Po v\u00edce ne\u017e dvaceti letech, kdy se zab\u00fdv\u00e1m v\u00fdb\u011brem a instalac\u00ed pecn\u00edho n\u00e1bytku a vysokoteplotn\u00edch komponent\u016f, jsem vid\u011bl, jak se \u0159ada materi\u00e1l\u016f objevila a zase zmizela. N\u011bkter\u00e9 vypadaj\u00ed na pap\u00ed\u0159e slibn\u011b, ale v praxi rychle sel\u017eou. Desky z karbidu k\u0159em\u00edku se st\u00e1le b\u011b\u017en\u011b pou\u017e\u00edvaj\u00ed, proto\u017ee \u0159e\u0161\u00ed probl\u00e9my, s nimi\u017e si oxid hlinit\u00fd, kordierit nebo mullit \u010dasto neporad\u00ed. Spojuj\u00ed v sob\u011b dobrou pevnost p\u0159i vysok\u00fdch teplot\u00e1ch s neobvykle vysokou tepelnou vodivost\u00ed, co\u017e umo\u017e\u0148uje konstrukt\u00e9r\u016fm provozovat rychlej\u0161\u00ed cykly a p\u0159esto dos\u00e1hnout dlouh\u00e9 \u017eivotnosti. Nejedn\u00e1 se o nejlevn\u011bj\u0161\u00ed variantu, ale v mnoha z\u00e1vodech se v dlouhodob\u00e9m horizontu uk\u00e1\u017eou jako nejhospod\u00e1rn\u011bj\u0161\u00ed \u0159e\u0161en\u00ed.<\/p>\n
Desky z karbidu k\u0159em\u00edku se vyr\u00e1b\u011bj\u00ed z zrn karbidu k\u0159em\u00edku, kter\u00e1 jsou bu\u010f spojena reak\u010dn\u00edm pojivem, nebo slinuta. P\u0159i v\u00fdrob\u011b s reak\u010dn\u00edm pojivem se pr\u00e1\u0161ek karbidu k\u0159em\u00edku sm\u00edch\u00e1 s uhl\u00edkem nebo k\u0159em\u00edkem, vytvaruje se lisov\u00e1n\u00edm nebo vytla\u010dov\u00e1n\u00edm a pot\u00e9 se vypaluje v atmosf\u00e9\u0159e bohat\u00e9 na k\u0159em\u00edk. K\u0159em\u00edk reaguje s uhl\u00edkem a vytv\u00e1\u0159\u00ed dal\u0161\u00ed karbid k\u0159em\u00edku, kter\u00fd spojuje p\u016fvodn\u00ed zrna dohromady. U slinut\u00fdch verz\u00ed se pou\u017e\u00edv\u00e1 vysoce \u010dist\u00fd pr\u00e1\u0161ek SiC s mal\u00fdm mno\u017estv\u00edm slinovac\u00edch p\u0159\u00edsad a vypaluj\u00ed se p\u0159i velmi vysok\u00fdch teplot\u00e1ch, \u010dasto nad 2000 \u00b0C, aby se dos\u00e1hlo hust\u00fdch t\u011bles. Oba postupy umo\u017e\u0148uj\u00ed v\u00fdrobu desek o tlou\u0161\u0165ce obvykle 6 mm a\u017e 25 mm, kter\u00e9 se dod\u00e1vaj\u00ed ve standardn\u00edch rozm\u011brech nebo v tvarech na m\u00edru pro pecn\u00ed police, izola\u010dn\u00ed desky a podp\u011bry.<\/p>\n
Nejv\u00fdrazn\u011bj\u0161\u00ed vlastnost\u00ed je tepeln\u00e1 vodivost. V\u011bt\u0161ina keramick\u00fdch materi\u00e1l\u016f je \u0161patn\u00fdm vodi\u010dem tepla, ale desky z karbidu k\u0159em\u00edku b\u011b\u017en\u011b dosahuj\u00ed hodnoty 20\u201340 W\/m\u00b7K nebo i v\u00edce, v z\u00e1vislosti na t\u0159\u00edd\u011b a hustot\u011b. To m\u00e1 velk\u00fd v\u00fdznam u v\u00fdpalov\u00e9ho n\u00e1\u0159ad\u00ed. P\u0159i v\u00fdpalu porcel\u00e1nu nebo technick\u00e9 keramiky police samy absorbuj\u00ed a uvol\u0148uj\u00ed teplo. Desky s vysokou tepelnou vodivost\u00ed se zah\u0159\u00edvaj\u00ed a ochlazuj\u00ed rychleji ne\u017e ekvivalenty z oxidu hlinit\u00e9ho nebo kordieritu, tak\u017ee lze zkr\u00e1tit cel\u00fd cyklus vypalov\u00e1n\u00ed. Vid\u011bl jsem z\u00e1vody, kter\u00e9 po p\u0159echodu na police z SiC zkr\u00e1tily dobu vypalov\u00e1n\u00ed o 15\u201325 %, co\u017e p\u0159\u00edmo sni\u017euje spot\u0159ebu plynu nebo elekt\u0159iny na tunu produktu.<\/p>\n
Odolnost proti tepeln\u00e9mu \u0161oku p\u0159edstavuje dal\u0161\u00ed praktickou v\u00fdhodu. Vzhledem k tomu, \u017ee materi\u00e1l rychle vede teplo, z\u016fst\u00e1vaj\u00ed teplotn\u00ed rozd\u00edly v desce p\u0159i rychl\u00e9m oh\u0159evu nebo ochlazov\u00e1n\u00ed men\u0161\u00ed. Koeficient tepeln\u00e9 rozta\u017enosti je na keramiku rovn\u011b\u017e relativn\u011b n\u00edzk\u00fd. D\u00edky t\u00e9to kombinaci mohou desky bez prasklin vydr\u017eet stovky cykl\u016f mezi pokojovou teplotou a 1400\u20131600 \u00b0C, pokud jsou spr\u00e1vn\u011b podep\u0159eny. V jedn\u00e9 tov\u00e1rn\u011b na dla\u017edice, se kterou jsem spolupracoval, praskaly kordieritov\u00e9 police p\u0159i rychl\u00fdch cyklech ka\u017ed\u00fdch n\u011bkolik m\u011bs\u00edc\u016f; n\u00e1hradn\u00ed desky z SiC vydr\u017eely p\u0159i stejn\u00e9m programu vypalov\u00e1n\u00ed v\u00edce ne\u017e dva roky.<\/p>\n
Mechanick\u00e1 pevnost p\u0159i vysok\u00fdch teplot\u00e1ch je rovn\u011b\u017e vynikaj\u00edc\u00ed. Karbid k\u0159em\u00edku si zachov\u00e1v\u00e1 u\u017eite\u010dnou pevnost v ohybu i p\u0159i teplot\u00e1ch v\u00fdrazn\u011b nad 1200 \u00b0C, na rozd\u00edl od mnoha oxidov\u00fdch keramik, kter\u00e9 p\u0159i takov\u00fdch teplot\u00e1ch m\u011bknou. To umo\u017e\u0148uje, aby ten\u010d\u00ed desky unesly stejn\u00e9 zat\u00ed\u017een\u00ed, co\u017e d\u00e1le sni\u017euje tepelnou hmotnost a zvy\u0161uje energetickou \u00fa\u010dinnost. Odolnost proti od\u011bru je vynikaj\u00edc\u00ed, tak\u017ee desky pou\u017e\u00edvan\u00e9 v abrazivn\u00edm prost\u0159ed\u00ed nebo p\u0159i vysok\u00e9m zat\u00ed\u017een\u00ed se rychle neopot\u0159ebov\u00e1vaj\u00ed. Z chemick\u00e9ho hlediska odol\u00e1vaj\u00ed pom\u011brn\u011b dob\u0159e v\u011bt\u0161in\u011b kyselin a roztaven\u00fdch kov\u016f, i kdy\u017e p\u0159i teplot\u00e1ch nad p\u0159ibli\u017en\u011b 1200 \u00b0C na vzduchu pomalu oxiduj\u00ed a vytv\u00e1\u0159ej\u00ed ochrannou vrstvu oxidu k\u0159emi\u010dit\u00e9ho. V reduk\u010dn\u00edch nebo inertn\u00edch atmosf\u00e9r\u00e1ch si vedou je\u0161t\u011b l\u00e9pe.<\/p>\n
Tyto desky se pou\u017e\u00edvaj\u00ed p\u0159edev\u0161\u00edm v keramick\u00e9m pr\u016fmyslu a p\u0159i tepeln\u00e9m zpracov\u00e1n\u00ed. Nej\u010dast\u011bji se vyu\u017e\u00edvaj\u00ed jako police do pec\u00ed a podlo\u017eky pro vypalov\u00e1n\u00ed porcel\u00e1nu, sanit\u00e1rn\u00ed keramiky a pokro\u010dil\u00fdch keramick\u00fdch materi\u00e1l\u016f. Desky lze vyrobit tak, aby byly dostate\u010dn\u011b ploch\u00e9 a stabiln\u00ed, aby unesly velk\u00e9 nebo k\u0159ehk\u00e9 kusy bez proh\u00fdb\u00e1n\u00ed. Pou\u017e\u00edvaj\u00ed se tak\u00e9 ve v\u00fdm\u011bn\u00edc\u00edch tepla, sou\u010d\u00e1stech ho\u0159\u00e1k\u016f a n\u011bkter\u00fdch za\u0159\u00edzen\u00edch pro chemick\u00e9 procesy, kde je vy\u017eadov\u00e1na jak vysok\u00e1 tepeln\u00e1 vodivost, tak odolnost proti korozi. P\u0159i zpracov\u00e1n\u00ed polovodi\u010d\u016f slou\u017e\u00ed desky z vysoce \u010dist\u00e9ho SiC jako nosi\u010de desti\u010dek nebo susceptory, proto\u017ee zp\u016fsobuj\u00ed minim\u00e1ln\u00ed kovovou kontaminaci.<\/p>\n
Samoz\u0159ejm\u011b to s sebou nese ur\u010dit\u00e9 kompromisy. Desky z karbidu k\u0159em\u00edku jsou dra\u017e\u0161\u00ed na kilogram ne\u017e desky z oxidu hlinit\u00e9ho nebo kordieritu, tak\u017ee jejich pou\u017eit\u00ed se obvykle ospravedl\u0148uje del\u0161\u00ed \u017eivotnost\u00ed, rychlej\u0161\u00edmi cykly nebo men\u0161\u00edm po\u010dtem rozbit\u00fdch v\u00fdrobk\u016f p\u0159i vypalov\u00e1n\u00ed. Jsou tak\u00e9 k\u0159eh\u010d\u00ed ne\u017e ocel, tak\u017ee s nimi je t\u0159eba p\u0159i nakl\u00e1d\u00e1n\u00ed a vykl\u00e1d\u00e1n\u00ed zach\u00e1zet opatrn\u011b; pokud desku upust\u00edte na roh, obvykle se od\u0161t\u00edpne nebo praskne. Oxidace postupn\u011b zvy\u0161uje hmotnost a m\u016f\u017ee v pr\u016fb\u011bhu mnoha let m\u011bnit rozm\u011bry, i kdy\u017e p\u0159i b\u011b\u017en\u00fdch teplot\u00e1ch v peci je tento proces pomal\u00fd. Ve velmi vysokorychlostn\u00edch proudech plynu nebo p\u0159i pou\u017eit\u00ed ur\u010dit\u00fdch tavidel m\u016f\u017ee b\u00fdt probl\u00e9mem eroze, proto je d\u016fle\u017eit\u00fd v\u00fdb\u011br spr\u00e1vn\u00e9 t\u0159\u00eddy materi\u00e1lu.<\/p>\n
Z praktick\u00e9ho hlediska lze v\u00fdsledky zlep\u0161it dodr\u017eov\u00e1n\u00edm n\u011bkolika z\u00e1sad. Dbejte na to, aby byl v\u00fdpaln\u00fd n\u00e1\u0159ad\u00ed rovnom\u011brn\u011b podep\u0159en, aby desky nebyly vystaveny bodov\u00e9mu zat\u00ed\u017een\u00ed ani kroucen\u00ed. Mezi deskami nechte p\u0159im\u011b\u0159en\u00e9 mezery pro rozta\u017enost. P\u0159i p\u0159echodu z oxidov\u00e9ho vybaven\u00ed p\u0159epo\u010d\u00edtejte tepelnou hmotnost a m\u00edrn\u011b upravte vypalovac\u00ed k\u0159ivku; v opa\u010dn\u00e9m p\u0159\u00edpad\u011b m\u016f\u017ee rychlej\u0161\u00ed odezva SiC zp\u016fsobit p\u0159ekro\u010den\u00ed teploty, pokud se star\u00fd program nezm\u011bn\u00ed. Pravideln\u011b kontrolujte desky, zda nevykazuj\u00ed povrchovou oxidaci nebo po\u0161kozen\u00ed hran, a vym\u011b\u0148te je d\u0159\u00edve, ne\u017e ovlivn\u00ed kvalitu v\u00fdrobk\u016f.<\/p>\n
Podle m\u00fdch zku\u0161enost\u00ed dosahuj\u00ed nejlep\u0161\u00ed n\u00e1vratnosti ty z\u00e1vody, kter\u00e9 vn\u00edmaj\u00ed desky z karbidu k\u0159em\u00edku sp\u00ed\u0161e jako dlouhodobou investici ne\u017e jako p\u0159\u00edmou n\u00e1hradu. Sleduj\u00ed doby cyklu, spot\u0159ebu energie a \u017eivotnost p\u0159ed i po zaveden\u00ed zm\u011bny a p\u0159izp\u016fsobuj\u00ed podp\u016frn\u00e9 syst\u00e9my a manipula\u010dn\u00ed postupy tak, aby vyhovovaly tomuto materi\u00e1lu. Jakmile je toto provedeno, desky poskytuj\u00ed konzistentn\u00ed v\u00fdkon po stovky cykl\u016f s minim\u00e1ln\u00ed \u00fadr\u017ebou.<\/p>\n
Desky z karbidu k\u0159em\u00edku sice nenahrad\u00ed v\u0161echny ostatn\u00ed \u017e\u00e1ruvzdorn\u00e9 materi\u00e1ly, ale pokud dan\u00e1 aplikace vy\u017eaduje opakovan\u00e9 cykly vysok\u00fdch teplot, dobr\u00fd p\u0159enos tepla a p\u0159im\u011b\u0159enou \u017eivotnost, z\u016fst\u00e1vaj\u00ed jednou z nejspolehliv\u011bj\u0161\u00edch dostupn\u00fdch voleb. V mnoha provozech, se kter\u00fdmi jsem spolupracoval, ti\u0161e sn\u00ed\u017eily jak n\u00e1klady na energii, tak nepl\u00e1novan\u00e9 prostoje, ani\u017e by k jejich pou\u017eit\u00ed bylo zapot\u0159eb\u00ed speci\u00e1ln\u00edho vybaven\u00ed nebo vysoce specializovan\u00fdch dovednost\u00ed. Pr\u00e1v\u011b d\u00edky t\u00e9to kombinaci v\u00fdkonu a prakti\u010dnosti si i nad\u00e1le udr\u017euj\u00ed sv\u00e9 m\u00edsto v n\u00e1ro\u010dn\u00fdch tepeln\u00fdch procesech.<\/p>","protected":false},"excerpt":{"rendered":"
After more than twenty years specifying and installing kiln furniture and high-temperature components, I\u2019ve seen plenty of materials come and […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"footnotes":""},"categories":[5],"tags":[],"class_list":["post-398","post","type-post","status-publish","format-standard","hentry","category-product-related"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/posts\/398","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/comments?post=398"}],"version-history":[{"count":1,"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/posts\/398\/revisions"}],"predecessor-version":[{"id":399,"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/posts\/398\/revisions\/399"}],"wp:attachment":[{"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/media?parent=398"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/categories?post=398"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/siliconcarbideceramic.net\/cs\/wp-json\/wp\/v2\/tags?post=398"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}