{"id":53,"date":"2024-09-19T06:55:09","date_gmt":"2024-09-19T06:55:09","guid":{"rendered":"https:\/\/pwhtsolutions.net\/?p=53"},"modified":"2025-01-05T09:26:12","modified_gmt":"2025-01-05T09:26:12","slug":"tepelne-zpracovani-po-svarovani-2","status":"publish","type":"post","link":"https:\/\/pwhtsolutions.net\/cs\/post-weld-heat-treatment-2\/","title":{"rendered":"Tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed"},"content":{"rendered":"

Tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) je proces ur\u010den\u00fd k uvoln\u011bn\u00ed a redistribuci zbytkov\u00fdch nap\u011bt\u00ed vznikl\u00fdch p\u0159i sva\u0159ov\u00e1n\u00ed a z\u00e1rove\u0148 k metalurgick\u00fdm zm\u011bn\u00e1m, kter\u00e9 zvy\u0161uj\u00ed pevnost, ta\u017enost a hou\u017eevnatost.<\/p>\n

PWHT m\u016f\u017ee b\u00fdt u n\u011bkter\u00fdch kov\u016f pou\u017e\u00edvan\u00fdch v tlakov\u00fdch za\u0159\u00edzen\u00edch p\u0159edeps\u00e1na pr\u016fmyslov\u00fdmi p\u0159edpisy; jej\u00ed nezbytnost je v\u0161ak t\u0159eba pe\u010dliv\u011b posoudit v porovn\u00e1n\u00ed s n\u00e1klady a mo\u017en\u00fdmi nep\u0159\u00edzniv\u00fdmi \u00fa\u010dinky na vlastnosti materi\u00e1lu.<\/p>\n

Zbytkov\u00e1 nap\u011bt\u00ed<\/h2>\n

Zbytkov\u00e1 nap\u011bt\u00ed mohou vznikat b\u011bhem sva\u0159ov\u00e1n\u00ed v d\u016fsledku teplotn\u00edch gradient\u016f mezi svarov\u00fdm materi\u00e1lem a z\u00e1kladn\u00edm materi\u00e1lem a mohou dos\u00e1hnout kritick\u00e9 \u00farovn\u011b, co\u017e m\u016f\u017ee v\u00e9st k prask\u00e1n\u00ed nebo korozn\u00edmu prask\u00e1n\u00ed sou\u010d\u00e1st\u00ed s tlust\u00fdmi st\u011bnami. V\u011bt\u0161ina p\u0159edpis\u016f pro tlakov\u00e9 n\u00e1doby a potrub\u00ed stanov\u00ed tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT), pokud sva\u0159ovan\u00e9 d\u00edly p\u0159ekro\u010d\u00ed ur\u010dit\u00e9 konstruk\u010dn\u00ed meze kluzu, aby se omezil mo\u017en\u00fd k\u0159ehk\u00fd lom.<\/p>\n

PWHT je proces ur\u010den\u00fd k odstran\u011bn\u00ed nebo redistribuci zbytkov\u00fdch nap\u011bt\u00ed a k podpo\u0159e popou\u0161t\u011bn\u00ed, sr\u00e1\u017een\u00ed a st\u00e1rnut\u00ed ve svarov\u00e9m kovu, co\u017e v kone\u010dn\u00e9m d\u016fsledku zvy\u0161uje hou\u017eevnatost, ta\u017enost a odolnost proti korozn\u00edmu prask\u00e1n\u00ed. Pro \u00fa\u010dinn\u00fd proces PWHT je v\u0161ak t\u0159eba l\u00e9pe porozum\u011bt jeho mechanism\u016fm.<\/p>\n

Za t\u00edmto \u00fa\u010delem se pou\u017e\u00edv\u00e1 anal\u00fdza kone\u010dn\u00fdch prvk\u016f (MKP) k simulaci nap\u011b\u0165ov\u00fdch pol\u00ed v modelech pru\u017en\u00e9 a pru\u017en\u011b-plastick\u00e9 anal\u00fdzy pro sva\u0159ence s r\u016fznou tlou\u0161\u0165kou st\u011bny. Rovn\u011b\u017e je pou\u017eit komplexn\u00ed p\u0159\u00edstup k modelov\u00e1n\u00ed te\u010den\u00ed, aby bylo mo\u017en\u00e9 pochopit, jak plastick\u00e1 deformace a zp\u011btn\u00e9 nap\u011bt\u00ed p\u0159isp\u00edvaj\u00ed k odleh\u010den\u00ed zbytkov\u00fdch nap\u011bt\u00ed.<\/p>\n

V\u00fdsledky ukazuj\u00ed, \u017ee PWHT m\u016f\u017ee v\u00e9st k uspokojiv\u00e9mu sn\u00ed\u017een\u00ed zbytkov\u00e9ho nap\u011bt\u00ed a zlep\u0161en\u00ed vlastnost\u00ed materi\u00e1lu v \u0161irok\u00e9m rozsahu materi\u00e1l\u016f sva\u0159enc\u016f, p\u0159i\u010dem\u017e kone\u010dn\u00e1 pevnost v tahu se po o\u0161et\u0159en\u00ed bl\u00ed\u017e\u00ed konstruk\u010dn\u00ed hodnot\u011b. Dal\u0161\u00ed v\u00fdzkum by se m\u011bl zam\u011b\u0159it na vytvo\u0159en\u00ed vhodn\u00e9ho vztahu mezi \u010dasem, teplotou a tlou\u0161\u0165kou pro siln\u011bj\u0161\u00ed sva\u0159ence podroben\u00e9 PWHT, aby se minimalizovala rizika spojen\u00e1 s k\u0159ehk\u00fdm lomem a zv\u00fd\u0161ila celkov\u00e1 spolehlivost jejich sva\u0159enc\u016f.<\/p>\n

Tvrdost<\/h2>\n

Tvrdost kov\u016f je ukazatelem jejich mikrostruktury a m\u016f\u017ee m\u00edt z\u00e1sadn\u00ed vliv na to, zda jsou sva\u0159ovac\u00ed postupy nebo p\u0159\u00eddavn\u00e9 kovy vhodn\u00e9 pro ur\u010dit\u00e9 aplikace. Nadm\u011brn\u011b tvrd\u00e9 mikrostruktury maj\u00ed tendenci b\u00fdt m\u00e9n\u011b tv\u00e1rn\u00e9 a hou\u017eevnat\u00e9 ne\u017e m\u011bk\u010d\u00ed kovy, proto m\u016f\u017ee b\u00fdt n\u011bkdy nutn\u00e9 tepeln\u00e9 zpracov\u00e1n\u00ed, aby se zlep\u0161ily mechanick\u00e9 vlastnosti nebo sn\u00ed\u017eila n\u00e1chylnost k prask\u00e1n\u00ed.<\/p>\n

PWHT (Process Warm Heat Treatment) je forma tepeln\u00e9ho zpracov\u00e1n\u00ed pou\u017e\u00edvan\u00e1 k odstran\u011bn\u00ed zbytkov\u00fdch nap\u011bt\u00ed a zv\u00fd\u0161en\u00ed pevnosti, ta\u017enosti a hou\u017eevnatosti svaru. PWHT m\u016f\u017ee tak\u00e9 pomoci zabr\u00e1nit vzniku trhlin zp\u016fsoben\u00fdch tepeln\u00fdm cyklov\u00e1n\u00edm nebo korozn\u00edm prask\u00e1n\u00edm; jejich pot\u0159eba z\u00e1vis\u00ed na typu kovu\/tlou\u0161\u0165ce\/rozm\u011bru a tak\u00e9 na parametrech sva\u0159ov\u00e1n\u00ed\/po\u017eadavc\u00edch na obsluhu.<\/p>\n

P\u0159edpisy \u010dasto stanov\u00ed, \u017ee sva\u0159ovan\u00e9 materi\u00e1ly nebo sva\u0159ence nad ur\u010ditou tlou\u0161\u0165ku vy\u017eaduj\u00ed z d\u016fvodu ochrany po sva\u0159ov\u00e1n\u00ed tepeln\u00e9 zpracov\u00e1n\u00ed. D\u016fvodem je skute\u010dnost, \u017ee n\u011bkter\u00e9 kovy jsou n\u00e1chyln\u011bj\u0161\u00ed ke korozn\u00edmu prask\u00e1n\u00ed pod nap\u011bt\u00edm nebo maj\u00ed vy\u0161\u0161\u00ed riziko selh\u00e1n\u00ed svaru ne\u017e jin\u00e9, zat\u00edmco r\u016fzn\u00e9 sva\u0159ovac\u00ed procesy vytv\u00e1\u0159ej\u00ed tvrd\u0161\u00ed usazeniny ne\u017e jin\u00e9.<\/p>\n

Hou\u017eevnatost<\/h2>\n

P\u0159i sva\u0159ov\u00e1n\u00ed mohou vznikat zbytkov\u00e1 nap\u011bt\u00ed, kter\u00e1 v kombinaci se zat\u011b\u017eovac\u00edmi nap\u011bt\u00edmi ohro\u017euj\u00ed hou\u017eevnatost materi\u00e1lu. \u0158\u00edzen\u00fd proces oh\u0159evu a chlazen\u00ed zn\u00e1m\u00fd jako PWHT m\u016f\u017ee pomoci zlep\u0161it mechanick\u00e9 vlastnosti, zm\u00edrnit zbytkov\u00e1 nap\u011bt\u00ed a zv\u00fd\u0161it pevnost a tvrdost svarov\u00fdch spoj\u016f; jeho nezbytnost z\u00e1vis\u00ed na n\u011bkolika faktorech, v\u010detn\u011b parametr\u016f sva\u0159ov\u00e1n\u00ed a po\u017eadavk\u016f na provoz; anal\u00fdza lomov\u00e9 mechaniky s pou\u017eit\u00edm p\u0159edpokl\u00e1dan\u00fdch \u00farovn\u00ed nap\u011bt\u00ed a velikosti vad m\u016f\u017ee pomoci ur\u010dit, zda je PWHT nutn\u00e1.<\/p>\n

Pro v\u00fdpo\u010det minim\u00e1ln\u00ed po\u017eadovan\u00e9 hou\u017eevnatosti pro konkr\u00e9tn\u00ed materi\u00e1ly a tlou\u0161\u0165ku pr\u016f\u0159ezu byl navr\u017een jednoduch\u00fd model. Po\u017eadavky na lomovou hou\u017eevnatost (K mat) pak byly odhadnuty pro dv\u011b r\u016fzn\u00e9 pravd\u011bpodobnosti selh\u00e1n\u00ed, P f = 0,05 a P f = 0,5, s pou\u017eit\u00edm korelace mezi lomovou hou\u017eevnatost\u00ed a Charpyho energi\u00ed podle p\u0159\u00edlohy J normy BS 7910.<\/p>\n

Jak ukazuj\u00ed n\u00ed\u017ee uveden\u00e9 obr\u00e1zky, v\u00fdsledky na\u0161\u00ed anal\u00fdzy ukazuj\u00ed, \u017ee i relativn\u011b mal\u00e9 sn\u00ed\u017een\u00ed teploty PWHT m\u016f\u017ee v\u00fdrazn\u011b sn\u00ed\u017eit odhadovan\u00e9 minim\u00e1ln\u00ed po\u017eadavky na K mat. To je pravd\u011bpodobn\u011b zp\u016fsobeno \u00fa\u010dinkem PWHT, kter\u00fd sni\u017euje omezen\u00ed hrotu trhliny a zlep\u0161uje prodlou\u017een\u00ed trhliny tv\u00e1rn\u00fdm trh\u00e1n\u00edm; v\u00fdsledky nav\u00edc ukazuj\u00ed, \u017ee PWHT m\u016f\u017ee tak\u00e9 v\u00fdrazn\u011b zlep\u0161it r\u00e1zovou hou\u017eevnatost laserem sva\u0159ovan\u00fdch vzork\u016f t\u00edm, \u017ee obnov\u00ed jejich p\u016fvodn\u00ed k\u0159ehk\u00fd lomov\u00fd re\u017eim s \u0159\u00ed\u010dn\u00edmi vzorci pozorovan\u00fdmi u neo\u0161et\u0159en\u00fdch vzork\u016f.<\/p>\n

Ta\u017enost<\/h2>\n

Pod pojmem tv\u00e1rnost se rozum\u00ed schopnost materi\u00e1lu plasticky se deformovat p\u0159ed vznikem trhlin p\u0159i nam\u00e1h\u00e1n\u00ed, na rozd\u00edl od pru\u017en\u00e9 deformace, kter\u00e1 se po uvoln\u011bn\u00ed nap\u011bt\u00ed zm\u011bn\u00ed v deformaci zp\u011btnou. Duktilita je ned\u00edln\u00fdm faktorem p\u0159i navrhov\u00e1n\u00ed sou\u010d\u00e1st\u00ed, proto\u017ee ukazuje, jak velkou deformaci m\u016f\u017ee sou\u010d\u00e1st vydr\u017eet, ne\u017e sel\u017ee; v\u011bt\u0161\u00ed duktilita znamen\u00e1 v\u011bt\u0161\u00ed pravd\u011bpodobnost jej\u00ed deformace p\u0159i extr\u00e9mn\u00edm zat\u00ed\u017een\u00ed.<\/p>\n

Ta\u017enost materi\u00e1l\u016f do zna\u010dn\u00e9 m\u00edry z\u00e1vis\u00ed na jejich chemick\u00e9m slo\u017een\u00ed, krystalov\u00e9 struktu\u0159e a teplot\u011b zkou\u0161en\u00ed. Kovy maj\u00ed tendenci vykazovat v\u011bt\u0161\u00ed ta\u017enost, proto\u017ee jejich kovov\u00e9 vazby umo\u017e\u0148uj\u00ed sd\u00edlen\u00ed elektron\u016f valen\u010dn\u00ed slupky mezi v\u00edce atomy, a t\u00edm umo\u017e\u0148uj\u00ed atom\u016fm kovu snadno se pohybovat kolem sebe a z\u00e1rove\u0148 absorbovat s\u00edly, kter\u00e9 by u jin\u00fdch materi\u00e1l\u016f zp\u016fsobily rozt\u0159\u00ed\u0161t\u011bn\u00ed.<\/p>\n

A\u010dkoli jsou tv\u00e1rnost a kujnost \u00fazce spojeny, z\u016fst\u00e1vaj\u00ed odli\u0161n\u00fdmi vlastnostmi. Ta\u017enost se vztahuje ke schopnosti kovu odol\u00e1vat tahov\u00fdm roztahovac\u00edm sil\u00e1m, zat\u00edmco kujnost se vztahuje k tomu, jak dob\u0159e zvl\u00e1d\u00e1 tlakov\u00e9 nam\u00e1h\u00e1n\u00ed zp\u016fsoben\u00e9 kladivem nebo lisov\u00e1n\u00edm. Ob\u011b vlastnosti je t\u0159eba br\u00e1t v \u00favahu p\u0159i v\u00fdb\u011bru materi\u00e1l\u016f pro konkr\u00e9tn\u00ed aplikace; materi\u00e1ly s vysokou ta\u017enost\u00ed, jako je zlato, lze natahovat jen do t\u00e9 doby, ne\u017e dojde k jejich zlomen\u00ed, zat\u00edmco materi\u00e1ly s ni\u017e\u0161\u00ed ta\u017enost\u00ed, jako je m\u011b\u010f, se mohou natahovat jen do velmi mal\u00e9 tlou\u0161\u0165ky, ne\u017e se pod tlakem zlom\u00ed.<\/p>","protected":false},"excerpt":{"rendered":"

Tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) je proces ur\u010den\u00fd k uvoln\u011bn\u00ed a redistribuci zbytkov\u00fdch nap\u011bt\u00ed vznikl\u00fdch p\u0159i sva\u0159ov\u00e1n\u00ed a z\u00e1rove\u0148 k metalurgick\u00fdm zm\u011bn\u00e1m, kter\u00e9 zvy\u0161uj\u00ed pevnost, ta\u017enost a hou\u017eevnatost. PWHT m\u016f\u017ee b\u00fdt u n\u011bkter\u00fdch kov\u016f pou\u017e\u00edvan\u00fdch v tlakov\u00fdch za\u0159\u00edzen\u00edch p\u0159edeps\u00e1na pr\u016fmyslov\u00fdmi p\u0159edpisy; jej\u00ed nezbytnost je v\u0161ak t\u0159eba pe\u010dliv\u011b posoudit v porovn\u00e1n\u00ed s n\u00e1klady a potenci\u00e1ln\u00edmi ... <\/p>\n

P\u0159e\u010dt\u011bte si v\u00edce “Post Weld Heat Treatment”<\/span><\/a><\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-53","post","type-post","status-publish","format-standard","hentry","category-product-related"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/53","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/comments?post=53"}],"version-history":[{"count":1,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/53\/revisions"}],"predecessor-version":[{"id":54,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/53\/revisions\/54"}],"wp:attachment":[{"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/media?parent=53"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/categories?post=53"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/tags?post=53"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}