Aluminium mus txog kev lag luam los ntawm cov saw hlau ntawm plaub qhov kev ua haujlwm sib txawv: ua kom cov ore ua kom huv si alumina, txo cov alumina mus rau molten hlau, nrum hlau rau hauv ib nrab- cov khoom tiav, thiab ua cov khoom ntawd rau hauv cov khoom tiav. Txhua theem muaj nws tus kheej cov khoom sib npaug, kev xav tau ntawm lub zog thiab kev tswj kom zoo, thiab cov kev txwv tsis pub dhau theem pib txiav txim siab seb qhov twg tuaj yeem ua tiav hauv qab.
Refining Bauxite rau hauv Alumina
Cov saw hlau pib nrog bauxite, ib qho tom qab ore nplua nuj nyob hauv hydrated aluminium oxides. Cov txheej txheem Bayer dissolves cov ore nyob rau hauv kub sodium hydroxide nyob rau hauv siab, hloov cov txhuas bearing minerals rau soluble sodium aluminate thaum hlau, titanium thiab silica bearing tebchaw nyob insoluble. Cov residue no, hu ua av nkos liab, yog lim tawm thiab khaws cia rau hauv lub pas dej ua ke vim nws cov alkalinity thiab ntim siab.
Cov dej ntshiab sodium aluminate tau txias thiab muab noob rau hauv cov nag lossis daus, qhov twg aluminium hydroxide crystallises tawm ntau hnub. Cov crystals yog ntxuav thiab ces calcined nyob rau hauv rotary kilns ntawm txog 1,000 C kom tshem tawm chemically khi dej, yielding anhydrous alumina (Al2O3).
Cov khoom sib npaug yog qhov tseeb tshaj plaws los txiav txim qhov ntsuas ntawm cov kauj ruam no. Kwv yees li ntawm 4 mus rau 5 tonnes ntawm bauxite yog siv los tsim 2 tonnes ntawm alumina, thiab kev ua kom zoo yog ib qho ntawm lub zog siv zog tshaj plaws ntawm tag nrho cov saw hlau. Silica cov ntsiab lus nyob rau hauv ore yog tus nqi tseem ceeb tsav tsheb, vim hais tias reactive silica siv caustic soda thiab nce noj ntawm ob qho tib si alkali thiab lub zog.
Smelting hauv Hall-Heroult Cells
Alumina hloov mus rau hlau txhuas los ntawm electrolytic txo nyob rau hauv carbon lined hlwb. Lub alumina yog yaj nyob rau hauv molten cryolite ntawm li 950 C, uas txo qhov kub ntawm kev ua hauj lwm mus rau ib theem uas yuav siv tau rau kev ua hauj lwm tas mus li thaum khaws cov electrolyte conductive.
Cov pa roj carbon anodes poob rau hauv da dej thiab noj tsis tu ncua, tso carbon dioxide raws li cov pa oxygen los ntawm alumina ua ke nrog cov pa roj carbon. Cov tam sim no ncaj qha nyob rau hauv thaj tsam ntawm 150,000 txog 300,000 amperes ib kab ntawm tes cais cov aluminium oxygen daim ntawv cog lus, thiab cov molten aluminium, ua denser dua li da dej, sau rau hauv qab ntawm tes. Hlau yog siphoned tawm txhua 24 mus rau 48 teev thiab xa mus rau hauv ladles mus rau lub tsev cam khwb cia.
Kev siv hluav taws xob yog qhov tseem ceeb ntawm cov nqi khiav haujlwm. Lub xovtooj ntawm tes niaj hnub siv kwv yees li 13 txog 15 kWh ib kilogram ntawm txhuas tsim, thiab cov anodes thiab cell hauv ob sab phlu yog cov khoom siv uas yuav tsum tau hloov ntawm lub voj voog uas tau npaj tseg. Qhov no yog vim li cas smelters nyob qhov twg hluav taws xob pheej yig thiab ruaj khov, thiab yog vim li cas incremental nce nyob rau hauv tam sim no efficiency txhais ncaj qha mus rau hauv tus nqi thiab carbon kev ua tau zoo.
Casting thiab Rolling rau Semi-Cov khoom tiav
Cov hlau ua kua yog hloov mus rau hauv ib nrab- cov khoom tiav hauv lub tsev cam khwb cia. Direct chill (DC) casting tsim dov slabs txog li 30 tonnes rau cov khoom tiaj tus, nrog rau extrusion billets rau cov khoom ntev. Cov txheej txheem casting, tshwj xeeb tshaj yog txias tus nqi, tswj cov qauv ingot thiab tus nqi ntawm kev sib cais uas yuav tsum tau muab tshem tawm tom qab.
Homogenization:slabs yog tuav ntawm 500 mus rau 600 C rau 8 mus rau 24 teev cycles kom yaj thiab rov faib cov khoom sib cais thiab ua kom cov qauv sib xws rau dov.
Kub dov:thickness yog txo los ntawm li 600 hli mus rau 2 mus rau 10 hli nyob rau hauv ib tug reversing zeb los ntawm ntau dhau ntawm qhov kub thiab txias.
Txias Rolling:cov kub dov coil yog ntxiv txo kom meej gauges, nqis mus txog 0.006 hli rau ntawv ci, nrog thickness kam rau ua nyob rau hauv li ntawm ntxiv los yog rho tawm 3 feem pua.
Intermediate annealing:Ib qho 350 C anneal yog siv los ntawm cov txheej txheem txias dov los kho cov ductility kom txo qis ntxiv yog ua tau yam tsis muaj ntug tawg.
Ntsuas tswj, flatness thiab deg huv si yog saib xyuas tsis tu ncua nyob rau theem no, vim hais tias ib tug dov tsis xws luag yuav raug kho tom qab ntawm cov txheej txheem saw.
Shaping thiab Forming Methods
Semi- cov khoom tiav tau hloov mus rau qhov tiav geometry los ntawm ib qho ntawm ntau txoj hauv kev, txhua qhov sib tw rau qhov loj me, kam rau ua thiab ntim ntau lawm:
Extrusion:billets rhuab mus txog 500 C raug thawb los ntawm kev tuag ntawm qhov siab mus txog li 100 MPa, ua rau ntev ntu ntu ntu profiles rau kev tsim kho, thauj thiab siv hluav taws xob.
Closed tuag forging:Cov hlau kub yog zoo li ntawm qhov sib tw tuag kom cov nplej ntws raws li txoj kev thauj khoom, uas yog vim li cas forged ncua kev kawm ntawv thiab cov kauj tsheb kauj vab nqa hnyav hnyav loads.
Kev kub siab tuag casting:molten hlau yog txhaj rau hauv cov hlau tuag ntawm qhov siab tshaj li ntawm 70 MPa, muab cov phab ntsa nyias nyias, nyob ze ntawm qhov chaw zoo nkauj rau cov vaj tsev thiab cov hlua khi ntawm lub voj voog siab.
Kev kos duab sib sib zog nqus:daim ntawv yog kos rau hauv khob thiab tom qab ntawd redrawn los ua seamless haus cov kaus poom thiab zoo li nyias phab ntsa ntim.
Additive manufacturing:Selective laser melting tsim complex brackets thiab tshav kub exchanger cores txheej los ntawm txheej, ib txoj kev uas siv cov pa tooling yuav impractical.
Kev kho deg thiab ua tiav
Kev ua tiav txiav txim siab seb qhov ua haujlwm li cas hauv kev pabcuam thiab ntev npaum li cas nws khaws nws cov tsos.
Anodizing:Cov txheej txheem electrolytic uas loj hlob ib txheej ntxeem tau oxide mus txog li 25 microns tuab, siv rau architectural profiles thiab cov neeg siv khoom uas hardness thiab huab cua tsis kam.
Hmoov txheej:electrostatically siv polymer txheej kho ntawm li 200 C, muab cov xim ruaj khov thiab sab nraum zoov huab cua.
Conversion txheej:ib tug nyias chemical zaj duab xis uas txhim kho cov xim adhesion thiab ntxiv kev tiv thaiv corrosion tsis hloov qhov ntev, dav siv rau aerospace thiab automotive Cheebtsam.
Mechanical polishing thiab txhuam:tsim kho kom zoo nkauj thiab tsis tshua muaj kev sib txhuam qhov chaw rau architectural thiab khoom siv.
Laser Texturing:tsim tswj micro grooves uas txhim kho lubricant tuav ntawm zawv zawg qhov chaw thiab cov cuab yeej tsim.
Cov lus nug nquag
Q: Ntau npaum li cas bauxite xav tau los ua alumina?
Raws li daim duab ua haujlwm, 4 mus rau 5 tonnes ntawm bauxite yog siv los tsim 2 tonnes ntawm alumina. Qhov sib piv pes tsawg nyob ntawm qhov muaj alumina cov ntsiab lus ntawm cov ore thiab nyob rau ntau npaum li cas reactive silica yuav tsum tau tsis lees paub thaum lub sij hawm zom mov.
Q: Cov av nkos liab yog dab tsi thiab vim li cas nws thiaj khaws cia rau hauv lub pas dej?
Liab av nkos yog cov insoluble residue tshuav tom qab bauxite zom, ua los ntawm hlau, titanium thiab silica bearing tebchaw ua ke nrog residual alkali. Nws alkalinity thiab ntim yuav tsum tau engineered ntim, thiab nws yog lub ntsiab ib puag ncig tswj cov khoom ntawm lub refining theem.
Q: Vim li cas thiaj siv cryolite hauv aluminium smelting?
Cryolite dissolves alumina thiab cia qhov txo qis ntawm 950 C, zoo hauv qab lub melting point ntawm ntshiab alumina. Qhov ntsuas kub qis dua yog qhov ua rau muaj kev lag luam txuas ntxiv electrolysis siv tau.
Q: Yuav tsum muaj hluav taws xob ntau npaum li cas?
Ib qho kev txo qis niaj hnub siv li ntawm 13 mus rau 15 kWh ib kilogram ntawm txhuas, uas ua rau cov nqi hluav taws xob thiab lub zog ruaj khov rau kev txiav txim siab hauv qhov chaw smelter.
Q: Qhov txawv ntawm qhov kub dov thiab txias dov yog dab tsi?
Kub dov txo cov slab thickness ntawm li 600 hli mus rau 2 mus rau 10 hli ntawm qhov kub thiab txias, qhov twg cov hlau yog mos thiab txo ib tug pass yuav loj. Txias dov ces siv lub kauj mus rau qhov ntsuas kawg, nqes mus txog 0.006 hli, nrog ntau nruj dua thickness kam rau ua thiab zoo dua nto tiav.
Q: Dab tsi shaping txheej txheem yuav tsum tau xaiv rau ib feem?
Extrusion suits tus ntoo khaub lig seem profiles, forging suits load bearing qhov chaw uas xav tau kev txaus siab grain txaus, tuag casting suits nyias phab ntsa vaj tse nyob rau hauv siab ntim, sib sib zog nqus nqus ntim seamless ntim, thiab additive manufacturing suits tsawg ntim complex geometries.
