Dab tsi yog hlau nyob hauv PTFE cua sov phaj thiab vim li cas?

Lub PTFE cua sov phaj yog yas dawb rau sab nrauv tab sis muaj hlau sab hauv uas tau kub liab. Cov hlau twg tuaj yeem coj tau qhov ntawd thiab vim li cas peb tsis siv cov hlau tooj liab? Nws tseem ceeb npaum li cas ntawm cov alloy siv, vim tias nws cuam tshuam qhov kub ntawm lub caij tau txais, nws kav ntev npaum li cas, thiab nws sib npaug npaum li cas.

Nyob rau hauv lub tshav kub phaj ntawm PTFE yog ib tug precisely manufactured resistive hlau los yog etched ntawv ci ntawm tej yam hlau. Cov tooj liab zoo tib yam, lossis txawm tias stainless hlau, yuav luv luv hauv lub plawv dhia. Tooj liab muaj cov hluav taws xob tsis tshua muaj hluav taws xob, yog li koj yuav xav tau ib qho ntev ntawm cov xaim kom tau txais cov wattage xav tau, ntxiv rau nws yuav oxidize thiab yaj ntawm qhov kub uas xav tau rau kev lag luam cua sov. Hloov chaw, cov neeg tsim khoom xaiv los ntawm ob tsev neeg ntawm kev ua tau zoo resistant alloys: Nichrome (ib qho sib xyaw ntawm npib tsib xee thiab chromium) thiab Kanthal (ib qho hlau chromium-aluminium alloy). Cov ntaub ntawv no tsis raug xaiv los ntawm lub caij nyoog, lawv yog cov khoom lag luam ntawm ntau xyoo ntawm kev tsim metallurgical, ua tib zoo yoog raws li cov kev xav tau ntawm hluav taws xob cua sov.

Nichrome, feem ntau 80% npib tsib xee thiab 20% chromium (NiCr 80/20) yog cov neeg ua haujlwm rau feem ntau PTFE daim hlau. Nws cov hluav taws xob tiv taus yog li 1.08-1.13 μΩ·cm, kwv yees li 50 npaug ntawm tooj liab. Lub siab resistivity txhais tau hais tias ib tug luv luv ntev ntawm cov hlau los yog ib tug compact foil tsim yuav muab qhov tsim nyog kuj thiab lub zog tso zis yog li lub caij yuav ua tau me me kom haum snugly ntawm lub rwb thaiv tsev txheej thiab PTFE plhaub. Kanthal yog FeCrAl alloy (feem ntau 22% Cr, 5.5% Al, sib npaug Fe) nrog kev tiv thaiv ntau dua hauv qee qib thiab yuav ua haujlwm ntawm qhov kub thiab txias txog 1400℃hauv huab cua. Ob lub alloys muaj ib yam dab tsi tooj liab tsis: thaum pib rhuab, lawv tsim ib tug tiv thaiv oxide txheej. Nichrome tsim ib qho ruaj khov Cr₂O₃ nplai, Kanthal ib txheej Al₂O₃ ruaj khov. Cov ceramic no-zoo li daim tawv nqaij nres ntxiv oxidation thaum nws tsim, thiab cov hlau tuaj yeem "glow cherry liab" rau ntau txhiab teev yam tsis tau hlawv. Lub caij lub alloy zoo li lub cav ntawm lub rhaub - nws qhov zoo txiav txim siab kev ua haujlwm thiab kev ua haujlwm ntev.

Lwm qhov tseem ceeb tshaj plaws yog qhov kub coefficient of resistance (TCR). Nichrome muaj qhov kub tsis tshua muaj coefficient ntawm tsis kam (TCR) - feem ntau nyob ib ncig ntawm 0.0004 Ω / degree. Cov khoom ua kom sov sab hauv, los ntawm chav tsev kub txog 800℃thiab nws qhov kev tiv thaiv txawv me ntsis. Qhov ruaj khov ntawm qhov tso zis no txhais tau tias nws tuaj yeem kwv yees tau thiab tsis tu ncua yam tsis tas yuav tsum muaj kev tswj xyuas nruj kom ua rau nws. Lub phaj ua tiav setpoint smoothly thiab tswj nws kom raug. Kanthal muaj TCR siab dua me ntsis tab sis nws qhov kub zoo dua lub zog thiab oxide adhesion ua rau nws zoo meej thaum cov neeg tsim qauv thawb rau qhov kub siab tshaj plaws los yog thaum lub phaj yuav tsum tiv taus luv luv dua -kub excursions. Nyob rau hauv ob qho xwm txheej, metallurgical zoo ntawm cov hlau yog qhov tseem ceeb. Txawm tias me me impurities - leej faj, carbon, los yog cov hlau tsis zoo - tuaj yeem ua rau cov chaw tsis muaj zog uas ua rau tsis ua hauj lwm los ntawm kub- qhov chaw loj hlob los yog intergranular corrosion.

Qhov teeb meem tseem ceeb hauv engineering yuav zoo li yog qhov kev sib cuam tshuam ntawm cov hlau kub no nrog rau ib puag ncig PTFE encapsulation. Cov khoom tiv thaiv ua haujlwm ntawm qhov kub thiab txias 300-600℃siab dua sab nraud PTFE nto. Qhov chaw ua haujlwm raug nyob ruaj ntseg nyob rau hauv 200-230℃(nruam-siv txwv rau PTFE), tab sis cov hlau nws tus kheej tuaj yeem ci ntawm 700-900℃. Lub tshav kub yuav tsum dhau los ntawm cov txheej txheej insulating mus rau lub plhaub PTFE yam tsis tau tshaj qhov muag muag ntawm fluoropolymer ntawm lub polymer-hlau interface. Qhov no yog ua tiav los ntawm kev tswj xyuas kom zoo ntawm lub zog ceev thiab qhov tseeb rwb thaiv tsev thickness. Cov chaw kub hauv cheeb tsam tuaj yeem ua rau sab hauv-tawm degradation ntawm PTFE, vim yog qhov tsis sib xws hauv cov hlau lossis cov khoom siv ntau dhau. Qhov no suav nrog embrittlement, micro-voids lossis thaum kawg dielectric tsis ua haujlwm. Nrog rau txoj cai alloy thiab kev txuag kev thauj khoom, PTFE tuaj yeem khaws cov tshuaj tsis muaj zog thiab cov tshuab ua suab nrov rau ntau xyoo.

Rau cov qauv kuaj thiab teeb pom kev zoo-kev lag luam daim ntawv thov- tas li- da dej kub, wafer ua, los yog hnyav rov qab-Nichrome tseem yog qhov pov thawj, ntseeg tau xaiv. Nws kev sib xyaw ua ke ntawm kev ua haujlwm ruaj khov, tus nqi tsim nyog thiab kev tiv thaiv rau lub sijhawm ntev oxidation tau ua tiav ntau tshaj li ib puas xyoo. Rau cov qauv tsim nrog flux siab heev los yog thaum lub phaj yuav tsum tau tiv nrog ceev ceev thermal cycling thiab ua tau nto spikes ntawm 250 degree, tshwj xeeb Kanthal qib los yog ntau dua ua tau zoo FeCrAl hom raug xaiv. Cov alloys no yuav tsum tau nruj dua kev ua haujlwm ntev thiab lub zog siab dua - kev suav ceev kom PTFE encapsulation zoo siab. Cov neeg tsim khoom zoo tsuas yog siv tau ntawv pov thawj, traceable alloy hlau lossis ntawv ci nrog cov ntawv pov thawj zeb kuaj cov ntawv pov thawj hais txog qhov muaj pes tsawg leeg, kev tiv thaiv thiab txoj kab uas hla tolerances. Cov ntsiab lus pheej yig lossis tsis muaj kev lees paub tuaj yeem muaj cov qib chromium lossis txhuas tsis sib xws, ua rau oxidation ntxov ntxov thiab tsis ua haujlwm tom qab ob peb puas teev.

Thaum kawg, nws los txog rau qhov kev xaiv tsim qauv yooj yim: qhov muaj pes tsawg leeg ntawm cov khoom cua sov hlau. Nws yog qhov tsis pom zoo uas txiav txim siab seb lub phaj puas yuav muab cov cua sov tsis sib xws rau ib xyoo caum lossis hlawv tawm tom qab ob xyoos ntawm kev pabcuam. Kawm paub cov ntaub ntawv zais cia no tuaj yeem pab peb nkag siab tias vim li cas qee lub tshuab cua sov PTFE tuaj yeem tiv taus lwm tus los ntawm qhov loj. Tib yam siv tau rau txhua qhov kev ua haujlwm siab - cov cuab yeej ua tau zoo uas cov khoom siv tau zoo yog qhov tseem ceeb: txoj cai alloy, zoo sib xws rau cov ntaub ntawv nyob ib puag ncig thiab kev ua haujlwm, hloov cov cua sov uas yooj yim rau hauv kev ntseeg siab, ntev - lub neej. Xaiv cov hlau sab hauv kom zoo thiab ua tib zoo, thiab cov phaj PTFE dawb rau sab nraud yog ntau tshaj li lub rhaub dej - nws yog qhov ntsiag to, corrosion-cov pov thawj ua haujlwm uas cov neeg ua haujlwm ua haujlwm tuaj yeem tso siab rau ntau xyoo.