{"id":285,"date":"2025-09-01T09:10:10","date_gmt":"2025-09-01T09:10:10","guid":{"rendered":"https:\/\/pwhtsolutions.net\/?p=285"},"modified":"2025-09-01T09:10:10","modified_gmt":"2025-09-01T09:10:10","slug":"tepelne-zpracovani-po-svarovani-uhlikove-oceli","status":"publish","type":"post","link":"https:\/\/pwhtsolutions.net\/cs\/post-weld-heat-treatment-for-carbon-steel\/","title":{"rendered":"Tepeln\u00e9 zpracov\u00e1n\u00ed uhl\u00edkov\u00e9 oceli po sva\u0159ov\u00e1n\u00ed"},"content":{"rendered":"

Tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) pom\u00e1h\u00e1 uvolnit a p\u0159erozd\u011blit zbytkov\u00e1 nap\u011bt\u00ed, kter\u00e1 vznikla b\u011bhem sva\u0159ovac\u00edch proces\u016f; toto zpracov\u00e1n\u00ed \u010dasto vy\u017eaduj\u00ed normy pro materi\u00e1ly p\u0159ekra\u010duj\u00edc\u00ed ur\u010dit\u00e9 po\u017eadavky na tlou\u0161\u0165ku.<\/p>\n

Rychlost oh\u0159evu a ochlazov\u00e1n\u00ed je t\u0159eba pe\u010dliv\u011b regulovat, aby se zabr\u00e1nilo tepeln\u00e9mu \u0161oku, deformaci nebo nerovnom\u011brn\u00e9mu uvoln\u011bn\u00ed pnut\u00ed. PWHT lze prov\u00e1d\u011bt bu\u010f v peci, nebo pomoc\u00ed lok\u00e1ln\u00edch elektrick\u00fdch odporov\u00fdch p\u0159ikr\u00fdvek \u010di podlo\u017eek.<\/p>\n

\u017d\u00edh\u00e1n\u00ed<\/h2>\n

PWHT v\u00fdrazn\u011b sni\u017euje \u00farove\u0148 zbytkov\u00fdch tahov\u00fdch nap\u011bt\u00ed v oblastech svar\u016f, av\u0161ak zcela je neodstra\u0148uje. V\u011bt\u0161ina \u00fanavov\u00fdch cykl\u016f st\u00e1le vede ke vzniku v\u00fdlu\u010dn\u011b tahov\u00fdch nap\u011bt\u00ed, kter\u00e1 mohou b\u00fdt mimo\u0159\u00e1dn\u011b \u0161kodliv\u00e1.<\/p>\n

P\u0159i \u00fapln\u00e9m \u017e\u00edh\u00e1n\u00ed se hypoeutektoidn\u00ed a eutektoidn\u00ed f\u00e1ze zah\u0159\u00edvaj\u00ed na teploty p\u0159ibli\u017en\u011b o 50 \u00b0C vy\u0161\u0161\u00ed ne\u017e jsou jejich p\u0159\u00edslu\u0161n\u00e9 teploty Ac3 a Ac1 a pot\u00e9 se postupn\u011b ochlazuj\u00ed, aby se dos\u00e1hlo struktur bl\u00ed\u017e\u00edc\u00edch se rovnov\u00e1\u017en\u00e9mu stavu. Tento proces pom\u00e1h\u00e1 zabr\u00e1nit vod\u00edkov\u00e9 k\u0159ehkosti a z\u00e1rove\u0148 sni\u017euje riziko prask\u00e1n\u00ed pod vlivem okoln\u00edho prost\u0159ed\u00ed.<\/p>\n

Bodov\u00e9 tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) u mal\u00fdch sou\u010d\u00e1st\u00ed je mo\u017en\u00e9, mus\u00ed se v\u0161ak prov\u00e1d\u011bt opatrn\u011b. Nespr\u00e1vn\u00e9 dimenzov\u00e1n\u00ed a um\u00edst\u011bn\u00ed p\u00e1s\u016f pro v\u00fddr\u017e, oh\u0159ev a regulaci teplotn\u00edho gradientu m\u016f\u017ee v\u00e9st ke zk\u0159iven\u00ed nebo zborcen\u00ed konstruk\u010dn\u00edch sou\u010d\u00e1st\u00ed, p\u0159\u00edpadn\u011b k katastrof\u00e1ln\u00edmu selh\u00e1n\u00ed v d\u016fsledku nestability zbytkov\u00e9ho nap\u011bt\u00ed. Je nutn\u00e9 pou\u017e\u00edt izolaci, aby se teploty v oh\u0159\u00edvan\u00fdch p\u00e1smech udr\u017eely na stabiln\u00ed \u00farovni; rovn\u011b\u017e je nutn\u00e9 pou\u017e\u00edt teplom\u011bry s automatick\u00fdm z\u00e1znamem.<\/p>\n

Normalizace<\/h2>\n

Toto zpracov\u00e1n\u00ed, kter\u00e9 se obvykle pou\u017e\u00edv\u00e1 u n\u00edzkolegovan\u00fdch ocel\u00ed, odstra\u0148uje hrubozrnnou strukturu vzniklou sva\u0159ov\u00e1n\u00edm a zlep\u0161uje vlastnosti materi\u00e1lu. Nav\u00edc sni\u017euje riziko k\u0159ehk\u00e9ho lomu a z\u00e1rove\u0148 zabra\u0148uje vzniku voln\u00fdch tepeln\u00fdch pnut\u00ed v oblasti svaru.<\/p>\n

Zah\u0159\u00e1t\u00ed kovu na teploty nad horn\u00ed kritickou hodnotu a n\u00e1sledn\u00e9 dr\u017een\u00ed v t\u00e9to teplot\u011b po dobu \u00fam\u011brnou tlou\u0161\u0165ce pr\u016f\u0159ezu, po kter\u00e9m n\u00e1sleduje ochlazov\u00e1n\u00ed v prost\u0159ed\u00ed o pokojov\u00e9 teplot\u011b za kontrolovan\u00fdch podm\u00ednek. Tento proces vytv\u00e1\u0159\u00ed jemnozrnn\u00e9 struktury a rovnom\u011brn\u00e9 mikrostruktury, kter\u00e9 pom\u00e1haj\u00ed uvolnit vnit\u0159n\u00ed nap\u011bt\u00ed, \u010d\u00edm\u017e se materi\u00e1l st\u00e1v\u00e1 pru\u017en\u011bj\u0161\u00edm z hlediska tv\u00e1\u0159en\u00ed i praktick\u00e9ho pou\u017eit\u00ed.<\/p>\n

\u00dapln\u00e1 normalizace, kter\u00e1 se nej\u010dast\u011bji pou\u017e\u00edv\u00e1 u uhl\u00edkov\u00fdch a uhl\u00edko-manganov\u00fdch ocel\u00ed, m\u016f\u017ee v ur\u010dit\u00fdch p\u0159\u00edpadech \u00fa\u010dinn\u011b nahradit kalen\u00ed. Bohu\u017eel v\u0161ak \u00fapln\u00e1 normalizace neodstra\u0148uje v\u0161echna zbytkov\u00e1 nap\u011bt\u00ed; normy pro \u00fanavovou pevnost mohou vy\u017eadovat dal\u0161\u00ed renormalizaci, aby se tento rozd\u00edl zohlednil.<\/p>\n

Odstra\u0148ov\u00e1n\u00ed stresu<\/h2>\n

Odstran\u011bn\u00ed nap\u011bt\u00ed se pou\u017e\u00edv\u00e1 ke sn\u00ed\u017een\u00ed vnit\u0159n\u00edch nap\u011bt\u00ed v materi\u00e1lu zp\u016fsoben\u00fdch v\u00fdrobn\u00edmi procesy, jako je tv\u00e1\u0159en\u00ed a obr\u00e1b\u011bn\u00ed, nap\u0159\u00edklad tlakov\u00e9ho nap\u011bt\u00ed na povrchu nebo tahov\u00e9ho nap\u011bt\u00ed v j\u00e1dru. Odstran\u011bn\u00ed nap\u011bt\u00ed je podobn\u00e9 \u017e\u00edh\u00e1n\u00ed v tom, \u017ee zahrnuje zah\u0159\u00e1t\u00ed materi\u00e1lu na vy\u0161\u0161\u00ed teplotu po stanovenou dobu a n\u00e1sledn\u00e9 pomal\u00e9 ochlazen\u00ed po stanovenou dobu.<\/p>\n

Odstran\u011bn\u00ed nap\u011bt\u00ed p\u0159in\u00e1\u0161\u00ed n\u011bkolik v\u00fdhod, mezi n\u011b\u017e pat\u0159\u00ed sn\u00ed\u017een\u00ed pevnosti svaru v tahu a zv\u00fd\u0161en\u00ed \u00fanavov\u00e9 pevnosti v m\u00edstech s lok\u00e1ln\u00edmi vruby a koncentr\u00e1tory nap\u011bt\u00ed, p\u0159i\u010dem\u017e z\u00e1rove\u0148 doch\u00e1z\u00ed ke zv\u00fd\u0161en\u00ed mezikrystalick\u00e9 precipitace karbid\u016f. Odstran\u011bn\u00ed nap\u011bt\u00ed v\u0161ak m\u016f\u017ee b\u00fdt negativn\u011b ovlivn\u011bno nespr\u00e1vn\u00fdmi technikami chlazen\u00ed, regulac\u00ed teploty nebo sva\u0159ovac\u00edmi technikami pou\u017e\u00edvan\u00fdmi b\u011bhem proces\u016f PWHT; pro dosa\u017een\u00ed maxim\u00e1ln\u00edch v\u00fdsledk\u016f je nezbytn\u00e9, aby byly tyto faktory b\u011bhem tohoto procesu uplat\u0148ov\u00e1ny ve spr\u00e1vn\u00fdch \u010dasov\u00fdch okam\u017eic\u00edch a p\u0159i spr\u00e1vn\u00fdch teplot\u00e1ch.<\/p>\n

Temperov\u00e1n\u00ed<\/h2>\n

N\u00edzk legovan\u00e9 uhl\u00edkov\u00e9 oceli vy\u017eaduj\u00ed tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT), aby se dos\u00e1hlo dostate\u010dn\u011b pevn\u00e9 a hou\u017eevnat\u00e9 mikrostruktury. Tento proces spo\u010d\u00edv\u00e1 v oh\u0159\u00e1t\u00ed sou\u010d\u00e1sti na ur\u010ditou teplotu po del\u0161\u00ed dobu a n\u00e1sledn\u00e9m postupn\u00e9m ochlazen\u00ed.<\/p>\n

Zm\u011bny metalurgick\u00e9 struktury mohou p\u0159isp\u011bt ke sn\u00ed\u017een\u00ed pravd\u011bpodobnosti opo\u017ed\u011bn\u00e9ho prask\u00e1n\u00ed a ke zv\u00fd\u0161en\u00ed ta\u017enosti, jako\u017e i ke zlep\u0161en\u00ed odolnosti svar\u016f proti korozi, hou\u017eevnatosti, r\u00e1zov\u00e9 pevnosti a odolnosti proti k\u0159ehk\u00e9mu lomu.<\/p>\n

PWHT se obvykle prov\u00e1d\u00ed pomoc\u00ed regulovateln\u00fdch syst\u00e9m\u016f p\u0159edeh\u0159evu a oh\u0159evu s termo\u010dl\u00e1nky strategicky rozm\u00edst\u011bn\u00fdmi tak, aby bylo zaji\u0161t\u011bno rovnom\u011brn\u00e9 zah\u0159\u00edv\u00e1n\u00ed bez deformace sou\u010d\u00e1st\u00ed. Bodov\u00e9 PWHT lze tak\u00e9 pou\u017e\u00edt u v\u011bt\u0161\u00edch sou\u010d\u00e1st\u00ed, jako jsou obvodov\u00e9 svary na trubk\u00e1ch nebo uzav\u00edrac\u00ed svary na dlouh\u00fdch tlakov\u00fdch n\u00e1dob\u00e1ch, a\u010dkoli technick\u00e9 proveden\u00ed t\u00e9to techniky m\u016f\u017ee b\u00fdt n\u00e1ro\u010dn\u011bj\u0161\u00ed kv\u016fli rozd\u00edl\u016fm v tepeln\u00e9 rozta\u017enosti, kter\u00e9 by mohly zp\u016fsobit zna\u010dn\u00e9 deformace.<\/p>","protected":false},"excerpt":{"rendered":"

Post Weld Heat Treatment, or PWHT, helps relax and redistribute residual stresses that have been introduced during welding processes, often required by codes for materials exceeding certain thickness requirements. Heating and cooling rates must be carefully managed in order to prevent thermal shock, distortion or uneven stress relief. PWHT may be performed using either a … <\/p>\n

P\u0159e\u010dt\u011bte si v\u00edce “Post Weld Heat Treatment For Carbon Steel”<\/span><\/a><\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-285","post","type-post","status-publish","format-standard","hentry","category-pwht-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/285","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=285"}],"version-history":[{"count":1,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/285\/revisions"}],"predecessor-version":[{"id":286,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/285\/revisions\/286"}],"wp:attachment":[{"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/media?parent=285"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/categories?post=285"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/tags?post=285"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}