hauv tej cuab yeej, uas yuav ua xeb los yog ua ib tug pib taw tes rau corrosion.Passivation kuj tshem tawm sulfides tshwm nyob rau saum npoo ntawm dawb-txiav stainless hlau alloys.
Cov txheej txheem ob-kauj ruam muab qhov zoo tshaj plaws corrosion kuj: 1. Kev tu, ib qho yooj yim tab sis qee zaum overlooked txheej txheem;2. Acid da dej los yog kev kho mob passivation.
Kev tu yuav tsum yog qhov tseem ceeb.Surfaces yuav tsum tau ntxuav kom huv si ntawm roj, coolant los yog lwm lub khw khib nyiab kom zoo corrosion kuj.Machining khib nyiab los yog lwm yam khw av yuav tsum tau ua tib zoo wiped los ntawm ib feem.Ua lag luam degreasers los yog cov tshuaj ntxuav yuav siv tau los tshem tawm cov txheej txheem roj los yog coolants.Foreign teeb meem xws li thermal oxides tej zaum yuav tsum tau muab tshem tawm los ntawm txoj kev xws li sib tsoo los yog degreasers.
Qee lub sij hawm tus neeg teb xov tooj tuaj yeem hla kev tu yooj yim, ua yuam kev xav tias kev ntxuav thiab kev ua pa yuav tshwm sim ib txhij los ntawm qhov tsuas yog dipping ib feem ntawm cov roj hauv cov kua qaub da dej.Qhov no yuav tsis tshwm sim.Qhov no tsis tshwm sim.Conversely, paug cov roj reacts nrog cov kua qaub los tsim cov pa npuas.Cov npuas no sau rau ntawm qhov chaw ua haujlwm thiab cuam tshuam nrog passivation.
Txhawm rau ua qhov teeb meem loj dua, kev sib kis ntawm cov kev daws teeb meem passivation, uas qee zaum muaj cov tshuaj chlorides siab, tuaj yeem ua rau "flashing." Tsis zoo li tau txais cov yeeb yaj kiab oxide uas xav tau nrog lub ntsej muag zoo nkauj, huv si, corrosion-resistant nto, flash etching tuaj yeem ua rau lub ntsej muag hnyav lossis tsaus nti - nto deterioration uas passivation yog tsim los ua kom zoo dua.
Cov khoom ua los ntawm martensitic stainless hlau [sib nqus, me ntsis resistant rau corrosion, yield zog txog li 280 ksi (1930 MPa)] yog hardened ntawm elevated kub thiab ces tempered los xyuas kom meej qhov xav tau hardness thiab mechanical zog.Precipitation hardenable alloys, uas muaj zoo zog thiab corrosion kuj tshaj li martensitic tov cov khoom, cov khoom tiav, thiab cov khoom tiav, cov khoom siv tau zoo, thiab cov khoom siv tau ua tiav, thiab cov khoom siv tau zoo.
Nyob rau hauv cov ntaub ntawv no, ib feem yuav tsum tau muab ntxuav kom huv si nrog ib tug degreaser los yog ntxhua khaub ncaws kom tshem tawm tej yam kab mob ntawm tej tej dej ua ntej kev kho cua sov.Lwm yam, txiav cov kua seem ntawm ib feem yuav ua rau oxidation ntau heev.Qhov no yuav ua rau undersized qhov chaw rau dent tom qab lub teev tau raug tshem tawm los ntawm cov kua qaub los yog abrasive txoj kev.Yog hais tias txiav cov kua yog tso cai nyob twj ywm nyob rau hauv brightened abrasive vacuum, xws li cov huab cua uas tshwm sim nyob rau hauv lub vacuum. s ntawm corrosion kuj.
Tom qab ua kom huv si, cov hlau tsis huv tuaj yeem muab tso rau hauv lub pas dej ua kua qaub.Txhua yam ntawm peb txoj kev tuaj yeem siv - nitric acid passivation, nitric acid nrog sodium dichromate passivation, thiab citric acid passivation.Txoj kev siv yog nyob ntawm qib stainless hlau thiab cov txheej txheem kev lees paub.
Ntau cov qib corrosion-resistant chrome-nickel tuaj yeem passivated nyob rau hauv 20% (v/v) nitric acid da dej (Daim duab 1).Raws li qhia nyob rau hauv lub rooj, tsis tshua muaj resistant stainless hlau yuav passivated los ntawm kev ntxiv sodium dichromate rau ib tug nitric acid da dej, ua rau cov tshuaj ntau oxidizing thiab muaj peev xwm tsim ib tug passive zaj duab xis ntawm cov hlau nto. .Ob qhov sib ntxiv ntawm sodium dichromate thiab ntau dua concentration ntawm nitric acid txo lub sij hawm ntawm undesired flash.
Cov txheej txheem rau passivating dawb-machining stainless steels (tseem pom hauv daim duab 1) yog qhov txawv ntawm qhov uas tsis yog-dawb-machining stainless hlau qib.Qhov no yog vim thaum lub sij hawm passivation nyob rau hauv ib tug raug nitric acid da dej, ib co los yog tag nrho cov sulfur-muaj machinable qib sulfides raug tshem tawm, tsim microscopic discontinuities nyob rau hauv lub nto ntawm lub tshuab.
Txawm tias cov dej feem ntau siv tau zoo tuaj yeem tso cov kua qaub seem hauv cov kev tsis sib xws tom qab passivation.Qhov no cov kua qaub yuav tawm tsam qhov chaw ntawm qhov tshwj tsis yog nws tsis yog nruab nrab lossis tshem tawm.
Kom ua tau zoo passivate yooj yim machinable stainless hlau, Carpenter tau tsim cov txheej txheem AAA (Alkali-Acid-Alkali), uas neutralizes residual acid.Qhov passivation txoj kev yuav ua kom tiav nyob rau hauv tsawg tshaj li 2 teev.Ntawm no yog cov txheej txheem step-by-step:
Tom qab degreasing, soak cov khoom hauv 5% sodium hydroxide tov ntawm 160 ° F mus rau 180 ° F (71 ° C mus rau 82 ° C) rau 30 feeb.Tom qab ntawd yaug cov khoom kom huv si hauv dej.Tom qab ntawd, raus ib feem rau 30 feeb hauv 20% (v / v) nitric acid gal tov ntawm 3 12 oz / F (2 12 oz / F) nitric acid. 0 ° F (49 ° C) txog 60 ° C).Tom qab tshem tawm ib feem ntawm lub da dej, yaug nws nrog dej thiab muab tso rau hauv cov tshuaj sodium hydroxide rau lwm 30 feeb.Yau ib feem ntxiv nrog dej thiab qhuav, ua tiav AAA txoj kev.
Citric acid passivation yog nce nrov nrog cov tuam txhab uas xav kom tsis txhob siv cov ntxhia acids los yog cov kev daws teeb meem uas muaj sodium dichromate, nrog rau cov teeb meem pov tseg thiab kev txhawj xeeb txog kev nyab xeeb ntau dua nrog rau lawv siv.Citric acid yog suav tias yog ib puag ncig phooj ywg nyob rau hauv txhua txoj kev.
Thaum citric acid passivation muaj qhov zoo nkauj ntawm ib puag ncig zoo, cov khw uas tau ua tiav nrog inorganic acid passivation thiab tsis muaj kev txhawj xeeb txog kev nyab xeeb yuav xav nyob hauv chav kawm.Yog tias cov neeg siv no muaj lub khw huv si, cov khoom siv tu zoo thiab huv si, coolant tsis muaj ferrous khw fouling, thiab cov txheej txheem uas ua tau zoo, tej zaum yuav tsis muaj qhov xav tau tiag tiag rau kev hloov.
Passivation nyob rau hauv lub citric acid da dej tau pom tias yuav pab tau rau ntau yam stainless steels, nrog rau ob peb tus neeg stainless hlau qib, raws li qhia nyob rau hauv daim duab 2.Rau yooj yim, cov tsoos nitric acid passivation txoj kev nyob rau hauv daim duab 1 yog suav nrog.Nco ntsoov hais tias cov laus nitric acid formulations yog qhia nyob rau hauv ntim feem pua, thaum tshiab citric acid concentrations yog qhia nyob rau hauv qhov hnyav feem pua, thaum lub sij hawm tseem ceeb ntawm cov txheej txheem da dej yog ceev faj. al kom zam qhov "flashing" tau piav qhia ua ntej.
Passivation kev kho mob txawv raws li cov ntsiab lus chromium thiab machining yam ntxwv ntawm txhua qib.Nco ntsoov cov kab lus hais txog txheej txheem 1 lossis txheej txheem 2.Raws li pom nyob rau hauv daim duab 3, Txheej Txheem 1 cuam tshuam tsawg dua cov txheej txheem 2.
Cov kev sim kuaj tau pom tias cov txheej txheem citric acid passivation yog qhov ua rau "flashing" ntau dua li cov txheej txheem nitric acid. Cov khoom ua rau qhov kev tawm tsam no suav nrog kev da dej kub dhau, lub sij hawm da dej ntev dhau lawm, thiab da dej tsis sib haum.Citric acid cov khoom uas muaj corrosion inhibitors thiab lwm yam additives xws li wetting agents yog muag thiab tau tshaj tawm kom txo tau "flash corrosion".
Qhov kev xaiv zaum kawg ntawm txoj kev passivation yuav nyob ntawm seb qhov kev lees paub raug tswj los ntawm tus neeg siv khoom.Saib ASTM A967 kom paub meej.Nws tuaj yeem nkag mus rau ntawm www.astm.org.
Kev ntsuam xyuas feem ntau ua los ntsuas qhov chaw ntawm qhov chaw passivated.Cov lus nug kom teb yog, "Puas passivation tshem tawm cov hlau dawb thiab txhim kho corrosion tsis kam ntawm cov qib dawb txiav?"
Nws yog ib qho tseem ceeb uas cov qauv kev xeem sib tw nrog cov qib uas tau soj ntsuam. Cov kev xeem uas nruj dhau yuav ua tsis tiav cov ntaub ntawv zoo, thaum cov kev xeem uas xoob dhau yuav dhau qhov tsis txaus siab.
400 series nag lossis daus hardening thiab free-machining stainless hlau yog qhov zoo tshaj plaws ntsuas nyob rau hauv lub txee muaj peev xwm tswj tau 100% cov av noo (piv txwv ntub) rau 24 teev ntawm 95 ° F (35 ° C).Cov hlais feem ntau yog qhov tseem ceeb tshaj plaws, tshwj xeeb tshaj yog rau cov qib dawb-txiav.Ib qho laj thawj rau qhov no yog qhov kev taw qhia ntawm lub tshuab sulfide.
Qhov chaw tseem ceeb yuav tsum tau muab tso rau saum toj, tab sis ntawm 15 mus rau 20 degrees los ntawm ntsug kom tso cai rau kom tsis txhob ya raws. Cov khoom siv passivated zoo yuav tsis xeb, txawm tias nws yuav pom qee qhov xim me ntsis.
Austenitic stainless hlau qib kuj tuaj yeem ntsuas los ntawm kev ntsuas av noo.Thaum kuaj tau, cov tee dej yuav tsum muaj nyob rau saum npoo ntawm cov qauv, qhia tias cov hlau tsis muaj xeb los ntawm qhov muaj cov xeb.
Cov txheej txheem rau passivating feem ntau siv dawb-txiav thiab tsis-dawb-txiav stainless steels nyob rau hauv citric los yog nitric acid daws yuav tsum tau sib txawv txheej txheem.Daim duab 3 hauv qab no qhia cov ntsiab lus ntawm cov txheej txheem xaiv.
(a) Kho pH nrog sodium hydroxide.(b) Saib Daim duab 3 (c) Na2Cr2O7 sawv cev rau 3 oz/gallon (22 g/l) sodium dichromate hauv 20% nitric acid.Ib qho ntxiv rau qhov sib tov no yog 50% nitric acid tsis muaj sodium dichromate
Ib txoj hauv kev nrawm dua yog siv cov tshuaj hauv ASTM A380, "Txoj Cai Ua Haujlwm rau Kev Tu, Descaling, thiab Passivation ntawm Stainless Steel Parts, Equipment, thiab Systems." Qhov kev ntsuam xyuas muaj xws li so ib feem nrog tooj liab sulfate / sulfuric acid tov, ua kom nws ntub dej rau 6 feeb thiab saib xyuas cov tooj liab plating, thiab lwm txoj hauv kev tuaj yeem ua rau cov dej sib tov. tooj liab plating tshwm sim.Qhov kev ntsuam xyuas no tsis siv rau qhov chaw ua khoom noj khoom haus.Kuj, nws yuav tsum tsis txhob siv rau 400 series martensitic los yog tsawg chromium ferritic steels raws li cov txiaj ntsig tsis zoo yuav tshwm sim.
Keeb kwm, 5% ntsev tsuag tshuaj ntsuam ntawm 95 ° F (35 ° C) kuj tau siv los ntsuas cov qauv passivated.Qhov kev sim no nruj dhau rau qee qib thiab feem ntau tsis tas yuav tsum tau lees paub tias passivation zoo.
Tsis txhob siv cov tshuaj chloride ntau dhau, uas tuaj yeem ua rau muaj teeb meem flash tawm tsam.Yog tias ua tau, tsuas yog siv cov dej zoo uas muaj tsawg dua 50 feem ntawm ib lab (ppm) chloride.Kaw dej feem ntau txaus thiab tuaj yeem tiv taus txog li ob peb puas ppm chloride hauv qee kis.
Nws yog ib qho tseem ceeb uas yuav tsum tau hloov lub da dej tsis tu ncua kom tsis txhob poob lub peev xwm passivation, uas tuaj yeem ua rau xob laim thiab puas qhov chaw.Lub da dej yuav tsum tau khaws cia ntawm qhov kub thiab txias, vim qhov kub ntawm qhov khiav yuav ua rau muaj kev cuam tshuam hauv zos.
Nws yog ib qho tseem ceeb kom tswj tau cov kev hloov kho tshwj xeeb thaum lub sij hawm ua haujlwm siab kom txo tau qhov muaj peev xwm ntawm kev sib kis.A cov qauv tswj tau siv los ntsuas qhov ua tau zoo ntawm cov da dej.Yog tias cov qauv raug tawm tsam, nws yog lub sij hawm los hloov lub da dej.
Thov qhia kom meej tias qee lub tshuab ua stainless hlau nkaus xwb;siv tib lub coolant nyiam los txiav stainless hlau, tsis suav tag nrho lwm yam hlau.
DO cov khoom khib nyiab raug kho cais kom tsis txhob muaj kev sib cuag ntawm cov hlau-rau-hlau.Qhov no yog qhov tseem ceeb tshwj xeeb tshaj yog rau kev ua haujlwm tsis muaj hlau tsis muaj hlau, vim tias cov dej ntws dawb thiab cov dej ntws yaug yuav tsum tau diffuse sulfide corrosion khoom thiab tsis txhob tsim cov kua qaub hauv hnab ris.
Tsis txhob passivate carburized los yog nitrided stainless hlau qhov chaw.Qhov corrosion kuj ntawm qhov chaw kho tej zaum yuav raug txo mus rau qhov chaw uas lawv yuav raug tawm tsam nyob rau hauv lub passivation da dej.
Tsis txhob siv cov cuab yeej ferrous hauv qhov chaw ua haujlwm uas tsis huv tshwj xeeb.Steel grit yuav zam tau los ntawm kev siv cov khoom siv carbide lossis ceramic.
Tsis txhob hnov ​​​​qab tias corrosion tuaj yeem tshwm sim hauv chav da dej passivation yog tias qhov chaw tsis raug kho kom sov.High carbon, siab chromium martensitic qib yuav tsum hardened rau corrosion kuj.
Passivation feem ntau yog ua tom qab tempering tom qab siv qhov kub thiab txias uas tswj kev tiv thaiv corrosion.
Tsis txhob las mees cov nitric acid concentration nyob rau hauv lub passivation da dej.Lub sij hawm xyuas yuav tsum tau siv cov txheej txheem titration yooj yim muab los ntawm Carpenter.Tsis txhob passivate ntau tshaj ib tug stainless hlau nyob rau hauv ib lub sij hawm.Qhov no tiv thaiv cov nqi tsis meej pem thiab tsis txhob galvanic cov tshuaj tiv thaiv.
Hais txog cov kws sau ntawv: Terry A. DeBold yog ib tug stainless hlau alloy tshawb fawb thiab kev txhim kho tshwj xeeb thiab James W. Martin yog bar metallurgist ntawm Carpenter Technology Corp. (Nyeem, PA).
Nyob rau hauv lub ntiaj teb no ntawm kev ua kom nruj qhov chaw tiav specifications, yooj yim "roughness" kev ntsuas yog tseem muaj txiaj ntsig. Cia peb saib seb yog vim li cas qhov kev ntsuas saum npoo yog qhov tseem ceeb thiab yuav ua li cas nws tuaj yeem tshawb xyuas hauv khw hauv pem teb nrog cov khoom siv tau yooj yim.
Koj puas paub tseeb tias koj muaj qhov zoo tshaj plaws ntxig rau qhov kev ua haujlwm tig no?Kos lub nti, tshwj xeeb tshaj yog tias sab laug tsis muaj neeg saib xyuas.Chip yam ntxwv tuaj yeem qhia koj ntau.