Recycled steel, tseem hu ua lwm yam hlau, yog cov hlau yooj yim uas tau rov qab los ntawm cov khoom seem thiab ua tiav kom rov siv tau dua rau cov khoom tshiab. Tsis zoo li ntau lwm cov ntaub ntawv uas poob zoo tom qab siv dua, steel yog 100% recyclable -qhov no txhais tau tias nws tuaj yeem yaj thiab rov qab siv tau tas li yam tsis muaj kev txo qis hauv nws lub zog, kav ntev, lossis kev ua haujlwm. Nyob rau hauv luv luv, nws hloov "khoom hlau" mus rau hauv ib tug muaj txiaj ntsim kev pab, pab tsim kom muaj ib tug ntau ruaj khov thiab ncig kev lag luam uas cov ntaub ntawv khaws cia nyob rau hauv siv es tsis txhob muab pov tseg.
Yuav kom nkag siab txog cov hlau uas siv dua tshiab, nws yog ib qho tseem ceeb kom paub qhov twg nws cov khoom siv raw -steel seem- los ntawm.
Cov khoom siv hlau muaj peb qhov tseem ceeb: ncej-cov khoom siv khoom siv, xa ntawv- cov khoom siv hluav taws xob, thiab cov khoom pov tseg. Tshaj tawm- cov khoom siv khoom siv suav nrog qhov kawg- ntawm- cov khoom peb siv hauv lub neej niaj hnub, xws li tsheb qub, tub yees, tshuab ntxhua khaub ncaws, hluav taws xob, thiab cov kaus poom zaub mov. Tom qab- cov khoom seem hauv kev lag luam yog cov hlau ntau dhau thaum tsim khoom, xws li tawm- txiav los ntawm kev ua cov hlau lossis cov khoom tsis zoo uas tsis tuaj yeem ncav cuag lub khw. Kev rhuav tshem cov khib nyiab yog los ntawm kev rhuav tshem cov vaj tsev qub, txuas hniav, lossis lwm cov qauv, nrog rau cov kab hlau thiab cov rebar siv hauv kev tsim kho. Tag nrho cov khoom seem no tau sau thiab txheeb xyuas kom tshem tawm cov impurities ua ntej ua tiav rau hauv cov hlau siv dua.
Cov txheej txheem ntawm kev ua cov hlau rov ua dua yog yooj yim dua thiab zoo ib puag ncig ntau dua li tsim cov hlau tshiab (virgin) los ntawm cov hlau ore. Ua ntej, cov khib nyiab khib nyiab tau txheeb xyuas kom zoo- cov hlau nplaum sib nqus feem ntau yog siv los cais cov hlau los ntawm lwm cov hlau uas tsis yog- ferrous hlau xws li txhuas lossis tooj liab, vim cov hlau yog hlau nplaum thiab yooj yim txheeb xyuas. Tom qab ntawd, cov khib nyiab cais tau yaj hauv lub qhov cub hluav taws xob hluav taws xob (EAF), uas siv cov hluav taws xob siab -tsim hluav taws xob arcs los ua kom muaj cua sov heev (tshaj 1,600 degree) kom yaj cov hlau tag. Thaum lub sij hawm tus txheej txheem no, fluxes zoo li limestone yog ntxiv kom tshem tawm cov impurities seem, thiab alloys yuav raug ntxiv kom ua tiav qhov xav tau zoo rau kev siv sib txawv. Thaum kawg, cov hlau molten yog cam khwb cia rau hauv billets, tuav, los yog nplooj ntawv, uas tuaj yeem ua rau cov khoom siv hlau tshiab.
Ib qho ntawm qhov zoo tshaj plaws ntawm cov hlau siv dua tshiab yog nws cov txiaj ntsig ib puag ncig. Kev tsim cov hlau rov ua dua tshiab txuag ntau lub zog thiab cov peev txheej ntuj piv rau kev ua cov hlau nkauj xwb. Qhov nruab nrab, rov ua dua ib tuj ntawm cov hlau txuag 2,500 phaus hlau ore, 1,400 phaus thee, thiab 120 phaus limestone- thiab nws siv 74% tsawg zog dua li cov hlau los ntawm cov khoom siv raw. Nws kuj tseem txo qis cov pa hluav taws xob hauv tsev cog khoom loj: rov ua dua ib lub tsheb steel txiav emissions sib npaug rau 150 nkas loos roj av, thiab ib tuj ntawm cov hlau rov ua dua txo CO₂ emissions txog li 58% piv rau cov hlau nkauj xwb. Tsis tas li ntawd, cov hlau rov ua dua tshiab khaws ntau lab tons ntawm cov khoom seem ntawm qhov chaw pov tseg txhua xyoo, txo cov khib nyiab thiab ib puag ncig cov pa phem.
Recycled steel tsis tsuas yog eco-tus phooj ywg tab sis kuj raug nqi- zoo thiab ntau yam. Nws muaj lub zog thiab zoo ib yam li cov hlau tsis huv, yog li nws tuaj yeem siv tau nyob rau hauv yuav luag txhua daim ntawv thov uas siv cov hlau tshiab -los ntawm kev tsim kho (steel beams, rebar) thiab kev tsim tsheb (tsheb lub cev, qhov chaw) mus rau cov khoom siv hauv tsev, ntim khoom, thiab cov phiaj xwm kev tsim kho xws li txuas hniav thiab qhov. Niaj hnub no, nyob ib ncig ntawm 85-90% ntawm cov hlau tau siv thoob ntiaj teb, ua rau nws yog cov khoom siv rov ua dua tshiab los ntawm qhov hnyav hauv ntiaj teb. Raws li ntau lub teb chaws tsom mus rau kev ruaj khov thiab txo qis carbon emissions, cov hlau rov ua dua tshiab ua lub luag haujlwm tseem ceeb hauv kev tsim kom muaj kev nyab xeeb rau yav tom ntej, txhawb kev tiv thaiv ib puag ncig thiab kev txhim kho kev lag luam.