Brazing ntawm aluminium thiab aluminium alloys

1. Brazeability

Cov cuab yeej brazing ntawm aluminium thiab aluminium alloys tsis zoo, feem ntau vim tias cov oxide zaj duab xis ntawm qhov chaw yog qhov nyuaj rau tshem tawm. Aluminium muaj affinity zoo rau oxygen. Nws yog ib qho yooj yim los tsim ib tug ntom, ruaj khov thiab siab melting point oxide zaj duab xis Al2O3 ntawm qhov chaw. Nyob rau tib lub sijhawm, aluminium alloys uas muaj magnesium kuj yuav tsim ib qho chaw ruaj khov oxide zaj duab xis MgO. Lawv yuav cuam tshuam qhov ntub dej thiab kis ntawm solder. Thiab nyuaj rau tshem tawm. Thaum lub sij hawm brazing, cov txheej txheem brazing tuaj yeem ua tau tsuas yog nrog cov flux kom raug.

Qhov thib ob, kev ua haujlwm ntawm aluminium thiab aluminium alloy brazing yog qhov nyuaj. Lub melting point ntawm aluminium thiab aluminium alloy tsis txawv ntau ntawm cov khoom siv brazing cov hlau siv. Qhov kev xaiv kub ntau rau brazing yog nqaim heev. Kev tswj qhov kub thiab txias me ntsis yog ib qho yooj yim ua rau overheating los yog melting ntawm lub hauv paus hlau, ua rau cov txheej txheem brazing nyuaj. Qee cov aluminium alloys ntxiv dag zog los ntawm kev kho cua sov kuj yuav ua rau softening phenomena xws li kev laus los yog annealing vim brazing cua sov, uas yuav txo tau cov khoom ntawm brazed pob qij txha. Thaum lub sij hawm nplaim taws brazing, nws yog ib qho nyuaj rau txiav txim rau qhov kub thiab txias vim hais tias cov xim ntawm aluminium alloy tsis hloov thaum lub sij hawm cua sov, uas kuj yuav ua rau kom cov kev cai rau tus neeg teb xov tooj lub lag luam theem.

Ntxiv mus, corrosion kuj ntawm aluminium thiab aluminium alloy brazed pob qij txha yog yooj yim cuam tshuam los ntawm muab tub lim hlau thiab fluxes. Cov electrode muaj peev xwm ntawm txhuas thiab txhuas alloy yog qhov sib txawv ntawm cov solder, uas txo cov corrosion kuj ntawm kev sib koom tes, tshwj xeeb tshaj yog rau cov muag muag muag. Tsis tas li ntawd, feem ntau ntawm cov fluxes siv nyob rau hauv brazing ntawm txhuas thiab txhuas alloys muaj zog corrosivity. Txawm hais tias lawv raug ntxuav tom qab brazing, lub zog ntawm cov fluxes ntawm corrosion kuj ntawm cov pob qij txha yuav tsis raug tshem tawm tag nrho.

2. Cov khoom siv brazing

(1) Brazing ntawm aluminium thiab aluminium alloys yog ib txoj kev siv tsis tshua muaj, vim hais tias muaj pes tsawg leeg thiab electrode muaj peev xwm ntawm brazing muab tub lim hlau thiab lub hauv paus hlau yog qhov sib txawv heev, uas yooj yim ua rau electrochemical corrosion ntawm kev sib koom tes. Cov muag muag muag feem ntau yog siv cov zinc raws li cov khoom siv thiab cov tin lead solder, uas tuaj yeem muab faib ua qhov kub tsis tshua muaj (150 ~ 260 ℃), nruab nrab kub solder (260 ~ 370 ℃) thiab kub kub solder (370 ~ 430 ℃) raws li qhov kub thiab txias. Thaum siv cov tin lead solder thiab tooj liab los yog npib tsib xee yog ua ntej plated rau ntawm aluminium nto rau brazing, corrosion ntawm qhov sib koom ua ke tuaj yeem tiv thaiv, thiaj li txhim kho corrosion kuj ntawm kev sib koom tes.

Brazing ntawm aluminium thiab aluminium alloys yog dav siv, xws li lim cov lus qhia, evaporator, radiator thiab lwm yam khoom. Tsuas yog txhuas raws li cov khoom siv hlau tuaj yeem siv rau kev sib tsoo ntawm txhuas thiab txhuas alloys, ntawm cov txhuas silicon muab tub lim hlau yog siv dav tshaj plaws. Qhov tshwj xeeb ntawm daim ntawv thov thiab lub zog shear ntawm cov pob qij txha brazed yog qhia hauv Table 8 thiab cov lus 9 feem. Txawm li cas los xij, lub melting point ntawm no solder yog nyob ze rau ntawm lub hauv paus hlau, yog li ntawd lub cua sov kub yuav tsum nruj me ntsis tswj lub sij hawm brazing kom tsis txhob overheating los yog melting ntawm lub hauv paus hlau.

Table 8 daim ntawv thov Scope ntawm brazing muab tub lim rau txhuas thiab txhuas alloys

Table 9 shear zog ntawm txhuas thiab txhuas alloy pob qij txha brazed nrog txhuas silicon muab tub lim hlau

Aluminium silicon solder feem ntau yog muab rau hauv daim ntawv ntawm hmoov, muab tshuaj txhuam, xaim lossis ntawv. Qee qhov xwm txheej, cov hlau nplaum sib xyaw nrog txhuas ua cov tub ntxhais thiab txhuas silicon solder raws li cov cladding siv. Hom kev sib txuas ntawm cov phaj no yog tsim los ntawm txoj kev hydraulic thiab feem ntau siv los ua ib feem ntawm cov khoom siv brazing. Thaum lub sij hawm brazing, lub brazing muab tub lim hlau ntawm cov phaj sib xyaw melts thiab ntws raws li qhov kev txiav txim ntawm capillary thiab lub ntiajteb txawj nqus los sau qhov sib koom ua ke.

(2) Flux thiab shielding gas rau txhuas thiab aluminium alloy brazing, tshwj xeeb flux feem ntau yog siv los tshem tawm cov yeeb yaj kiab. Cov organic flux raws li triethanolamine, xws li fs204, yog siv nrog cov mos mos muag kub. Qhov kom zoo dua ntawm cov flux no yog tias nws muaj kev cuam tshuam me ntsis ntawm cov hlau hauv paus, tab sis nws yuav tsim cov roj ntau ntau, uas yuav cuam tshuam rau cov ntub dej thiab ua rau lub cev qhuav dej. Lub reactive flux raws li zinc chloride, xws li fs203 thiab fs220a, yog siv nrog nruab nrab kub thiab kub kub muag muag. Lub reactive flux yog heev corrosive, thiab nws residue yuav tsum tau muab tshem tawm tom qab brazing.

Tam sim no, lub brazing ntawm aluminium thiab aluminium alloys tseem yog dominated los ntawm flux zaj duab xis tshem tawm. Lub brazing flux siv muaj xws li chloride raws flux thiab fluoride raws flux. Chloride raws li flux muaj zog muaj peev xwm tshem tawm oxide zaj duab xis thiab zoo fluidity, tab sis nws muaj ib tug zoo corrosive nyhuv ntawm lub hauv paus hlau. Nws residue yuav tsum tau muab tshem tawm tag nrho tom qab brazing. Fluoride raws li flux yog ib hom tshiab flux, uas muaj cov nyhuv zoo tshem tawm cov yeeb yaj kiab thiab tsis muaj corrosion rau hauv paus hlau. Txawm li cas los xij, nws muaj qhov siab melting point thiab tsis zoo thermal stability, thiab tsuas yog siv tau nrog aluminium silicon solder.

Thaum brazing aluminium thiab aluminium alloys, lub tshuab nqus tsev, nruab nrab lossis inert cua feem ntau siv. Thaum siv lub tshuab nqus tsev vacuum, lub tshuab nqus tsev kawm ntawv feem ntau yuav ncav cuag qhov kev txiav txim ntawm 10-3pa. Thaum siv cov roj nitrogen lossis argon roj rau kev tiv thaiv, nws cov purity yuav tsum siab heev, thiab cov dej lwg taw tes yuav tsum qis dua -40 ℃

3. Brazing tshuab

Brazing ntawm aluminium thiab aluminium alloys muaj qhov xav tau siab rau kev ntxuav ntawm workpiece nto. Yuav kom tau txais cov khoom zoo, cov roj stain thiab oxide zaj duab xis ntawm qhov chaw yuav tsum tau muab tshem tawm ua ntej brazing. Tshem tawm cov roj stain rau saum npoo nrog Na2CO3 aqueous tov ntawm qhov kub ntawm 60 ~ 70 ℃ rau 5 ~ 10min, thiab tom qab ntawd yaug nrog dej huv; oxide zaj duab xis saum npoo tuaj yeem raug tshem tawm los ntawm etching nrog NaOH aqueous tov ntawm qhov kub ntawm 20 ~ 40 ℃ rau 2 ~ 4min, thiab tom qab ntawd ntxuav nrog dej kub; Tom qab tshem cov roj stain thiab oxide zaj duab xis rau saum npoo, lub workpiece yuav tsum tau kho nrog HNO3 aqueous tov rau gloss rau 2 ~ 5min, ces ntxuav hauv dej ntws thiab thaum kawg qhuav. Lub workpiece kho los ntawm cov txheej txheem no yuav tsum tsis txhob kov los yog kis nrog lwm yam av, thiab yuav tsum tau brazed nyob rau hauv 6 ~ 8h. Nws yog qhov zoo dua rau braze tam sim yog tias ua tau.

Cov txheej txheem brazing ntawm aluminium thiab aluminium alloys feem ntau suav nrog cov nplaim hluav taws xob, cov hlau nplaum thiab cov khoom siv hluav taws xob. Cov txheej txheem no feem ntau siv flux hauv brazing, thiab muaj cov kev cai nruj ntawm cov cua sov thiab tuav lub sijhawm. Thaum cov nplaim hluav taws kub hnyiab thiab soldering hlau brazing, tsis txhob tso cua sov ntawm qhov hluav taws xob ncaj qha los ntawm cov cua sov kom tiv thaiv cov dej ntws los ntawm overheating thiab tsis ua hauj lwm. Txij li thaum txhuas tuaj yeem yaj hauv cov mos muag muag nrog cov ntsiab lus zinc siab, cov cua sov yuav tsum tau nres thaum sib koom ua ke kom tsis txhob muaj cov hlau xeb. Qee zaum, lub brazing ntawm aluminium thiab aluminium alloys qee zaum tsis siv flux, tab sis siv ultrasonic los yog scraping txoj kev tshem tawm cov yeeb yaj kiab. Thaum siv scraping kom tshem tawm cov zaj duab xis rau brazing, ua ntej sov lub workpiece mus rau lub brazing kub, thiab tom qab ntawd txhuam lub brazing ib feem ntawm lub workpiece nrog rau qhov kawg ntawm lub solder pas nrig (los yog scraping cuab tam). Thaum tawg oxide zaj duab xis nto, qhov kawg ntawm lub solder yuav yaj thiab ntub lub hauv paus hlau.

Brazing txoj kev ntawm txhuas thiab txhuas alloys mas muaj xws li nplaim taws brazing, furnace brazing, dip brazing, nqus brazing thiab roj shielded brazing. Nplaim brazing feem ntau yog siv rau me me workpieces thiab ib daim ntau lawm. Txhawm rau kom tsis txhob muaj qhov tsis ua haujlwm ntawm cov flux vim yog kev sib cuag ntawm cov impurities hauv acetylene thiab cov flux thaum siv cov nplaim hluav taws xob oxyacetylene, nws tsim nyog siv cov roj cua compressed cua nplaim hluav taws xob nrog me ntsis txo kom tsis txhob oxidation ntawm lub hauv paus hlau. Thaum lub sij hawm tshwj xeeb brazing, lub brazing flux thiab muab tub lim hlau tuaj yeem muab tso rau ntawm qhov chaw brazed ua ntej thiab rhuab rau tib lub sijhawm nrog cov khoom ua haujlwm; Lub workpiece tseem tuaj yeem ua kom sov rau qhov kub ntawm lub brazing ua ntej, thiab tom qab ntawd lub solder dipped nrog flux tuaj yeem xa mus rau txoj haujlwm brazing; Tom qab cov flux thiab muab tub lim hlau yog yaj, cov nplaim hluav taws kub yuav tsum tau muab tshem tawm maj mam tom qab cov hlau muab tub lim yog sib npaug.

Thaum brazing txhuas thiab aluminium alloy nyob rau hauv lub cua kub cua sov, lub brazing muab tub lim hlau yuav tsum preset, thiab lub brazing flux yuav tsum tau melted nyob rau hauv distilled dej los npaj ib tug tuab tov nrog ib tug concentration ntawm 50% ~ 75%, thiab ces coated los yog sprayed nyob rau hauv lub brazing nto. Tus nqi tsim nyog ntawm cov hmoov brazing flux kuj tseem tuaj yeem them rau ntawm cov khoom siv hlau brazing thiab brazing nto, thiab tom qab ntawd cov khoom sib dhos yuav tsum muab tso rau hauv qhov cub rau cua sov brazing. Txhawm rau tiv thaiv lub hauv paus hlau los ntawm overheating los yog melting, cov cua kub yuav tsum nruj me ntsis tswj.

Muab tshuaj txhuam los yog ntawv ci solder feem ntau yog siv rau dip brazing ntawm txhuas thiab txhuas alloys. Cov khoom sib dhos yuav tsum tau preheated ua ntej brazing kom nws qhov kub thiab txias nyob ze rau qhov kub ntawm lub brazing, thiab ces muab tso rau hauv brazing flux rau brazing. Thaum lub sij hawm brazing, lub brazing kub thiab lub sij hawm brazing yuav tsum nruj me ntsis tswj. Yog tias qhov kub thiab txias heev, lub hauv paus hlau yog ib qho yooj yim rau yaj thiab cov solder yog ib qho yooj yim kom ploj; Yog hais tias qhov kub thiab txias yog tsawg, lub solder yog melted tsis txaus, thiab tus nqi brazing yuav txo. Lub brazing kub yuav tsum tau txiav txim raws li hom thiab qhov loj ntawm lub hauv paus hlau, muaj pes tsawg leeg thiab melting point ntawm cov muab tub lim hlau, thiab feem ntau yog nruab nrab ntawm cov kua kub ntawm cov muab tub lim hlau thiab cov solidus kub ntawm lub hauv paus hlau. Lub sij hawm dipping ntawm lub workpiece nyob rau hauv lub flux da dej yuav tsum xyuas kom meej tias lub solder yuav tag nrho yaj thiab ntws, thiab lub sij hawm txhawb yuav tsum tsis txhob ntev dhau. Txwv tsis pub, cov khoom silicon nyob rau hauv lub solder yuav diffuse mus rau hauv lub hauv paus hlau, ua rau lub hauv paus hlau nyob ze ntawm lub seam brittle.

Nyob rau hauv lub tshuab nqus tsev brazing ntawm txhuas thiab txhuas alloys, hlau ua hauj lwm activators feem ntau yog siv los hloov cov nto oxide zaj duab xis ntawm txhuas thiab xyuas kom cov ntub dej thiab kis ntawm solder. Magnesium tuaj yeem siv ncaj qha rau ntawm qhov chaw ua haujlwm hauv daim ntawv ntawm cov khoom, lossis nkag mus rau hauv cheeb tsam brazing hauv daim ntawv ntawm chav, lossis magnesium tuaj yeem ntxiv rau aluminium silicon solder ua cov khoom siv hlau. Rau lub workpiece nrog complex qauv, thiaj li yuav xyuas kom meej tag nrho cov nyhuv ntawm magnesium vapor nyob rau hauv lub hauv paus hlau thiab txhim kho lub brazing zoo, lub zos shielding txheej txheem yog feem ntau siv, uas yog, lub workpiece yog xub muab tso rau hauv ib lub thawv stainless hlau (feem ntau hu ua lub thawv txheej txheem), thiab ces muab tso rau hauv lub tshuab nqus tsev rau cua sov brazing. Nqus Brazed Txhuas thiab aluminium alloy pob qij txha muaj du nto thiab ntom brazed pob qij txha, thiab tsis tas yuav tsum tau ntxuav tom qab brazing; Txawm li cas los xij, cov khoom siv lub tshuab nqus tsev vacuum yog kim, thiab cov magnesium vapor ua rau lub qhov cub tawg tiag tiag, yog li nws yuav tsum tau ntxuav thiab khaws cia ntau zaus.

Thaum brazing aluminium thiab aluminium alloys hauv nruab nrab lossis inert cua, magnesium activator lossis flux tuaj yeem siv los tshem tawm cov yeeb yaj kiab. Thaum siv magnesium activator los tshem tawm cov yeeb yaj kiab, cov nyiaj magnesium xav tau qis dua li ntawm lub tshuab nqus tsev. Feem ntau, w (mg) yog li ntawm 0.2% ~ 0.5%. Thaum cov ntsiab lus ntawm magnesium yog siab, qhov zoo ntawm kev sib koom tes yuav raug txo. NOCOLOK brazing txoj kev siv fluoride flux thiab nitrogen tiv thaiv yog ib txoj kev tshiab tsim sai sai nyob rau hauv xyoo tas los no. Txij li cov residue ntawm fluoride flux tsis nqus dej noo thiab tsis corrosive rau txhuas, cov txheej txheem ntawm kev tshem tawm flux residue tom qab brazing tuaj yeem raug tshem tawm. Raws li kev tiv thaiv ntawm nitrogen, tsuas yog me me ntawm fluoride flux yuav tsum tau coated, cov hlau muab tub lim tuaj yeem ntub cov hlau hauv paus, thiab nws yooj yim kom tau txais cov pob qij txha zoo. Tam sim no, txoj kev NOCOLOK brazing no tau siv rau hauv kev tsim khoom ntawm txhuas radiator thiab lwm yam khoom.

Rau txhuas thiab txhuas alloy brazed nrog flux uas tsis yog fluoride flux, cov flux residue yuav tsum tau muab tshem tawm tag nrho tom qab brazing. Cov seem ntawm cov organic brazing flux rau txhuas tuaj yeem ntxuav nrog cov tshuaj organic xws li methanol thiab trichloroethylene, neutralized nrog sodium hydroxide aqueous tov, thiab thaum kawg ntxuav nrog dej kub thiab txias. Chloride yog cov seem ntawm brazing flux rau txhuas, uas tuaj yeem raug tshem tawm raws li cov hauv qab no; Ua ntej, soak hauv dej kub ntawm 60 ~ 80 ℃ rau 10min, ua tib zoo ntxuav cov seem ntawm lub brazed sib koom nrog txhuam, thiab ntxuav nws nrog dej txias; Tom qab ntawd tsau nws hauv 15% nitric acid aqueous tov rau 30 feeb, thiab thaum kawg yaug nrog dej txias.