Refractory materials are materials that break down by heat, pressure, or chemical attack and retain high strength and form at temperatures where they occur. Refractory materials are polycrystalline, multiphase, inorganic, non-metallic, porous and heterogeneous. They are usually composed of oxides or non-oxides (such as carbides, nitrides, etc.) of the following materials: silicon, aluminum, magnesium, calcium, and zirconium. Some metals with melting points >1850 degree, xws li niobium, chromium, zirconium, tungsten, tantalum, thiab lwm yam, kuj suav tias yog cov khoom siv refractory.
Cov ntaub ntawv refractory yog siv rau hauv qhov cub, kilns, incinerators thiab reactors. Refractories kuj tseem siv nyob rau hauv kev tsim cov crucibles thiab pwm rau casting iav thiab hlau, thiab nyob rau hauv lub cladding ntawm fuse systems rau foob pob ua ntxaij tsim qauv. Niaj hnub no, kev lag luam steel thiab hlau casting kev lag luam siv kwv yees li 60% ntawm tag nrho cov ntaub ntawv refractory.
Cov yam ntxwv ntawm cov khoom siv refractory
Cov ntaub ntawv refractory yuav tsum muaj tshuaj lom neeg thiab lub cev ruaj khov ntawm qhov kub thiab txias. Nyob ntawm qhov chaw ua haujlwm, lawv yuav tsum tiv taus thermal shock, chemically inert thiab / los yog muaj ntau yam thermal conductivity thiab coefficient ntawm thermal expansion.
Oxides ntawm aluminium (aluminium oxide), silicon (silica) thiab magnesium (magnesium oxide) yog cov ntaub ntawv tseem ceeb tshaj plaws siv hauv kev tsim cov refractories. Lwm oxide feem ntau pom nyob rau hauv cov ntaub ntawv refractory yog calcium (lime) oxide. Refractory av nplaum kuj tau siv dav hauv kev tsim cov khoom siv refractory.
Cov ntaub ntawv refractory yuav tsum raug xaiv raws li cov xwm txheej uas lawv yuav ntsib. Qee daim ntawv thov xav tau cov ntaub ntawv tshwj xeeb refractory. Zirconia yog siv thaum cov khoom yuav tsum tiv taus kub heev. Silicon carbide thiab carbon (graphite) yog ob qho khoom siv refractory siv nyob rau hauv qee qhov kub hnyav, tab sis lawv tsis tuaj yeem tiv nrog oxygen vim lawv yuav oxidize thiab hlawv.
binary compounds xws li tungsten carbide los yog boron nitride tuaj yeem ua tau zoo heev. Carbonite yog cov feem ntau refractory binary compound paub, nrog ib tug melting point ntawm 3890 degree. Lub ternary compound tantalum-hafnium carbide muaj ib lub siab tshaj plaws melting cov ntsiab lus ntawm tag nrho cov paub tebchaw (4215 degree).
Cov ntaub ntawv refractory tuaj yeem siv rau cov haujlwm hauv qab no:
Ua raws li thermal barrier ntawm lub thermal nruab nrab thiab lub thawv phab ntsa
Tiv thaiv lub cev siab thiab tiv thaiv qhov nruab nrab ntawm thermal los ntawm eroding lub thawv phab ntsa
Anti-corrosion
Muab thermal rwb thaiv tsev
Refractories muaj ntau yam kev siv tau zoo. Hauv kev lag luam metallurgical, cov ntaub ntawv refractory yog siv los ua kab rau hauv qhov cub, kilns, reactors, thiab lwm cov nkoj uas muaj thiab thauj cov xov xwm kub xws li hlau thiab slag. Refractories muaj lwm yam kev siv kub kub xws li combustion heaters, hydrogen reformers, ammonia thawj thiab theem nrab reformers, cracking furnaces, utility boilers, catalytic cracking units, cua sov thiab sulfur furnaces.
