Lub thermal conductivity ntawm hlau thiab nws siv

Co - ib yam khoom uas muaj ib tug siv lead ua qauv. Thaum rhuab, lawv yuav tau mus ntsib, hais tias yog, mus rau hauv ib tug dej lub xeev. Ib txhia ntawm lawv muaj ib tug uas tsis muaj melting point: lawv yuav tsum tau melted los tso ib tug dog dig diav thiab ua kom cov nplaim taws ntawm ib tug tswm ciab. Qhov no lead thiab tin. Lwm cov tej zaum yuav melted xwb nyob rau hauv tshwj xeeb furnaces. High melting point muaj tooj liab thiab hlau. Rau nws yuav txo tau rau tus hlau additive yog tswvcuab. Cov tau alloys (steel, bronze, cam khwb cia hlau, tooj dag) muaj ib tug melting point qis tshaj cov niam txiv hlau.

Los ntawm dab tsi lub melting kub ntawm cov hlau? Lawv tag nrho cov muaj tej yam ntxwv - Thaum tshav kub kub muaj peev xwm thiab thermal conductivity ntawm hlau. Lub tshav kub muaj peev xwm yog cov muaj peev xwm ntawm absorbing tshav kub thaum rhuab. Nws hais txog zauv index - tej thaum tshav kub kub. Nyob rau hauv nws yog ib tug muaj nuj nqis ntawm lub zog uas yog tau nqus ib chav tsev loj ntawm cov hlau uas yog rhuab los ntawm 1 ° C. Los ntawm no daim duab nyob ntawm lub roj noj nyob rau hauv cua sov ib tug hlau workpiece rau ib yam kev kub. Cov kev tshav kub ntawm feem ntau co yog nyob rau hauv lub ntau yam ntawm 300-400 J / (kg * K), hlau alloys - 100-2000 J / (kg * K).

Lub thermal conductivity ntawm co - yog cov kev hloov ntawm tshav kub ntawm lub kub tshaj rau lub colder hais los ntawm Fourier txoj cai nyob rau hauv lawv cov macroscopic immobility. Nws yog nyob ntawm cov qauv ntawm cov ntaub ntawv, nws tshuaj nyob tus yeees thiab lub hom interatomic daim ntawv cog lus. Nyob rau hauv cov hlau, lub tshav kub hloov lwm lub tsev yog nqa los ntawm electrons, lwm yam khoom cov ntaub ntawv - phonons. Lub thermal conductivity ntawm hlau yog siab dua, qhov ntau zoo meej crystalline qauv uas lawv muaj. Qhov ntau hlau impurities yog, qhov ntau distorted siv lead ua ntxaij ntoo, thiab rau sab hauv lub thermal conductivity. Alloying ua li distortion nyob rau hauv lub hlau qauv, thiab txo lub thermal conductivity nrog hwm rau cov niam txiv hlau.

Tag nrho cov hlau yog ib tug zoo thermal conductivity, tab sis ib tug ntau dua lwm cov. Piv txwv txog tej co - kub, tej tooj thiab nyiaj. Lower thermal conductivity - lub tin, txhuas thiab hlau. Nce thermal conductivity ntawm co yog ib qho kev kom zoo dua los yog ib tug disadvantage, nyob ntawm seb lub Scope ntawm lawv cov kev siv. Piv txwv li, nws yuav tsum tau ib lub tais hlau rau ceev cua kub ntawm cov khoom noj. Nyob rau tib lub sij hawm, siv cov co uas muaj thermal conductivity rau qhov siv thiab ua cookware leeg yuav ua rau nws yooj yim mus siv - lis heev sai sai rhuab, thiab mus rau lawv nws yog tsis yooj yim sua mus kov. Yog li ntawd, siv insulating cov ntaub ntawv ntawm no.

Lwm cov yam ntxwv ntawm cov hlau rau nws cov khoom - thermal expansion. Nws zoo nkaus li raws li ib qho kev nce nyob rau hauv volume ntawm cov hlau thaum nws yog rhuab thiab zuj zus lawm - thaum lub sij hawm txias. Qhov no tshwm sim yog kiag li tsim nyog los noj mus rau hauv tus account nyob rau hauv lub chaw ua khoom ntawm hlau cov khoom. Piv txwv li, yias hau ua txib, los ntawm Teapots kuj muab ib tug kis ntawm lub hau thiab lub vaj tse yog li ntawd thaum rhuab cover yog tsis jammed.

Rau txhua hlau twb xam coefficient ntawm thermal expansion. Nws yog txiav txim los ntawm cov cua kub ntawm 1 ° C xeem qauv muaj ib tug ntev ntawm 1 m. Qhov loj tshaj plaws coefficient yog lead, zinc, tin. Tsawg nws ntawm tooj liab thiab nyiaj. Txawm qis - hlau thiab kub.

Los ntawm cov tshuaj thaj chaw ntawm lub co raug muab faib ua ob peb pab pawg. Muaj active co (e.g., poov tshuaj los yog sodium) muaj peev xwm ntawm instantaneously reacting nrog cua los yog dej. Lub rau feem ntau active co constituting thawj pab pawg neeg ntawm cov periodic rooj yog hu ua alkaline. Lawv muaj me ntsis melting point thiab thiaj li mos mos hais tias lawv muaj peev xwm yuav txiav nrog ib tug riam. Combining nrog dej, lawv tsim alkaline daws teeb meem, li no lawv lub npe.

Qhov thib ob pab pawg neeg muaj lub alkaline ntiaj teb co -. Calcium, magnesium, thiab lwm yam Lawv nyob rau hauv ntau cov zaub mov thiab ib tug refractory khoom. Piv txwv ntawm cov hlau, thib peb thiab thib plaub pawg yuav pab raws li cov hlau lead thiab txhuas. Nws yog ib heev mos mos co thiab lawv yog feem ntau siv nyob rau hauv alloys. Cov kev hloov co (hlau, chromium, npib tsib xee, tooj liab, kub, silver) yog tsawg active, ib tug forging, thiab feem ntau siv nyob rau hauv muaj daim ntaub ntawv alloys.

Cov hauj lwm ntawm txhua hlau nyob rau hauv kab kev ua si characterizes nws muaj peev xwm yuav hnov mob. Qhov ntau active cov hlau, qhov yooj yim dua nws kim li oxygen. Lawv yog cov heev yooj yim mus cais los ntawm lub tebchaw, thaum uas tsis muaj kev ua si hom co muaj peev xwm yuav nrhiav tau nyob rau hauv nws cov ntshiab daim ntawv. Qhov tseem active ntawm lawv - poov tshuaj thiab sodium - Khaws kerosene tawm ntawm nws lawv tam sim ntawd oxidized. Ntawm co siv nyob rau hauv qhov kev lag luam, tooj liab yog cov tsawg kawg active. Therefrom ua tso tsheb hlau luam thiab dej kub thiab hluav taws xob nyob ntawm tej.