Koj tau ua kom paub tseeb tias cov khoom raug tshuab 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
Kev siv passivation tseem yog ib kauj ruam tseem ceeb hauv kev ua kom qhov kev tiv thaiv xeb yooj yim ntawm cov khoom siv stainless hlau thiab cov khoom sib dhos. Nws tuaj yeem ua qhov sib txawv ntawm kev ua tau zoo thiab kev ua tsis tiav ua ntej. Yog tias ua tsis raug, passivation tuaj yeem ua rau xeb.
Passivation yog ib txoj kev tom qab tsim khoom uas ua kom qhov kev tiv thaiv xeb ntawm cov hlau tsis xeb uas tsim cov khoom ua haujlwm siab tshaj plaws. Nws tsis yog kev kho kom tshem tawm cov av nplaum, thiab nws tsis yog ib qho txheej xim.
Tsis muaj kev pom zoo dav dav txog txoj kev ua haujlwm ntawm kev ua kom cov hlau tsis xeb ua haujlwm li cas. Tab sis nws paub tseeb tias muaj ib daim zaj duab xis oxide tiv thaiv rau ntawm qhov chaw ntawm cov hlau tsis xeb uas tau ua kom cov hlau tsis xeb. Daim zaj duab xis tsis pom no xav tias nyias heev, tsawg dua 0.0000001 nti tuab, txog li 1/100,000th ntawm qhov tuab ntawm cov plaub hau tib neeg!
Ib feem ntawm cov hlau tsis xeb uas huv si, tshiab, txhuam los yog pickled yuav tau txais cov zaj duab xis oxide no vim nws raug rau cov pa oxygen hauv huab cua. Hauv qab cov xwm txheej zoo tagnrho, cov txheej oxide tiv thaiv no npog tag nrho cov nto ntawm qhov.
Txawm li cas los xij, hauv kev xyaum ua, cov khoom tsis huv xws li cov av hauv khw lossis cov hlau me me los ntawm cov cuab yeej txiav tuaj yeem kis mus rau qhov chaw ntawm cov khoom siv hlau tsis xeb thaum lub sijhawm ua haujlwm. Yog tias tsis tshem tawm, cov khoom txawv teb chaws no tuaj yeem txo qhov ua tau zoo ntawm cov zaj duab xis tiv thaiv qub.
Thaum lub sijhawm ua haujlwm, cov hlau dawb me me tuaj yeem hnav tawm ntawm lub cuab yeej thiab kis mus rau saum npoo ntawm cov hlau tsis xeb. Qee zaum, ib txheej xeb nyias nyias yuav tshwm sim ntawm qhov. Qhov no yog qhov tseeb xeb ntawm cov hlau los ntawm lub cuab yeej, tsis yog ntawm cov hlau hauv paus. Qee zaum, cov kab nrib pleb ntawm cov hlau me me uas nkag los ntawm cov cuab yeej txiav lossis lawv cov khoom xeb tuaj yeem ua rau xeb ntawm qhov khoom nws tus kheej.
Ib yam li ntawd, cov khoom me me ntawm cov av ferrous yuav lo rau ntawm qhov chaw ntawm qhov khoom. Txawm hais tias hlau yuav zoo li ci ntsa iab hauv lub xeev machined, tom qab raug cua, cov khoom me me uas tsis pom ntawm cov hlau dawb tuaj yeem ua rau xeb ntawm qhov chaw.
Cov sulfides uas raug tso tawm kuj tuaj yeem ua teeb meem. Lawv los ntawm kev ntxiv sulfur rau hauv cov hlau tsis xeb kom txhim kho kev siv tshuab. Sulfides ua rau cov hlau muaj peev xwm tsim cov chips thaum lub sijhawm ua haujlwm, uas tuaj yeem raug tshem tawm ntawm lub cuab yeej txiav. Tshwj tsis yog tias cov khoom raug passivated kom raug, sulfides tuaj yeem dhau los ua qhov pib rau kev xeb ntawm cov khoom tsim tawm.
Hauv ob qho tib si, passivation yog qhov yuav tsum tau ua kom cov hlau tsis xeb tsis xeb zoo tshaj plaws. Nws tshem tawm cov khoom tsis huv ntawm qhov chaw, xws li cov av ferrous thiab cov hlau hauv cov cuab yeej txiav, uas tuaj yeem ua xeb lossis ua qhov pib rau xeb. Passivation kuj tshem tawm cov sulfides uas pom ntawm qhov chaw ntawm cov hlau tsis xeb uas txiav tau dawb.
Cov txheej txheem ob kauj ruam muab qhov zoo tshaj plaws tiv taus xeb: 1. Kev ntxuav, ib qho txheej txheem yooj yim tab sis qee zaum tsis quav ntsej; 2. Da dej kua qaub lossis kev kho mob passivation.
Kev ntxuav yuav tsum yog qhov tseem ceeb tshaj plaws. Cov nto yuav tsum tau ntxuav kom huv si ntawm cov roj, cov dej txias lossis lwm yam khib nyiab hauv khw kom tiv taus xeb zoo tshaj plaws. Cov khib nyiab hauv kev ua haujlwm lossis lwm yam av hauv khw tuaj yeem so kom huv si ntawm qhov khoom. Cov tshuaj ntxuav roj lossis cov tshuaj ntxuav lag luam tuaj yeem siv los tshem tawm cov roj ua haujlwm lossis cov dej txias. Tej yam txawv teb chaws xws li cov pa roj thermal yuav tsum tau tshem tawm los ntawm cov txheej txheem xws li kev sib tsoo lossis kev sib xyaw.
Qee zaum tus neeg ua haujlwm tshuab yuav hla dhau qhov kev ntxuav yooj yim, xav yuam kev tias kev ntxuav thiab passivation yuav tshwm sim tib lub sijhawm los ntawm kev muab ib feem uas muaj roj ntau rau hauv lub dab dej acid. Qhov no yuav tsis tshwm sim. Ntawm qhov tod tes, cov roj uas muaj kuab paug yuav ua rau cov kua qaub ua rau cov pa npuas. Cov npuas no sib sau ua ke rau ntawm qhov chaw ua haujlwm thiab cuam tshuam rau passivation.
Qhov ua rau qhov teeb meem zuj zus tuaj, kev ua qias tuaj ntawm cov tshuaj passivation, uas qee zaum muaj cov chlorides ntau, tuaj yeem ua rau "flashing." Tsis zoo li kev tau txais cov zaj duab xis oxide uas xav tau nrog lub ntsej muag ci ntsa iab, huv si, tiv taus corrosion, flash etching tuaj yeem ua rau lub ntsej muag etched hnyav lossis tsaus ntuj - qhov chaw puas tsuaj uas passivation yog tsim los ua kom zoo dua.
Cov khoom ua los ntawm cov hlau tsis xeb martensitic [sib nqus, tiv taus corrosion nruab nrab, lub zog tso zis txog li 280 ksi (1930 MPa)] raug kho kom ruaj khov ntawm qhov kub siab thiab tom qab ntawd tempered kom ntseeg tau tias qhov nyuaj thiab cov khoom siv kho tshuab xav tau. Cov hlau nplaum uas muaj zog thiab tiv taus corrosion zoo dua li cov hlau nplaum martensitic, tuaj yeem kho cov kua, ua ib feem ntawm tshuab, laus ntawm qhov kub qis dua, thiab tom qab ntawd ua tiav.
Hauv qhov no, qhov khoom yuav tsum tau ntxuav kom huv si nrog cov tshuaj degreaser lossis cov tshuaj ntxuav kom tshem tawm cov kua txiav ua ntej kho cua sov. Txwv tsis pub, cov kua txiav uas tseem nyob ntawm qhov khoom tuaj yeem ua rau muaj kev oxidation ntau dhau. Qhov xwm txheej no tuaj yeem ua rau cov khoom me me tawg tom qab cov nplai raug tshem tawm los ntawm cov kua qaub lossis cov txheej txheem abrasive. Yog tias cov kua txiav raug tso cai rau ntawm cov khoom tawv ci, xws li hauv lub cub tawg lossis huab cua tiv thaiv, qhov chaw carburization tuaj yeem tshwm sim, ua rau poob qhov tiv thaiv corrosion.
Tom qab ntxuav kom huv si, cov khoom ua los ntawm cov hlau tsis xeb tuaj yeem muab tso rau hauv lub dab dej uas muaj kua qaub passivating acid. Ib qho ntawm peb txoj kev siv tau - nitric acid passivation, nitric acid nrog sodium dichromate passivation, thiab citric acid passivation. Txoj kev twg yuav siv nyob ntawm qib ntawm cov hlau tsis xeb thiab cov qauv lees txais tshwj xeeb.
Cov qib chrome-nickel uas tiv taus xeb ntau dua tuaj yeem raug passivated hauv 20% (v/v) nitric acid da dej (Daim Duab 1). Raws li qhia hauv lub rooj, cov hlau stainless uas tsis tiv taus ntau dua tuaj yeem raug passivated los ntawm kev ntxiv sodium dichromate rau hauv nitric acid da dej, ua rau cov tshuaj oxidizing ntau dua thiab tuaj yeem tsim cov zaj duab xis passive ntawm qhov chaw hlau. Lwm txoj kev xaiv los hloov nitric acid nrog sodium chromate yog kom nce qhov concentration ntawm nitric acid mus rau 50% los ntawm ntim. Ob qho tib si ntxiv sodium dichromate thiab qhov concentration siab dua ntawm nitric acid txo qhov muaj feem ntawm qhov tsis xav tau flash.
Cov txheej txheem rau kev siv cov hlau tsis xeb uas tsis siv neeg ua kom dawb (kuj pom hauv Daim Duab 1) txawv me ntsis ntawm cov hlau tsis xeb uas tsis siv neeg ua kom dawb. Qhov no yog vim tias thaum lub sijhawm siv cov hlau tsis xeb hauv lub dab dej nitric acid ib txwm muaj, qee lossis tag nrho cov sulfides uas muaj sulfur raug tshem tawm, tsim cov kev tsis sib xws me me hauv qhov chaw ntawm cov khoom siv ua kom huv.
Txawm tias kev yaug dej zoo feem ntau tuaj yeem tso cov kua qaub seem hauv cov kev tsis sib txuas no tom qab passivation. Cov kua qaub no yuav tawm tsam qhov chaw ntawm qhov tshwj tsis yog tias nws raug neutralized lossis tshem tawm.
Yuav kom ua kom cov hlau stainless hlau uas yooj yim siv tau yooj yim passivate, Carpenter tau tsim cov txheej txheem AAA (Alkali-Acid-Alkali), uas ua rau cov kua qaub seem tsis muaj zog. Txoj kev passivation no tuaj yeem ua tiav hauv tsawg dua 2 teev. Nov yog cov txheej txheem ib kauj ruam zuj zus:
Tom qab tshem cov roj tawm lawm, muab cov khoom tso rau hauv 5% sodium hydroxide kua ntawm 160°F txog 180°F (71°C txog 82°C) li 30 feeb. Tom qab ntawd yaug cov khoom kom huv si hauv dej. Tom qab ntawd, muab cov khoom tso rau hauv 20% (v/v) nitric acid kua uas muaj 3 oz/gal (22 g/l) sodium dichromate li 30 feeb ntawm 120°F txog 140°F (49°C) txog 60°C). Tom qab tshem cov khoom tawm ntawm lub dab da dej, yaug nrog dej thiab muab tso rau hauv sodium hydroxide kua rau lwm 30 feeb. Yaug cov khoom dua nrog dej thiab ziab, ua tiav txoj kev AAA.
Kev siv citric acid passivation yog qhov nrov zuj zus nrog cov tuam txhab tsim khoom uas xav kom tsis txhob siv cov mineral acids lossis cov tshuaj uas muaj sodium dichromate, nrog rau cov teeb meem pov tseg thiab kev txhawj xeeb ntau dua txog kev nyab xeeb uas cuam tshuam nrog lawv siv. Citric acid suav tias yog tus phooj ywg ib puag ncig hauv txhua txoj kev.
Txawm hais tias kev siv citric acid passivation muaj cov txiaj ntsig zoo rau ib puag ncig, cov khw muag khoom uas tau ua tiav nrog kev siv inorganic acid passivation thiab tsis muaj kev txhawj xeeb txog kev nyab xeeb yuav xav nyob twj ywm. Yog tias cov neeg siv no muaj lub khw muag khoom huv si, cov khoom siv tau saib xyuas zoo thiab huv si, cov dej txias tsis muaj cov hlau hauv khw muag khoom qias neeg, thiab cov txheej txheem uas ua rau muaj txiaj ntsig zoo, tej zaum yuav tsis tas yuav hloov pauv tiag tiag.
Kev siv cov kua qaub citric acid hauv cov dej da dej tau pom tias muaj txiaj ntsig zoo rau ntau hom hlau tsis xeb, suav nrog ntau hom hlau tsis xeb, raws li pom hauv Daim Duab 2. Rau kev yooj yim, txoj kev siv cov kua qaub nitric acid ib txwm muaj hauv Daim Duab 1 suav nrog. Nco ntsoov tias cov qauv nitric acid qub tau qhia ua feem pua ​​​​​​ntawm qhov ntim, thaum cov kua qaub citric acid tshiab tau qhia ua feem pua ​​​​​​ntawm qhov hnyav. Nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias thaum siv cov txheej txheem no, kev sib npaug ntawm lub sijhawm ntub dej, qhov kub thiab qhov concentration yog qhov tseem ceeb kom tsis txhob muaj "flashing" piav qhia ua ntej.
Kev kho mob passivation sib txawv raws li cov ntsiab lus chromium thiab cov yam ntxwv machining ntawm txhua qib. Nco ntsoov cov kem xa mus rau Txheej Txheem 1 lossis Txheej Txheem 2. Raws li pom hauv Daim Duab 3, Txheej Txheem 1 muaj tsawg dua cov kauj ruam dua li Txheej Txheem 2.
Cov kev kuaj hauv chav kuaj tau qhia tias cov txheej txheem citric acid passivation yooj yim dua rau "flashing" dua li cov txheej txheem nitric acid. Cov yam ntxwv ua rau muaj qhov kev tawm tsam no suav nrog qhov kub da dej siab dhau, lub sijhawm ntev dhau, thiab kev ua qias tuaj ntawm da dej. Cov khoom citric acid uas muaj cov tshuaj tiv thaiv xeb thiab lwm yam khoom ntxiv xws li cov neeg sawv cev ntub dej muaj nyob hauv khw thiab tau tshaj tawm tias txo qhov kev cuam tshuam rau "flash corrosion".
Qhov kev xaiv kawg ntawm txoj kev passivation yuav nyob ntawm cov qauv kev lees txais uas tus neeg siv khoom tau tsim. Saib ASTM A967 kom paub meej ntxiv. Nws tuaj yeem nkag mus rau ntawm www.astm.org.
Feem ntau cov kev ntsuam xyuas raug ua los ntsuam xyuas qhov chaw ntawm cov khoom uas tau passivated. Lo lus nug uas yuav tsum teb yog, "Puas yog passivation tshem tawm cov hlau dawb thiab ua kom zoo dua qhov kev tiv thaiv corrosion ntawm cov qib txiav dawb?"
Nws yog ib qho tseem ceeb uas txoj kev xeem phim qhov qib uas tab tom ntsuas. Cov kev xeem uas nruj dhau yuav tsis dhau cov ntaub ntawv zoo, thaum cov kev xeem uas xoob dhau yuav dhau qhov tsis txaus siab.
Cov hlau stainless hlau 400 series uas tau ua kom tawv thiab siv tshuab dawb raug soj ntsuam zoo tshaj plaws hauv lub txee uas muaj peev xwm tswj tau 100% av noo (qauv ntub) rau 24 teev ntawm 95°F (35°C). Qhov seem feem ntau yog qhov tseem ceeb tshaj plaws, tshwj xeeb tshaj yog rau cov qib txiav dawb. Ib qho laj thawj rau qhov no yog tias cov sulfide ntev mus rau hauv lub tshuab, sib tshuam qhov chaw no.
Cov chaw tseem ceeb yuav tsum tau muab tso rau saum toj, tab sis ntawm 15 txog 20 degrees ntawm ntsug kom tso cai rau cov dej noo poob. Cov khoom siv passivated kom zoo yuav tsis xeb, txawm hais tias nws yuav pom qee qhov xim me ntsis.
Cov qib Austenitic stainless hlau kuj tseem tuaj yeem soj ntsuam los ntawm kev sim av noo. Thaum kuaj li ntawd, cov dej ntws yuav tsum muaj nyob rau ntawm qhov chaw ntawm cov qauv, qhia tias muaj hlau dawb los ntawm qhov muaj xeb.
Cov txheej txheem rau kev siv cov hlau tsis xeb uas feem ntau siv los txiav thiab tsis txiav hauv cov kua citric lossis nitric acid xav tau cov txheej txheem sib txawv. Daim duab 3 hauv qab no muab cov ntsiab lus ntawm kev xaiv cov txheej txheem.
(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. Lwm txoj hauv kev rau qhov sib tov no yog 50% nitric acid tsis muaj sodium dichromate.
Ib txoj kev ua sai dua yog siv cov tshuaj hauv ASTM A380, "Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems." Qhov kev sim no yog so qhov chaw nrog cov tshuaj tooj liab sulfate/sulfuric acid, ua kom nws ntub rau 6 feeb thiab saib seb puas muaj tooj liab plating. Lwm txoj hauv kev, qhov chaw tuaj yeem muab tso rau hauv cov tshuaj rau 6 feeb. Yog tias hlau yaj, tooj liab plating tshwm sim. Qhov kev sim no tsis siv rau ntawm qhov chaw ua zaub mov. Tsis tas li ntawd, nws yuav tsum tsis txhob siv rau 400 series martensitic lossis low chromium ferritic steels vim tias cov txiaj ntsig tsis tseeb yuav tshwm sim.
Keeb kwm, qhov kev sim tshuaj tsuag ntsev 5% ntawm 95 ° F (35 ° C) kuj tau siv los ntsuam xyuas cov qauv passivated. Qhov kev sim no nruj dhau rau qee qib thiab feem ntau tsis tas yuav tsum tau lees paub tias passivation ua haujlwm tau zoo.
Tsis txhob siv cov chlorides ntau dhau, uas tuaj yeem ua rau muaj kev phom sij. Yog tias ua tau, tsuas yog siv cov dej zoo uas muaj tsawg dua 50 feem ib lab (ppm) chloride. Cov dej kais feem ntau txaus thiab tuaj yeem tiv taus txog li ntau pua ppm chloride hauv qee kis.
Nws yog ib qho tseem ceeb uas yuav tsum hloov lub dab da dej tsis tu ncua kom tsis txhob poob lub peev xwm passivation, uas tuaj yeem ua rau xob laim thiab cov khoom puas tsuaj. Lub dab da dej yuav tsum tau tswj kom sov li qub, vim tias qhov kub tsis txaus yuav ua rau xeb hauv zos.
Nws yog ib qho tseem ceeb uas yuav tsum tswj lub sijhawm hloov cov tshuaj tshwj xeeb thaum lub sijhawm tsim khoom ntau kom txo qhov ua rau muaj kev ua qias tuaj. Ib qho qauv tswj tau siv los sim qhov ua tau zoo ntawm lub dab da dej. Yog tias cov qauv raug tawm tsam, nws yog lub sijhawm los hloov lub dab da dej.
Thov qhia meej tias qee lub tshuab ua cov hlau tsis xeb xwb; siv tib yam dej txias uas nyiam siv los txiav cov hlau tsis xeb, tsis suav nrog lwm cov hlau.
Cov khoom seem ntawm DO khib raug kho cais kom tsis txhob muaj kev sib cuag ntawm hlau. Qhov no tseem ceeb heev rau kev siv cov hlau tsis xeb dawb, vim tias yuav tsum muaj kev siv cov tshuaj passivation thiab cov tshuaj ntxuav kom huv si kom cov khoom sulfide corrosion kis mus rau lwm qhov thiab zam kom tsis txhob muaj cov kua qaub.
Tsis txhob siv cov khoom siv hlau tsis xeb uas muaj carburized lossis nitrided passivate. Qhov kev tiv thaiv corrosion ntawm cov khoom uas tau kho yuav raug txo kom txog rau thaum lawv raug tawm tsam hauv lub dab dej passivation.
Tsis txhob siv cov cuab yeej hlau hauv qhov chaw ua haujlwm uas tsis huv heev. Kev siv cov cuab yeej carbide lossis ceramic yuav zam tau cov xuab zeb hlau.
Tsis txhob hnov ​​qab tias xeb tuaj yeem tshwm sim hauv lub dab dej passivation yog tias qhov khoom tsis tau kho cua sov kom zoo. Cov qib carbon siab, cov qib chromium martensitic siab yuav tsum tau ua kom tawv rau kev tiv thaiv xeb.
Feem ntau passivation yog ua tom qab tempering tom qab siv cov kub uas tswj tau corrosion.
Tsis txhob tsis quav ntsej qhov concentration ntawm nitric acid hauv lub dab dej passivation. Kev kuaj xyuas tsis tu ncua yuav tsum tau ua los ntawm kev siv cov txheej txheem titration yooj yim uas Carpenter muab. Tsis txhob passivate ntau tshaj ib lub hlau stainless ib zaug. Qhov no tiv thaiv kev tsis meej pem kim thiab zam kev cuam tshuam galvanic.
Txog cov kws sau ntawv: Terry A. DeBold yog ib tus kws tshawb fawb thiab kws tsim khoom siv hlau tsis xeb thiab James W. Martin yog ib tus kws kho hlau ntawm Carpenter Technology Corp. (Reading, PA).
Hauv lub ntiaj teb uas muaj cov lus qhia txog qhov chaw tiav uas nruj zuj zus, kev ntsuas "roughness" yooj yim tseem muaj txiaj ntsig. Cia peb saib seb vim li cas kev ntsuas qhov chaw thiaj li tseem ceeb thiab yuav ua li cas thiaj kuaj xyuas nws hauv pem teb nrog cov cuab yeej ntsuas tau yooj yim.
Koj puas paub tseeb tias koj muaj lub ntxig zoo tshaj plaws rau qhov kev ua haujlwm tig no? Xyuas lub nti, tshwj xeeb tshaj yog tias tsis muaj neeg saib xyuas. Cov yam ntxwv ntawm lub nti tuaj yeem qhia koj ntau yam.