Tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed je proces, jeho\u017e c\u00edlem je minimalizovat a p\u0159erozd\u011blit zbytkov\u00e1 nap\u011bt\u00ed vznikl\u00e1 b\u011bhem sva\u0159ov\u00e1n\u00ed, kter\u00e1 by mohla zv\u00fd\u0161it n\u00e1chylnost k prask\u00e1n\u00ed zp\u016fsoben\u00e9mu vod\u00edkem nebo zp\u016fsobit jin\u00e9 formy poru\u0161en\u00ed materi\u00e1lu.<\/p>\n
PWHT se obvykle prov\u00e1d\u00ed pomoc\u00ed induk\u010dn\u00edho oh\u0159evu. Induk\u010dn\u00ed oh\u0159ev vyu\u017e\u00edv\u00e1 vysokofrekven\u010dn\u00ed st\u0159\u00eddav\u00fd elektrick\u00fd proud k vytv\u00e1\u0159en\u00ed magnetick\u00fdch pol\u00ed a v\u00ed\u0159iv\u00fdch proud\u016f pro oh\u0159ev kovu, podobn\u011b jako u PWHT, av\u0161ak rychleji.<\/p>\n
\u017d\u00edh\u00e1n\u00ed je jedn\u00edm z nej\u00fa\u010dinn\u011bj\u0161\u00edch tepeln\u00fdch \u00faprav pou\u017e\u00edvan\u00fdch v procesech po sva\u0159ov\u00e1n\u00ed a spo\u010d\u00edv\u00e1 v oh\u0159\u00e1t\u00ed ur\u010dit\u00e9 oblasti na specifickou teplotu po stanovenou dobu a jej\u00edm n\u00e1sledn\u00e9m postupn\u00e9m ochlazov\u00e1n\u00ed. \u017d\u00edh\u00e1n\u00ed pom\u00e1h\u00e1 uvolnit nap\u011bt\u00ed v materi\u00e1lech a z\u00e1rove\u0148 jim umo\u017e\u0148uje rovnom\u011brn\u011bj\u0161\u00ed rozta\u017enost a smr\u0161\u0165ov\u00e1n\u00ed v pr\u016fb\u011bhu \u010dasu.<\/p>\n
\u017d\u00edh\u00e1n\u00ed p\u0159isp\u00edv\u00e1 ke zlep\u0161en\u00ed fyzik\u00e1ln\u00edch vlastnost\u00ed tepeln\u011b ovlivn\u011bn\u00fdch z\u00f3n (HAZ) svaru. P\u0159i sva\u0159ov\u00e1n\u00ed doch\u00e1z\u00ed k vysr\u00e1\u017een\u00ed ur\u010dit\u00fdch prvk\u016f ze slitiny, jako jsou karbidy, co\u017e zp\u016fsobuje, \u017ee se HAZ st\u00e1v\u00e1 k\u0159eh\u010d\u00ed a n\u00e1chyln\u011bj\u0161\u00ed ke korozi; \u017e\u00edh\u00e1n\u00ed v\u0161ak m\u016f\u017ee tento \u00fa\u010dinek zm\u00edrnit a zv\u00fd\u0161it struktur\u00e1ln\u00ed integritu HAZ svaru.<\/p>\n
Technologie PWHT m\u016f\u017ee v\u00fdrazn\u011b sn\u00ed\u017eit riziko vzniku trhlin ve svarech zp\u016fsoben\u00fdch vod\u00edkem a zabr\u00e1nit tak\u00e9 jin\u00fdm druh\u016fm trhlin, jako jsou trhliny zp\u016fsoben\u00e9 torzn\u00edm nam\u00e1h\u00e1n\u00edm nebo cyklick\u00fdm nam\u00e1h\u00e1n\u00edm. Krom\u011b toho technologie PWHT usnad\u0148uje p\u0159\u00edpadn\u00e9 opravy \u010di v\u00fdm\u011bnu a zvy\u0161uje celkovou efektivitu v\u00fdroby.<\/p>\n
P\u0159i prov\u00e1d\u011bn\u00ed procesu PWHT je z\u00e1sadn\u00ed pou\u017e\u00edt vhodn\u00e9 metody oh\u0159evu a ochlazov\u00e1n\u00ed, aby bylo dosa\u017eeno co nejlep\u0161\u00edch v\u00fdsledk\u016f. Zejm\u00e9na by oh\u0159ev m\u011bl b\u00fdt dostate\u010dn\u00fd k zv\u00fd\u0161en\u00ed teploty v oblasti svaru, zat\u00edmco rychlost ochlazov\u00e1n\u00ed nesm\u00ed zp\u016fsobovat dal\u0161\u00ed tepeln\u011b indukovan\u00e9 nap\u011bt\u00ed. Izola\u010dn\u00ed materi\u00e1ly mohou pomoci udr\u017eet teplotu svaru rovnom\u011brnou i b\u011bhem procesu PWHT.<\/p>\n
Normalizace je metoda slou\u017e\u00edc\u00ed k uvoln\u011bn\u00ed vnit\u0159n\u00edch pnut\u00ed a ke zv\u00fd\u0161en\u00ed ta\u017enosti svar\u016f. Dosahuje se toho postupn\u00fdm zvy\u0161ov\u00e1n\u00edm teploty a n\u00e1sledn\u00fdm postupn\u00fdm ochlazov\u00e1n\u00edm \u2013 t\u00edm se zabra\u0148uje deformac\u00edm, kroucen\u00ed a naru\u0161en\u00ed struktur\u00e1ln\u00ed integrity tlakov\u00fdch za\u0159\u00edzen\u00ed d\u00edky zaji\u0161t\u011bn\u00ed rovnom\u011brn\u00e9 rychlosti ochlazov\u00e1n\u00ed v cel\u00e9m objemu. Normalizace nav\u00edc umo\u017e\u0148uje materi\u00e1lu ochlazovat se rovnom\u011brn\u00fdm tempem, \u010d\u00edm\u017e se sni\u017euje riziko vzniku trhlin.<\/p>\n
Normalizace spo\u010d\u00edv\u00e1 v p\u0159iveden\u00ed slo\u017eek slitiny do homogenn\u011bj\u0161\u00edho a izotropn\u011bj\u0161\u00edho stavu, co\u017e p\u0159isp\u00edv\u00e1 ke sn\u00ed\u017een\u00ed lok\u00e1ln\u00edch odchylek ve vlastnostech, kter\u00e9 ovliv\u0148uj\u00ed celkovou pevnost a trvanlivost svar\u016f, zat\u00edmco p\u0159erozd\u011blen\u00ed atom\u016f b\u011bhem tepeln\u00e9ho zpracov\u00e1n\u00ed omezuje vznik trhlin zp\u016fsoben\u00fdch vod\u00edkem ve svarech.<\/p>\n
Po\u017eadavky na tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) z\u00e1vis\u00ed na chemick\u00e9m slo\u017een\u00ed a tlou\u0161\u0165ce sva\u0159ovan\u00e9ho materi\u00e1lu. PWHT m\u016f\u017ee b\u00fdt p\u0159edeps\u00e1no normami pro kritick\u00e9 sou\u010d\u00e1sti potrub\u00ed nebo tlakov\u00fdch n\u00e1dob; nav\u00edc m\u016f\u017ee jeho pou\u017eit\u00ed prodlou\u017eit \u017eivotnost sn\u00ed\u017een\u00edm n\u00e1chylnosti ke korozi.<\/p>\n
PWHT lze prov\u00e1d\u011bt na r\u016fzn\u00fdch materi\u00e1lech a slitin\u00e1ch, v\u010detn\u011b ocel\u00ed s n\u00edzk\u00fdm i vysok\u00fdm obsahem uhl\u00edku. V z\u00e1vislosti na materi\u00e1lu a zam\u00fd\u0161len\u00e9m pou\u017eit\u00ed m\u016f\u017ee PWHT p\u0159isp\u011bt k uvoln\u011bn\u00ed zbytkov\u00fdch nap\u011bt\u00ed, k temperov\u00e1n\u00ed svar\u016f, ke sn\u00ed\u017een\u00ed obsahu vod\u00edku a ke zv\u00fd\u0161en\u00ed pevnosti v tahu, odolnosti proti te\u010den\u00ed a lomov\u00e9 hou\u017eevnatosti svar\u016f.<\/p>\n
Odstran\u011bn\u00ed zbytkov\u00e9ho nap\u011bt\u00ed pomoc\u00ed PWHT (neboli tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed, zkr\u00e1cen\u011b PWHT) je dopl\u0148kov\u00fd proces tepeln\u00e9ho zpracov\u00e1n\u00ed, kter\u00fd se pou\u017e\u00edv\u00e1 k odstran\u011bn\u00ed zbytkov\u00e9ho nap\u011bt\u00ed ve sva\u0159ovan\u00fdch kovov\u00fdch sou\u010d\u00e1stech. K dosa\u017een\u00ed tohoto c\u00edle zahrnuje tento proces dlouhodob\u00e9 zah\u0159\u00edv\u00e1n\u00ed kovu pod jeho teplotn\u00ed rozsah f\u00e1zov\u00e9 transformace a n\u00e1sledn\u00e9 pomal\u00e9 ochlazov\u00e1n\u00ed \u2013 t\u00edm se sni\u017euje tvrdost a z\u00e1rove\u0148 zvy\u0161uje pru\u017enost a zlep\u0161uje ta\u017enost; materi\u00e1l je tak m\u00e9n\u011b n\u00e1chyln\u00fd k prask\u00e1n\u00ed a z\u00e1rove\u0148 se sni\u017euje riziko vzniku korozn\u00edho prask\u00e1n\u00ed pod nap\u011bt\u00edm v d\u016fsledku drsn\u00fdch nebo kysel\u00fdch podm\u00ednek okoln\u00edho prost\u0159ed\u00ed.<\/p>\n
Zkou\u0161ky zbytkov\u00e9ho nap\u011bt\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) mohou b\u00fdt p\u0159edeps\u00e1ny sva\u0159ovac\u00edmi normami a konstruk\u010dn\u00edmi normami pro tlakov\u00e9 n\u00e1doby a potrub\u00ed, jeliko\u017e kumulativn\u00ed zat\u00ed\u017een\u00ed m\u016f\u017ee p\u0159ekro\u010dit mezn\u00ed hodnoty materi\u00e1lu stanoven\u00e9 p\u0159i n\u00e1vrhu, co\u017e m\u016f\u017ee v\u00e9st k poru\u0161e svaru, po\u0161kozen\u00ed konstrukce a zran\u011bn\u00ed osob.<\/p>\n
Odstran\u011bn\u00ed pnut\u00ed m\u00e1 nav\u00edc tu v\u00fdhodu, \u017ee pom\u00e1h\u00e1 p\u0159edch\u00e1zet prask\u00e1n\u00ed zp\u016fsoben\u00e9mu vod\u00edkem (HIC), kter\u00e9 je vyvol\u00e1no vysok\u00fdmi koncentracemi vod\u00edku v okol\u00ed pronikaj\u00edc\u00edmi do sva\u0159ovan\u00fdch materi\u00e1l\u016f b\u011bhem sva\u0159ovac\u00edch proces\u016f. HIC lze zabr\u00e1nit zah\u0159\u00e1t\u00edm materi\u00e1l\u016f bezprost\u0159edn\u011b po sva\u0159ov\u00e1n\u00ed, \u010d\u00edm\u017e se vod\u00edk vytla\u010d\u00ed z oblasti svaru d\u0159\u00edve, ne\u017e zp\u016fsob\u00ed HIC. Z tohoto d\u016fvodu se takov\u00e9to tepeln\u00e9 o\u0161et\u0159en\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) obvykle pou\u017e\u00edv\u00e1 u dlouh\u00fdch sou\u010d\u00e1st\u00ed, jako jsou trubky nebo uzav\u00edrac\u00ed svary tlakov\u00fdch n\u00e1dob.<\/p>\n
P\u0159i mnoha sva\u0159ovac\u00edch procesech vznik\u00e1 b\u011bhem sva\u0159ov\u00e1n\u00ed vod\u00edk, kter\u00fd je t\u0159eba odv\u00e9st ze sva\u0159ovan\u00e9ho kovu a z\u00f3ny ovlivn\u011bn\u00e9 teplem (HAZ), aby se zabr\u00e1nilo vzniku trhlin zp\u016fsoben\u00fdch vod\u00edkem (HIC). Obvykle to zahrnuje zv\u00fd\u0161en\u00ed teploty a\u017e na jej\u00ed maxim\u00e1ln\u00ed hodnotu a n\u00e1sledn\u00e9 pomal\u00e9 sni\u017eov\u00e1n\u00ed, av\u0161ak aby tento postup fungoval \u00fa\u010dinn\u011b, je nutn\u00e9 p\u0159ijmout i dal\u0161\u00ed opat\u0159en\u00ed, jako je udr\u017eov\u00e1n\u00ed spr\u00e1vn\u00fdch teplot p\u0159edeh\u0159evu a mezi\u0161vov\u00fdch teplot.<\/p>\n
Touto metodou lze sn\u00ed\u017eit zbytkov\u00e9 nap\u011bt\u00ed ve svarov\u00e9m kovu na p\u0159ijatelnou \u00farove\u0148, i kdy\u017e nedoch\u00e1z\u00ed k \u00fapln\u00e9mu odstran\u011bn\u00ed st\u00e1vaj\u00edc\u00edch tahov\u00fdch zbytkov\u00fdch nap\u011bt\u00ed.<\/p>\n
B\u011b\u017en\u00e1 praxe vy\u017eaduje, aby byl materi\u00e1l udr\u017eov\u00e1n p\u0159i sv\u00e9 nejvy\u0161\u0161\u00ed teplot\u011b po odpov\u00eddaj\u00edc\u00ed dobu, kter\u00e1 z\u00e1vis\u00ed na jeho tlou\u0161\u0165ce a druhu. \u010c\u00edm d\u00e9le tato f\u00e1ze trv\u00e1, t\u00edm ni\u017e\u0161\u00ed jsou \u00farovn\u011b zbytkov\u00e9ho nap\u011bt\u00ed.<\/p>\n
Normalizace je dal\u0161\u00ed \u00fa\u010dinn\u00e1 technika ke sn\u00ed\u017een\u00ed tvrdosti svaru, kter\u00e1 je obzvl\u00e1\u0161t\u011b u\u017eite\u010dn\u00e1 u materi\u00e1l\u016f vystaven\u00fdch vysok\u00e9mu obsahu soli a pov\u011btrnostn\u00edm vliv\u016fm, nebo\u0165 pom\u00e1h\u00e1 omezit deformaci jejich struktury. Tento postup spo\u010d\u00edv\u00e1 v oh\u0159\u00e1t\u00ed materi\u00e1lu na jeho maxim\u00e1ln\u00ed teplotu a n\u00e1sledn\u00e9m pomal\u00e9m ochlazen\u00ed \u2013 to z\u00e1rove\u0148 umo\u017e\u0148uje odstranit p\u0159\u00edpadn\u00fd p\u0159ebytek vod\u00edku, kter\u00fd se mohl nahromadit, a t\u00edm zabr\u00e1nit vzniku HIC.<\/p>","protected":false},"excerpt":{"rendered":"
Post weld heat treatment is a process designed to minimize and redistribute residual stresses introduced during welding, which could increase susceptibility to hydrogen-induced cracking or cause other forms of structural failures. PWHT is typically performed using induction heating. Induction heating utilizes high frequency alternating electrical current to generate magnetic fields and eddy currents for metal … <\/p>\n